A Study of Fungal Diseases Occurring on Stored Tomatoes of Balkhu Agriculture and Vegetable Market, Nepal

Tomatoes are one of the most widely produced and consumed vegetable in Nepal. Fungal pathogens deteriorate the quality and quantity of tomato and cause health hazards to the consumers as well as economic loss to the traders. This study was carried out to identify some fungal diseases associated with post-harvest deterioration of stored tomato fruits in Balkhu Agriculture and vegetable Market of Kathmandu, Nepal. Collected samples were cultured in Potato Dextrose Agar (PDA) media in complete randomized design. Fifteen species of fungi namely Alternaria alternata, A. solani, Aspergillus niger, Botrytis cinerea, Fulvum fulva, Colletotrichum truncatum, Curvularia spicifera, Fusarium oxysporum, Dipodascus geotrichum, Mucor mucedo, Penicillium chrysogenum, Phytophthora infestans, Boeremia exigua, Pythium aphanidermatum and Rhizopus stolonifer were identified. These were responsible for 14 different diseases of Alternaria fruit rot, Anthracnose, Black mold rot, Botrytis Bunch Rot, Damping off/ fruit rot, Drechslera mold, Fusarium rot, Mucor rot, Penicillum rot, Boeremia blight, Phytophthora rot, Rhizopus rot, Russet, and, Sour rot. The presence of these fungi and corresponding rot diseases on stored tomato indicates the need for management of fungi, farm sanitation and improved market in order to prevent field-to-storage transmission of pathogen.

Perlakuan Benih Cabai (Capsicum annuum L.) dengan Rizobakteri secara Tunggal atau Kombinasi dapat Mengendalikan Phytophthora capsici dan Meningkatkan Pertumbuhan Tanaman

<p>ABSTRACT</p><p>Seed treatment of hot pepper using rhizobacteria is an alternative to fungicide use in controlling phytophthora rot disease. The objectives of this research were to evaluate: (1) the effectiveness of rhizobacteria isolates in inhibiting Phytophthora capsici growth and (2) the effect of seed treatment using rhizobacteria on plant growth, and incidence of phytophthora blight disease. This research consisted of two experiments, all experiments were arranged in completely randomized design using one factor. The first experiment (in vitro) consisted of nine levels i.e. sevencombination isolates of rhizobacteria, metalaxyl and control. The second experiment (in the green house) consisted of six levels of seed treatments i.e. ST116B rhizobacteria, CM8 rhizobacteria, ST116B + CM8 rhizobacteria, metalaxyl, positive control and negative control. Results of in vitro experiment showed that all rhizobacteria, single or combinations, were able to inhibit P. capsicigrowth. The highest inhibition were shown by CM8, ST116B + CM8, and ST116B consecutively.Seed treatments of hot pepper using ST116B, CM8, and ST116B + CM8 rhizobacteria increased the number of leaves 6 weeks after transplanting and reduced the incidence of phytophthora blight disease. There were no significant differences whether the rhizobacteria was applied singly or in combination of the two. Rhizobacteria ST116B was suggested for pepper seed treatment before planting.</p><p>Keywords: metalaxyl, phytophthora blight disease, rhizobacteria</p><p> </p><p>ABSTRAK</p><p>Perlakuan benih cabai menggunakan rizobakteri merupakan alternatif pengganti fungisida dalam mengendalikan penyakit busuk phytophthora, yang disebabkan oleh cendawan patogen Phytophthora capsici. Penelitian ini bertujuan (1) mengevaluasi keefektifan kombinasi isolat rizobakteri dalam menghambat pertumbuhan P. capsici, dan (2) mengetahui pengaruh perlakuan benih dengan rizobakteri dalam meningkatkan vigor benih dan pertumbuhan tanaman, serta dalam mengurangi kejadian penyakit busuk phytophthora. Penelitian ini terdiri atas dua tahap percobaan, menggunakan rancangan acak lengkap satu faktor. Percobaan pertama (in vitro) terdiri atas sembilan taraf yaitu tujuh kombinasi isolat rizobakteri, metalaksil, dan tanpa perlakuan (kontrol). Percobaan kedua (di rumah kaca) terdiri atas enam taraf perlakuan benih yaitu rizobakteri ST116B, CM8, ST116B + CM8, metalaksil, kontrol positif, dan kontrol negatif. Hasil percobaan in vitro, semua perlakuan rizobakteri baik tunggal maupun yang dikombinasikan mampu menghambat pertumbuhan patogen P. capsici. Persentase daya hambat tertinggi berturut-turut ditunjukkan oleh isolat rizobakteri CM8, kombinasi isolat rizobakteri ST116B + CM8, dan isolat rizobakteri ST116B. Perlakuan benih dengan rizobakteri ST116B, CM8, dan ST116B + CM8 tidak dapat meningkatkan vigor benih, namun secara nyata meningkatkan pertambahan jumlah daun pada minggu ke enam setelah pindah tanam, dan menurunkan kejadian penyakit busuk phytophthora. Tidak terdapat perbedaan nyata pengaruh rizobakteri yang diaplikasikan secara tunggal maupun kombinasi dua isolat. Rizobakteri ST116B disarankan untuk digunakan dalam perlakuan benih cabai sebelum tanam.</p><p>Kata kunci: metalaksil, penyakit busuk phytophthora, rizobakteri</p>

An Evaluation of Cucurbits for Susceptibility to Cucurbitaceous and Solanaceous Phytophthora capsici isolates

Cucumber (Cucumis sativus) and squash (Cucurbita spp.) production in Michigan is limited by the oomycete pathogen Phytophthora capsici. Cucumber, summer squash, and winter squash fruit were evaluated for susceptibility to five isolates of P. capsici. Detached fruit were inoculated with a 5-mm-diameter culture plug of mycelia and sporangia and were incubated in a laboratory or greenhouse. Lesion and pathogen growth diameters were measured and pathogen growth density was visually assessed. All P. capsici isolates incited rot, with significant differences found among fruit type and pathogen isolate. Straightneck squash (Cucurbita pepo), slicing cucumber, and butternut squash (C. moschata) exhibited more severe symptoms than the other fruit tested. Summer and winter squash seedlings were evaluated in greenhouse experiments, in which P. capsici-infested millet seed (approximately 1 g) were placed on the surface of soilless potting media. Disease severity was visually assessed every 2 days for 14 days post inoculation. Crop type, pathogen isolate, or the crop type–pathogen isolate interaction term were significant for symptom appearance and area under the disease progress curve values. Differences in susceptibility of butternut squash and zucchini cultivars were observed following inoculation with solanaceous isolate 13351. Results from this study can refine management programs for Phytophthora rot.

First Report of Phytophthora Rot on Alders Caused by Phytophthora alni subsp. alni in Spain

Phytophthora alni, a soil- and waterborne pathogen, causes aggressive root and collar rot on riparian alder populations (1,2,4). The disease has been described from several European countries with a destructive impact in Great Britain (1,2). All European alder species and the red alder (Alnus rubra) are highly susceptible. P. alni has multiple variants that have been placed in three subspecies: P. alni subsp. alni, P. alni subsp. uniformis, and P. alni subsp. multiformis (1). In July 2009, a survey of symptoms of Phytophthora rot from A. glutinosa at 20 riparian stands along the Avia River in Galicia (northwest Spain) was conducted. Affected trees showed symptoms of Phytophthora rot including abnormally small, sparse, and yellowish foliage, dieback in the canopy, necroses of the inner bark and cambium, and bleeding cankers on the trunks (2,4). Phytophthora spp. were baited from saturated rhizosphere soil and watercourses using oak leaflets (4). Roots and tissue from fresh active inner bark lesions were transferred to selective medium V8-PARPH agar (4) and incubated for 7 days at 22°C in the dark. A Phytophthora sp. was isolated, transferred to carrot agar (CA), and incubated in the dark. Colonies were appressed, often irregular in outline, and with limited aerial mycelium (1). Growth on CA occurred from 4 to 31°C with optimum growth at 23 to 25°C. Chlamydospores were not observed. Ellipsoid, nonpapillate, noncaducous sporangia had a length/breadth average ratio of 1.4. Nesting and extended internal proliferation occurred. Oogonia, antheridia, and oospores were abundantly produced in a single culture. Oogonia with tapered stalks were spherical (mature oogonia 38 to 50 μm in diameter) and some had ornamented walls or bullate protuberances (1,2). Antheridia were large, amphigynous, and predominantly two-celled (23 to 37 × 16 to 23 μm). Oospores were plerotic. Distorted comma-shaped or smaller oogonia and aborted oospores were observed (1). Amplification of DNA was accomplished by using sequence-characterized amplification region-PCR primers (3). The amplicon sizes obtained were identical to P. alni subsp. alni (3). Internal transcribed spacer (ITS)-DNA and nadh1 mitochondrial gene were also amplified. DNA sequences of ITS and mt-DNA regions were deposited in GenBank (Nos. GU108602 and GU108603). Comparison of the sequences showed 100% homology with P. alni subsp. alni (GenBank Nos. FJ746679 and DQ202490). P. alni subsp. alni was recovered from trees at 3 of 20 riparian alder stands with symptoms. Pathogenicity of one representative isolate was confirmed by inoculating 10 3-year-old A. glutinosa seedlings grown in pots. One shallow cut was made into the bark at the collar level. A colonized agar plug, from the margin of an actively growing colony of P. alni subsp. alni, was inserted beneath the flap that was sealed with Parafilm. Five controls seedlings received only sterile CA agar plugs. Plants were incubated at 24°C and 95% humidity for 30 days. On inoculated plants, necroses progressed bidirectionally from the wound, and dead leaves and wilting of shoots were observed. P. alni subsp. alni was recovered from inoculated seedlings, but not from controls. To our knowledge, this is the first report of Phytophthora rot on alder caused by P. alni subsp. alni in Spain. References: (1) C. M. Brasier et al. Mycol. Res. 108:1172, 2004. (2) J. Gibbs et al. For. Comm. Bull. 126, 2003 (3) R. Ioos et al. Eur. J. Plant Pathol. 112:323, 2005. (4) T. Jung et al. Plant Pathol. 53:197, 2004.