ETIOLOGY AND DIVERSITY OF SHEATH ROT FUNGAL PATHOGENS OF RICE
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Date
2023-02-11
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University of Agricultural Sciences, Bangalore
Abstract
Sheath rot disease of paddy caused by Sarocladium oryzae is one of the emerging diseases in the world. Study was carried out to understand etiology, characterization and seed transmission of sheath rot associated fungal pathogens, and to elucidate the diversity of fungal sheath rot pathogens in rice. Etiology studies and pathogencity of 22 isolates collected from Karnataka revealed that Sarocladium oryzae and Fusarium spp. are the causal organisms for sheath rot disease. Morphological and cultural haracterisation was carried out for all the isolates. Isolate SHTNGO-2 showed lowest growth rate of 0.30 mm/day, whereas, highest by SHMV1W having 8.25 mm/day. Virulence test of inoculation of pathogens, recorded largest lesion length of 3.3 cm in SHYDO-1 (Sarocladium oryzae), while, smallest lesion length of 0.4 cm recorded in SHSRG1W (Fusarium spp). Molecular characterization using ITS1/4 identified isolates to be Sarocladium oryzae. Fusarium oxysporum, Fusarium fujikuroi, Fusarium equiseti, and Fusarium proliferatum. Based on cultural, morphological characteristics and pathogenicity, 13 isolates were identified as Fusarium spp., while, 9 were identified as Sarocladium. Interaction studies of combined inoculation of Sarocladium oryzae and Fusarium proliferatum recorded larger lesion length of 3.1 cm, as compared to their individual inoculations. Jyothi seeds infected with sheath rot showed decreased germination. S. oryzae was found to be internally seed borne, while, Fusarium internally and externally seed
borne. Phylogenetic tree showed less diversity among Sarocladium oryzae isolates and higher
among Fusarium spp. Isolates.