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Evaluation of fungicides for their efficacy against seed-borne fungi of Sorghum (Sorghum bicolor)
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Evaluation of fungicides for their efficacy against seed-borne fungi of Sorghum (Sorghum bicolor)

  1. About ICRISAT: www.icrisat.org ICRISAT’s scientific information: http://EXPLOREit.icrisat.org June 2019 Evaluation of fungicides for their efficacy against seed-borne fungi of Sorghum (Sorghum bicolor) Rajan Sharma, BD Devamani and P Humayun Plant Quarantine Unit, Research Program - Asia, International Crops Research Institute for the Semi-Arid Tropics, Patancheru-502324, Telangana, India Introduction Sorghum germplasm exchange has played a significant role in crop improvement programmes by providing wide genetic diversity world over. However, there is an inherent risk of introduction of new exotic pathogens or new/more virulent races of a pathogen into new areas. The basic principle of plant quarantine is to regulate the movement of seed material to mitigate the associated pest risk. Salvaging, a process of disinfecting infected seed, is an important quarantine strategy to prevent the introduction of new pathogens or virulent races into new areas. Sorghum seed is known to be infected by a large number of seed-borne fungal pathogens that necessitates the identification of effective fungicides for seed treatment. Therefore, an effort was made to evaluate the efficacy of different fungicides against seed-borne fungi of sorghum to select the best fungicide for seed treatment. Material and Methods The Infected seeds were treated with fungicides to eradicate seed borne fungi (Table 1). Seeds treated with different fungicides were assayed for seed borne fungi by employing standard blotter method; untreated seeds served as a control. The Petri plates containing treated and untreated seeds were incubated at 22 ±2 °C under near ultra violet (NUV) light with 12h alternate cycles of light and dark for seven days. After incubation, seeds were examined for the presence of fungi under stereo-binocular microscope. The fungi were identified based on the morphological characters (Ellis, 1971; Barnett, 1972; Ahmed KM and Ravinder Reddy Ch 1993) and data were expressed as per cent infected seed. Table 1. Details of fungicides tested. Fungicides Trade Name Dosage (g/kg of seeds ) Carbendazim 12% + Mancozeb 63%WP Saaf 2 Tebuconazole 50 %+Trifloxystrobin 25%WG Nativo 0.5 Carbendazim +Thiram 1:1ratio 3 Captan 70% + Hexaconazole 5%WP Taqat 2 Tricyclazole 75%WP Beam 2 Tebuconazole 2%DS Raxil 1 Metalaxyl 4% + Mancozeb 64%WP Ridomil Gold 2 Tridemefon 25%WP Bayleton 2 Myclobutanil 10%WP Index 2 Dimethomorph 50%WP Acrobat 2 Thiophanate methyl 70%WP Roko 2 Fig 1. Percent reduction of fungal infection by different fungicides. Results and discussion ▪▪ Seven fungi, Curvularia sp. (29%), Bipolaris sp. (24%), Fusarium spp. (21.5%), Phoma sorghina (18.5%), Rhizophus sp. (16.5%), Exserohilum turcicum (11%) and Alternaria alternate (3.5%) were detected in the infected sorghum seeds in control plates (Fig 2 & 3). ▪▪ Seed treatment with Saaf @ 2 g/kg seed significantly reduced (95%) seed borne fungi over control followed by Nativo @ 0.5 g/kg seed (91%) (Fig 1). ▪▪ The presently recommended fungicide, carbendazim + thiram (1:1) @ 3 g/kg seed, being used for salvaging the infected sorghum seeds recorded 89 percent reduction over control. ▪▪ In addition to reduction in seed borne fungal infection, there was increase in seed germination as well (Fig. 2). Fig 3. Photomicrographs of sorghum seed borne fungi. Fig 2. Seed germination in treated and untreated sorghum seed. UntreatedTreated Conclusion Seed treatment with Saaf (Carbendazim 12% + Mancozeb 63%WP) @ 2 g/kg seed could be recommended to eliminate the seed borne fungal infection in sorghum for the safe exchange of seed material as well as cleaning of sorghum seed for regeneration for conservation. References Ahmed KM and Ravinder Reddy Ch. 1993. A pictorial guide to the identification of seedborne fungi of sorghum, pearl millet, finger millet, chickpea, and groundnut. Information Bulletin no.34. Patancheru. AP 502324, India: International Crops Research Institute for the Semi-Arid Tropics 200pp. ISBN 92-9066-251-4. Burnett HL. 1972. Illustrated genera of Imperfect Fungi. Burges Pub Com., Minnesota, 213 pp. Ellis MB. 1971. Dematiaceous hyphomycetes. Kew, Surrey, England: Commonwealth Mycological Institute. 608 pp. Growth and sporulation of Alternaria alternata on seed Conidia of Alternaria alternata Growth and sporulation of Curvularia sp. on seed Conidia and conidiophore of Curvularia sp. Growth and sporulation of Bipoloris sp. on seed Conidia of Bipolaris sp. Growth and sporulation of Fusarium sp. on seed Conidia of Fusarium sp. Growth and sporulation of Exserohilum turcicum on seed Conidia of Exserohilum turcicum Growth and sporulation of Rhizopus sp. on seed Pycnidia of Phoma sorghina on seed
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