IMPACT OF SEED-BORNE INOCULUM, IRRIGATION, AND CROPPING PATTERN ON PROPAGATION OF BIPOLARIS SOROKINIANA AND EPIDEMIOLOGY OF FOLIAR BLIGHT AND COMMON ROOT ROT IN SPRING WHEAT

摘要

Bipolaris sorokiniana is a principal agent of seedling blight, spot blotch, root rot and black point of spring wheat in Nepal. The impact of seed-borne inoculum levels (SIL), irrigation, and cropping pattern on the multiplication of B. sorokiniana propagules and progress of foliar blight and common root on wheat is not well understood. To get insight on it, two wheat genotypes (cvs Sonalika and BL 1473) each with four SILs (5, 35, 65 and 95%) were field-evaluated in a strip-split-plot design under irrigated and non-irrigated conditions during 2002-03 at Rampur, (Chitwan, Nepal). The experiments were duplicated under fallow-wheat and rice-wheat system. The study revealed that the propagation of B. sorokiniana and the severity of foliar blight and root rot was positively influenced by SIL and susceptibility of wheat cultivars, while irrigation and cropping pattern had a lower impact. There was a significant positive association (r = 0.83, P < 0.01) between SIL with B. sorokiniana frequency on leaf and stem up to flowering stages indicating that seed-borne inoculum levels had high influence in the early establishment of foliar blight. There was a high positive correlation of SIL with pathogen frequency on root at all four growth stages (r values 0.93 to 0.99, P < 0.01) and root rot index (r = 0.75, P < 0.05) suggesting that SIL had a strong impact on common root rot. The outcome of this study will be useful to develop strategies of integrated management of foliar blight and root rot on wheat.