Resistance of some Oryza spp. accessions to brown leaf spot (Drechslera oryzae) and its relationship with plant age

摘要

Effect of age of the plant on the resistance against Drechslera oryzae causing brown leaf spot (BLS) was studied on 44 accessions lines belonging to different Oryza spp.viz., O. glaberrima, O. nivara, O.rufipogon,, O. australiensis and O. brachyanthaas well as 9 cultivars belonging to O. saliva in the screen house. No disease symptoms were observed at the seedling stage. However, a significant increase in mean BLS score was observed from 90 to 150 days after sowing irrespective of the Oryza spp. Thus scoring at /before 150 days after sowing may not be able to predict whether a host genotype will remain resistant or become susceptible to BLS with age. Hence, selection for resistance to BLS in rice improvement programmes should preferably be delayedtill the leaves start showing senescence. BLS resistant lines identified during the present studies, especially those belonging to species with AA genome viz., O. glaberrima, O. nivara and O. rufipogon, easily crossable with O. saliva also having the same genome may serve as important donors of BLS resistance for the cultivated rice, O. saliva.