Effect of surface seeding on foliar blight severity and wheat performance.

摘要

Spot blotch, caused by Cochliobolus sativus, is a serious disease constraint to wheat (Triticum aestivum L.) yields under rice-wheat systems in the lowlands of South Asia. The surface seeding of wheat, which is becoming popular as a resource conserving technology on resource-poor farms, might provide a more conducive environment for early foliar blight development. During 2002 and 2003 wheat growing seasons, replicated studies were conducted in farmers' fields in Nepal to determine the effects of surface seeding in comparison with conventional seeding on foliar blight development and agronomic performance, using the wheat varieties Rohini, BL 1473, Bhrikuti, and a farmer variety. The experiment was conducted in a strip-plot layout with strips of wheat varieties and fungicide treatments (sprayed or unprotected) in a randomized block with three replicates. The area under the disease progress curve (AUDPC) was estimated using multiple foliar blight assessments on flag leaf (AUDPC-FL) and on whole plants (AUDPC-WP). Grain yield, thousand-kernel weight (TKW) and kernels per spike (KPS) were also evaluated. Conventional tillage and surface seeding differed significantly for AUDPC, grain yield, TKW and KPS. In the fungicide-unprotected plots, the AUDPC-FL and AUDPC-WP values were, respectively, 8 and 34% higher under surface seeding than conventional tillage. On average, surface seeding produced 25% higher grain yield, 1.3 g higher TKW, and 1.8 more KPS than conventional tillage. The four wheat varieties differed significantly for all traits under both conventional tillage and surface seeding. The average foliar blight induced reductions in grain yield, TKW, and KPS were 16, 12, and 15%, respectively, under conventional tillage. The corresponding reductions were 23, 13, and 19% under surface seeding. Rohini produced the highest grain yields under both conventional tillage (2.67 t ha-1) and surface seeding (3.58 t ha-1). Under both seeding systems, Rohini showed the highest and BL 1473 the lowest grain yield reductions due to disease. Despite a higher spot blotch severity, the higher grain yield under surface seeding is suggestive of its adoption on wetlands under rice-wheat cropping systems. The four varieties responded differently to the tillage methods' effect on spot blotch severity and grain yield, suggesting the importance of tillage method in cultivar selection when considering the effect of microenvironment on susceptibility to foliar diseases. The findings have implications for foliar blight management using surface seeding as a resource conservation technology in the warm regions of South Asia..