Phenotypic and molecular identification of some blast resistance genes and biochemical responses of rice genotypes against rice blast pathogen

The current investigation was carried out to identify some isolates of Magnaporthe oryzae (anamorph: Pryicularia oryzae), the causal fungus of blast disease, and to assess their virulence against monogenic lines and other rice genotypes. In addition, the biochemical changes after inoculation with blast pathogen were evaluated. The linked markers to blast resistance genes were identified, the potential gene(s) operating in genotypes were assessed at field conditions. Twenty-seven isolates were identified as six race groups; the ID group was highly distributed, followed by group IC. Resistance genes Pii (IRBLi-F5), Piz-5 (IRBLz5-CA (R) and Pit (IRBLt- K59) were completely resistant to test races. New promising lines i.e. GZ10686-2-1-3-4, GZ10848-1-2-2-1, GZ11190-3-13-4-1, and GZ11312-3-3-1-3 were resistant for test races under artificial inoculation, and induced the highest activity for defense-related enzymes i.e. phenylalanine ammonia-lyase (PAL), chitinase, and the test antioxidant enzyme i.e. peroxidase (POX) and ascorbate peroxidase (APX). Molecular analysis confirmed the existence of genetic variation and the similarity percentage among genotype pairs was as low as 10%. The more genes a specific genotype was carrying, the more resistance and durability are expected. There was collinearity between the superiority of promising lines GZ10848-1-2-2-1 and GZ11190-3-13-4-1 and their respective number of blast-linked genes where they have the highest number of blast-linked genes. Under field evaluation, the advanced promising lines performed well in grain yield compared to the cultivated varieties, especially GZ10848-1-2-2-1, and GZ11190-3-13-4-1, and resistance to blast disease.