Screening rice (Oryza sativa L.) genotypes for susceptibility and tolerance to leaf blast under artificial inoculation in field conditions

Blast disease caused by the Pyricularia oryzae is one of the major diseases of rice, which reduces the rice yield to 70-80% in some years. Appropriate methods of controlling this disease have always been of interest to the researchers, especially the introduction of tolerant cultivars has always been one of the most important breeding objectives of rice breeders. The objective of the present study was to screen rice genotypes for tolerance to leaf blast disease under field conditions. In this research, 121 rice genotypes from the germplasm collection of the Rice Research Institute of Iran (RRII) and International Rice Research Institute (IRRI) were selected and planted in a 11×11 lattice design with two replications under artificial inoculation with fungus causing the blast disease in research fields of RRII, Rasht, Iran, in 2015. The studied traits including the number of spots, number of sporulating spots, infected level, infected percentage, infected type and area under disease progressive curve (AUDPC) in inoculated plants with fungus in the blast nursery were measured. The results showed that there was a significant difference (P<0.01) among genotypes for all traits and most of the studied traits had high broad-sense heritability as well as phenotypic and genotypic coefficient of variation. Cluster analysis for classification of genotypes based on leaf blast related traits showed that the studied genotypes could be divided into three different groups based on leaf blast susceptibility and tolerance. In total, the results of the current study showed that among the studied genotypes, eight genotypes were tolerant to leaf blast disease and the most important and prominent genotypes of which were Neda and Khazar. The tolerant genotypes can be used to obtain leaf blast tolerant varieties in future breeding programs.