Morphological and pathological variation among Drechslera graminea isolates, the incitant of barley stripe disease

Different isolates varied in their colony colour and sporulation potential. However, there were not many differences in the conidial dimensions of the isolates. Based on these morphological characteristics, the isolates of D.graminea were grouped into three groups, viz. D_1, D₂ and D₃. Isolates of group D₁ had white to dirty white fluffy colonies with no sporulation. Isolates of group D₂ were jet black with appressed mycelial growth and high sporulation. Group D₃ isolates were grey having appressed colony growth and were non-sporulating. Maximum number of isolates belonged to group D₁with 15 isolates. Pathological behaviour of different isolates on four barley cultivars viz. PL 172, Pl 419, PL 426 and a local variety of H.P. revealed that isolate Dg₁₈ was more pathogenic on cultivar PL 172, moderately on a local variety of H.P. and less pathogenic on variety PL 419 and PL 426. Likewise, Dg₁₇ was more pathogenic on PL 419 and a local variety of H.P. and less pathogenic on PL 172 and PL 426. Isolates Dg₅, Dg₉, and Dg₁₀ produced more disease on PL 172. However Dg₂ could produce almost similar level of disease on all the four barley cultivars. All other isolates were found moderate to less virulent on either one or all the four barley cultivars. Differential behaviour of different isolates on barley cultivars suggests the presence of pathological strains of pathogen.