Blast disease influence on agronomic and quality traits of rice varieties under Mediterranean conditions

Abstract

The effects of Pyricularia oryzae, the causal agent of blast disease in rice, on plant growth, grain yield, and grain quality under Mediterranean conditions were studied in 2002 and 2003. Four rice varieties were grown under high and low disease pressure, achieved by early inoculation with the blast fungus and by natural infection, respectively. Results showed that inoculation affected the overall plant growth and yield and resulted in a reduction in plant height, number of productive tillers per plant, grain weight, and grain yield. The magnitude of the reduction was dependent on the varietals' susceptibility to the disease. Both types of the disease (leaf blast and neck blast) were negatively correlated with grain yield. It was estimated that each unit increase in leaf blast rating and neck blast resulted in 5.97 and 0.23 g plant^{-1} yield reduction, respectively. Grain quality traits were less affected by the disease treatments compared to the agronomic traits. The most pronounced effect of the disease was on total milling yield, which in some cases was reduced by inoculation up to 11%.