Pyramiding of Blast Resistance Genes Pi-1 and Pi-2 in Tarom Mahalli Rice Cultivar

Blast (Magnaporthe grisea) is the most important disease of rice in Mazandaran province, north of Iran, which causes severe damages annually on susceptible cultivars. Tarom Mahalli is a local aromatic cultivar with high cooking quality and marketability, but very susceptible to blast. To protect this cultivar and similar susceptible cultivars against rice blast, farmers have to use high amounts of chemicals every year. In the present study, an attempt was done to transfer rice blast resistance genes Pi-1 and Pi-2 from near isogenic lines C101LAC and C101A51 (as male parents) to Tarom Mahalli (as femate parent) to develop a resistant cultivar with high cooking cultivar. Necessary crosses and backcrosses were accomplished between parents and hybrids developed during three years were selected based on morphological, virulence and molecular markers (RG64 and C481). Selected plants were finally exposed to a mixture of races of the pathogen prevalent in Mazandaran. Based on the results of this investigation, several plants were selected that had morphological and physiological characteristics of Tarom Mahalli and carried Pi-1 and Pi-2 resistance genes. The infection types of the hybrids were 1-2, while those of the Tarom Mahalli were 4 and 5. Although some morphological and qualitative characteristics of the progenies were slightly different from those of Tarom Mahalli, but transferance of resistance genes gave it a satisfactory protection against the disease.