Jackfruit decline caused by Phytophthora palmivora (Butler) L. M. Borines, V. G. Palermo, G. A. Guadalquiver, C. Dwyer, A. Drenth, R. Daniel & D. I. Guest Australasian Plant Pathology Journal of the Australasian Plant Pathology Society ISSN 0815-3191 Volume 43 Number 2 Australasian Plant Pathol. (2014) 43:123-129 DOI 10.1007/s13313-013-0241-z 1 23 Your article is protected by copyright and all rights are held exclusively by Australasian Plant Pathology Society Inc.. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com”. 1 23 Author's personal copy Australasian Plant Pathol. (2014) 43:123–129 DOI 10.1007/s13313-013-0241-z Jackfruit decline caused by Phytophthora palmivora (Butler) L. M. Borines & V. G. Palermo & G. A. Guadalquiver & C. Dwyer & A. Drenth & R. Daniel & D. I. Guest Received: 30 May 2013 / Accepted: 20 June 2013 / Published online: 7 July 2013 # Australasian Plant Pathology Society Inc. 2013 Abstract In the late 1990’s a decline syndrome emerged in jackfruit orchards in the Eastern Visayas region of the Philippines. Symptoms included trunk cankers, wilting and dieback of the canopy and, in many cases, tree death. The decline resulted in significant yield losses for farmers. A survey was conducted to assess disease incidence and to identify the causal organism. Fifty two percent of farms surveyed had a disease incidence greater than 50 %. On some farms 100 % of trees were affected. While Fusarium, Pythium, Colletotrichum and Phytophthora species were isolated during disease surveys only Phytophthora was shown to consistently cause decline symptoms in artificially inoculated jackfruit. Healthy jackfruit seedlings, detached leaves and fruit inoculated with Phytophthora isolates expressed similar symptoms to those observed in the field. Based on morphological and molecular characteristics the pathogen was identified as Phytophthora palmivora. Keywords Nangka . Root rot . Dieback . Canker . Oomycete L. M. Borines : V. G. Palermo : G. A. Guadalquiver Department of Pest Management, Visayas State University, Visca, Baybay City 6521, Leyte, Philippines C. Dwyer : A. Drenth Centre for Plant Science, Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, GPO Box 267, Brisbane, Queensland 4001, Australia R. Daniel Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Private Bag 4008, Narellan 2567, Australia D. I. Guest (*) Faculty of Agriculture and Environment, The University of Sydney, Biomedical Building C81, Sydney 2006, Australia e-mail: david.guest@sydney.edu.au Introduction Jackfruit (Artocarpus heterophyllus Lam.) is an important tree crop in tropical and subtropical regions, grown in home gardens and commercially in orchards (Elevitch and Manner 2006; Sangchote et al. 2003). The primary economic product is the fruit, but the tree is also used for timber, fodder, dyes and traditional medicines (Haq 2006). In the Eastern Visayas region of the Philippines, jackfruit is a high-value fruit marketed as a ‘flagship commodity’. It has the potential to provide sustainable incomes for local farmers through the domestic market, and export opportunities, as quality and production increase and infrastructure improves. From 1996 until 2008, jackfruit was promoted in the Eastern Visayas through a ‘plant now, pay later’ (PNPL) Government-run scheme resulting in large-scale plantings now covering more than 200 ha on the islands of Samar and Leyte alone. However, the jackfruit plantings have been affected by an unidentified decline with symptoms of leaf chlorosis, wilting, defoliation, trunk cankers and, in many cases, tree death. The symptoms were particularly severe in areas prone to flooding or poor drainage, or in wet seasons. In some orchards 100 % of jackfruit trees were affected and farmers were re-planting with alternative crops. An assessment conducted between 2006 and 2008 of the distribution of jackfruit planting material found that of all the jackfruit seedlings planted, 63 % were still alive and 44 % were productive (Torres et al. 2011). Diagnosing the cause of jackfruit decline was critical to the development and dissemination of disease management strategies and the survival of the industry. Several diseases of jackfruit have been reported in the literature, however, details about the incidence and severity of symptoms are scarce and crop losses appear to be minimal compared to the newly emerged decline reported here (Haq 2006; Sangchote et al. 2003). The most significant diseases reported from major jackfruit growing regions (India, Sri Author's personal copy 124 L.M. Borines et al. Lanka, Bangladesh and Thailand) include leaf spots, dieback, fruit rots and pink disease (Table 1). Many of the diseases are more severe during wet seasons, under high relative humidity and temperature, or in orchards with poor air circulation. Fruit and blossom rots caused by Rhizopus artocarpi are a significant problem with crop losses as high as 32 % reported (Soepadmo 1992). The male inflorescences and young fruits are attacked and only a small proportion of them mature. The infected fruit rot slowly, mummify and fall from the tree (McMillan 1974; Roy 1983). Leaf spots are commonly caused by Colletotrichum species, Corynespora cassiicola, Phyllosticta artocarpina and Septoria artocarpi. Table 1 Summary of known pathogens and diseases of jackfruit Disease Anthracnose Pathogen Symptoms Colletotrichum gloeosporiodes Brown lesions on leaves, twigs and fruit; leaf and blossom blights. Corynespora leaf spot Corynespora cassiicola Irregular spots on leaves and, less often, on stems, roots and flowers. Possibility of shot-hole development and defoliation Diplodia fruit and collar rot Diplodia theobromae Lesions on fruit, twigs and branches. Rhizopus rot or transit rot Rhizopus oryzae, Male inflorescences and young fruit are R. artocarpi, R. stolonifer covered in a mass of black spores and white mycelium; results in poor fruit development and premature fruit drop; can also affect overripe fruit that have not been harvested. Brown root and crown rot Phellinus noxius Roots and base of tree become encrusted as soil is held together by mycelium. Cracking of bark and gummosis. Wood becomes discoloured, dry, friable and honeycombed. Basidiocarps develop and girdle base of tree causing wilting and yellowing of foliage and tree death. Phytophthora root, fruit Phytophthora palmivora Lesions on fruit surfaces. Can cause and stem rot and P. citrophthora entire fruit to rot. Pink disease Erythricium salmonicolor White patches develop on trunk, branch and twigs and expand to encircle entire branch appearing salmon pink in colour. Infected branches may wilt and defoliate Pinglap disease Unknown Severe wilt or dieback syndrome resulting in partial or whole tree death Miscellaneous leaf diseases Alternaria sp., Botryodiplodia Leaf spots theobromae, Cercospora sp. Colletotrichum orbiculare, Nigrospora sphaerica, Pestalotiopsis versicolour, Pseudocercospora artocarpi, Phyllosticta artocarpina, Septoria artocarpi Curvularia sp. Infects young shoots and petioles of leaves Defoliation Phomopsis sp. Pestalotiopsis elasticola Grey leaf blight Uredo artocarpii Rust Root rot Pythium spendens, Infect roots and stem base of seedlings Phytophthora sp., Fusarium sp., Rhizoctonia sp., Nematodes Aphelenchoides sp., Helicotylenchus dihystera, Helicotylenchus multicinctus, Hemicriconemoides cocophilus, Meloidogune sp., Pratylenchus sp. and Ximphenema brevicolle Reference Sirayoi 1993, Srivasta and Mehra 2004 Sangchote et al. 2003 Sangchote et al. 2003 Nelson 2005, Butani 1978, Pandey et al. 1979, McMillan 1974 Putter 1998, Trujillo 1971 Haq 2006 Holliday 1980 Morton 1987, Trujillo 1970, 1971 Basak 1995, Butani 1978, Haq 2006, Shaw 1984 Haq 2006 Haq 2006 Vevai 1971, Zhang et al. 2003 Basak 1995, Singh 1980 Haq 2006 Sangchote et al. 2003 Author's personal copy Jackfruit decline caused by Phytophthora palmivora (Butler) Pink disease, caused by the fungus Erythricium salmonicolor, is widespread, causing wilting and defoliation of infected trunks, branches and twigs. The disease is more severe in the rainy season, and in trees with a dense canopy. Dieback has been reported to be caused by Botryodiplodia theobromae, a fungus that affects growing shoots, causing discolouration of the bark as it spreads downwards, ultimately killing the tree (Haq 2006). The bacterium Erwinia carotovora also causes dieback resulting in leaf yellowing and gummy exudates from the stems and branches (Ton et al. 1990). Phytophthora has not previously been confirmed as the cause of dieback and decline of jackfruit. Phytophthora species, including P. palmivora, have been associated with fruit, stem and root rot of the related species breadfruit (A. integer) and chempedek (A. altilis) (Drenth and Guest 2004; Lim 1990). A disease of unknown cause referred to as ‘Pingelap’ resulted in severe devastation of breadfruit crops in the Pacific in the 1970s and again in the 1990s (Sangchote et al. 2003; Trujillo 1970). While several fungi have been isolated, including Rhizopus, Phomopsis and Pythium, none have been shown to be pathogenic. Trujillo (1970) noted that the symptoms were similar to those caused by P. palmivora but the association has not been confirmed by isolation and reinoculation (Koch’s Postulates). In the southern Philippines, the newly emerged decline has affected the roots, trunks, branches and fruit of jackfruit. Root and collar rot and stem lesions developed on infected trees, followed by wilting and loss of canopy cover. In many cases, the entire tree died and some orchards had 100 % tree losses. Under high relative humidity or wet conditions, water soaked lesions also developed on leaves and fruit. The decline caused a significant decline in tree health and productivity. In the nursery, affected seedlings wilted and died. A summary of known diseases of jackfruit are presented in Table 1. More detailed descriptions of jackfruit diseases and disorders are given by Haq (2006) and Sangchote et al. (2003). In order to develop management strategies to reduce the impact of jackfruit decline it was paramount that the cause of the decline was identified so that science-based improvements could be developed for the jackfruit orchards and disseminated to the industry. This study aimed to determine the cause of jackfruit decline in the Philippines and more specifically to: (1) describe the symptoms of the decline of the jackfruit trees (2) determine if the symptoms and cause of the decline were the same for different regions in the southern Philippines (Leyte and Samar) (3) identify the causal agent and confirm Koch’s postulates (4) determine if there was a correlation between disease incidence and the age of the trees 125 Materials and methods Distribution of jackfruit decline In order to determine the range and extent of symptoms and the impact of the decline forty-two jackfruit orchards on Leyte and Samar Islands in the Eastern Visayas Region of the Philippines were surveyed. The number of trees, age, disease symptoms and disease incidence (% of trees showing symptoms) were recorded. Plant and soil samples were collected from selected orchards for pathogen isolation. Pathogen isolation Tissue samples from canker lesions, roots, leaves and samples of soil near the rhizosphere of affected trees were collected and taken back to the laboratory for isolation. Samples were plated directly onto onion agar (200 g red onion, 17 g agar/L distilled water), carrot agar (200 g carrots, 17 g agar/L distilled water) and water agar (17 g agar/L distilled water), supplemented with Streptomycin (0.1 mg/L), Benomyl (0.05 mg/L) and Rose Bengal (500 mg/L). Samples were also baited using disinfected Kuomintang (Catharanthus roseus) or eggplant (Solanum melongena) fruit then isolated onto onion agar. Cultures were incubated at room temperature (23 °C) and examined microscopically for growth and characterisation of the organisms. Pathogenicity studies Pure cultures of each isolate grown on onion agar (OA) for 45 days at 23 °C were used to inoculate detached leaves, fruit and healthy jackfruit seedlings. Jackfruit cultivar EVIARC Sweet was used in all experiments. Young, fully emerged leaves were detached then disinfected with 1 % NaOCl, rinsed three times with sterile water and dried with paper tissue. Cut petioles were wrapped with moist cotton wool and the leaves placed inside sterile Petri dishes lined with sterile moistened paper tissue. A mycelial plug (9 mm diameter) was placed mycelial side down onto the surface of the detached leaves. The plug was removed after 48 h and the inoculated leaves were observed daily for the development of lesions. Uninoculated leaves were included as a control. Leaves were incubated at 23 °C under natural light regimes. The pathogen was re-isolated from leaf lesions 5-7 days after inoculation by surface sterilising the leaves in 70 % ethanol and plating sections on to onion agar as described above. To assess the development of symptoms on stems, onemonth-old jackfruit seedlings were inoculated by making a Vcut halfway up the stem and inserting an agar plug, mycelial side down, into the slit. The inoculation point was sealed with parafilm. The mycelial plug and parafilm were removed after Author's personal copy 126 L.M. Borines et al. Pathogen identification 48 h and the stem observed for the development of lesions. The pathogen was re-isolated 24 days after inoculation by plating on to onion agar. To confirm the infection of roots, one-month-old jackfruit seedlings grown in 25 cm pots filled with 3.5 L potting medium (1:1 w/w garden soil and fine river sand, sterilised in a pressure cooker twice for 1 h at 103 kPa) were inoculated by adding 100 g of mungbean inoculum (autoclaved mungbean seeds inoculated, then incubated in Erlenmeyer flasks at 23 °C for 14 days under natural light regimes) around the roots. Control plants were inoculated in the same way using sterile mungbeans. The seedlings were examined daily for the development of symptoms. After 9 days the seedlings were harvested, roots washed and the pathogen reisolated from soil and roots by baiting with eggplant fruit for 3 days and then plating onto onion agar. Detached immature jackfruit, 2.5 months from flowering, was sprayed with 70 % ethanol and allowed to air dry. A cut (~10 mm) was made on the fruit using a sterile scalpel and an agar disc of the culture was inserted into the wound and sealed with transparent tape. The inoculated fruit was placed in individual crates and wrapped with nylon tulle bag to prevent entry of insects. The fruit was maintained at room temperature (23 °C) and observed daily for lesion development. The pathogen was reisolated from lesions by plating onto onion agar. The pathogen was reisolated from inoculated plant tissues showing distinctive disease symptoms by surface sterilising and plating onto modified onion agar. Isolated cultures were compared to the originally isolated cultures. Colony morphology was examined after 4-5 days growth at 23 °C under 12 h light. Small pieces of agar with mycelium were also suspended in sterile water in Petri dishes to induce sporulation. Wet mounts of each isolate were examined under the microscope to observe hyphal characteristics and reproductive structures. Nine isolates were selected for DNA-based identification (Table 2) according to the method of Drenth et al. (2006). These isolates are stored in the Phytophthora culture collection at the University of Queensland. Results Disease symptoms Jackfruit decline affected all parts of the jackfruit tree including the roots, trunks, branches, leaves and fruit of jackfruit resulting in a significant reduction in tree health and productivity. Severe Table 2 Response of jackfruit to inoculation with isolates from jackfruit orchards and the identity of isolates Isolate No. Sample Source Location Symptoms development on inoculated jackfruit (S = stem canker; L = leaf lesion; R = root lesion; W = wilting, F = fruit lesion) S L R X X X VSU001 VSU003 VSU004 VSU005 VSU006 Lower trunk canker Leaf Soil Durian leaf Soil Abuyog, Leyte Mahaplag, Leyte Calbayog, Samar Calbayog, Samar Sogod, Leyte X X X X Xb X X X Xb UQ7177d UQ7178d UQ7179d UQ7180d UQ7181d UQ7182d UQ7183d UQ7184d UQ7185d Roots Roots Nursery potting mix Roots Soil Roots Root with soil Roots with soil Soil Casilda, Biliran, Leyte Ormoc City, Leyte Abuyog, Leyte Baybay, Leyte DA-RIARC, Abuyog, Leyte DA-RIARC, Abuyog, Leyte Catarman, Northern Samar Salcedo, Eastern Samar DA-RIARC, Abuyog, Leyte X X X X X X X X X Xc Xc X Xc X X X X Wa F X X X X X X X X X X X X X X Identification based on cultural, morphological and DNA Characteristics X X X X X Pythium sp. P. palmivora P. palmivora P. palmivora Pythium sp. P. palmivora P. palmivora P. palmivora P. palmivora P. palmivora P. palmivora P. palmivora P. palmivora P. palmivora DA-RIARC Department of Agriculture a Following root inoculation b Pin-size, water-soaked c Blight d Selected for DNA/PCR based identification; UQ codes indicate isolates lodged in the Phytophthora collection at the University of Queensland; VSU codes indicate isolates from the collection at VSU Author's personal copy Jackfruit decline caused by Phytophthora palmivora (Butler) 127 y = 7.3598x R2 = 0.4075 Disease incidence (% infection) 100 90 80 70 60 50 40 30 20 10 0 0 5 10 15 20 Orchard age (years) Fig. 3 Correlation between disease incidence and age of trees in the jackfruit orchard surveyed on Leyte and Samar Islands. R2 =0.4075 incidence ranged from 0% to 100 % (Fig. 2). Twenty-two of the 42 (52.4 %) farms surveyed had a disease incidence of 50 % or higher and the median disease incidence was 50 %. There was a weak correlation between disease incidence and orchard age (R2 =0.4075; Fig. 3). Pathogen isolation and characterisation Fig. 1 Symptoms of jackfruit decline in the field. a Canker lesions at the collar of an infected tree developing at the soil line; b Canker lesions on the trunk of an infected tree; c loss of canopy cover as a result of infection; d lesions on jackfruit seedlings in a commercial nursery cankers developed at the collar (Fig. 1a) and on the trunk (Fig. 1b) of infected trees. Cankers were particularly severe in orchards with poor drainage and those that were subjected to periodic flooding. As the infection progressed, leaves wilted and became yellow and there was a loss of canopy cover (Fig. 1c). In many cases, the entire tree died. Under high relative humidity or wet conditions, water soaked lesions were observed on leaves and fruit (Fig. 1d). Disease incidence Forty-two farms were surveyed on Leyte and Samar Islands. The number of trees per farm ranged from 30 to 4,000 and their age ranged from 2 months to 17 years old. Disease 100 Disease incidence (% infection) Fig. 2 Disease incidence (percentage infected trees) and in jackfruit orchards surveyed on Leyte and Samar Islands. The dashed line indicates the median disease severity While several organisms were isolated from diseased tissue, only Phytophthora palmivora and Pythium spp. were found to be pathogenic on jackfruit under experimental conditions (Table 2). The Phytophthora species was positively identified as P. palmivora based on cultural, morphological and molecular characteristics (Fig. 4). Phytophthora palmivora infected all jackfruit tissues that were inoculated and was reisolated to confirm Koch’s Postulates. Cankers and brown lesions developed on the stem within 4 days of inoculation (Fig. 5a). Infected seedlings that were root-inoculated began to wilt within 7 days after inoculation (Fig. 5b) and subsequently died; some as early as 9 days after inoculation (Fig. 5c). Water-soaked, dark lesions, more than 2 cm in diameter developed on inoculated leaves within 4 days of inoculation (Fig. 5d). Dark lesions also began to develop on inoculated fruit 2 days after inoculation and mycelial growth was visible after 7 days (Fig. 5e). 90 80 70 60 50 40 30 20 10 0 Farms Author's personal copy 128 L.M. Borines et al. Fig. 4 Cultural and morphological characteristics of representative isolates of Phytophthora palmivora. a Culture grown on onion agar at 23 °C for 5 days (UQ7177); b hyphae; c chlamydospores and d papillate, caducuous sporangia of representative isolates Inoculation of leaves with the Pythium sp. isolates (VSU001 and VSU006) lead to the development of pinsized, water soaked lesions within 4 days. No canker lesions were observed on inoculated stems. Yellowing and wilting, attributed to root infection, was observed on inoculated seedlings, but this did not lead to plant death. No symptoms developed in jackfruit inoculated with Fusarium sp. isolates. Discussion This study confirms P. palmivora as the cause of jackfruit decline disease in the Eastern Visayas region of the Philippines. The b c d e i j Inoculated a Control Fig. 5 Symptoms on jackfruit seedlings, leaves and fruit artificially inoculated with Phytophthora palmivora (VSU005). a lesions on stems of jackfruit seedlings, b root lesions, and c wilting of seedlings 24 days after inoculation; d leaf lesions (UQ7177) 5 days after inoculation and e fruit 8 days after inoculation compared with f–j control inoculations on the plant parts (sterile water alone) organism was consistently isolated from jackfruit trees showing symptoms including trunk cankers, chlorosis and wilting of the foliage, root lesions and tree death. A description of the symptomology has been provided above. When healthy seedlings, leaves and fruit were inoculated using the P. palmivora isolates the symptoms that developed were similar to those observed in the field. Phytophthora palmivora has previously been isolated from jackfruit in the Philippines but its association with the complex of symptoms now referred to as ‘jackfruit decline’ was never confirmed by re-inoculation (Tsao et al. 1994). While other organisms including Pythium sp. and Fusarium sp. were isolated during the surveys, they are not considered to be the primary pathogen. f g h Author's personal copy Jackfruit decline caused by Phytophthora palmivora (Butler) Inoculation of jackfruit seedlings with Pythium resulted in root damage, and the organism may contribute to root disease in the field. The other organisms did not lead to the development of symptoms and may be more likely to be involved as secondary inhabitants of damaged tissues. Phytophthora diseases are among the most economically significant diseases of fruit tree crops in the tropics (Drenth and Guest 2004). The survey of jackfruit orchards in Leyte and Samar indicated that 85 % of orchards were affected by the decline. Jackfruit decline consists of a range of different symptoms all caused by the one pathogen, so it was expected that the disease incidence would be greater in older orchards as the different plant parts from the same and different plants become infected if left untreated and population levels increase. While disease was more severe in older orchards, the correlation between age and disease severity was not high although disease incidence was generally lower on farms with younger plantings. This may be due either to better management, following the extension of disease management strategies, or insufficient time for disease to become established. The results of our study confirm P. palmivora as the cause of jackfruit decline in the southern Philippines. The survey results clearly indicate that the decline has a significant impact on yields and the long term viability of plantations, and consequently, farmer incomes. The confirmation of the causal organism enables the development of appropriate and effective management strategies. Acknowledgments This project was conducted as part of the Australian Centre for International Agricultural Research (ACIAR) project HORT2007/067/2. We acknowledge the Philippine Council for Agriculture and Aquatic Resources Research and Development, the Department of Agriculture, Leyte, Visayas State University and the jackfruit farmers of Leyte and Samar for their support. References Basak AB (1995) Fruit rot disease of jackfruit caused by Colletotrichum gloeosporioides Penz in Chittagong. Bangladesh J Bot 24:197–199 Butani DK (1978) Pests and diseases of jackfruit in India and their control. 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