Plant growth suppression due to sheath blight and the associated yield reduction under double rice-cropping system in central China.

摘要

Sheath blight (Rhizoctonia solani) is a devastating disease in intensive and high-input rice production systems, which accounts for most of the rice fungicide consuming worldwide. To determine the responses of different nitrogen rates, planting densities, and fungicide application on rice growth and grain yield, four field experiments in 2009 and 2010 were conducted under double rice-cropping system in Wuxue County, Hubei province, central China. The results showed that sheath blight infestation without fungicide application had significant negative effect on leaf area index and biomass production rather than tiller number, compared with that of fungicide application treatment. Fungicide application significantly inhibited sheath blight severity, and subsequent increased rice yield consistently compared with control. Sheath blight was further initiated uniformly by artificial infection at panicle initiation stage. Similarly, inoculation significantly increased sheath blight severity and caused yield reduction (%) from 12.1% to 48.6%. In inoculated or in non-sprayed plots, yield reduction (%) caused by fungus was almost greatest under highest nitrogen rate and densest planting density, accompanied by significant growth suppression in terms of leaf area index and biomass accumulation. Furthermore, the results indicated that sheath blight infestation reduced rice yield mainly by decreasing biomass production and grain filling (%), rather than by harvest index (%) or sink size.