Molecular and morpho-pathological variation in Bipolaris oryzae (Breda de Haan) shoem. causing brown spot of rice in North India

摘要

Isolates of Bipolaris oryzae were analyzed morpho-pathologically and molecularly using RAPD to determine the intraspecific variability. Isolates varied considerably with respect to morphological characters like conidial size, sporulation, septation, and colony growth rate. The isolates differed significantly in respect of their pathogenic ability. Pathogenic diversity was estimated using EUCLID coefficient of dissimilarity that ranged from 0.11 to 0.98. Two major clusters were observed at 35% level of dissimilarity. Most of the isolates showing higher virulence (D3, D2, Dll, Dl) could also either sporulate more or vegetatively grow faster or both compared to weakly virulent isolates (D5, D6, D7, D9). Varieties Supar Basmati, Pusa Sugandh, Basmati 386, Basmati 370, Pusa Basmati 1 and PR 113 exhibited lesser disease progression when challenged with different isolates compared to PR 116, PR 114, PR 108, PR 115, PR 118 and Pusa 44. The isolates were further tested for their variability with RAPD primers. Twenty RAPD primers were screened, of which seven gave amplification. Based on the molecular similarity of the RAPD profiles, the isolates were grouped in to two major clusters. This study establishes the variability among B. oryzae isolates in northIndian states. Geographical origins of the isolates could not be correlated with molecular and pathological diversity but to a certain extent, there was association between molecular, cultural and pathological diversity.