LAUSR

A disease survey was conducted in the green gram (Vigna radiata) growing areas of Bharuch, Gujarat, India in February 2020. Root rot was observed on cultivar NVL-585 in 30 fields surveyed, with 15 to 20% of disease incidence. Infected plants showed foliar chlorosis, brown discoloration, dark black brittle roots with necrotic lesions, and dead plants. The root rot causal agent was isolated on potato dextrose agar (PDA) from 25 symptomatic samples collected from 10 diseased plants and pure cultures were obtained using single hyphal tip method. The cultures were grayish black with a smooth texture. Conidia were single celled, elliptical to oval in shape and were 5.2 to 6.5μm (n=25) in length and 2.7 to 3.4µm in width. Plastic pots (15 cm in diameter) were filled with autoclaved soil (1.5 kg/pot) inoculated with a 15-day-old culture of the fungus at 3 g/ kg (108 cfu/g). After 7 days, the local green gram cultivar HUM 16 was sown into the pots. Seedlings were thinned to 10 for each pot. Chlorosis of leaves, rotting roots, and even plant death were observed at 20, 30 and 40 days after seeding. The experiment was conducted twice to fulfill the Koch postulates. The fungus was reisolated from the root rot samples, and identical colony morphology was observed as seen previously. Based on the cultural characteristics and conidial morphology, the fungus belonged to Ectophoma sp. (Boerema et al. 2004). ITS, D1 and D2 regions of LSU and β-tubulin were used for molecular identification. The BLASTn analysis of ITS, D1 and D2 region of LSU gene and β-tubulin gene sequences of Isolate G80 showed a 100% similarity with accession number MH858623 (Vu et al. 2019), 99.82% similarity with MH870612 (Vu et al. 2019) and 100% similarity with MN983939 (Hou et al. 2020). Gene sequence has been submitted to NCBI GenBank, and accession numbers for ITS, D1 and D2 region of LSU and β-tubulin are MW165415, MW813868 and LC656357, respectively. The pathogen was previously reported from other hosts like Fuchsia× hybrida, Origanum vulgare, Lavandula angustifolia, Cicer arietinum and Coriandrum sativum. It can cause substantial economic damage to a wide range of commercially important crops. To the best of our knowledge, this is the first report of E. multirostrata causing root rot disease of green gram in India.