Blast Disease of Black Glutinous Rice Germplasms Under Inoculation at Seeding and Tillering Stages

Black rice is an alternative source of blast disease resistance and appropriate screening method is necessary tobe proposed. The objectives were to 1) evaluate leaf blast disease of different black glutinous rice genotypes,and 2) determine correlations between disease symptoms at seedling and tillering stages. Leaf blast disease for25 black glutinous rice genotypes and 3 check genotypes were observed at Khon Kaen University, Thailand in2013 and 2014. HY 71, Niawdam Gs.no.21629, Khaokam Gs.no.88084, KKU-GL-BL-05-003, KKU-GL-BL-05-004, KKU-GL-BL-06-010 and KKU-GL-BL-06-023 were high resistant genotypes across growth stages, timesof evaluation and years. Seedling and tillering stages were significantly different for severity index.Correlation coefficients between severity indices at seeding and tillering stages in 2013 and 2014 for evaluationat 7 days after inoculation (DAI) were 0.34 (p<0.01) and 0.29 (p<0.01), respectively, and for evaluation at 14DAI were 0.40 (p<0.01) and 0.41 (p<0.01), respectively. Correlation coefficients between severity indicesevaluated at 7 and 14 DAI for growth stages and years varied from 0.34 to 0.50 (p<0.01). The results suggestedthat screening of leaf blast disease at only seedling stage was not enough to identify resistant genotypes.