Evaluation of genetic diversity of resistance to blast disease in some Iranian and aerobice rice genotypes

The blast disease with the causal agent Magnaporthe oryzae B. C. Couch and anamorph Pyricularia grisea CookeSacc is one of the most important plant diseases in the world. Because of its rapid and destructive release under favorable conditions of relative umidity, it is the main disease of rice. This research was conducted to evaluate the genetic diversity of 53 rice genotypes inclouding Iranian lowland and non-local aerobic rice in terms of resistance to blast disease. The field experiments were conducted in two years as a randomized complete block design with three replications during spring and summer 2017 and 2018. To calculate the area under the disease progress curve (AUDPC), sampling was done in five steps from the occurrence of blast disease. After mean comparison, genotype ranking was done by Arunachalam method to determine general resistance. The result showed that Nemat, Sepidrood, IR82589-B-B-84-3, IR82589-B-B-114-3, IR82635-B-B-143-1, IR83749-B-B-46-1, IR81422-B-B-200-4, IR82310-B-B-67-2, IR82616-B-B-64-3 cultivars achived the highest scores, and as a result, they were in the resistant group. Hassan Saraei, Chamapudar, Ghasroldashti, Shahpasad, Domsiah, Anbarbou, Ahlamitarom, Sadri, Rashtisard cultivars with the highest disease severity, received the lowest rating and were classified as highly susceptible and semi-sensitive genotypes. Genotypes were divided into 6 groups based on cluster analysis results and confirmed the results of Arunachalam. Discriminant function analysis considering two groups of Iranian and non-local rice with Wilks' lambda statistics 0.561 showed a significant difference between two groups (p < 0.001). Based on this analysis, two groups showed the most difference based on infection type, AUDPC and severity of disease in third stage.