Agricultural Reviews, 38 (1) 2017 : 15-28 AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com Print ISSN:0253-1496 / Online ISSN:0976-0539 Diseases infecting ginger (Zingiber officinale Roscoe): A review Gupta Meenu* and Manisha Kaushal1 Department of Vegetable Science, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan-173230, India. Received: 30-03-2016 Accepted: 06-01-2017 DOI:10.18805/ag.v0iOF.7305 ABSTRACT Ginger (Zingiber officinale Roscoe) is an important spice crop in India, which is also one of the leading producer and exporter of ginger in the world. During cultivation, the crop is severely infected by various diseases of them soft rot, yellows, Phyllosticta leaf spot, storage rot, bacterial wilt, mosaic, chlorotic fleck are important. These diseases reduce the potential yields drastically. The geographical distribution, losses, symptoms, causal organism, disease cycle, epidemiology and host resistance, cultural, biological, chemical and integrated management of above mentioned diseses have been discussed in the present paper. Key words: Bacterial wilt, Phyllosticta leaf spot, Soft rot, Storage rot, Viral diseases, Yellows. Ginger (Zingiber officinale Roscoe) is an important spice crop in India, the leading producer and exporter of ginger in the world. The productivity of ginger in India is 40,903MT with annual income of Rs. 44.04 crores in the year 2010-2011 (Dohroo et al., 2012). In India, major ginger growing states are Kerala, Sikkim, Meghalaya, West Bengal, Orissa, Tamil Nadu, Karnataka, Andhra Pradesh, Maharashtra and Himachal Pradesh. During cultivation, the crop is severely affected by various diseases of fungal, bacterial and viral origin and reduce its potential yields drastically reduced. 1. SOFT ROT In warm and humid conditions, it may assume serious proportions and cause significant losses. It is prevalent in almost all ginger growing areas of the world. The disease was first recorded during the year 1907 from Surat, Gujrat, India (Butler, 1907). Symptoms: Ginger crop is affected by this disease throughout the growing period. Almost all parts of the plant including sprouts, roots, developing rhizome and collar region of the pseudostem are vulnerable to infection. Symptoms of soft rot first appear on above ground parts at the collar region in the form of watery, brown lesions. These lesions then enlarge and coalesce, causing the stem to rot and collapse (Dohroo, 2005). On the leaves, the initial symptoms caused by the basal infection appear as yellowing of the tips of older leaves first with the chlorosis gradually moving downward along the margin involving the rest of the leaf blade and, eventually, the leaf sheath. As on older leaves progress, younger leaves start developing a similar symptom progression until the entire plant dies (ISPS, 2005). Once it happens, diseased stems can be easily dislodged because of little structural integrity between and rhizomes. Rhizomes from diseased plants appear brown, water soaked, soft and rotten, and will decay gradually (Dohroo, 2005). Causal Organism: Several species of Pythium have been reported to cause soft rot disease in different parts of the world. Pythium spp. are fungal-like microorganisms belonging to the family Pythiaceae in the order Peronosporales of the phylum Oomycota, a member of the kingdom Stramenopila (Webster and Weber, 2007). The mycelium of P. aphanidermatum is colourless, sometimes lustrous and occasionally slightly yellowish due to abundant oospores or hyphal swellings or grayish lilac (Dohroo et al., 2012). The main hyphae are up to 10 µm wide. Sporangia consisting of terminal complexes of swollen hyphal branches of varying length and up to 20 µm wide. Oogonia terminal, globose, smooth, 20-25 µm in diameter. Anthredia mostly intercalary, sometimes, broadly sac shaped, 10-14 µm wide, 2/ oogonium, monoclinous or diclinous, oospores aplerotic (18-22 µm) in diameter, wall 1-2 µm thick. Zoospores are released either by a pore developed at the tip of sporangium or by bursting of vesicle. Sporangia are never detached from the hypha. The oospores are smooth walled, plerotic (oospore wall fused with oogonial wall) and spherical in shape measuring 12.0-20.0 µm in diameter (Dohroo, 1982). For confirming the identity of the pathogen by molecular techniques, Wang et al. (2003) established a booster PCR method for detection of P. myriotylum using a specific primer selected from rDNA ITS1 region coupled with universal primer ITS2. It was successfully applied to *Corresponding author’s e-mail: meenugupta1@gmail.com Department of Food Science and Technology, Dr YS Parmar University of Horticulture and Forestry, Nauni, Solan (HP) 173230, India. 1 16 AGRICULTURAL REVIEWS Table 1: Reports of Pythium spp. associated with ginger with identification based on morphological and/or molecular techniques and pathogenicity on ginger. Species Countries recorded Species confirmed by Pythium aphanidermatum (Edson) Fitz Bangladesh China India Japan India Australia Fiji Hawaii India Australia Fiji India Korea Taiwan Australia Japan India Malaysia India Japan Fiji India Japan Korea M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, M, P. deliense Meurs P. graminicola Subram P. myriotylum Drechsler P. spinosum Sawada P. splendens Braun P. ultimum Trow P. vexans de Bary P. zingiberis Takahashi MT, MT, MT, P MT, P MT P P MT, MT, MT, P P P P MT, P MT, P MT MT, P P P P P P P P P P P P M: Morphology, MT: Molecular technique, P: Pathogenicity confirmed by Koch’s postulates. (Le et al., 2014) the detection of P. myriotylum in naturally infected ginger rhizomes but not from DNA of ginger rhizomes collected from field without target fungus. A simple technique for producing oospores in P. myriotylum, causing soft rot of ginger has been demonstrated by Yella et al. (2006). Disease cycle and epidemiology: There are two ways by which the disease is carried over and perpetuated, firstly through diseased rhizomes as oospores in scales (Thomas, 1938) and secondly through oospores in soil. Pythium species are capable of saprophytic survival in plant debris. The infected plant debris remaining in the field forms an important source of primary inoculum. Such plant parts may contain large number of perennating oospores. The disease is both seed and soil borne. The wet soil conditions, high soil moisture and soil temperature are the most important factors influencing the development of this disease. Severity of disease is more in areas where rainfall is high or rhizomes are planted in heavy clay soil and poor drainage. The optimum temperature for germination of P. aphanidermatum and P. myriotylum is about 34oC (maximum is 40oC) and for P. pleroticum is 25-30oC. A warm and humid climate predisposes the plant to infection at sprouting stage, because of its tender and succulent tissues (Dake, 1995). MANAGEMENT Soft rot is considered as a complex disease problem. Various available methods should be combined to obtain satisfactory control of this devastating disease. Cultural practices: Cultural practices including seed selection, crop rotation, tillage, organic amendment, drainage and quarantine are commonly employed on ginger fields to control soft rot and limit the spread of Pythium spp. in fields that are unaffected (Le et al., 2014). Infected rhizomes are important sources of perennation and spread of the disease. The best method to manage the disease is the use of disease free rhizomes during planting (Dohroo, 1993). Harvey and Lawrence (2008) believed that crop rotations could change Pythium spp. populations, suggesting that each crop would be associated with particular Pythium spp. and potential inoculum could be reduced to some extent by crop rotation. Rames et al. (2013) also concluded that species richness of fungal and bacterial soil populations were significantly greater in plots with a 4-year program of summer and winter crop rotations or a continuous growth of pasture grass (Digitaria eriantha sub sp. pentzii), where all the green biomass was returned to the fields before the ginger was grown, than in plots treated with fumigant or left as bare fallow. Volume 38 Issue 1 (2017) Soil amendments alter the soil reaction, change the spectrum of soil microflora and thus affect the pathogens existing in soil (Dohroo, 1993; Dohroo and Pathania, 1997). Reduction in soft rot incidence after addition of soil amendments like oil seed cakes, neem cake and other organic matter from various plants in the field was recorded (Sadanandan and Iyer, 1986; Thakore et al., 1987). Integration of neem seed powder and punarnava (Boerhavia diffusa) leaves, instead of poultry manure, into soil at the time of land preparation also reduced soft rot intensity in ginger by up to 89% in comparison to the untreated control (Gupta et al., 2013). Amendment of organic matter, including poultry manure and sawdust (200 t/ha) enriched diversity of soil microbial communities in these ginger fields (Rames et al., 2013). These practices also increased soil carbon levels and water infiltration rates which supported growth and yield of ginger and helped to suppress soft rot on ginger (Smith et al., 2011; Stirling et al., 2012). Neem seed cake was found most effective with least average mortality of 20.3 per cent followed by poultry manure (22.7 %) while evaluating organic and inorganic amendments to manage rhizome rot in pot culture studies (Kadam et al., 2014). Kumar et al. (2012) also found that Schima wallichii and Datura spp. were the best mulches with regard to suppressing soft rot caused by P. aphanidermatum with the level of disease incidence at 12 and 14%, respectively, compared to 48% in a non-mulched treatment. Smith and Abbas (2011) suggested that good water drainage was important in soft rot management because of zoospores production by Pythium spp. which were able to swim and spread in free water. Biological management: Trichoderma spp. are the most widely used biocontrol agents for control of soft rot of ginger. Non-volatile and volatile compounds produced by T. viride could inhibit the growth of P. myriotylum recovered from infected ginger by 70 and 100%, respectively when assessed in vitro (Rathore et al., 1992). In addition, T. harzianum and T. saturnisporum also showed strong antagonism against P. splendens in vitro (Shanmugam et al., 2013a). Along with Trichoderma spp., several rhizobacteria were also antagonistic and showed significant inhibition of P. myriotylum growth in dual culture assays (Bhai et al., 2005). Dohroo et al. (2012) found that growth of P. aphanidermatum on PDA amended with onion and garlic extracts at 5% and 7.5% (v/v), respectively, was completely inhibited by poisoned food technique. Fresh and stored cow urine also strongly inhibited the growth of P. aphanidermatum at a concentration of 20% (v/v) by using the similar technique (Rakesh et al., 2013). Use of Jeevatu, particularly Jeevatu based organic liquid manure, was found to play a vital role in soft rot control and no further spread of the disease was observed after the application of Jeevatu based organic liquid manure in the field in Lalitpur district of Nepal (Poudyal, 2012). 17 Ram et al. (2000) found that the percent of soft rot on Trichoderma. spp. coated ginger was 2-3 times less than that of the untreated control. Suppression of soft rot was even better, reducing soft rot incidence up to four times, once seed ginger was first surface disinfested with 1% HOCl for 5 min and soaked in a suspension of Trichoderma spp. talc-based formulation (6 x 107 CFU/L) and followed by three applications of talc-based formulation (3 x 106 CFU/ g) to the soil at 15 day intervals from the time of planting (Shanmugam et al., 2013b). An application of T. harzianum + Glomus mosseae + fluorescent Pseudomonad strain G4 limited infection of P. splendens to 10% compared with 30, 43, and 50% infection in treatments with T. harzianum, G. mosseae, and G4 as single treatments, respectively (Gupta et al., 2010). Moreover, antagonists also play a role as plant growth promoters. Growth and yield of ginger growing in soil with antagonistic agents were better compared to soil without biocontrol agents application (Bhai et al., 2005; Gupta et al., 2010; Shanmugam et al., 2013a). A mixture of Burkholderia cepacia + T. harzianum recorded a maximum rhizome production efficiency of 84% with reduction of soft rot incidence of 79.7% under polyhouse conditions. Such reduction of soft rot incidence was attributed to the increase in products of defense gene chitinase and which might be involved in disease suppression. In field experiments, the same mixture reduced the rhizome rot to 49.3% and an increased rhizome yield with an average increase of 60.0% over the untreated control (Shanmugam et al., 2013b). Praveen and Sharma (2014) screened crude extracts of 20 plant species against P. aphanidermatum in vitro and found that Jacaranda mimosifolia, Moringa olifera gave the best inhibitory activity of 27.7%. Host resistance: Developing a Pythium resistant variety would be ideal for effective soft rot disease management. Indrasenan and Paily (1974) reported that Maran cultivar was resistant against soft rot caused by P. aphanidermatum. Setty et al. (1995a) evaluated eighteen ginger cultivars against soft rot (Pythium sp.) under field conditions and none was found resistant, however, cultivars Supraba and Himachal Pradesh demonstrated less than 3 per cent disease incidence. Senapati and Sugata (2005) screened 134 ginger varieties available in Koraput, Orissa, India and found one resistant cultivar and eight others with moderate resistance. Kavita and Thomas (2008) found that the accessions of Zingiber zerumbet were the most suitable candidates for donating soft rot resistance to cultivated ginger. Bhai et al. (2013) screened 650 ginger accessions and showed that only 7 percent of the accessions were having the relative resistance to the pathogen. Chemical management: Pythium spp. can survive in the soil for a long period once introduced (Hoppe, 1966). Therefore, the management of soft rot becomes difficult. Chemicals such as mancozeb, ziram, guazatine, propineb 18 AGRICULTURAL REVIEWS and copper oxychloride effectively controlled soft rot when used as 30 minutes dip treatments for rhizomes (Dohroo and Sharma, 1986; Thakore et al., 1988). An experiment conducted on a naturally infested field with P. aphanidermatum in Raigarh, India, showed that seed dipping applications with Ridomil MZ at a rate of 1.25 g/L could increase survival of rhizomes by about 30 percent in comparison to hot water treatment at 51oC for 30 min (Singh, 2011). Seed coating with Fytolan (copper oxychloride) 0.2 percent + Ridomil 500 ppm + Bavistin (carbendazim) 0.2 percent+ Thimet could keep ginger rhizomes free from soft rot in a pot trial (Rajan et al., 2002). Similarly, Smith and Abbas (2011) found that fungicides such as metalaxyl, Ridomil, Maxam XL (fludioxonil) and Proplant (propyl carbamate hydrochloride) applied as a seed treatment could give significantly better control of soft rot caused by P. myriotylum than sole carbendzim seed treatment in a pot trial. Different chemicals have also been tested by various workers as soil drench against soft rot of ginger. Soft rot was reduced by zineb, captafol, methyl bromide, mercuric chloride, thiram, phenyl mercury acetate, copper oxide and mancozeb (Doshi and Mathur, 1987). Dohroo et al. (1984) found metalaxyl application quite effective for the control of rhizome rot. Dipping of seed one day before planting and soil drenching with a mixture of metalaxyl plus captafol 3 months after planting controlled soft rot of ginger (Rathaia, 1987). Fosetyl-Al, metalaxyl, oxadixyl, propamocarb and ethazole (epidiazole) were also evaluated against P. aphanidermatum. Metalaxyl formulations (Ridomil 5G and Apron 35 WS) gave best control of the disease when used as soil and seed treatments (Ramachandran et al., 1989). Srivastava (1994) managed soft rot (P. aphanidermatum) in Sikkim effectively by drenching the soil with zineb or mancozeb following rhizome treatment with carbendazim and incorporating Thiodan dust into the soil to control insect invasion. Nath (1993) suggested planting of ginger under shade after treating with 1 per cent formaldehyde. Treated rhizomes grown under shade had 19.4 per cent incidence of soft rot (P. myriotylum) as compared to 41.3 per cent incidence in treated rhizomes grown without shade. Integrated management: Management of soft rot is difficult by following a single approach because it does not work effectively to suppress the pathogens under field conditions. Therefore, an integrated approach was suggested by Smith and Abbas (2011) which was mainly based on cultural practices and a strict quarantine procedure to manage the disease, while Mathur et al. (2002) found that soil solarization and application of fungicides could effectively minimize the incidence of soft rot caused by P. myriotylum. Rhizome treatments with Ridomil MZ (metalaxyl + mancozeb) at 6.25 g/L in addition to soil drench with Thimet (Phorate) and Ridomil MZ at 10 L/3x1 m plot at 60 days after sowing gave the best control of P. myriotylum on an experimental ginger field in southern Rajasthan, India. The treatments performed even better in solarized plots achieved by sealing thick transparent polythene film over the soil surface for 20 days. Lokesh et al. (2012) suggested that seed ginger could be solarized at 47oC under 200 mm polyethylene sheet for 30 min for Pythium spp. disinfestations. However, longer periods (up to 4 weeks) of soil solarization caused significant reduction in the populations of Pythium spp. and a lower disease incidence in solarized plots (Deadman et al., 2006). Dohroo and Gupta (2014) reported combined applications of bioagents more effective in reducing the disease than the individual treatments. T. harzianum+ P. fluorescens + B. subtilis gave minimum disease incidence on rhizomes (8.64 %) as well as on tillers (12.50 %). Copper oxychloride rhizome treatment effectively suppressed the disease development (5.16%) at 150 days after planting in the field followed by neem extract rhizome treatment (Lalfakawma et al., 2014). A two years field study indicated that rhizome treatment in hot water at 47°C for 30 min and soil application of T. harzianum @ 2.5 kg/ 50 kg FYM/ha, followed by three drenching of mancozeb @ 0.25% were most effective in limiting the incidence of soft rot on ginger besides having their significant response in improving the growth and yield (Dohroo et al., 2015). 2. YELLOWS Yellows disease is one of the serious problems of ginger because it has become more widely spread wherever warm and humid environmental conditions prevail. It was first described by Simmonds (1955) from Queensland. Symptoms: Yellowing of the margins of the lower leaves is the initial symptom which gradually spreads, covering the entire leaves. Older leaves dry up initially followed by the younger ones. Plants may show a premature drooping, wilting, yellowing and drying in patches or in whole bed. Plants may show stunting. In rhizomes, a cream to brown discolouration accompanied by shriveling is commonly seen. Central core rot is also prominent. Rotting of roots is common and the rhizome formation is affected. In final stages of decay, only the fibrous tissues remain within the rhizomes. A white cottony fungal growth may develop on the surface of stored rhizomes. In dry rot, though the leaves become pale but no soft rot of collar region is observed. Such plants cannot be easily pulled out. Mycelial growth in the form of white, peach or buff coloured cushions can be seen on the surface of rhizomes (Dohroo, 1982). Causal organism: The disease is caused by Fusarium oxysporum Schlechtend ex Fr. f.sp. zingiberi Truzillo (Yang et al., 1988). Other species of Fusarium such as F. solani (Mart.) Sacc., F. equiseti (Corda) Sacc. and some unidentified Fusarium spp. were also reported to be associated with ginger rhizomes. Sharma and Dohroo (1990) reported F. Volume 38 Issue 1 (2017) oxysporum as the major cause of yellows from Himachal Pradesh. The second most frequently isolated species was F. solani (Dohroo, 1987; Chauhan and Patel, 1990), however, F. moniliforme Sheld., F. graminearum Achwabe and F. equiseti (Sharma and Dohroo, 1980; Bhardwaj et al., 1988b; Dohroo, 1987) were also found associated with the diseased plants. Isolates of F. oxysporum f. sp. zingiberi differed in their aggressiveness (Dohroo and Sharma, 1992b). F. equiseti (Forda) Sacc. produces microconidia and macroconidia. Microconidia are aseptate measuring 6.5 – 10.0 x 3.0 – 4.0 µm in size. Macroconidia are 1 to 3 septate, sickle to spindle shaped measuring 23.5- 33.0 x 3.0- 4.0 µm in size. Sporodochial formation is rare (Dohroo, 1982). Ramteke and Kamble (2011) investigated the effect of carbon and nitrogen sources, temperature, pH levels and light spectra on mycelial growth of benomyl sensitive and resistant isolates of F. solani (Mart.) Sacc. Sucrose was found to be the best source of carbon, whereas calcium nitrate was the best source of nitrogen. The fungus grew at temperatures ranging from 10 to 35ºC with optimum growth at 25ºC while no growth was observed at 5ºC and 40ºC. The most suitable pH level for the growth was 4.5. Pappallardo et al. (2009) analysed genetic variation among 29 isolates of F. oxysporum f.sp. zingiberi using DNA amplification fingerprinting (DAF). Within these isolates, three haplotypes were identified based on 17 polymorphic bands generated with five primers. Two groups showed very little genetic variation (98.6% similarity), whereas the third single isolate was quite distinct in terms of its molecular profile (77.2% similarity). Shanmugan et al. (2013b) studied genetic variability of 32 Fusarium isolates from diseased ginger rhizomes from Western Himalayas in India. They were analyzed by the unweighted pair group method with arithmetic averaging using randomly amplified polymorphic DNA amplicons. Of two major clusters formed, one was dominated by F. oxysporum and the other by F. solani. Morphological, cultural, pathological and molecular variability among F. oxysporum f.sp. zingiberi isolates were studied by Gupta et al. (2014). Molecular variability revealed 0 to 80% variation among nineteen isolates and they were grouped into two different major groups each comprising of ten and nine isolates, respectively. Disease cycle and epidemiology: The seasonal carryover of fungus inoculum takes place through infected rhizomes and soil. The fungus survives in soil as chlamydospores which may remain viable for many years in the field. The fungus spreads through infected seed rhizomes and about 87% of field infection is due to infected rhizomes (Dohroo, 1989a). The secondary spread of the disease can also take place through irrigation water and by mechanical means. For the development of yellows disease, a temperature range of 15 to 30oC is favourable (the optimum being 23-29oC) accompanied by very high humidity and 19 continuous presence of free water (Sharma and Jain, 1978). Maximum disease incidence occurred when soil temperature ranged from 24 to 25oC and the soil moisture from 25 to 30 per cent (Sharma and Dohroo, 1989). MANAGEMENT Cultural practices: The main mode of disease spread is through contaminated rhizomes. Therefore, the selection of healthy seed rhizomes has been found an effective control measure for the disease (Rana, 1991; Dohroo, 1993). Smith et al. (2011) found greatest (74.2 t/ha) rhizome yield and minimal (7.0%) losses to pathogens in the pasture lay that had been cultivated prior to ginger planting. Stirling et al. (2012) reported that organic inputs, tillage and rotation practices did not influence yellows disease. Results of bioassays were too inconsistent to draw firm conclusions, even soil management practices had little impact on disease severity. Sharma et al. (2012) observed plant spacing of 25 × 30 cm, seed rhizome size of 50 to 75 g to be optimum for better crop return and lower disease incidence. Chemical management: Efficacy of a variety of chemicals has been evaluated for the management of this disease by different workers and they have found very promising effect of different chemicals against the disease (Singh and Gomez, 2001; Singh et al., 2004; Meena and Mathur, 2005; Usman, 2006; Stirling et al., 2006). Systemic and contact fungicides like Bavistin 50WP, Ridomil Gold MZ-72 and contact fungicides like Captan, Dithane M-45, copper oxychloride and Bordeaux mixture etc. were reported effective against the disease (Sagar, 2006; Hasnat et al., 2014). Biological management: Applications of Trichoderma spp. are very effective biological mean for plant disease management especially for the soil borne pathogens. Growth of F. oxysporum f.sp. zingiberi was inhibited effectively by T. harzianum and Gliocladium virens (Sharma and Dohroo, 1991), T. viride and T. harzianum (Khatso and Ao, 2013), T. viride (Amreen and Kumar, 2013). Besides Trichoderma spp., the efficiency of six Streptomyces species was tested against F. oxysporum f.sp. zingiberi by Manasa et al. (2013) following dual culture method and agar well diffusion method. In both the assays, marked inhibitory activity was observed in case of S. species SSC-MB-02. Application of a mixture of Bacillus cepacia + T. harzianum, recorded an increased rhizome production and decreased incidence of yellows in a polyhouse. In field experiments, the said mixture reduced yellows and increased rhizome yield of 45.9 percent and 60.0 percent, respectively, over control (Shanmugam et al., 2013a). Talc-based formulations of the plant growth promoting rhizobacteria strain XXBC-TN (Bacillus subtilis) and a mixture of S2BC-1 (B. subtilis) with TEPF-Sungal (Burkholderia cepacia), known to inhibit F. oxysporum and F. solani, were developed for rhizome dressing and soil application in ginger fields. The strain mixture recorded the maximum rhizome 20 AGRICULTURAL REVIEWS production (85.2%) with fewer yellows and reduced rhizome rot incidences (87.8% and 88.4%) over the control in a polyhouse. This was associated with an increase in the defense enzymes chitinase, -1,3-glucanase, and polyphenol oxidase. Furthermore, the strain mixture treatment promoted plant growth and enhanced rhizome production by 45.8%. In field experiments, the PGPR strain mixture reduced yellows and rhizome rot incidences by about 50.5%, which was comparable to that of carbendazim and mancozeb fungicide mixture (Shanmugam et al., 2013b). Among 14 plant extract tested against F. solani, maximum inhibition of mycelial growth was noticed in Ferula asafeotida powder extract (68.51%) followed by Ocimum leaf extract (60.16%) (Sagar et al., 2007). Alcoholic leaf extracts of Swietenia macrophylla King, Azadirachta indica A. Juss., Hyptis suaveolens (L.) Poit., Polyalthia longifolia ( Sonn.) Thw., Boerhaavia repens L. var. diffusa ( L.) Hook. and Tithonia diversifolia A. Gray had 100 percent control against both sensitive and resistant isolates of F. solani at 25 percent concentration (Ramteke and Kamble, 2011). Host resistance: By using resistant or less susceptible cultivars of ginger the disease can be managed to a great extent. Cultivars like SG 666 (Dohroo, 1989b) and Kerala local (Rana and Arya, 1991) have been reported to show fewer incidences of yellows under field trials in Himachal Pradesh. Priya and Subramanian (2008) reported the presence of a resistance (R) gene of CC–NBS–LRR class of plant resistance genes. Both direct PCR amplification from genomic DNA as well as cDNAs, yielded a 0.6 kb DNA sequence indicating the absence of an intron. Sequence analysis of the PCR amplicon obtained from the genomic DNA showed very high homology to R-genes and this Rgene is present in only resistant varieties. Sharma et al. (2012) reported cultivar “Majauley” to be moderately susceptible while none was found to be tolerant against rhizome rot and wilt disease complex of ginger. Integrated management: Dohroo (1995) suggested an integrated approach to combat the yellows disease of ginger which included treatment of seed rhizomes with mancozeb and carbendazim and use of biocontrol agents T. harzianum, T. hamatum and G. virens as seed treatment and soil application. Hasnat et al. (2014) observed the lowest disease incidence (27.78%) in Ridomil Gold which was statistically similar with the plots which were applied with poultry waste, Bavistin 50WP, Dithane M-45 and saw dust at 240 days after planting. 3. PHYLLOSTICTA LEAF SPOT Phyllosticta leaf spot disease is becoming increasingly important in many of the states due to severe leaf rot and blight it causes. The disease was first reported from Godavari district of Andhra Pradesh and Malabar area of Kerala, erstwhile Madras state (Ramakrishnan, 1942). Symptoms: Initial symptoms of the disease are small oval to elongated spots on the leaves, measuring 1-10 mm x 0.5 4 mm. Later on, the spots show white papery centre and dark brown margins with a yellowish halo surrounding it (Ramakrishnan, 1942). The spots increase in size and coalesce to form larger lesions. The affected leaves become shredded and may suffer extensive desiccation. Symptoms appear first on younger leaves. As the plants put forth fresh leaves, these get infected subsequently. Causal organism: Phyllosticta leaf spot is caused by Phyllosticta zingiberi T.S. Ramakr. The fungus forms amphigynous, subglobose, dark brown ostiolate pycnidia on the host measuring 78 to 150 µm in diameter. On standard media, the fungus forms pycnidia having 100-270 µm diameter bearing hyaline, unicellular, oblong, big guttulate spores measuring 3.7 to 7.4 x 1.2 to 2.5 µm (Ramakrishnan, 1942). Disease cycle and epidemiology: The infected debris or seed serves as primary inoculum for the disease. In leaf, pycnidiospores and mycelia remain viable for 14 months under laboratory conditions (Brahma and Nambiar, 1982). Pycnidia survive in the leaf debris throughout the summer having temperature range of 30 to 35oC. The pycnidiospores remain viable in soil even at 25 cm depth for 6 months. The optimum temperature range for mycelial growth of Phyllosticta was 25.0 to 27.5oC with maximum and minimum to be 32.5 and 10.0oC, respectively. At 5 and 35oC complete inhibition of mycelial growth was observed (Cerezine et al., 1995). The extent of dispersal of causal fungus depends upon the intensity of precipitation. Higher intensity of rain accompanied by wind seems to exert greater impact on target leaf so that spores are splashed to greater distances resulting in liberation of greater amount of spores and increasing disease incidence. The disease begins to appear towards the end of June. During this period, the temperature varies between 23.4 to 29.6oC and relative humidity is between 83.3 to 90.2 per cent. Later in July when the number of rainy days and total rainfall increase, the disease aggravates and spreads very fast (Brahma and Nambiar, 1984). Sood and Dohroo (2005) reported the influence of environmental factors viz., air temperature, relative humidity and rainfall on the disease development to an extent of 85.5 per cent. Ginger plants up to the age of 6 to 7 months are susceptible to the disease and two weeks old leaves are most susceptible. It was observed that temperature range of 23 to 280C with intermittent rain favoured disease development. Disease incidence was found to be less when ginger is grown under partial shade or as intercrop in coconut gardens (Senapati et al., 2012). Continuous cultivation of ginger in the same field builds up higher concentrations of incoculum and early infection of the plant reduce the vigor leading to reduction in the rhizome yield (Singh, 2015). Volume 38 Issue 1 (2017) MANAGEMENT Cultural practices: Shade plays an important role in reducing the severity of Phyllosticta leaf spot. Farmers of the Sikkim state observed that partial shading of mandarian orange provided a favourable environment for growth of ginger and disease intensity remained often less as compared to that of open cultivation (Patiram Upadhaya et al., 1995). The disease severity and sun burn was statistically lower in heavy shade in comparison to open sun grown ginger. However, considering all the parameters viz; reduction in Phyllosticta leaf spot and sun burn of leaves, increased the number of tillers per clump and yield, growing of ginger in partial shade may be recommended to avoid the fungicidal spray for controlling Phyllosticta leaf spot and consequently avoiding fungicidal pollution (Singh et al., 2004). Chemical management: Sprayings of Bordeaux mixture, zineb and maneb have been reported effective in checking the disease (Sohi et al., 1973). Twelve sprays or mixture of benomyl (0.1%), mancozeb (0.2%) and soluble boron (0.1%) and iprodione (0.2%) alone were most effective in reducing the disease (Grech and Frean, 1988). In Brazil, Cerezine et al. (1995) found highest reduction in the disease progress with chlorothalonil. One spray of carbendazim (0.15%) and two sprays of mancozeb (0.25%) gave good protection against the disease and resulted in higher yield under pot culture experiment (Verma and Vyas, 1981). Sood and Dohroo (2005) found that rhizome treatment as well as foliar sprays with Bordeaux mixture (1%), Companion (0.2%), Indofil M-45 (0.25%), Unilax (0.2%) and Baycor (0.05%) were effective in checking the disease severity, however, Bordeaux mixture and Companion effectively increased the rhizome yield of ginger. Host resistance: None of the 18 cultivars tested in Karnataka were resistant to Phyllosticta leaf spot (Setty et al., 1995b). However, the cultivars Narasapatom, Tura, Nadia, Tetraploid and Thingpani were classed as moderately resistant with a disease index less than 5 per cent. In Himachal Pradesh, none of the tested material of ginger was rated resistant to P. zingiberi, however, 8 lines showed moderate resistance (Dohroo et al., 1986b). Different workers obtained variable results and none of the tested cultivars showed high degree of resistance (Dohroo et al., 1986b; Rao et al., 1995). Nageshwar Rao et al. (1995) screened 100 accessions of ginger for their reaction and tolerance to leaf spot under field conditions and of them, 11 accessions were found tolerant and a further 42 were moderately tolerant. Senapati et al. (2012) found that PGS-16, PGS-17 and Anamica as moderately resistant out of 135 ginger cultivars tested. 4. STORAGE ROTS Ginger rhizomes are stored for seed and commercial purpose in different types of storage structures. During storage, rhizomes are attacked by number of fungi and bacteria. 21 Causal organism: During storage, different fungi have been found associated with the ginger rhizomes, which result in rotting and decaying of the rhizomes (Dohroo, 1993). These fungi include F. oxysporum Schlechtend ex Fr., P. deliense Meurs and P. myriotylum Drechs. (Sharma and Jain, 1977), Geotrichum candidum Link (Mishra and Rath, 1989), Aspergillus flavus Link ex. Fr. (Geeta and Reddy, 1990), Cladosporium lennissimum, Gliocladium roseum Bainer, Graphium album (Corda) Sacc., Mucor racemosus Fresen., Stachybotrys sansevieriae, Thanatephorus cucumeris (Frenk) donk and Verticillium chlamydosporium Goddard (Dohroo and Sharma, 1992a). Pythium ultimum, Fusarium oxysporum and Verticillium chlamydosporium were found associated with storage rot of ginger. The disease was noticed in storage pits from January, which reached its maximum intensity in April at 15.5oC temperature and 67.5 per cent relative humidity (Dohroo, 2001). Penicillium brevicompactum was the predominant species isolated from 85% of the rhizomes displaying visible mold growth (Overy and Frisvad, 2005). Moreira et al. (2013) reported positive pathogenicity tests for Acremonium murorum, Acrostalagmus luteo-albus, Fusarium sp., F. oxysporum, Lasiodiplodia theobromae and Sclerotium rolfsii associated with the post-harvest rot of ginger rhizomes in the Serrana region of Espírito Santo, Brazil. MANAGEMENT Cultural practices: Storage of rhizomes under cooled conditions may prolong storability by reducing weight loss and sprouting but may result in higher pathogen incidence than storage at room temperature. Packing of rhizomes in PVC film also reduces weight loss but increases incidence of fungal infection (Lana et al., 1993). Ram and Thakore (2009) showed that storage rot could be effectively minimized by dipping rhizomes of ginger in an extract of Allium sativum @ (10% w/v) or in a combined suspension of P. fluorescens and T. harzianum @ 0.5% for 30 min before storage. Jadhav et al. (2013) reported that storage rot could be effectively reduced by dipping ginger rhizome in garlic extract @ 20% w/v for 30 minutes before storage. Chemical management: Okwuowulu and Nnodu (1988) suggested pre-storage chemical treatments of ginger rhizomes with benomyl (750 ppm) and/or gibberellic acid (150 ppm) to reduce the incidence of storage rots. Dipping of rhizomes in imazalil or prochloraz at 0.8 g a.i. per litre and then storing at 10oC gave good protection against the infection with fungi such as Botryodiplodia, Aspergillus, Diplodia, Fusarium, Rhizoctonia and Pythium in storage (Grech and Swarts, 1990). A combined application of mancozeb and carbendazim to ginger rhizomes controlled storage rot of ginger (Dohroo et al., 1986a; Dohroo and Malhotra, 1995). Under stored conditions, application of 0.3% Ridomil MZ resulted in the lowest incidence of disease 22 AGRICULTURAL REVIEWS (Singh et al., 2004). Steeping of rhizomes in carbendazim (0.1%) for 60 minutes before storage also controlled storage rots and reduced the disease incidence from 71.4 to 18.2 per cent (Sharma and Dohroo, 1991). biotype IV had a wide host range including tomato, potato, Zinnia elegans, Capsicum frutescens, Physalis peruviana and eggplant. Biotype II of R. solanacearum was also isolated from potato plants (Hayward et al., 1967). Under storage conditions, postharvest dipping of aureofungin (0.02%) and Benomyl (0.2%) provided better control of the disease (Haware et al., 1973). Disease incidence under storage was reduced from 71.4 to 18.2 per cent by steeping the rhizomes in carbendazim (0.1%) for sixty minutes (Sharma and Dohroo, 1991). In Indonesia, the race 1 of biovar III of R. solanacearum was considered as the cause of ginger wilt (Mulya et al., 1990). Dohroo (1991) reported occurrence of bacterial wilt of ginger in Himachal Pradesh. The wilt incidence increased when abundant nematodes were there in the ginger soil (Samuel and Mathew, 1986). The host range of R. solanacearum race 4 was restricted to edible ginger (Nelson, 2013). Fourteen species of ginger belonging to Zingiberaceae and Costaceae were evaluated for susceptibility to Ralstonia solanacearum (Rs) race 4 (ginger strains) by several methods of inoculation, including tests to simulate natural infection. Twelve of 14 species tested were highly susceptible to all strains of Rs race 4 upon stem inoculation, and susceptible plants wilted within 21 days (Paret et al., 2008). Amongst various fungicides used for dipping the rhizomes before storage, mancozeb is known to persist longer than carbendazim (Sharma et al., 1992). Mancozeb residues were observed even after 120 days of storage. However, the health risk in carbendazim treated rhizomes is low as compared to mancozeb if they are consumed after peeling. Dohroo (2001) reported that pre-storage treatment with Topsin-M and Bavistin each at 0.2 per cent concentration for 60 minutes reduced incidence of storage rot, loss in rhizome weight, surface shriveling, sprouting of ginger and increased the recovery of the rhizomes. 5. BACTERIAL WILT Bacterial wilt is widespread and exceedingly destructive in several countries. Bacterial wilt has been reported for the first time from Malabar region in the Madras presidency in 1941 by Thomas. In India, this disease occurred since middle of the century but Mathew et al. reported it in 1979 from Kerala. Symptoms: On the collar region, water soaked patches or linear streaks appear. These symptoms are followed by yellow to bronze colouration of margins of the lower-most leaves which gradually progresses upwards. At later stages, the leaves become flaccid with intense yellowish bronze colour and droop ultimately exhibiting typical wilt symptoms. In the infected plants, leaf sheaths look yellowish to dull green. The leaves roll up and the whole plant dries up finally. The pseudostems can be easily separated with a gentle pull and can be broken off at the base. At advanced stage the pseudostem appears slimy. The plants which are infested by the disease stand persistently and do not collapse. If the affected rhizomes are pressed, a milky bacterial exudate oozes out. When infected tissues are steeped in clear water for a while, the water turns cloudy and milky. Causal organism: The disease is caused by Ralstonia solanacearum (Smith) Yabuuchi et al. Three biotypes of R. solanacearum have been described and biotype III causes the wilt in India (Dake et al., 1988). However, Pegg et al. (1974) reported that biotype III of the bacterium caused slow wilt whereas biotype IV caused rapid wilting and death of infected plants. R. solanacearum biotype III was found restricted only to ginger and its common weeds whereas The genetic diversity of R. solanacearum strains isolated from ginger growing on Hawaii island was determined by analysis of amplified fragment length polymorphisms (AFLPs). R. solanacearum strains from ginger in Hawaii island showed a high degree of similarity at 0.853 and strains from ginger in Hawaii were genetically distinct from local strains from tomato (race 1) and heliconia (race 2) (Yu et al., 2003). Kumar and Sarma (2004) detected Isolates of R. solanacearum of ginger with NCM-ELISA and biovars on the basis of membrane protein pattern on SDS-PAGE and biovar specific protein from R. solanacearum could be isolated. R. solanacearum was detected by PCR from rhizomes and soil (Kumar and Anandaraj, 2006; Kumar and Abraham, 2008) and using real time PCR from rhizomes (Thammakijjawat et al., 2006). Disease cycle and epidemiology: R. solanacearum spreads by infested soil adhering to hands, boots, tools, vehicle tires, and field equipment; in water from irrigation or rainfall; and by infected ginger rhizomes (Janse, 1996). This bacterium infects ginger roots and rhizomes through openings where lateral roots emerge or through wounds caused by handling, parasitic insects, or root-knot nematodes (Swanson et al., 2005). The pathogen survives in soils within infected plant debris and as free-living bacteria. Ginger crops can be completely lost to the disease in heavily infested soils (Nelson, 2013). MANAGEMENT Cultural practices: Currently, the bacterial wilt management depends on selection of disease free seed rhizomes, rhizome treatment by hot air or hot water or rhizome solarization, periodical rouging of infected plants and crop rotation with non-host plants to reduce the disease causing potential of soil. Indrasenan et al. (1981) suggested selection of healthy Volume 38 Issue 1 (2017) seed rhizomes, eradication of weeds and adoption of an effective crop rotation as control measures for the disease. Almost all the cultivars were susceptible to wilt pathogen (Indrasenan et al., 1982). Tsang and Shintaku (1998) found that ginger rhizome when exposed to heat for 30 min at 50°C (122°F) and 45 min at 49°C (120°F), respectively, bacteria were eliminated. Exposing ginger seed pieces to hot air at 75% RH until their center temperatures attained 49°C (120°F) for 30 and 60 min and 50°C (122°F) for 30 min, resulted in minimal injury to the hosts. More than 87% of the seed pieces germinated without adverse effect on growth. Chemical management: Treatment of seed rhizomes with emisan plus plantomycin for 30 minutes followed by three sprayings, first at 30 days after planting and others at an interval of 15 days, also gave good control of the disease (Ojha et al., 1986). Sinha et al. (2000) evaluated five antibiotics in vitro and in vivo against bacterial wilt of ginger. Streptomycin and streptopenicillin were superior over the other antibiotics against the pathogen under both conditions. Biological management: Bacillus subtilis strain 1JN2, Myroides odoratimimus 3YW8, B. amyloliquefaciens 5YN8, and Stenotrophomonas maltophilia 2JW6 showed biocontrol efficacies greater than 50% in greenhouse against bacterial wilt of ginger (Yang et al., 2012). 6. MOSAIC The symptoms appear as yellowish and dark green mosaic pattern on leaves. The affected plants show stunting. The virus causing mosaic in ginger has spherical particles with diameter of 23 to 38 µm. It showed positive serological reaction with antiserum of cucumber mosaic virus (CMV). The virus is known to be transmitted by sap to different plants known to be hosts of CMV (Su, 1980). Nambiar and Sarma (1974a) reported that sap transmission from ginger to ginger, ginger to Nicotiana tabacum var. Harrison Special, N. tabacum var. rustica, N. tabacum var. xanthii, N. glutinosa, Elettaria cardamom, Curcuma longa and C. aromatica gave negative results. 7. CHLOROTIC FLECK The chlorotic fleck virus was characterized and described by Thomas (1986). He detected the virus in ginger imported from Australia and a number of countries. The geographical distribution of the virus was uncertain, and thought to include India, Malaysia and Mauritius. 23 The ginger chlorotic fleck virus (GCFV) has isometric particles about 30 nm diameter, with a sedimentation coefficient of 111s and readily purified from infected ginger leaf tissue. The purified preparations contained a major species of single stranded RNA MW 1.5 x 106 and major coat protein MW 29 x 103. At pH 7, the particles formed a single zone in both cesium chloride and cesium sulphate gradients, with buoyant densities of 1.355 g/cm3 (fixed virus) and 1.297 g/cm3 (unfixed virus), respectively. The virus particles migrated as two electrophoretic components and were liable when treated with 10mM EDTA, 1M NaCl, 10 mM tris pH 8.25 or when negatively stained with potassium phosphotungstate. The virus was transmitted by Myzus persicae, Pentalonia nigronervosa, Rhopalosiphum maydis or R. padi. Possible affinities of GCFV with the subemovirus group was also described by Thomas (1986). 8. MINOR DISEASES Some diseases of minor importance have also been reported on ginger like Cercospora leaf spot caused by Cercospora zingibericola (Kar and Mandal, 1969), anthracnose caused by Colletotrichum zingiberis (Nema and Aggarwal, 1960), Pyricularia leaf spot caused by Pyricularia zingiberi (Rathaiah, 1979), basal rot caused by Sclerotium rolfsii (Mehrotra, 1952; Haware and Joshi, 1973) and Septoria leaf spot caused by Septoria zingiberis (Sundaram, 1961). CONCLUSION Ginger occupies an important place in spices throughout the world and India is one of the leading producer and exporter of ginger in the world. However, during cultivation this crop is infected by a myriad of diseases caused by different fungal, bacterial and viral pathogens which reduce the potential yields drastically. For reducing the losses caused by these pathogens, a sound knowledge of occurrence, distribution, symptoms, biology, perpetuation, transmission and epidemiological factors is required. Further, an insight into management practices such as cultural practices, host resistance, biological, chemical management and an integration of these practices is needed. Therefore, an effort has been made to review geographical distribution, losses, symptoms, causal organism, disease cycle, epidemiology, host resistance, cultural, biological, chemical and integrated disease management strategies of diseases infecting ginger. REFERENCES Amreen, T. and Kumar, V.B.S. (2013). Sensitivity of Fusarium oxysporum f.sp. zingiberi causing ginger yellows against antagonist and fungicides. Environ. Ecol. 31: 663-666. Bhai, R.S., Kishore, V.K., Kumar, A., Anandaraj, M. and Eapen, S.J. (2005). Screening of rhizobacterial isolates against soft rot disease of ginger (Zingiber officinale Rosc.). JOSAC 14: 130-136. Bhai, R.S., Sasikumar, B. and Kumar, A. (2013). Evaluation of ginger germplasm for resistance to soft rot caused by Pythium myriotylum. Indian Phytopath. 66: 93-95. 24 AGRICULTURAL REVIEWS Bhardwaj, S.S., Gupta, P.K., Dohroo, N.P. and Shyam, K.R. (1988). An addition to fungi causing rhizome rot of ginger. Plant Dis. Res. 3: 66. Brahma, R.N. and Nambiar, K.K.N. (1982). Survival of Phyllosticta zingiberi Ramakr., causal agent of leaf spot of ginger. In: Proceedings of National Seminar on Ginger and Turmeric. (Nair, M.K., Prem Kumar T., Ravindran, P.N. and Sarma, Y.R., Eds.) CPCRI, Kasargod, pp. 123-125. Brahma, R.N. and Nambiar, K.K.N. (1984). Spore release and dispersal in ginger leaf spot pathogen Phyllosticta zingiberi. In: Proceedings of National PLACROSYM-V 1982. (Bavappa, K.V.A. et al., eds.), Placrosym Standing Committee. Butler, E.J. (1907). An account of genus Pythium and some Chytridiaceae. Mem. Dep. Agric. India (Bot. Ser.) 1: 70. Cerezine, P.C., Olinisky, I.A., Bittencourt, M.V.L. and Valerio Folho, W.V. (1995). Phyllosticta leaf spot on ginger. Cultural characterization of the pathogen and effect of chemical treatment on disease control in Morrestes, Parana state, Brazil. Pesqui. Agropecul. Bras. 30: 477-487. Chauhan, H.L. and Patel, M.H. (1990). Etiology of complex rhizome rot of ginger (Zingiber officinale) in Gujarat and in vitro screening of fungicides against its causal agents. Indian J. Agric. Sci. 60: 80-81. Dake, J.N. (1995). Diseases of ginger (Zingiber officinale Rosc.) and their management. J. Spices Arom. Crops 4: 40-48. Dake, J.N., Ramachandran, N. and Sarma, Y.R. (1988). Strategies to control rhizome rot (Pythium spp.) and bacterial wilt (Pseudomonas solanacearum) of ginger. J. Coffee Res. 18: 68-72. Deadman, M., Al Hasani, H. and Al Sa’di, A. (2006). Solarization and biofumigation reduce Pythium aphanidermatum induced damping-off and enhance vegetative growth of greenhouse cucumber in Oman. J. Plant Pathol. 88: 335-337. Dohroo N.P. and Sharma S.L. (1986). Evaluation of fungicides for the control of rhizome rot of ginger in storage. Indian Phytopath. 36: 691-693. Dohroo, N.P. (1982). Further studies on rhizome rot of ginger (Zingiber officinale Rosc.). Ph.D. Thesis, HPKVV, Solan, HP. Dohroo, N.P. (1987). Pythium ultimum on Zingiber officinale. Indian Phytopath. 40: 275. Dohroo, N.P. (1989a). Seed transmission of pre-emergence rot and yellows of ginger. Plant Dis. Res. 4: 73-74. Dohroo, N.P. (1989b). Peroxidase and polyphenol oxidase activities in rhizome rot of ginger. Indian Phytopath. 42: 167. Dohroo, N.P. (1991). New record of bacterial wilt of ginger in Himachal Pradesh. 2nd Phytopath. North Zone Meet, April 29-30, 1991. 16 p (Abst.). Dohroo, N.P. (1993). Final ICAR Report on Multilocational Project on Rhizome rot of ginger. UHF, Solan. 38p. Dohroo, N.P. (1995). Integrated management of yellows of ginger. Indian Phytopath. 48: 90-92. Dohroo, N.P. (2001). Etiology and management of storage rot of ginger in Himachal Pradesh. Indian Phytopath. 54: 49-54. Dohroo, N.P. (2005). Diseases of ginger. In: Ginger, the Genus Zingiber (Ravindran, P.N. and Babu, K.N., Eds.), CRC Press, Boca Raton, pp. 305-340. Dohroo, N.P. and Gupta, M. 2014. Effect of bioagents on management of rhizome diseases, plant growth parameters and nematode population in ginger. Agric. Sci. Digest. 34: 41 – 44. Dohroo, N.P. and Malhotra, R. (1995). Control of storage rot of ginger in Himachal Pradesh. pp. 199-202. In: Integrated Disease Management and Plant Health. (Gupta, V.K. and Sharma, R.C., Eds.), Scientific Publishers, Jodhpur. Dohroo, N.P. and Pathania, N. (1997). Ginger diseases management. pp. 247-250. In: Neem in Sustainable Agriculture. (Narwal, S.S., Tauro, P. and Bisla, S.S., Eds.). Scientific Publishers, Jodhpur, India. Dohroo, N.P. and Sharma, M. (1992a). New host records of fungi from India. Indian Phytopath. 45: 280. Dohroo, N.P. and Sharma. S.K. (1992b). 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Studies on the soft rot of ginger (Zingiber officinale Rosc.) caused by Pythium aphanidermatum (Edson) Fitz. Agric. Res. J. Kerala 11: 53-56. Indrasenan, G., Kumar, K.V., Mathew, J. and Mamen, M.K. (1981). The mode of survival of Pseudomonas solanacearum (Smith) Smith causing bacterial wilt of ginger (Zingiber officinale Rosc. Agric. Res. J. Kerala 19: 93-95. Indrasenan, G., Kumar, K.V., Mathew, J. and Mamen, M.K. (1982). Reaction of different types of ginger to bacterial wilt caused by Pseudomonas solanacearum (Smith) Smith. Agric. Res J. Kerala 20: 73-75. ISPS. (2005). Experiences in Collaboration. Ginger Pests and Diseases. Indo-Swiss Project Sikkim Series 1, 75p. Jadhav, S.N., Aparadh, V.T. and Bhoite, A.S. (2013). Plant extract using for management of storage rot of ginger in Satara Tehsil (M.S.). Internat. J. Phytopharm. Res. 4: 1-2. Janse, J. (1996). Potato brown rot in Western Europe – history, present occurrence and some remarks on possible origin, epidemiology and control strategies. Bulletin OEPP/EPPO 26: 679–695. Kadam, R.V., Jagtap, G.P. and Dey, U. (2014). Management of rhizome rot (Pythium aphanidermatum) in ginger through amendments. J. Pl. Dis. Sci. 9: 209-213. Kar, A.K. and Mandal, M. (1969). New Cercospora spp. from West Bengal. Trans. Brit. Mycol. Soc. 53: 337-360. Kavitha, P.G. and Thomas, G. (2008). Evaluation of Zingiberaceae for resistance to ginger soft rot caused by Pythium aphanidermatum (Edson) Fitzp. PGR newsletter Biodiveristy International 152: 54-57. Khatso, K. and Ao, N.T. (2013). Biocontrol of rhizome rot disease of ginger (Zingiber officinale Rosc.). Internat. J. Bioresource Stress Manag.. 4: 317-321. Kumar, A. and Abraham, S. (2008). PCR based detection of bacterial wilt pathogen, Ralstonia solanacearum in ginger rhizomes and soil collected from bacterial wilt affected field. J. Spices Aromatic Crops 17: 109-113. Kumar, A. and Anandaraj, M. (2006). Method for isolation of soil DNA and PCR based detection of ginger wilt pathogen, Ralstonia solanacearum. Indian Phytopath. 59: 154-160. Kumar, A. and Sarma, Y.R. (2004). Characterization of Ralstonia solanacearum causing bacterial wilt in ginger. Indian Phytopath. 57: 12-17. Kumar, A., Avasthe, R.K., Borah, T.R., Lepcha, B. and Pandey, B. (2012). Organic mulches affecting yield, quality and diseases of ginger in mid hills of North Eastern Himalayas. Indian J. Hortic. 69: 439-442. Lalfakawma, C., Nath, B.C., Bora, L.C., Srivastava, S. and Singh, J.P. (2014). Integrated disease management of Zingiber officinale Rosc. rhizome rot. The Bioscan 9: 265-269. Lana, M.M., Casali, V.W.D., Finger, F.L. and Reis, F.P. (1993). Evaluation of postharvest storage of ginger rhizomes. Hortic. Bras. 11: 139-141. Le, D.P., Smith, M., Hudler, G.W. and Aitken, E. (2014). 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