THE GENUS PYTHIUM - An-Najah National University

THE GENUS PYTHIUM 

In the West Bank and Gaza Strip 

by 

DR. MOHAMMED S. ALl - SHr A YEH 

Department of Biological Sciences 

An - Najah National University 

Published by 

Research and Documentation Centre 

An- ajah National University - Nablus 

1986

,I.' 

Copyright © 1986 by The Resarch and Documentation Centre, 

An': Najah National University, Nablus

PREFACE 

This monograph is aimed at providing a well illustrated guide to the species of 

Pythium in the West Bank and Gaza Strip. 

A key for all the species recovered is given. However, the reader is advised to 

always check through the description given to the species to make sure that he 

has made the right identification. This description has been based on several 

freshly recovered isolates that came from different habitats in order to account 

for inter and intraspecific variations. 

A guide to the isolation methods is also provided. Also, information on the 

distribution and host range of the different species is given. 

I believe that we still have a lot to learn about this important group of fungi 

especially with respect to their physiology, genetics, and taxonomy. However, 

this book has covered fundamental topics on the genus Pythium and that it 

would be particularly useful to students of mycology, botany, plant pathology, 

ecology, and biology 

ACKNOWLEDGNENTS 

I would like to exprees my gratitude to a number of people who directly or 

indirectly helped in the preparation of this monograph. 

I am in the first place indebted to the Dea n of the Research and Documentation 

Centre for allowing the publication of this book. 

I also wish to express special thanks to my research students, laboratory 

technicians, and research assistants at the Department of Biological Sciences, 

and friends who have offered help and encouragement when I most needed it. 

Lastly but no means least I acknowledge the financial support donated 

generously by the Department of Biological Sciences throughout this work.

Summary 

CONTENTS 

J. Introduction 

II. Materials and Methods 

III. Key to Pythium spp isolated in the West Bank and Gaza Strip. 

I V. Desceiptions of species 

V. Host list 

V I. References 

VII. Index of fungal names. 

VIII. Arabic abstract. 

1 

2-4 

5-9 

10 - 15 

16 - 66 

67 - 68 

69 -74 

75 - 76 

78

SUMMARY 

A key to the 48 taxa of Pythium recorded so far from the West Bank and 

Gaza Strip is given.isolation and preservation methods are also provided. 

The following species are described and illustrated: P. acanthicum Drechsler, 

P. anandrum Drechsler, P. aphanidermatum (Edson) Fitzp, P. coloratum 

Vaartaja, P. conidiophorum loki, P. debaryanum auct non Hesse, P. dissimile 

Vaartaja, P. dissotocum Drechsler, P. echinulatum Matthews, P. graminicola 

Subramaniam, P. intermedium de Bary, P. irregulare Buisman, P. iwayamqi S. 

Ita, P. mamillatum Meurs, P. middletonii Sparrow, P. monospermum Pringsh, 

P. nagaii S. Ita & Tokunga, P. oligandrum Drechsler, P. papillatum Matthews, 

P. paroecandrum Drechsler, P. pulchrum Minden, P. rostratum Butler, P. 

salpingophorum Drechsler, P. spinosum Sawada, P. splendens Braum, P. 

sylvaticum Campbell & Hendrix, P. torulosurn Coker & Patterson, P. ultimum 

var sporangiiferum Drechsler, P. ultimum Trow var ultimum, P. vantrepoolii V. 

Kouyeas, and P. vexans de Bary. Descriptions were produced from the study of 

several isolates in order to account for intraspecific variation. 

The other 17 taxa were outlined briefly. These taxa were isolated only once or 

twice and/ or failed to from sexual reproductive structures following their 

identification (P. deliense Meurs, P. dimorphum Hendrix & Campbell, P. 

hypogynum Middelton, P. myriotylum Drechsler, P. orthogonon Ahrens, P. 

periplocum Drechsler, P. pyrilobum Vaartaja, and P. tracheiphilum Matta), 

taxa without oogonia (P. group 'F', P. group 'G', P. group 'HS', and P. group 

'L'), and taxa described by the author in 1982 from Britain (P. lucens, P. 

lutarium, p. minor, p. pachycaule, and P. parvum) and were also isolated from 

the West Bank. 

Occurence of the different taxa in the West Bank and Gaza Strip as well as in 

other neighbouring countries is briefly outlined. All known records of rare 

species are mentioned. 

All known host records of Pythium from the West Bank and Gaza Strip are 

also listed.

I. INTRODUCTION 

The genus Pythium is now regarded as the type genus of the family Pythiaceae 

Schroter in the order Peronosporales of the class Ooomycetes (Waterhouse, 

1973; Plaats-Niterink, 1981). The genus was introduced by Pringsheim (1858). 

His genus was based on two fungi, Pythium monospermum and P. entophytum. 

The latter fungus was transferred to Lagenidium (Zopf, 1890), so that P. 

monospermum remained as the type species. Pringsheim (1858) placed Pythium 

in the Saprolegniaceae, but de Bary (1881) placed the genus in the 

Peronosporaceae. Schroter (1897) created the family Pythiaceae for the genera 

Pythium and Nematosporangium. Butler (1907) did not accept Nematosporangium 

as representing a distinct group of species, so he included all the species under 

Pythium. 

Monographs on the genus have been published by Butler (1907), Matthews 

(1931), Sideris (1931, 1932), Middelton (1943), and Frezzi (1956). Waterhouse 

(1967, 1968) compiled the original descriptions and illustrations of all Pythium 

taxa described at that time; a total of )79 taxa. She produced a key for eighty 

nine taxa which she considered as .valid and rejected ninety taxa. This key 

depended heavilly on the original descriptions of the species. Since many of 

these were produced from the study of single isolates, without taking into 

consideration the possible sources or ranges of variation, original descriptions 

were often inadequate for comparative purposes. As a result the key frequently 

has to depend upon small differences in reproductive cell-size; it also emphasizes 

some nonmorphological characters. Robertson (1980) produced a key to the 

twenty seven species of Pythium recorded so far from New Zealand; illustrations 

and descriptions were given for sixteen species. Plaats-Niterink (1981) published 

the latest monograph of the genus Pythium. She recognised and described eighty 

five species, seven of which are heterothallic. Descriptions were again based on 

single isolates. Therefore, extent of intraspecific variation was not accounted for 

in both Robertson and Plaats-Niterink keys. However, it is difficult to assess 

intraspecific variation from published descriptions since the majority of these 

were prepared from single isolates. 

Pythium species occupy a wide diversity of habitats. They can be found as 

saprobes in fresh and salt water and in soil, and as parasites in aquatic and 

terrestrial plant material, fresh water and marine algae, fungi, invertebrates and 

vertebrates (Middleton, 1943; Plaats-Niterink, 1981). 

Species of Pythium have been often referred to as 'sugar fungi' (Garret, 1951; 

Burges, 1958), a term which infers their inability to degrade complex 

carbohydrate polymers, like cellulose. However, it has been recently found that 

several species of Pythium are capable of degrading cellulose (Taylor & Marsh, 

1963; Tribe, 1966; Willoughby & Redhead, 1973; Park, 1980 a,b; Deacon, 1979). 

It has been therefore suggested (Deacon, 1979) that the cellulolytic activity of 

Pythium species removes these fungi from the substrate group 'sugar fungi'. 

2

Pythium species such as P. periplocum, and P. acanthicum have been 

reported as mycoparasites on both other species of Pythium such as P. ultimum, 

P. debaryanum, P. irregulare and P. salpingophorum (Haskins, 1963; Deacon, 

1976; Vesely, 1978; Deacon & Henry, 1978) and other fungi such as Fusarium 

roseum (Deacon & Hery, 1978). Pythium oligandrum was found by Deacon 

(1976) to be an efficient mycoparasite of Rhizoctonia solani, Fusarium 

culmorum and a Trichoderma species and the possibility of using this fungus in 

bilogical control of damping-off diseases has been considered (Deacon, 1976; 

Vesely, 1978). 

Pythium species have also been reported from nests, intestines, feathers of free 

living birds in Czechoslovakia and Yugoslavia (Hubalek, 1974 a,b), and 

droppings of birds previousely fed with these fungi (Thornton, 197 I). Pythium 

species have also been recorded from fish (Scott & O'Bien, 1962), Daphnia and 

Bosmina (Peterson, 19lOj Plaats-Niterink, 1972, 1975), and crustacean eggs and 

mosquito larvae (Stanghellini, 1974). The extent of pathogenicity to animals is 

not known. Austwick & Copland (1974) found that Hyphomyces destruens-equi 

which might be a Pythium species, is probably pathogenic to horses. Pythium 

spp are distributed worldwide (Tompkins, 1975; Domsch et ai., 1980; Plaats- 

Niterink, 1981). Some species such as P. ultimum, P. rostratum, and P. 

irregulare have appeared consistently in the lists derived from the majority of the 

reports in the literature (Vaartaja, 1968; Hendrix & Campbell, 1970; Plaats- 

Niterink, 1975; Robertson, 1980; Ali, 1982, 1985). On the other hand other 

species such as Pythium deliense, P. aphanidermatum and P. myriotylum have a 

high temperature optimum and are apparently restricted in distribution and 

economic range to warm climates (Garren, 1970; McCarter & Littrell, 1970; Ali, 

1985).Of the.eighty five species recognized by Plaats-Niterink (1981) more than 

sixty species are either known only from original description or have been 

recorded so seldom that comments on their distribution are impossible. 

Many Pythium species are soil inhabitants, living saprophytically or 

parasitically (Stanghellini, 1974; Domsch et al., 1980; Ali, 1982) Some Pythium 

species are among the most destructive plant pathogens (Agrios, 1978). Their 

pathogenic capacity is largely determined by the availability of pectolytic and 

cellulolytic enzymes. Phytotoxins and indolic growth factors have also been 

isolated from a number of species (Blok, 1973). The majority of Pythium species 

are capable of parasitising seeds, seedlings, and older stages of a wide range of 

plants (Robertson, 1980) causing damping-off disease. However, the greatest 

damage is done to the seeds and the roots of seedlings either before or after 

emergence (Agrios, 1978). Their role as plant pathogens depends on several 

factors, including density of potential inoculm (of which inoculm potential is a 

function, Dick,1981), soil water content, soil temperature and pH, competition 

of other microorganisms-and cation content (Hendrix & Campbell, 1973; Plaats- 

Niterink, 1981). 

3

Little is known about the distribution of population of Pythium species in soil 

either on a global or on a local basis, particularly in quantitative terms. The 

introduction of selective media has enabled estimates of propagule numbers to 

be made. Pvthium population under pine in Georgia (U.S.A.) were determined 

by Otrosina and Marx (1975) who found means for numbers of propagules from 

all sites to range from 0-5.2 propagules.g dry wt-I over all seasons; isolates 

corresponding to the Pythium irregulare-P. debaryanum complex were most 

frequently isolated. Lumsden et al. (1976) and Pieczarka & Abawi (1978) studied 

Pythium species population in bean fields in Maryland and New York 

respectiverly, and found Pythium isolates with spherical sporangia and which 

did not produce oogonia and P. uftimum to be most frequent. 

Pythium population in forest nursery soils in Australia and Canada and in the 

south eastern United States were studied by Vaartaja (1964,1968) and Hendrix 

& Campbell (1968) respectively. They found P. irregulare to be the most 

abundant species. 

The distribution of Pythium were studied by Hendrix & Campbell (1970) in 

different soils from many parts of the USA. Heterothallic forms together with 

isolates referable as P. irregulare- P. debaryanum complex, were found to 

dominate Pythium flora in the soils studied. 

Twenty eight to thirty five years ago,Remy (1950), Warcup (1952) and Barton 

(1958)all concluded that Pythium species were abundant in cultivated soils but 

infrequent in uncultivated, undisturbed soils. However their conclusions were 

based on recovery techniques which are known to be less satisfactory for 

quantitative studies, thus making direct comparisons of population levels 

impossible. Using a selective medium (VP3) and the surface-soil-dilution-plate 

procedure, Ali (1982), Ali-Shtayeh et af (l986a,b), Ali-Shtayeh & Dick (1986); 

and Dick & Ali-Shtayeh (1986) studied Pythium populations in a large number 

of cultivated and uncultivated soils in Britian and found Pythium species to be 

more abundant in cultivated farmland soils than in undisturbed, uncultivated 

parkland soils. Species widely distributed in uncultivated soils were P. 

sylvaticum, P. rostratum, P. parvum, and P. acanthicum .. The abundant and 

widespread species in cultivated farmland soils were P. minor, P. parvum, P. 

rostratum and P. vanrerpoolii. 

Pythium populations in a wide range of irrigated and nonirrigated fields in the 

West Bank and Gaza Strip have been studied by the author. A part of this work 

has now been published (Ali, 1985, Ali-Shtayeh, 1985,1986 a,b). 

In this monograph a guide to the isolation and identification of Pythium 

species is provided. Descriptions are also provided for 31 species. The remaining 

species isolated from the West Bank and Gaza Strip are outlined briefly. All the 

plants from which Pvthium species have been recovdred are listed. 

4

II. MATERIALS AND METHODS 

A. Isolationjrom soil: 

ISOLA TION TECHNIQllrs 

a. Use of Selective media and soil dilution technique: 

I. Collection ofsamples: From each site (from 45 fields) four soil samples each 

approximately 250 g fresh weight were taken with a trowel from an area of 

approximately 4m2 at a depth of 0-1 Ocm (Picczark a & Abawi. 1978). The four 

samples were put into a plastic bag. 

2. Prepartion of soil suspensions: Soil suspensions in 0.09% sterile water agar 

were made from each composite sample using 50g soil aliquots. Soil dilutions of 

1:50; I: 100; 1:250; 1:500; were used depending on anticipated population 

densities in the soils sampled CAli, 1985a) 

3. Selective medium and the surface-soil-dilution plating: Plates of VP3 

medium, prepated within the previous 36h, were incoulated by pipetting a I em' 

aliquot of the soil dilution onto the surface. The aliquot was spread over the 

surface of the plate using a sterile, bent glass rod, and the plate rotated by hand 

to give an even spread. The VP3 medium was prepared as follows: Sucrose, 20g; 

MgS04. 7H20, IOmg; ZnCI2, I mg; FeS04. 7H20, 0.02mg; Mo03, 0.02mg; 

CuS04. 5H20, O.02mg; thiamine hydrochloride, 100).1gcorn meal agar (C:MA), 

17g; Oxoid No. I agar, 23g, made up to 990 ml with demineralized water and 

autoclaved. Vancomycin 75mg; PCNB, 100mg; penicillin 50000 units; pimaricin, 

5mg, and rose bengal 2.5mg were mixed in 5ml sterile destilled water and added, 

with a further Sml of rinsings of a sterile disilled water. to the agar when it had 

cooled to SO-Ssoc. After addition, mixing was achieved by thorough rotation of 

the 2L flask by hand before bouring onto the plates. When the medium in the 

plates had solidified, the plates were stored in the dark because pimaricin is 

sensitive to light (Schmitt henner, 1973). 

4.1ncubation and detection of Pythium colonies: Inoculated plates were 

incubated at 22-2So C for 24-48hr and examined for the presence of Pythium 

species. SOil particles, bacterial contaminants and Mortierella spp were removed 

from the surface of isolation plates by washing the agar surface under tap water. 

b. Baiting technique: 

Several kinds of baits were used for the isolation of Pythium species from soil 

and aquatic habitates. Sterilized plant parts such as apples twigs, and leaves 

were used. Autoclaved corn kernels and lupin seeds were also frequently 

employed. Animal material such as flies. Drosophil a and snake skin were also 

used as baits. Paper squares pre-soaked in Richard's solution (Ali, 1982, CM1, 

1983) containing 5 mgjL pimaricin were also found to be effective in trapping 

Pythium spp from soil and water. 

5

B. Isolation of Pythium spp from infected plant parts: 

Pythium spp were isolated from infected plant tissue by plating on the VP3 

medium plates or on plates of 2% water agar containing 5 mg( L pimarinin. 

Excised plant material was first washed under running tap water for about 2 

hours, surface-sterilised in 0.5% sodium hypchlorite for 3 miniutes, rinsed in 

sterile distilled water, blotted dry on sterile filter paper, and then plated on the 

agar plates. The plates were then incubated at 22-250 C for 24-48 hours and 

examined for the presence of Pythium colonies. 

MAINTENANCE OF STOCK CULTURES 

Stock cultures of representative isolates of Pythium species studied were 

maintained either in water culture in 100mi conical flasks (Dick, 1965), or on 

CMA slants (Robertson, 1980; Plaats-Niterink., 1981) in 100mi universal bottles. 

All the stock cultures were kept at 100e. 

IDENTIFICA TION OF PYTHIUM SPECIES 

Transfer of colonies from rough cultures: Small excisions from growing margin 

of Pythium colonies. on the isolation plates or on rinsed baits were cut off and 

either transferred directly to water culture with 1-2 autoclaved corn kernels per 

dish, or to corn meal agar (CMA) or 2% water agar plates, and then transferred 

into water culture after they had been incubated for 24-48h at 220 C. 

Representative isolates of the isolated species (3 of each) are maintained at the 

Fungal Culture Collection of An-Najah University (Ali-Shtayeh, 1986b). 

Induction of sporangial and zoospore formation: For production of sporangia 

and zoospores, dishes were half-filled with sterile distilled water (OW) or with 

an autoclaved mixture of one part filtered pond water and two parts distilled 

water (DDW). Two grass blades (Emerson, 1958), boiled for IS minutes, were 

then placed on or near the hyphal tips. Coloized grass blades were then 

transferred to new dishes half-filled with water (OW or OOW as appropriate), 

incubated for 24-48 h at 10-22° C, rinsed daily with water from the same source, 

and examined periodically for 2-7 days for zoosporangia . If zoospores were not 

produced at these temperatures, cultures were put in a refrigerator at 2-50 C for 

1-2 h before they were examined for zoospore production. Changing the water 

and chilling the cultures may enhance both the production of sporangia and the 

discharge of zoospores (Ali, 1982). 

Induction of sexual structures formation: For production of sexual structures 

similar blocks of agar containing hyphal tips were flooded with OW. Two boiled 

corn kernels were placed adjacant to the hyphal tips and cultures were then 

incubated at 22 0 C for 7-14 days before they were examined. When oogonia were 

not produced in water culture, isolates were grown on Schmitthenner's medium 

(Schmitthenner, 1962) or on CMA supplemented with wheat germ oil (500 

mg( L) to provide sterols needed for sexual reproduction (Hendrix & Papa, 

1974). Schmitthenner's medium and CMA supplemented with wheat germ oil 

were found to be satisfactory for oogonial production and microscopic 

examination was easy because of the clear substrate. 

6

Microscopic examination: Microscopic examinations were made on living 

material, either under the low power (X 10) on undisturbed water culture, or 

under high powers (X45, X60, X 100, using water mounts ringed with nail 

varnish. Occasionally material fixed and stained in lactophenol cotton blue was 

also used. 

Taxonomic characteristics observed: When Pythium isolates were examined 

microscopically the following characteristics were taken into account: 

I. Sporangia, sporangial shape (filamentous, toruloid or lobulated, globose or 

sublobose), details of sporangial papilla; sporangial location (terminal, 

intercalary, catenulate or noncatenulate); sporangial dimensions; and subsequent 

developent (proliferation, deciduousness, production of zoospores, evidence of 

direct germination). 

2. Hyphal swellings, their morphology, dimensions, location and 

germination). 

3. Oogonia, oogonial wall (smooth or spiny, regular or irregular); oogonial 

dimension; oogonial location (terminal or intercalary). 

4. Antheridia, number per oogonium; origin (monoclinous, diclinous, 

hypogynous, intercalary); application (lateral, terminal); stalk (including length 

of stalk and distance of origin from basal septum of oogonium); shape (clubshaped, 

bell-shaped, elongate, round or inflated); branching of antheridial stalk; 

contact interface with oogonia (broad, narrow). 

5. Oospore, oospore wall (smooth or reticulate, thickness, colour) wether it 

filled (plerotic) or did not fill (aplerotic) the oogonial cavity; appearance of the 

ooplast; number of oospores per oogonium; oospore dimensions. 

6. Mycelium (septation, branching, swellings), and appressorial development 

in agar cultures. 

7. Colony morphology, growth form and mycelial density on the agar plates; 

aerial mycelium. (see Fig I.) 

Measurements and observations on the above-mentioned morphological 

features of representative isolates of Pythium recovered from the West Bank and 

Gaza Strip from 1982-1985 were recorded on measurement data sheets prepared 

for this purpose. All measurements were taken using an ocular micrometer and 

an oil immersion lens xIOO. Biometric data were collected for hyphal diameter, 

sporangia or hyphal swellin~s, oogonia, spines, oospores, oospore wall and 

reserve globules. Means and 95% confidence intervals were calculated. Statistical 

checks were made initially to verify that twenty five structures were sufficient to 

characterize the population. 

7

f-ig. I. (ll()n~ morphllIU!!\' (It Pv tluuru srI' on eM A at 2)!'C. (A) Y lutarium, 

11

Growth rate and temperature limits of Pythium spp: To determine temperaturegrowth 

relationships of Pythium species, representative isolates were grown on 

CMA for 24 h at 0,5,10,15,20,25,30,35,37, and 42 0 C. Plates were inoculated 

with 5-mm discs of inoculum and then incubated at the above range of 

temperatures. Three replicate plates were used for each temperature aRd average 

linear growth of each isolate was calculated. 

9

III. KEY TO PYTHIUM SPP. ISOLATED IN THE WEST BANK AND GAZA 

STRIP. 

Living isolates of the species so far reported from the West Bank and Gaza 

Strip were examined. Illustrated descriptions are given for those marked (*) in 

the key. The other species included in the key are noted briefly. 

2(1) 

3(2) 

4(3) 

5(4) 

6(5) 

7(6) 

8(5) 

Oogonia and antheridia produced in single 

cultures Oogonia and antheridida not or scarcely 

produced in single cultures 

Oogonial wall smooth or occasionally with few 

projections 

Oogonial wall ornamented with spines 

SPECIES WITH SMOOTH OOGONIA 

Sporangia filamentous, inflated or not 

Sporangia globose or subglobose, proliferating or 

not (sometimes only hyphal swellings present) 

Sporangia not or slightly inflated 

Sporangia inflated, lobulated or toruloid 

SPORANGIA FILAMENTOUS, NOT OR SLIGHTLY INFLATED 

Oospores plerotic 

Oospores aplerotic 

Oogonia usually with 1-3 papillae, 15.3± 0.4 -95% 

c.1. urn diam; antheridia usually lacking 

Oogonia smooth; antheridia present 

Oogonia 21.6± 0.7)Jm diam; antheridia diclinous, 

sometimes branched; hyphal swellings occasionally 

present 

Oogonium l7.2± 0.6-95% c.1. urn diam; 

antheridia monoclinous and diclinous, not 

branched; hyphal swellings absent 

Oogonia 26.6± 1.4-95% urn diam, when 

elongated then 44-110 urn long, globose, sac 

shaped or trumpetshaped, usually with a long 

thick neck-cell 

Oogonia 19.7± 0.8-95% c.1..um diam, globose or 

pyriform, thick neck-cells absent 

10 

2 

47 

3 

17 

4 

25 

5 

9 

6 

8 

P. papillatum* 

7 

P.lutarium 

P. monospermum* 

P. coloratum* 

P. pachycaule

9(4) 

10(9) 

11(10) 

12(11) 

13(12) 

14(12) 

15(11) 

16(15) 

17(2) 

18(17) 

SPORANGIA FILAMETOUS, INFLATED 

Antheridia absent or rare and then hypogynous 

Antheridia present 

Oogonia smooth 

Oogonia spiny 


Oospores plerotic 

Antheridia usually intercalary 

Antheridia usually not intercalary 

Oogonial stalk typically curved towards antheridia 

Oogonia stalk straight 

Sporangia consisting of inflated toruloid parts 

and discrete globose elements 

Sporangia consisting of inflated lobulate elements; 

discrete globose sporangia absent 

Oogonia 26.1± 1.3-95% C.I urn diam, antheridia 

up to 6/ oogonium 

Oogonia smaller, 20)Jm diam ill average; 

antheridia up to 3/ oogonium 

Oogonia 18.8± 0.6-95% C.Lum diam; antheridial 

stalks originating 15-25 .um below oogonium, 

oospore wall thick, 2-4 ..urn thick 

Oogonia 15.6± 0.5-95% C.I..um diam; antheridial 

stalks originating at a distance of 1-2..umfrom the 

oogonium, oospore wall thinner 1-2..um thick 

SPECIES WITH ORNAMENTED OOGONIA 

Sporangia unknown, hyphal swellings present, 

oogonial prejections cylindrical; antheridia 1- 

3/ oogonium, usually monocIinous 

Sporangia present 

Sporangia filamentous or toruloid 

Sporangia globose, oval, ellipsoidal or elongated 

11 

P. dissimile* 

10 

II 

P. periplocum 

P.deliense 

P. aphanidermatum" 

P. pyrilobum 

P. myriotylum 

P. graminicolum 

P. vanterpoolii* 

P. torulosum* 

12 

15 

13 

14 

16 

P. spinosum" 

18 

lY 

20

19( 18) 

20(18) 

21(20) 

22(20) 

23(22) 

24(23) 

25(3) 

26(4) 

27(26) 

28(27) 

Sporangia not inflated; antheridia usually absent 

rarely present and then monoclinous; oogonial 

projectiuns few, blunt 

Sporangia inflated; antheridia present; oogonial 

projections numerous, blunt 

Sporangia consisting of irregular subglobose elements 

Sporangia single not forming complexes 

Antheridia often absent.oogonial projections 

conical, acute, up to II .um long 

Antheridia present usually monoclinous; oogonial 

projections conical, blunt, up to 5 ..urn long 

Sporangia proliferous; antheridia absent 

Sporangia nonproliferous, antheridia present 

Antheridia mostly hypogynous 

Antheridia monoclinous and diclinous 

Oogonial projections numerous, conical and often 

curved 

Oogonia smooth or with a varying number of 

blunt conical or finger-like projections up to 5 

projections/ oogonium 

SPECIES WITH SUB GLOBOSE SPORANGIA 

Sporangia not proliferating or only hyphal 

swellings present 

Sporangia proliferating 

SPROANGIA SUBGLOBOSE, NON-PROLIFERATING, 

OR ONLY HYPHAL SWELLINGS PRESENT 

Sporangia consisting of subglobose elements only 

Sporangia consisting of both globose or pyriform 

elements and toruloid parts 

Subglobose zoosporic sporangia present 

No zoosporic sporangia, only hyphal swellings present 

Oospores plerotic or nearly so 


12 

P. papillatum* 

P. periplocum 

P. oligandrum" 

P. acanthicum" 

21 

22 

P.anandrum* 

23 

P. echinulatum" 

24 

P. mamillatum* 

P. irregu/are* 

26 

45 

27 

P. pyri/obum 

28 

41 

29 

33

29(28) 

30(29) 

31(30) 

32(31) 

33(28) 

34(33) 

35(34) 

36(35) 

37(35) 

38(37) 

39(3) 

Antheridia typically hypogynous 

Antheridia mono - or diclinous occasionally 

hypogynouns or absent 

Antherid ia monoclinous, typically sessile or 

hypogynous, oogonia usually intercalary 

Antheridia never hypogynous, oogonia terminal 

or intercalary 

Oogonia 15.1± 0.6-95% c.Iurn diam, intercalary, 

often in chains of 2-5; antheridia often absent 

Oogonia terminal and intercalary, antheridia present 

22 urn diam in average, thick-walled chalmydospores 

present. maximum temperature 300C 

Sporangia 18 urn diam in average, chlamydospores 

absent, maximum temperature about 400C 

Oogonia smooth 

Oogonial wall with finger-like projections 0-5/ oogonium 

Antheridia typically bell-shaped, I or rarely 2/ oogonium 

Antheridia not bell-shaped 

Oogonia mostly intercalary often in chains 

Oogonia mostly terminal, occasionally intercalary 

Antheridia 1-2/ oogonium mostly hypogynous 

occasionally monociinous or diciinous, sporangia 

occasionally catenulate together through 

lateral growths 

Antheridia 1-5/ oogonium, mostly monociinous, 

sometimes sessile, diclinous, occasionally hypogynous 

or intercalary, sporangia not catenulate 

Antheridia mostly monoclinous originating immediately 

from below the oogonium, occasionally hypogynous. 

Antheridia monociinous and diciinous, stalked, 

never hypogynous 

No sporangia and toospores sproduced, hyphal 

swellings germir ate by germ tubes 

Sporangia and zoospores produced at room 

temperature; hyphal swellings absent 

Sporangia>26 urn diam III average 

Sporangia

40(39) Oogonia 19.7± 0.8-95% C.I)lm diam; antheridia 

1-2(-3)/ oogonium, not branched. 

41(27) Oogoni~sproduced in singlecultures, oospores plerotic 

Oogonia not produced in single cultures' 

oospores aplerotic ' 

42(41) Antheridia absent 

Antheridia present 

43(42) Oogonia intercalary often in chains; oospores 

typically single; antheridia 1-2/oogonium, typically 

hypogynous 

Oogonia oftern terminal; oospores 1-5/oogonium; 

antheridia I-51 oogonium, monoclinousor diclinous 

44(41) Hyphal swellings up to 32 (av. 26.4± 0.5-95% C.I) 

JIm diam, usually germinating by 1(-2) germ tubes 

each 

Hyphal swellings up to 44 (av 40»)lm diam, often 

with dark, densely granulated contents, each 

usually germinating by 1-5 germ tubes 

Oogenia 26.4± 1.3 - 95% C.I. urn diam, antheridia 

1-2 (-5) oogonium, occasionally branched, 2-3 

branches 

SPORANGIA PROLIFERATING 

45(25) Oogonia 16.0 urn diam in average, often in 

chains; oospores plerotic; antheridia often absent, 

when present monoclinous or diclinous 

Oogonia 17.5,um diam in average; oospores 

aplerotic, antheridia monoclinous, diclinous, 

or hypogynous 

14 

P. debaryanum 

42 

44 

P. conidiphorum* 

43 

P.parvum 

P. minor 

P. sylvaticum" 

P. splendens 

P. lucens 

P. salpingophorum" 

46

46(45) 

47(1) 

48(47) 

49(48) 

50(48) 

51(47) 

52(51) 

Oogonia mostly intercalary, occasionally terminal 

22.8± 1.1-95%C.lllm diam; antheridia monoclinous, 

stalked or sessile, diclinous or hypogynous 

Oogonia terminal 18.6± 0.6-95% C.I JIm diam, 

antheridia single, stalked, monoclinous; no 

diclinous or hypogynous antheridia present 

HETEROTHALLIC SPECIES AND SPECiES WITHOUT OOGONIA 

Sporangia and zoospores produced 

Sporangia not produced, only subglobose hyphal 

swellings present 

Sporangia filamentous inflated or not, oogonia 

not produced in dual cultures 

Sporangia globose non-proliferating, oogonia 

produced or not in dual cultures 

Sporangia filamentous not inflated 

Sporangia lobulated inflated 

Sporangia globose, nonproliferating; oogonia not 

produced in dual cultures 

Sporangia globose catenulate, non proliferating, 

oogonia produced in dual cultures 

Oogonia not produced in dual cultures 

Oogonia produced in dual cultures 

Hyphal swellings large 40 AIm diam in average, 

often with dark, densely granulated contents, 

germinating with 1-5 germ tubes; antheridia 1-8 / oogonium 

Hyphal swellings smaller, 24.4 JIm diameter in average, with 

brownish coloured contents, germinating with \-2 germ tubes; 

antheridia 2-4/ oogonium 

15 

P. middletonii* 

P. nagaii* 

4-8 

51 

49 

50 

P. group 'F' 

P. group 'L' 

P. group 'G' 

P. intermedium" 

P. group 'HS' 

52 

P. splendens" 

P. sylvaticum"

IV. DESCRIPTIONS OF SPECIES 

Whenever possible two to three isolates of each Pythium species have been 

deposited in the Fungus Culture Collection of An-Najah University (F C C A 

U). The following scale is used to describe the degree of presence of Pythium 

species in soil: constantly present, found in 80-100% of soils; mostly present, 

found in 60-80% of soils; often present, found in 40-60% of soils; seldom 

present, found in 20-40% of soils; and rare, found in 1-20% of soils. 

PYTHIUM ACANTHICUM Drechsler, J. Wash. Acad. Sci. 20:408 (1930) Figs 

2-7 

COLONY MORPHOLOGY: Colonies on CMA showing a distinct rosette 

pattern; no aerial mycelium. MYCELIUM: Main hyphae 2.5-5 (av.3.2).um wide. 

SPORANGIA: often intercalary, occasionally terminal; subglobose 15-28 (av. 

20.6± 2.1-95% C. Ij um diam, often forming complexes of irregular subglobose 

elements attached together by filamentous portions. Zoospores produced in 

water culture at room temperature. OOGONIA:Mostly terminal,occasionally 

intercalary, globose 14.0-24.0 (av. 20.6 ± 0.6-95% C.I) .urn in diam; wall 

echinulate, spines conical with blunt tips, 1-6 (av. 3.5).um long. ANTHERIDIA: 

1(-2)joogonium, mostly monoclinous arising at distance upt to 25)lm below 

oogonium base, rarely diclinous, often possessing branched vegetative 

prolongations; antheridial cells often inflated with few constrictions applied to 

the oogonium with narrow or broad contact interph ase. OOSPORES: plerotic, 

17-21 (av.19.4 ± 0.5-95% C.I).um diam, wall 1.5 ± 0.12 95% C.I.um thick, 

coplast 9-13 (av. 10) .urn diam. TEMPERATURE-GROWTH 

RELATIONSHIPS: Minimum 10 0 C ,optimum25-30 0 C, maximum 37 0 C, Daily 

growth rate on CMA at 25 0 C 9mm. 

MATERIAL EXAMINED: ex soil, Tulkarm (FCCAU IOU); ex soil, Gaza 

(FCCAU 101.2) ex Malus sylvestris (L.) Mill, Nablus (FCCAU 101.6), and 

several other isolates. 

OCCURRENCE: Infrequently isolated from diseased roots, stream water, and 

stream bed. 

16

Figs. 2-7 Pythium acanthicum. (2,3) habit showing hyphae and oogonia. (4.5) 

sporangia. (6,7) oogonia and antheridia (Bars= 10 urn). 

17

PYTHIUM ANANDRUM Drechsler J. Wash. A cad. Sci. 20:410 (1930) Figs 

8-19 

COLONY MORPHOLOGY: Colonies on CMA forming a radiate pattern 

with scanty aerial mycelium. SPORANGIA: Terminal, elongate (35-50)X(25-35) 

avo 41X30.um diam, usually papillate, proliferating. Zoosperes formed at room 

temperature, discharge tubes short up to Ifl um long; zoospores rarely forming 

and germinating within the sporangium. OOGONIA: Terminal, globose, 23-29 

(av. 26.5 ± 0.8-95% C.l.) .um diam, ornamented with conical pointed spines, 

3-11 (av. 2.5).urn long. ANTHERIDIA: Lacking. OOSPORES: Aplerotic 20-25 

(av. 22.9 ± 0.6-95% c.!.) urn thick. Ooplast 12-17 (av. 14) .um, 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 50 C, optimum 

20-250 C, maximum 300C. Daily growth rate on CMA at 250C 18mm diam. 

MATERIAL EXAMINED: ex :Lantana sp, Nablus (FCCAU 139.1); ex 

stream water, Til-Nablus (FCCAU 139.2); and ex stream bed, Nablus (FCCAU 

139.3). 

OCCURRENCE: Infrequently isolated from diseased roots, stream water, and 

. stream bed. 

18

Figs. 8-11. Pythium anandrumn. Sporangia, some proliferating. (Bars:lO urn). 

\9

Figs. 12-15. Pythium anandrum. (12,14) habits showing hyphae, oogonia and 

sporangia. (13) proliferating sporangium. (15) zoospores forming and 

germinating inside a sporangium. (Bars-IO .urn). 

20

Figs. 16-19. Pythiurn anandrurn. Oogonia (Bars=10.um). 

_ 21 __ 

I

PYTHIUM APHANIDERMATUM(Edson) Fitzp, Mycologia 15:168 Figs 20- 

23 

COLONY MORPHOLOGY: Colonies on CMA forming a diffuse growth 

pattern with cotony aerial mycelium. MYCELIUM: Main hyphae up to II urn 

wide. SPORANGIA:Mosdy terminal consisting of complexes of swollen 

torulated hyphai bodies. Zoospores formed at room temperature. OOGONIA:Tertnlnai, 

globose, smooth 18-29 (av. 22.7 ± 0.1-95% C.I),um diam. ANTHERIDIA:Mostiy 

intercalary, occasionaly monoclinous or diclinous, 1(-2)/ oogonium. OOSPORES: 

aplerotic) 15-25 (av. 19.2 ± 0.6-95% C.I) urn diam. wall 1-2 (av. 1.2 ± 0.3-95% 

c.I.)pm thick. Ooplast 5-12 (av. 9.3) urn ciam. TEMPERATURE-GROWTH 

RELATIONSHIPS: Minimum 10 0C, optimum 35-40 0C, maximum 40 0 C Daily 

growth rate on CMAat 25 0 C 28mm. 

MATERIAL EXAMINED: ex Solanum melongona L., Ram Alla' (FCCAU 

102.27); ex Cucurbita sp, Nablus (FCCAU 102.26); ex Citrus sp, Gaza (FCCAU 

102.25) ex soil Jordan Valley (FCCAU 102.10), and several other isolates. 

OCCURRENCE: Frequently isolated from diseased roots and damped-off 

seedlings, and often present (in 45% of the fields) in irrigated soils; it was not 

found in nonirrigated fields. This species was also recorded from Cucurbitaceae 

and tomato in Palestine (Reichert, 1939), and thought to be 'common in soils in 

Israei' (Solei & Pinkas, 1984). 

22

Figs. 20-23. Pythium aphanidermatum.i an habit showing hyphae and inflated 

filamentous sporangia. (2! -23) oogonia with intercalary antheridia (Bars: 10 

urn). 

23

PYTHIUM COLORATUM , Vaartaja, Mycologia 57:417 (1965). Figs 24-26 

COLONY MORPHOJ..,OGY: Colonies on CMA forming an indistinct 

chrysanthemum growth pattern; no development of aerial mycelium. 

MYCELIUM: Main hyphe 3-6 (av. 4) um wide. SPORANGIA:Filamerrtous, 

terminal Or intercalary, slightly inflated. Zoospores formed at room 

temperature, vesicles up to 55 urn diam. OOGONIA: Terminal, or occasionally 

intercalary, globose Or pyriform, smooth sometimes with papilla, 17-23 (av. 19.7 

± 0.8-95% C-I) urn diam. ANTHERIDIA: Diclinous and monoclinous, 1- 

4/ oogonium, clavate, crooknecked, antheridial stalk sometimes branching into 

two branches with a septum at the branching point, one antheridial cell is borne 

at each branch. OOSPORES: Aplerotic, 12-19 (av. 16.2 ± 0.7-95% C.I) .urn 

diam, wall 1-2 (av. 1.7 ± 0.2-95% C.l.).um thick. Ooplast 6-11 (av. 7.7)um diam. 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 5 0C, optimum 

250C, maximum 300C. Daily growth rate on CMA at 25 0C 13.8mm. 

MA TERIAL EXAMINED: ex Raphanus sativus L., Ram AlIa' (FCCAU 

/03.6); ex Lens culinaris Medik, Nablus (FCCAU 103·7); ex soil, Bethlehem 

(FCCAU 103.1), and several other isolates. 

OCCURRENCE: Infrequntly isolated from diseased roots and stream water, 

and rarely from soil (found in 15% of the soils sampled). 

PYTHIUM CONIDIOPHORUM Jokl, OSlo bot. Z. 67:33-36 (1918) Figs 27- 

29 

COLONY MORPHOLOGY: Colonies on CMA forming a diffuse pattern; no 

development of aerial mycelium. MYCELIUM: Main hyphae 3-6.um wide, no 

catenulate appressoria ever observed. SPORANGIA and zoospores not formed. 

HYPHAL SWELLINGS: Terminal and intercalary, globose, dark, granulated, 

usually germinating by several germ tubes, 16-30 (av, 21.8±0.8-95% Cd.uim 

diam. OOGONIA: Mostly terminal, occasionally intercalary, smooth, 7-16 (av. 

13.1 ± 0.5-95% C.l.),um diam. ANTHERIDIA: Absent. OOSPORES: Plerotic, 

wall 1-2.5 (av. 1.8± 0.2-95% C.l.),um thick. TEMPERATURE-GROWTH 

RELATIONSHIPS:Minimum 0-5 0 C, optimum 200 C, maximum 30-35 C. Daily 

growth rate on CMA at 25 0 C 12mm. 

MATERIAL EXAMINAD: ex soil, Bethlehem (FCCAU 115.1);and ex 

stream bed, Nablus (FCCAU 115.2; FCCAU 115.3). 

OCCURRENCE: Rarely isolated from soil (found in 2% of the fields sampled 

and stream bed. 

24

Figs. 24-29. (24-26) Pvthium c%rotum;(24) sporangia! vesicle; (25,26) oogonia 

with antheridia. (27-29)P. conidiophorum;(27) habit showing hyphae and 

hyphal swellings; (28,29) oogonia. (Bars: 10 urn). 

25

PYTHIUM DEBARYANUM auct. non Hesse, Waterhouse, Mycol. Pap. 109, 

15pp. (1967) (as de Baryanum); Hesse, Inaug. Diss. Halle: 1-76(1874). Figs. 

30-33 

COLONY MORPHOLOGY: Colonies on CMA showing a radiate growth; 

some aerial mycelium developed especially around petri dish margin. 

MYCELIUM: Main hyphae 2.5-6 (av. 3.4)llm wide. SPORANGIA: Terminal or 

intercalary, globose to subglobose, 15-35 (av. 24.1 ± 1,7-95% c.!.) urn diam. 

Zoospores produced at 5-1S-C. OOGONIA: Mostly terminal, globose, 16-25 (av. 

19.7 ± 0.8-95% c.i.) urn diam. ANTHERIDIA: 1-2(-3)foogonium, mostly 

monoclinous, originating at some distance from oogonium base, never 

hypogynous or sessile, occasiounally diclinous, mostly club-shaped. OOSPORES: 

Aplerotic, 15-20 (av. 16.4 ± 0.4-95% c.L).um diam, wall 1-2 (av. 1.2 ± 0.195% 

c.i.) urn thick, ooplast 7-11 (av. 8.9 ± 0.3 95% C.I.) .urn diam. 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 5° C, optimum 

23-30oC, maximum 350C. Daily growth rate on CMA at 250C 23.8 mm. 

MATERIAL EXAMINED: ex Psidium guayava L., Nablus (FCCAU 

104.3);ex Prunus amygdalus (L.) Batch, Nassareyeh (FCCAU 104.4); and ex 

soil, Hebron (FCCAU 104.1). 

OCCURRENCE: Infrequently isolated from roots, and rarely from soil 

(found in 6% of the soils sampled). This species was also isolated from diseased 

roots of Cucumis sativus L. and Lycopersicon esculentum Mill in Jordan, 

(Mamluk, Skaria & Abu-Blan, unpublished, in Mamluk et al., 1984; Vestal, 

1954). 

PYTHIUM DELIENSE Meurs, Phytopath.Z. 7:179 (1934). 

OCCURRENCE: Rarely isolated from irrigated fields (in 9% of the soils 

sampled); it was absent in nonirrigated fields. 

26

Figs. 30-35. (30-33) Pythium debaryanum; oogonia and antheridia. (34.35) 

Pythium intermedium; catenulate sporangia. (Bars: 10 urn). 

27

PYTHIUM DIMORPHUM Hendrix & Campbell, Mycologia 63:979 (1971). 

OCCURENCE: This species was isolated only once from a soil in Tulkarem. 

PYTHIUM DISSIMILE Vaartaja, Mycologia 57:421 (1965). Figs 36-41 

COLONY MORPHOLOGY: Colonies on CMA forming a radiate growth 

pattern; no development of aerial mycelium. MYCELIUM: Main hyphae 2.5-6 

(av. 3).Almwide. SPORANGIA: Terminal or intercalary,consisting of complexes 

of toruloid outgrowths of hyphae. Zoospores readilly produced at 1O-20oC. 

OOGONIA:Terminal, occasionaly intercalary, globose, smooth 10-15 (av. 12.4 

± 0.4-95% c.1.).Alm diam. ANTHERIDlA:Mostly lacking, rarely hypogynous, 

monoclinous or diclinous. OOSPORES: Plerotic, wall 1-1.5 (av. 1.0 ± 0.4-95% 

c.I.)..um thick. Ooplast 5-8 (av. 6.3)..um diam. TEMPERATURE-GROWTH 

e 

RELA TIONSHIPS: Minimum ro-c, optimum 20-25°C, maximum 30C. Daily 

o 

growth rate on CMA at 25C 6.4mm. 

MATERIAL EXAMINED: ex Viciafabae L., Jenin (FCCAU 106.6); ex soil, 

Gaza (FCCAU 106.1), Nablus (FCCAU 106.2), and several other isolates. . 

OCCURRENCE: infrequently isolated from diseased roots, and also rarely 

from irrigated soils (found in 14% of these soils); it was absent in nonirrigated 

soils. Only a few records are known for this species. It has been recorded from 

soil and Pinus radiata in Australia (Vaartaja, 1965), from soil in the Netherlands 

(Plaats - Niterink, 1975), from agricultural soils in Germany (in Plaats- 

Niterink, 1981), from cultivated soils in England (Ali, 1982) and the West Bank 

of Jordan (AIi, 1985) 

28

Figs. 36-41. Pythium dissimile. (36,37) inflated toruloid sporangia. (38,39) 

oogonia with hypogynous antheridia. (40,41) oogonia. (Bars= 10urn). 

29

PYTHIUM DISSOTOCUM Drechsler 1. Wash. Acac. Sci. 20:402 (930). 

COLONY MORPHOLOGY: Colonies on CMA forming a distinct 

chrysanthemum growth pattern; no development of aerial mycelium. 

MYCELIUM: Main hyphae 4-7 (av. 4.3),um wide. SPORANGIA: Filamentous, 

slightly inflated. Zoospores formed at IO-20°C. OOGONIA: Mostly terminal, 

sometimes intercalary, subglobose, smooth, 15-22 (av. 18.4 ± 0.7-95% ~.I.),um 

diam, occasionaly with papilla. ANTHERIDIA: 1-3/ oogonium. Mostly 

monoclinous commonly sessile arising from the oogonial stalk immediately 

below the oogonium, sometimes diclinous, antheridial stalks unbranched. 

OOSPORES:Aplerotic, 12.5-18 (av. 15.1 ± 0.5-95% c.I.)..um diam, wall 1-2.5 

(av. 1.4 ± 0.13-95% C.lJ .um thick. Ooplasts 6-12 (av. 8) .nm diam. 

TEMPERATURE-GROWTH RELATIONSHIPS:Minimum 5C, optimum 20- 

25 0 C, maximum 35 0 C. Daily growth rate on CMA at 25 0 C 11.4mm. 

MATERIAL EXAMINED:ex Lens culinaris Medik, Tubas (FCCAU 136.4); 

and ex soil, Nablus (FCCAU 136.1 & FCCAU 136.2). 

OCCURRENCE:Infrequently isolated from diseased roots, and rarely from 

soil (found in only one soil). This species was also recorded from soil in the 

Lebanon (Ahrens, 1971). 

3()

Figs. 42-47. Pythium dissotocum. (42,43) habits showing hyphae, filamentous 

sporangia, and oogonia. (44-47) oogonia with antheridia (Bars= IO.llm). 

31

PYTHIUM ECHINULATUM Matthews, Studies on the Genus Pythium, 

(Univ. of Carolina Press) p. 101 (1931). Figs 48-54 

COLONY MORPHOLOGY:Colonies on CMA forming a rosette growth 

pattern; no development of aerial mycelium. MYCELIUM:Main hyphae 3-7 (av. 

4.4),um wide. SPORANGIA: Subglobose to elongate, terminal or intercalary, 

sometimes 3 to 5 in a chain, (13-40)x( l3-33) avo 27x24..um diam. Zoospores 

produced at 5-20° C. OOGONIA: Terminal or intercalary, subglobose, 17-23 (av 

20.9± 0.5-95% c.i.) .urn diam, provided with conical pointed spines 8-14 

(av.11.0) AIm long. ANTHERIDIA: Typically hypogynous, 1-2/ oogonium. 

rarely monoclinous sessile. OOSPORES:Aplerotic (oospore vol. I oogonium vol.- 

0.69),single, sometimes 2/00gonium, 15-21 (av. 18.5± 0.4-95% C. I.),.um diam, 

wall 1-1.5 (av. 1.2± 0.1-95 % C.I.)llm thick. Ooplast 7-11 (av. 9.6)..um diam. 

TEMPERATURE-GROWTH RELATIONSHIPS:Minimum 5°C, optimum 20- 

30 0 C, maximum 35 0 C. Daily growth rate on CMA at 25 0C 8.4mm. 

MATERIAL EXAMINED: ex soil, Nablus (FCCAU 127.1), Jenin(FCCAU 

127.2), and Ram Alia" (FCCAU 127.3). 

OCCURRENCE:Seldom present in irrigated fields (found in 23% of these 

soils); it was absent in nonirrigated fields. 

32

Figs. 48-54. Pythium echinulatum. (48,50,52-54) oogonia, (49) vesicle with 

zoospores. (50) sporangium with a discharge tube. (Bars- \0 urn). 

33

PYTHIUM GRAMINICOLA Subramaniam, Bull. Agric. Res. Pusa 

177:5(1928) (as 'graminicolum'i. Figs 55-59 

COLONY MORPHOLOGY:Colonies on CMA forming a radiate pattern 

with scanty aerial mycelium. MYCELIUM:Main hyphae 2.5-4(av. 3.4»)Jm wide. 

Appressoria subglobose or irregular. SPORANGIA: Terminal or intercalary, 

consisting of inflated lobulated irregular complexes of hyphal bodies. Zoospores 

formed at 5-20 0C. OOGONIA:Terminal or intercalary, smooth, globose, 20-33 

(av. 26.1± 1.3-95% c.I.»).lm diam. ANTHERIDIA: 1-3/ oogonium, mostly 

monoclinous, occasiounally diclinous; antheridial stalk sometimes branching 

into two branches each bearing an antheridial cell, occasionally entwining the 

oogonial stalk. OOSPORES:Plerotic, occasionally 2-3 oospores/ oogonium; wall 

1-3(av. 2.5± 0.1-95% C.I) .um thick. Ooplast 10-18 (av. 13.4)..um diam. 

TEMPERATURE-GROWTH RELATIONSHIPS:Minimum So C, optimum 

2SoC, maximum 300e. Daily growth rate on CMA at 2SoC 7mm. 

MATERIAL EXAMINED: ex soil, Nassareyeh (FCCAU 141.1; FCCAU 

141.2; FCCAU 141.3). 

OCCURRENCE: Isolated only once from an irrigated field under vegetables 

after wheat. 

PYTHIUM HYPOGYNUM Middleton, Mem. Torrey bot. Club 20:69(1943). 

OCCURRENCE: Rarely isolated from irrigated fields (found in 14% of the 

soils): it was absent in nonirrigated fields. 

34

Figs. 55-59. Pvthium graminicola. (55) habit showing hyphae and sporangia. 

(56-59) oogonia with autherid ia. (Bals: 10 urn). 

35

PYTHIUM INTERMEDIUM de Bary Bot. Ztg: 554 (1881). Figs 34-35 

COLONY MORPHOLOGY:Colonies on CMA forming a radiate pattern.no 

development of aerial mycehum. MYCELIUM: Main hyphae 3.5-7(av. 4.8»)lm 

wide. SPORANGIA: Subglobose or spherical, 16-24(av. 19.4).um diam, mostly 

terminal, occasionally intercalary, 2-8 in a. chain. Zoospores formed in water 

culture in the presence of grass blade at 5-15C 

SEXUAL STRUCTURES: Attempts to produce oogonia in dual cultures were 

not successful; identification was based on vegetative structures. 

TEMPERATURE _ GROWTH RELATIONSHIPS: Minimum 5°C, optimum 

250C, maximum 300e. Daily growth rate on CMA at 25°C 21mm. 

MATERIAL EXAMINED: ex Rosa sp, An-Najah University campus 

(FCCAU 107.2);ex soil, Nablus (FCCAUI07.1), and Ram AlIa (FCCAUl07.3) 

and several other isolates. 

OCCURRENCE:Infrequently isolated from diseased roots, and rarely from 

soil (found in 12% of the soils sampled). This species was also recorded from soil 

in the Lebanon(Ahrens, 1971) and from fresh water in Egypt(El-Hissy, 1974). 

PYTHIUM IRREGULARE Buisman,Meded. phytopath. Lab. Willie 

Commelin Scholten 11:1-51(1927). 

COLONY MORPHOLOGY:Colonies on CMA forming a diffuse pattern, 

with a moderate amount of aerial mycelium. MYCELIUM:Main hyphae 3-7(av. 

3.3) urn wide.SPORANGIA:Globose 13-35(av.25.3)jJm diam, terminal and 

intercalary. Zoospores produced at 1O-15oe. OOGONIA:Globose to irregular, 

intercalary and terminal, 15-23 (av. 18.5 ± 0.6-95% C.I.) urn diarn, smooth or 

with a few blunt conical finger-like projections, up to 5/ oogonium. 

ANTHERIDIA: 1-2(-3)/ oogonium, mostly monoclinous, usually stalked arising 

at some distance from oogonium base, occasionally sessile or hypogynous; 

antheridial stalks sometimes branched. OOSPORES:Aplerotic; IO-18(av. 15.0± 

-95% C.l.j nm diam, wall 0.5-1.5 (av. 0.9 ± 0.1-95% C.I)..um thick. Ooplast 6-10 

(av. 7.7).um diam. TEMPERATURE - GROWTH RELATIONSHIPS: 

Minimum lOoC, optimum 30oC, maximum 3SoC. Daily growth rate on CMA at 

250C l lmm. 

36

MATERIAL EXAMINED: ex Vitia fabae, Jenin (FCCAU 108-3), Viola 

tricolor, Nablus (FCCAU 108.4), Euphorbia pulcherrima(R. Grah.) Willd., 

Jericho(FCCAU 1O~.5):ex soil, Hebron(FCCAU 108.1), and several other 

isolates. 

OCCURRE;\lCE:Frequently isolated from diseased roots and damped-off 

seedlings and also often present in soil(found in 45% of the soils sampled). This 

species was also recorded from soil in the Lebanon (Ahrens, 1977). 

PYTHIUM IW A YAMI S. ito, Trans. Sapporo nta. Hist. Soc. 14: 13(1935). 

Figs. 60-64; 63-64 

COLONY MORPHOLOGY: Colonies on CMA forming diffuse pattern with 

no aerial mycelium. MYCELIUM: Hyphae 3-7(av.4.8»).lm wide. SPORANGIA: 

Mostly terminal, occasionally intercalary, globose, some of which thick-walled 

germinating by germ tubes, 20-43(av.28.8»).lm diam. Zoospores formed at 10-200 

C. OOGONIA:Mostly terminal, occasionally intercalary, globose, smooth, 15- 

28(av. 23.8± 0.6-95% C.I»).lm diam. ANTHERIDIA:I-3/00gonium, monoc1inous 

or dic1inous, antheridial stalks occasionally branching into 2-3 branches. 

OOSPORES:Aplerotic, 14-22(av. 19.5± 0.5-95% c.I.) jim diam. Ooplast 9- 

13(av.ll»).lm diam. TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 

50 C,optimum 25 0C, maximum 30oC. Daily growth rate on CMA at 25 0C 14mm. 

MATERIAL EXAMINED: ex Lycopersicon esculentum Mill, Tulkarem 

(FeCAU 109.6), Allium cepa L., Jenin (FCCAUI09.7), and Triticum aestivum 

L., Nablus (FCCAU 109.8); and ex soil, Bethlehem (FCCAUl09.1). 

OCCURRENCE:Frequently isolated from diseased roots and damped-off 

seedlings, but seldom present in soil (found in 24% of the soils sampled).' 

PYTHIUM LUCENS Ali-Shtayeh, Bot. J. Lin. Soc. 91: 297-317 (1985). 

OCCURRENCE: This species was originally isolated from soil in England. It 

seems to be rare in this area: it was isolated only once from an irrigated feild in 

the Jordan Valley • 

37

Figs. 60-64. (60-62) Pythium irregulare, (60) intercalary oogonia and sporangia, 

(61,62) oogonia with antheridia; 63-64) P. iwayamai, (63) oogonium with 

antheridiurn, (64) intercalary conidium. (bars, 10 .urn). 

38

PYTHIUM LrTARIL:\l Ali - Shtaveh, Boi.:'. Lin. Soc. 91:297-317(1985). 

OCCURRENCE:This species was originally isolated from soil in England. In 

this area it was infrequently isolated from diseased roots, and seldom present in 

soil(found in 24% of soils sampled). 

PYTHIUM MAMILLATUM Meurs, Wortelrot veroorzaakt door schimmels 

uit de geslachten Pythium en Aphanomyces, Diss. Univ. Utrecht, p 44(1928) 

Figs. 65-72 

COLONY MORPHOLOGY:Colonies on CMA forming indistinct rosette 

pattern with development of some aerial mycelium. MYCELlUM:Main hyphae 

3-7(av.4.2) 

ellipsoidal 

.um wide. SPORANGIA:Terminal and intercalary, globose or 

13-30 x 11-27(av. 20.3 x 18.6).um diam; zoospores formed at 1O-20C, • 

emmision tubes short, up to 5 ..urn long; rarely proliferating inernally. 

OOGONIA:Terminal or intercalary, globose, 12-22(av.17.9± -95% C.I) urn 

diam, provided with many projections, 4-9(av. 5.5).um long, projections obtuse, 

conical and often curved; occasionally smooth oogonia present. ANTHERIDIA: 

1-2/ oogonium, mostly monoclinous and originating at a distance from 

oogonium base, rarely sessile arrising just below oogonium base, occasionally 

diclinous; antheridial stalks rarely branched, antheridial cells mostly clavate. 

OOSPORES: Plerotic, 11-20(av. 16.7± 0.7-95% c.1.)..um diam. Ooplast 6-11 

(av. 8.5)..um diam. TEMPERATURE-GROWTH RELATIONSHIPS:Minimum 

50C, optimum 250C, maximum 37oC. Daily growth rate on CMA at 250C 21.88. 

MATERIAL EXAMINED: ex soil, Ram Alia' (FCCAUI28.1; FCCAU128.2; 

FCCAU 128.3). 

OCCURRENCE: Rarely isolated from soil, it was found in only one of the 

soils sampled. 

39

Figs. 65-72. Pythium mamillatum. (65) habit showing hyphae and sporangia. 

(66;70-72) oogonia with antheridia. (67) oogonium and empty sporangium. 

(68,69) sporangia. (BarsetO .um), 

40

PYTHIUM MIDDLETON II Sparrow, Aquatic Phycomycetes(Univ. of Mitch. 

Press), p.1038(1960). 

COLONY MORPHOLOGY:Colonies on CMA forming chrysanthemum 

pattern with no aerial mycelium. MYCELIUM:Main hyphae 3-8(av. 4).um wide. 

SPORANGIA: Globose, ovoid, proliferating internally, (25-50)x(21-38) (av. 38 

x 35) urn diam. emmision tubes short, zoospores formed at 10-20 C. 

OOGONIA: Mostly intercalary, occasionally terminal, subglobose, 15-30(av. 

22.8± 1.1-95% C.I.) ..urn diam. ANTHERIDIA:Monoclinous, stalked or 

commonly sessile, diclinous and hypogynous; mostly 1/ oogonium. 

OOSPORES: Aplerotic, 14-25(av.19.0± 0.9 -95% c.1.)..um diam, wall 1-2 (av. 

I.4± 0.2 -95% c.1.)..um thick; ooplast 6-15(av,IO.3)..um diam. TEMPERATURE 

- GROWTH RELATIONSHIPS: Minimum IOoC, optimum 250C, maximum 

30°C. Daily growth rate on CMA at 25°C 1O.lmm. 

MATERIAL EXAMINED: ex Diospyros kaki L.,Tulkarem(FCCA U II 1.8) 

and lens culinaris Medik, Tubas(FCCA U 111.9);ex soil, Nablus(FCCA U 111.1);ex 

stream water, Nablus(FCCAU 111.10), and several other isolates. 

OCCURRENCE: Infrequently isolated from diseased roots, seldom present in 

soil (found in 24% of the soils studied) and also infrequently isolated from 

stream water. This species was also recorded from damped-off soyabeans in 

Egypt (EI-Helaly et al., 1972) and from diseased roots of avocado in 

Israel{Pinkas et al. 1981) 

PYTHIUM MINOR Ali-Shtayeh, Bot. J. Lin. Soc. 91:297-317{l985). 

OCCURRENCE:Seldom present in soil (found in 27% of the soils sampled), 

and also found in stream water. 

41

Figs. 73-78. Pythium middletonii.(3)habil showing hyphae and sporangia. 

(74,75) sporangia, one proliferating internally. (76-78) oogonia with antheridia. 

(Bars; \0 .urn). 

42

PYTHIUM MONOSPERMUM Pringsh., Jb. wiss. Bot. 2:288(1858). Figs. 79- 

84. 

COLONY MORPHOLOGY:Colonies on CMA showing a chrysanthemum 

pattern with no aerial mycelium. MYCELIUM: Main hyphae 5-8(av. 5.2) urn 

wide. SPORANGIA:Filamentous, noninflated. Zoospores produced at 5_20°C. 

OOGONIA:Terminal and intercalary, smooth, l5-20(av. l7.2± 0.6-95% C.!.)).lm 

diam. ANTHERIDlA:I-2(-5)joogonium, monoclinous and diclinous, OOSPORES: 

Plerotic, wall 1-2(av. I.O± 0.1-95% C.I.) urn thick; ooplast 5-8 (av. 7.3),um 

diam. TEMPERATURE-GROWTH RELATIONSHIPS:Minimum 50C, optimum 

250C, maximum 300e. Daily growth rate on CMA at 250C 11.6mm·.;" 

MATERIAL EXAMINED: ex soil, Jenin(FCCAU 113.1; FCCAU 113.3). 

OCCURRENCE: Rarely isolated from soil; it was found in only one of the 

fields sampled. 

PYTHIUM MYRIOTYLUM Drechsler, J. Wash. Acad. Sci. 20:404(1930). 

OCCURRENCE:lnfrequently isolated from diseased roots and rarely from 

soil (found in one field). Other records from the region come from peanuts in 

Israel(Frank, 1968) and Libya(Pucci, 1969). 

PYTHIUM NAGAII S. Ito & Tokunga, J. Fac. Agric. Hokkaido Univ. 

32:209( 1933). Figs. 85-90,85 

COLONY MORPHOLOGY:Colonies on CMA showing a diffuse pattern;scanty 

aerial mycelium developed. MYCELIUM: Main hyphae 3-5(av.3.5) urn wide. 

SPORANGIA: Terminal, ovoid, occasionally globose, (I8-35)x(l5-25) (av. 

25x21) .um diarn, occasionally proliferating; zoospores produced at 1O-150C. 

OOGONIA: Terminal, occasiounally intercalary, smooth, 16-23 (av. 18.6± 0.6 

43

Figs. 79-84. Pvthium monospermum. Oogonia with antheridia. (Bars; 10 urn). 

44

Figs. 85-90. (85) Pythium nagaii, oogonium with antheridium; (86-88) p. 

paroecandrum,oogonia with antheridia; (89-90) P. pulchrum. (89) oogonium 

with hypogynous antheridium, (90) catenulate sporangia. (Bars: 10urn). 

45

-95% CI.) .urn diam. ANTHERIDIA: Mostly monoclinous, occasionally 

diciinous,I(-2)/oogonium, clubshaped. OOSPORES:Aplerotic, 15-18(av. 15.5± 

0.4- 95% Cl.) ..urn diam; ooplast 7-10 (av. 8) .urn diam. TEMPERATURE- 

GROWTH RELATIONSHIPS:Minimum 5°C, optimum 25°C, maximum 300C. 

Daily growth rate on CMA at 25 C OI5.6mm. 

MATERIAL EXAMINED: ex stream bed, Nablus (FCCAU 144.2). 

OCCURRENCE:Isolated only once from stream bed near Nablus. 

PYTHIUM OLIGANDRUMDrechsler, J. Wash Acad. Sci. 20:409(1930) Figs. 

91-94 

COLONY MORPHOLOGY: Colonies on CMA show no special pattern; no 

development of aerial mycelium. MYCELIUM: Main hyphae 3-6 (av. 4»).Im 

wide. SPORANGIA: Terminal or intercalary, consisting of complexes of 

subglobose elements connected together with filamentous parts, 18-35 (av,2.5) 

...urndiam. Zoospores formed at 1O-20oC OOGONIA: Terminal or intercalary, 

globose, 15-26 (av.20.8± 0.8-95% C.I.)...um diam, provided with conical pointed 

projections, 5-11 (av. lO)pm long. ANTHERIDIA: Mostly lacking, diclinous or 

occasionally monoclinous, antheridial cells often applied lengthwise closely to 

the oogonium, sometimes lobulated or constricted. OOSPORES: Aplerotic 

(oospore volume/oogonium volume=0.70), 13-20 (av. 18.5± 0.6-95% C.l.Lum 

diam, wall 1-2 (av. 1.7± -95% C.I.)...um thick, ooplast 6-13 (av.9.8)...um diam. 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 1

Figs. 91-94. Pythium oligandrum.(91) habit showing hyphae, sporongia and 

oogonia. (92) sporongia and oogonia (9.\. 94) oogonia. (Bars, 10 AIm). 

47

PYTHIUM ORTHOGONON Ahrens, Z. Pflkrhk.Pflschutz . 78:177(1971). 

OCCURRENCE: Infrequently isolated from diseased roots and rarely from 

soil (found in 6% of the soils sampled). In addition to its original isolation. from 

the Lebanon (Ahrens, 1971) this species was also recorded from cultivated soils 

in England (Ali, 1982) and the West Bank of Jordan (Ali,1985). 

PYTHIUM PACHYCAULE Ali-Shtayeh, Bot. J. Lin. Soc. 91:297-317(1985). 


soil (found in 6% of the soils sampled). 

PYTHIUM PAPILLATUM Matthews, J. Elisha Mitchell scient. Soc .. 43:231 

(1928). Figs. 95-100 

COLONY MORPHOLOGY: Colonies on CMA showing a vague 

chrysanthemum pattern; no development of aerial mycelium. MYCELIUM: 

Main hyphae 3.5-6 (av. 4.1) .um wide. SPORANGIA: Filamentous, slightly 

thicker than hyphae, branched or unbranched, terminal or lateral. Zoospores 

produced at 1O-26c. OOGONIA: Terminal, occasionally, globose, smooth, 13- 

18 (av. 15.3± 0.4-95% C.l).llm diam, or provided with 1-5 papillae, papilla up to 

15 .urn long. ANTHERIDIA: Mostly lacking, occasionally 1/ oogonium 

monoclinous, mostly sessile originating just from below oogonium base. 

OOSPORES: Plerotic, wall 0.5-1 (av. 0.8± 0.195% C.I).llm thick; ooplast 5-8 

(av. 7.2) .urn diam. 

o 

minimum 10 C, optimum 

• 25 C 1.6mm. 

TEMPERATURE-GROWTH 

• 0 

25 C, maximum 30 C. Daily 

RELATIONSHIPS: 

growth rate on CMA at 

MATERIAL EXAMINED: ex stream water, Nablus (FCCAU 146.2). 

OCCU REN CE: This species seems to be very rare. Only a few records have 

been published since it was first isolated from soil in the USA. These other 

records came from Hordeum vulgare in the USA (Middleton, 1943), from water 

in the USSR (Meshcheryakova & Logvinenko, 1970), and from soil in England 

(Ho , 1975; Ali 1982). In this work, the species was isolated from a freshwater 

stream near Nablus. 

48

Figs. 95-100. Pythium papillaturn. (95) filamentous sporangia. (96-99) oogonia 

with papillae. (100) oogonium with sessile rnonoclinous ant herid iurn. (Bars: 10 

.um). 

49

PYTHIUM PAROECANDRUM Drechsler, J. Wash. Acad. Sci. 20:406 (1930). 

Figs. 86-88. 

COLONY MORPHOLOGY: Colonies on CMA showing a radiate pattern. 

MYCELIUM: Main hyphae 3-8 (av. 4.6).,um wide. SPORANGIA: Subglobose 

or ellipsoidal, 17-33 (av. 23.0± 1.4-95% CI)).lm diam. terminal or intercalary, 

sometimes 2-3 in a chain, zoospores produced at 10-20 C. OOGONIA: globose, 

mostly intercalary, occasionally in chains, occasionally terminal, smooth, 16-28 

..urn (av. 22.8± 1.0-95% CI.) .um diam. ANTHERIDIA: 1-2(-5)foogonium, 

monoclinous, sometimes sessile, occasionally diclinous, sometimes intercalary or 

hypogynous. OOSPORES: Aplerotic, 15-23 (av. 18.1± 1.3-95% CI)..um diam. 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 5' C, optimum 

25° C, maximum 30°C Daily growth rate on CMA at 25°C 14.8mm. 

MATERIAL EXAMINED: ex Vilis vinifera L., Hebron (FCCAU 117.3), 

Solanum melongona L., Nablus (FCCAU 117.4); ex soil, Gaza (FCCAU 117.3), 

and several other isolates. 

OCCURENCE: Frequently isolated from diseased roots and rotted collars, 

and seldom present in soil (found in 30% of the soils sampled). This species was 

also recorded from soil in the Lebanon (Ahrens, 1971). 

PYTHIUM PARVUM Ali-Shtayeh, Bal. J. Lin. 91:297-317(1985). 

OCCURRENCE: Infrequently isolated from diseased roots, and also seldom 

present in soil (found in 24% of the soils sampled). 

PYTHIUM PERIPLOCUM Drechsler, J. Wash. Acad. Sci. 20:405 (1930). 



50 I

PYTHIUM PULCHRUM Minden, Mykol. UntersBer. 1:277(1916). Figs. 89- 

90. 

COLONY MORPHOLOGY: Colonies on CMA showing an indistinct 

chrysanthemum pattern; no development of aerial mycelium. MYCELIUM: 

Main hyphae 3-5 (av. 4.2) urn wide. SPORANGIA: Globose, ellipsoidal, 

occasionally catenulate up to 3 in a chain, 20-41 (av. 30).um diam, zoospores 

produced at 1O-2dC. OOGONIA: Mostly intercalary, occasionally terminal up 

to 5 in a series, smooth, 18-37 (av. 23.4± 1.2-95% c.I.) urn diam. 

ANTHERIDIA: 1-2(-3)/oogonium, mostly hypogynous. occasionally monoclinous 

or diclinous. OOSPORES: Aplerotic, 16-29 (av. 19.4± 0.7-95% c.I.).um diam, 

ooplast 9-13 (av. 1O.5)umdiam. TEMPERATURE-GROWTH RELATIONSHIPS: 

Minimum 5 0C, optimum 25 0C, maximum 30oC. Daily growth rate on CMA at 

25 0C 17mm. 

MATERIAL EXAMINED: ex Malva sp, Nablus (FCCAU 129.3), Monistera 

deliciosa, Qalqilyeh (FCCAU 129.4), ex soil, Gaza (FCCAU 129.1), and several 

other isolates. 

OCCURRENCE: Infrequently isolated from diseased roots, and seldom 

present in soil (found in 30% of the soils sampled). This species was also 

recorded from Iraq (Al-Doory et al. , 1959). 

PYTHIUM PYRILOBUM Vaartaja, Mycologia 57:425 (1965). 

OCCURRENCE: Infrequently isolated from diseased roots, and rarely form 


51

PYTHIUM ROSTRA TUM Butler, Mem. Dep. Agric. bot. Ser. 

Figs. 101-103 

1:84 )1907) 

COLONY MORPHOLOGY: Colonies on CMA showing a chrysanthemum 

pattern; no development of aerial mycelium. MYCELIUM: Main hyphae 3-6 

(av. 3.6) .um wide. SPORANGIA: Terminal or intercalary, globose and 

subglobose, 15-35 (av. 23.1) .nm diam, zoospores produced at 10_20° C. 

OOGONIA: Mostly intercalary, occasionally terminal, subglobose, smooth, 14- 

25 (av. 18.7± 0.9-95% c.!.)..um diam, often in chains. ANTHERIDIA: 1-2 per 

oogonium, monocIinous, often sessile originating immediately below oogonium 

base, or hypogynous. OOSPORES: Plerotic (oospore volume/ oogonium volum- 

0.75),13-23 (av. 17.0± 0-7-95% c.l.)..um diam, wall 1-2 (av. 1.3± 0.1-95% C.I.) 

urn thick, ooplast 6-11 (av. 8.8) ..urn diam. TEMPERATURE-GROWTH 

RELATIONSHIPS: Minimum 5' C, optimum 15-20· C, maximum 30C. Daily 

growth rate on CMA at 25°C 5.6mm. 

MATERIAL EXAMINED: ex Zea mays, Nassareyeh (FCCAU 119.25), 

Citrus sinensis (L) Osbeck, Nablus (FCCAU 119.26); ex soil, Jenin (FCCAU 

119.10), and many other isolates. 

OCCURRENCE: Frequently isolated from diseased roots, and also 

constantly present in soil (found in 85% of the soils sampled). This species was 

also isolated from soil in the Lebanon (Ahrens, 1971) and Iraq (AI-Doory et al. 

1959). 

PYTHIUM SALPINGOPHORUM Drechsler, J. Wash. A cad. Sci. 20:507 

(1930). Figs 109-114. 

COLONY MORPHOLOGY: Colonies on CMA showing no special pattern; 

no development of aerial mycelium. MYCELIUM: Main hyphae 3-6 (av. 3.6) 

J.Im wide, occasionally developing elongated or ovate, often catenulate 

appressoria present. SPORANGIA: Mostly terminal, occasionally intercalary, 

sometimes catenulate, occasionally proliferating, subglobose to globose, 17-28 

(av. 22.5) J.Im diam, zoospores produced at 10-26 C, emmision tube usually 

formed near a septum. OOGONIA: Mostly intercallary, frequently in chains of 

52

Figs. 101-108. (101-103) Pythium rostratum, (101,102) oogonia with 

hypogynous antheridia, (103) empty sporangium with discharge tube; (104-106) 

p. spinosum, oogonia with antheridia; (107-108) P. splendens. (107) hypha I 

swelling, and (108) oogonium with antheridia. (Barssl Ourn). 

53

2-5, globose, smooth, 10-19 (av. 15.1± 0.6-95% C.I.) ..urn diameter. 

ANTHERIDIA: Mostly absent, occasionally monocIinous and originating just 

below oogonium base or diclinous, 1-2/ oogonium. OOSPORES: Plerotic, wall 

1-2 (av. 1.5± 0.1-95% Cil.) ..urn thick. TEMPERATURE-GROWTH 

RELATIONSHIPS: Minimum 5" C, optinum 25° C, maximum 30" C. Daily 

growth rate on CMA at 25"C 16mm. 

MATERIAL EXAMINED: ex soil, Nablus (FCCAU 120.1), Ram Alia 

(FCCAU 120.2), and Bethlahem (FCCAU 120.3). 

OCCURRENCE: Only a few records of this species are known. It has been 

isolated from soil in Germany (Schultz, 1950), Canada (Vaiirtaja, 1968), 

England (Ali, 1982) and the West Bank of Jordan (Ali, 1985) and from diseased 

plants in Germany (Schultz, 1950) and the USA (Middleton, 1943; Horsefall & 

Kertesz, 1933). In this work the species was infrequently isolated from diseased 

roots, seldom isolated from soil (found in 21% of the soils sampled), and was 

also infrequent in stream water. 

PYTHIUM SPINOSUM Sawda apud Sawda & Chen, Trans. nat. Hist. Soc. 

Formosa 16:199 (1926). Figs 104-106. 

COLONY MORPHOLOGY: Colonies on CMA showing a diffuse pattern 

with some aerial mycelium. MYCELIUM: Main hyphae 2.5-6(av. 4.4),um wide. 

SPORANGIA and zoospores not produced. HYPHAL SWELLINGS: 

Inercalary and terminal, globose and subglobose 13-35(av. 19.3).um diam; 

usually germinating by 1-3 germ tubes. OOGONIA: Terminal or occasionally 

intercalary, globose, 14-20(av. l7.1 ± 0.5- 95% c.l.j urn diam, echinulate, spines 

blunt digitate, 2-17(av. 10.0).um long. ANTHERIDIA: 1(-3)1 oogonium, mostly 

monocJinous, occasionally dicJinous. OOSPORES: Plerotic (oospore vol I 

oogonium v::Q.7S),14-18(av. IS.S± 0.S-9S% c.I.).um diam, wall O.S-I (av. 0.9± 

0.1 -95% C.I.) .urn thick, ooplast 6-9 (av. 8.1).um diam. TEMPERATURE- 

GROWTH RELATIONSHIPS: Minimum S·C, optimum 2S'C, maximum 3SoC. 

Daily growth rate on CMA at 2SC 20.5mm. 

MATERIAL EXAMINED: ex soil, Nablus(FCCAU 147.1),' and Gaza 

(FCCAU 147.2;FCCAU 147.3). 

OCCURRENCE: Rarely isolated from irrigated fields (found in 14% of the 

soils sampled). 

54

Figs. 109-114. Pythium salpingophorum. (109,111) oogonia. (110, 112, 114) 

sporangia, some proliferating. (113) apprressoria. (Bars; 10 11m). 

55

PYTHIUM SPLENDENS Braun, J. agric. Res. 30: 1043-1062(192S) Figs. 101- 

108; 107-108. 

COLONY MORPHOLOGY: Colonies on CMA showing radiate pattern with 

some aerial mycelium. MYCELIUM: Main hyphae 3-6(av. 4.S»)lm wide. 

SPORANGIA and zoospores not formed. HYPHAL SWELLINGS: Mostly 

terminal, rarely intercalary, globose, 3S-46 (av. 40) .um diam, often with dark 

densely granulated contents, germinating each by 1-5 germ tubes. SoEXUAL 

REPRODUCTION: Oogonia and antheridia scarcely produced in single 

cultures. This species was distinguished from other species by its large mostly 

terminal hyphal swellings. TEMPERATURE-GROWTH RELATIONSHIPS: 

Minimum 5°C, optimum 2S-30' C, maximum 35°C. Daily growth rate on CMA 

at 2S~C 28mm. 

MATERIAL EXAMINED: ex. Citrus sinensis (L.) Osbeck, Nablus (FCCAU 

121.1); ex Cucurbita pepo L. var me/opera, Ram Alia (FCCAU121.10);ex 

Ficus elastica L., Tulkarem(FCCAU 121.IS);ex soil, Jordan Valley(FCCAU 121.3), 

and many other isolates 

OCCURRENCE: Frequently isolated from diseased roots, seldom present in 

soil(found in 21% of the soils sampled), and also infrequently isolated from 

stream water. 

PYTHIUM SYLVATICUM Campbell & Hendrix, Mycologia 59:274(1967). 

Fig. liS 

COLONY MORPHOLOGY: Colonies on CMA showing a diffuse pattern 

with some aerial mycelim. MYCELIUM: Main hyphae 3.5-IO(av. 5.5»).lm wide. 

SPORANGIA and zoospores not formed. Hyphal swellings: Intercalary or 

terminal, globose, up 'to 32(av. 26.4± 0.5-95% c.1.) urn diam. OOGONIA: 

Scarcely produced in single culture, formed abundantly in dual cultures of 

compatible isolates, contact line formed between the compatible isolates sharp 

to the side of antheridial isolate and diffuse towards the other isolate. Terminal 

or intercalary, subglobose or ovate, 21-28(av. 23.0± 0.7-95% c.!.»).lm diam. 

ANTHERIDIA: Diclinous, 1-4/oogonium;antheridial stalks mostly branched, 

often entwining oogonial stalk. OOSPORES: Aplerotic, 15-23(av. 19.4 ± 0.5- 

95% c.t) urn thick, ooplast 5-10 .um diam. TEMPERATURE-GROWTH 

RELA TIONSHIPS: Minimum 5 0C, optimum 25-30oC, maximum 350C. Daily 

growth rate on CMA at 2SoC 23.7 mm. 

56

FIgs. 115-120. (115) Pythium sylvaticum: habit showing hyphae, oogonia and 

antheridia. (116-117) P. tracheiphilum; (116) sporangia, (117) oogonium and 

antheridium. (118-120) p. ultimum var ultimum; (118,119) oogonia with 

antheridia; (120) hyphal swelling. (Barss lf) urn). 

57

MATERIAL EXAMINED: ex Lens culinaris Medik, Jenin (FCAAU 132.4, 

antheridial); ex soil, Nablus (FCCAU 132.1; FCCAU 132.2, FCCAU 132.3, 

oogonial). 

OCCURRENCE: Infrequently isolated from diseased roots, and rarely from 

soil (found in one soil). 

PYTHIUM TORULOSUM Coker & Paterson, J. Elisha Mitchell scient. 

Soc.42:247. Figs 121-126 

COLONY MORPHOLOGY: Colonies on CMA showing rosette pattern; no 

development of aerial mycelium. MYCELIUM: Main hyphae 3-5(av. 3.5»).lm 

wide. SPORANGIA: Consisting of toruliod inflated branched elements, 

zoospores formed at 10-20"C. OOGONIA: Terminal, sometimes intercalary, 

smooth, 14-19(av. IS.6± 0.5-95% C.!.) .um diam. ANTHERIDIA: 1-2(- 

3)/ oogonium, monoclinous originating at a distance of I-S(-12) urn from the. 

oognium base, occasionally diclinous. OOSPORES: Plerotic, 13.5-17.5(av. 

IS.I± 0.S-9S% C.I.)..um diam, wall 1-1.5 (av. l.l± 0.1-9S% C.I.)..um thick. 

ooplast 6-IO(av. 7.4»).lmdiam. TEMPERATURE-GROWTH RELATIONSHIPS: 

Minimum S·C, optimum 30' C, maximum 3l C. Daily growth rate on CMA at 

25"C 9.7mm. 

MATERIAL EXAMINED: ex Dianthus caryophyllus L., Nablus (FCCAU 

133.1; FCCAU 133.2; FCCAU 133.3). 

OCCURENCE: This species was isolated only from diseased roots of 

Dianthus caryophyllus L. It was also recorded from soil in the Lebanon 

(Ahrens, 1971). 

58

Figs. 121-126. Pythium torulosum. (121) toruloid sporangium. (/22-126). 

oogonia with antheridia. (Bars= 10 urn). 

59

PYTHIUM TRACHEIPHILUM Matta, Phytopath. medit. 4:51(965) 

Figs 116-117 

OCCURRENCE: Rarely isolated from irrigated soils (found in 9% of these 

soils); it was not detected in nonirrigated soils. 

PYTHIUM ULTIMUM VAR SPORANGIIFERUM Drechsler, Sydowia 

14:107(1960) (as 'sporangiferum'), 

This variety differs from var ultimum by its production of zoospores at room 

temperature. 

OCCURRENCE: Rarely isolated from soil; it was infrequently isolated from 

a citrus orchard near Nablus. 

PYTHIUM ULTIMUM VAR ULTIMUM Trow, Ann. Bot. 15:300(1901) 

Figs 118-120 

COLONY MORPHOLOGY: Colonies on CMA forming a diffuse pattern 

with some aerial mycelium. MYCELIUM: Main hyphae 3-7 (av. 4),um wide. 

SPORANGIA and zoospores not formed. HYPHAL SWELLINGS: Globose, 

intercalary, sometimes terminal, 20-35(av. 25.3± 1.7-95% c.1.) .nm diam. 

OOGONIA: Terminal, sometimes intercalary, smooth, 16-35 (av. 20.8± 0.5-95% 

C.I) JIm diam. ANTHERIDIA: 1(-3)/ oogonium, monoclinous, mostly sessile 

originating just below oogonium base, occasionally hypogynous or dic1inous. 

OOSPORES: Aplerotic, 13-24 (av. 17,0± 0.5-95% c.r.i urn diam, wall 1-1.5 (av. 

1.2± 0.1-95% C.I.).llm thick, ooplast 7-14 (av. 1O± 0.4-95% C.I.).llm diam. 

o 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 5 C, optimum 

250C, maximum 30oC. Daily growth rate on CMA at 250C 14mm. 

60

MATERIAL EXAMINED: ex Brassica oleracea L., var. botrytis, Ram Alla 

(FCCAU 123.80), Cucurbita sp., Nablus (FCCAU 123.77), Citr~s sp, Nablm 

(FCCAU 123.79); ex soil, Gaza (FCCAU 123.15), and many other isolates. 

OCCURRENCE: This is the most frequently isolated species from diseased 

roots and damped off-seedlings; it was frequently isolated from 32 of the 52 host 

plants from which species of Pythium have been isolated in the West Bank or 

the Gaza Strip. It is the commonest Pythium species in this area; it is constantly 

present in soil

PYTHIUM VANTREPOOLII V. Kouyeas, and H. Kouyeas, Annis Inst. 

phytopath. Benaki, N.S. 5:210(1963). Figs 127-131 

COLONY MORPHOLOGY: Colonies on CMA showing a rosette pattern 

with some aerial mycelium. MYCELIUM: Main hyphae 2.5-5 (av. 3.3),um wide. 

SPORANGIA: Termihal or intercalary, consisting of catenulate, or globose to 

elongate unbranched outgrowths of mycelium. Zoospores produced at 10-12oc. 

OOGONIA: Terminal or intercalary, globose, smooth, 14-22 (av. 18.8 ± 0.6 

-95% c.r.) .urn diam. ANTHERIDIA: 1(-3)/ oogonium usually monoclinous 

originating at 15-35 urn from oogonium base, occasionally diclinous, soon 

vanishing after fertilization. OOSPORES: Plerotic, wall 1.5-5 (av.2.7± 0.2 -95% 

c.r.) urn thick, ooplast 5-10 (av. 8.2± 0.5 -95% c.!.) urn diam. 

TEMPERATURE-GROWTH RELATIONSHIPS: Minimum 5 0C, optimum 

20-250C, maximum 300C. Daily growth rate on CMA at 25°C 8.3 mm. 

MATERIAL EXAMINED: ex Triticum aestivum L., El Hamra (FCCAU 

123.10); ex soil, Nablus (FCCAU 125.1, FCCAU 125.2; and FCCAU 125.3), and 

several other isolates. 


irrigated fields (found in 9% of the soils sampled). Other records of this species 

come from Sinapis. Secale and Triticum in Germany (Krober & Kiewnick, 1977, 

1978), from Agrastis in the USA (Muse et al., 1974), from maize in Malaysia 

(Liu, 1977), and from soil in England (Ali, 1982). 

62 

r

Figs. 127-131. Pyihium vanterpoolii. (127) habit showing hyphae, toruloid 

sporangia, and oogonia. (128) toruloid sporangia. (129-131) oogonia with 

antheridia. (Bars: 10 urn). 

63

PYTHIUM VEXANS de Bary, J. BOI. Paris 14:105-106 (1896). Figs 132-136 

COLONY MORPHOLOGY: Colonies on CMA showing an indistinct 

chrysanthemum pattern with some aerial mycelium. MYCELIUM: Main hyphae 

2.5-4 (av. 3)..um wide. SPORANGIA: Intercelary or terminal, subglobose to 

avoid, 15-19 (av. 16.0± 0.7-95% c.I.) urn diam, produced in water culture after 

10 days, xoospores produced at 5-15 0C. OOGONIA: Terminal or intercalary, 

subglobose, 15-26 (av. 21.6± 0.8-95% c.!.) .nm diam. ANTHERIDIA: 1(- 

2)/ oogonium, mostly monoclinous arising at some distance from oogonium 

base, rarely diclinous; antheridial cells typically bell-shaped. OOSPORES: 

Aplerotic, 15-21 (av. 18.8± 0.7-95% C.I.)J.lm diam, wall 1-2 (av. 1.6± 0.1 -95% 

c.1.) .um, ooplast 7-13 (av. 9.9± 0.5 -95% c.1.) urn diam. TEMPERATURE- 

GROWTH RELATIONSHIPS: Minimum 5 0C, Optimum 25 0C, maximu 35°C. 

Daily growth rate on CMA at 25 0C 10.8 mm. 

MATERIAL EXAMINED: ex Allium cepa L., Ram Alla' (FCCAU 126.9)m 

ex Sesbania aegyptiaca, Nablus (FCCA U 126.10); ex soil, Tulkarem (FCCA U 

126.1), and several other isolates. 

OCCURRENCE: Infrequently isolated from diseased roots, and also seldom 

present in soil (found in 36% of the soils sampled). Other records in the region 

come from soil in the Lebanon (Ahrens, 1971) and from soil in Iraq (Al-Doory 

et al. 1959).

Figs. 132-136. Pythium vexans. (132) empty sporangium with a discharge tube. 

(133-136) oogonia with antheridia. (Bars, IOpm). 

65

PYTUIUM GROUP 'F' 


seedlings, rarely from soil (found in 18% of the soils sampled), and commonly 

isolated from fresh water streams. 

PYTHIUM GROUP 'G' 


soil (found in 12% of the fields sampled). 

PYTUIUM GROUP 'US' 


seedlings; it has been isolated from seventeen host plants in the West Bank or 

the Gaza Strip. Constantly present in cultivated fields; it was recovered from all 

soils sampled. 

PYTHIUM GROUP 'L' 

OCCURRENCE: Infrequently isolated from diseased roots, rarely from soil 

(found in 6% of the soils sampled), and commonly isolated from fresh water 

streams. 

66

V.HOST LIST 

A list of the vascular host plants from which species of Pythium have been 

isolated in the West Bank and Gaza Strip is presented below. 

Pythium species are indicated by numbers: 

(I) P. acanthicum, (2) P. anandrum, (3) P. aphanidermatum, (4) P. coloratum, 

(5) P. debaryanum, (6) P. dissimile, (7) P. dissotocum, (8) P. intermedium, (9) P. 

irregulare, (10) P. iwayamai, (II) P. lutarium, (12) P. middletonii, (13) P. 

myriotylum (14) P. oligandrum, (IS) P. orthogonon, (16) P. pachycaule, (17) P. 

paroecandrum, (18) P. parvum, (19) P. periplocum, (20) P. pulchrum, (21) P. 

pyrilobum, (22) P. rostratum, (23) P. splendens, (24) P. sylvaticum, (25) P. 

torulosum, (26) P. ultimum var ultimum, (27) P. vanterpoolii, (28) P. vexans, 

(29) P. group 'HS', (30) P. group 'F', (31) P. group 'L', (32) P. group 'G'. 

Alcea officinalis L., hollyhock (26) (29) (30) 

Allium cepa L., onion (10) (14) (17) (18) (26) (28) 

Arachis hypogaea L., peanut (26) 

Arum sp. L., 'lords and ladies' (10) (22) (26) 

Brassica oleracea L., var. botrytis, cauliflower (14) (26) 

Capsicum fructescens L., pepper (14) 

Carica papaya L., papaya (26) 

Citrus limon (L.) Burm, lemon (22) 

Citrus nobilis Lour; mandarine orange (14) (26) 

Citrus sinensis (L.) Osbeck, sweet orange (14) (21) (22) (23) (26) • 

Chrysanthemum segetum L., corn marigold (26) 

Convolvulus arvensis L., bind weed (23) 

Convolulus scammonia, scamong (3) (9) (26) (23) (30) 

Cucumis melo L., sweet melon (26) 

Cucurbita pepo L., var melopero, marrow (3) (14) (23) (26) (29) 

Cydonia oblonga Mill, quince (29) 

Dahlia variabi/lis (Wild.) Desf, dahlia (29) 

Dianthus caryophyllus L., carnation (3) (13) (19) (25) (31) 

Diospyros kaki L., oriental persimon (12) (17) (29) 

Dryopteris filix-mas (L) Schott, male fern (26) 

Euphorbia pulcherrima (R. Grah.) Willd, poinsettia (10) (26) (29) 

Ficus elastica Roxb (26) 

Ficus sp (23) 

Jasminium fructicans L., jasmine (26) 

67

Lantana sp, lantana (2) 

Lens culinaris Medik, lentil (4) (7) (12) (24) (26) (29) 

Lycopersicon esculentum Mill, tomato (10) (14) 

Majoranasyriaca (L.) Rafin (16) 

Mangifera indica L., mango (26) 

Malus sylvestris (L.) Mill, apple (I) (9) (26) 

Malva crispa, curled mallow (14) (29) 

Malva sp. L., mallow (20) (26) (29) (30) (31) 

Monstera deliciosa (20) (22) (23) (26) 

Notobasis syriaca (L.) Cass, Syrian plumed thistle (~2) (26) 

Olea europaea L., olive (10) (13) (26) (29) (30) 

Phaseo/us vulgaris L., common bean (14) 

Pothos aureus (26) (29) 

Prunus amygdalus (L.) Batch, almond (5) (26) 

Prunus avium L., plums (21) 

Psidium guayava L., guava (5) (9) (29) (30) 

Raphanus sativus L.,common radish (4) (24) (26) (30) 

Rosa sp, rose (8) (16) (22) (26) 

Schinus molle L., false pepper (3) (23) (26) 

Sesbania aegyptiaca, L., sesban (26) (28) 

Solunum me/ongona L., eggplant (3) (10) (II) (17) (26) (29) (30) 

So/anum rantonnetii (26) (29) (32) 

Solanum tuberosum L., potato (26) (29) 

Spinacia oleraceae L., spinach (15) 

Triticum aestivum L., wheat (10) (22) (27) (29) 

Viciafabae L.,broad bean (6) (9) (14) (18) (22) (26) 

Viola tricolor L., pansy (9) (22) (26) (30) 

Vitis vinifera L., grape (17) (21) (22) (30) 

Zea mays L., maize (26) (29) (31)

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74

VII. INDEX OF FUNGAL NAMES 

Fusarium culmorum 3 

Fusarium roseum 3 

Hyphomyces destrucns-equi 3 

Lagenidium 2 

Mortierella spp 5 

Nematosporangium 2 

P. accantnicum 3,4, 12, 16, 17,67 

P.anandrum 12, 18, I9,2~2I,67 

P. aphanidermatum 3, 11, 22, 23, 67 

P. coloratum 10, 24, 25, 67 

P. conidiophorum 14, 24, 25 

P. debaryanum 3, ~ I~ 2~2~ 67 

P. deliense 3, 11,26 

P. dimorphum 28 

p. dissimile 11,28,29,67 

P. dissotocum 30,31,67 

P. echinulatum 12, 32, 33 

P. entophytum 2 

P. graminicola 11, 34, 35 

P. hypogynum 13, 34 

P. intermedium 15, 27, 36, 67 

P. irregulare 3, 4, 12, 13, 36, 38, 67 

P. iwayamai 13, 37, 38, 67 

P. lucens 8, 14, 37 

P. lutarium 8, 10, 39, 67 

P. mamillatum 12, 39, 40 

P. middletonii 15, 41, 42, 67 

P. minor 4,8,14,41 

P. monospermum 2, 10, 43, 44 

P. myriotylum 3,11,43,67 

P. nagaii 15, 43, 45 

Pi oligandrum 3,12,46,47,67 

P. othrogonon 13, 48, 67 

P. pachycaule 8, 10, 48, 67 

P. papillatum 10, 12, 48, 49 

P. paroecandrum 13, 45, 50, 67 

75

P.parvum ~~1~5~67 

P. periplocum 3. II. 12.50.67 

P. pulchrum 13.45.51.67 

P. pyrilobum 11. 12.51.67 

P. rostratum 3.4.8. 13.52.53.67 

P. salpingophorum 3. 13. 14. 52. 55 

P. spinosum 11. 53. 54 

P. splendens 14. 15. 53. 56. 67 

P. sylvaticum 4. 14. 15.56.57.67 

P. torulosum 11, 58, 59, 67 

P. tracheiphilum 13. 57. 60 

P. ultimum var sporangiiferum 13. 60 

P. ultimum var ultimum 3. 4, /3. 57. 60. 67 

P. vanterpoolii 4. II. 62. 63. 67 

P. vexans 13. 64. 65. 67 

P. group 'F' 15,66,67 

P.group 'G' 15,66,67 

P. group 'US' 15,66,67 

P. group'L' 15,66. 67 

Rhizoctonia Solani 3 

Trichoderma 3 

76

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THE GENUS PYTHIUM - An-Najah National University

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