Screening brown spot resistance in rice genotypes at the seedling stage under water stress and irrigated conditions

The nursery resistance of 95 rice genotypes to brown spot (BS) was evaluated under water stress and irrigated conditions during 2017 and 2018. Disease assessment was done by calculating the final brown spot index, area under the disease progress curve and apparent infection rate. Susceptible genotypes demonstrated high disease indices at both the hydrological treatments in comparison to resistant genotypes. Water shortage at the seedling stage caused an increasing rate of disease severity in rice genotypes; however, the responses varied among genotype. These findings suggest that the evaluation of resistance to brown spot disease could be done under water stress conditions. Among genotypes tested, 13 genotypes, i.e. Gharib-Siyah-Reihani, Ghashangeh, Gerdeh, Shahpasand, Neda, Sange-Tarom, Hasani, Dasht, Gohar, Kanto 51, Khazar, Koohsar and Mohammadi-Chaparsar exhibited seedling resistance to brown spot disease at both hydrological conditions which could be recommended for cultivation and further breeding utilization to develop promising resistant lines in management of the brown spot disease.