Abstract:
Rice blast disease is caused by a devastating fungus, Magnaporthe Oryzae, which causes major yield loss in the rice crop not only in Pakistan but also allover the world. Magnaporthe oryzae possesses a unique characteristic of retro transposons that enables it to produce multiple strains within a single cropping season. This rapidly evolving pathogen is highly difficult to manage with conventional methods like chemical control because it does not produce efficient results for a longer period of time. In addition to this, a resistant cultivar with a single R gene is also not a promising solution. However, a broad spectrum resistant cultivar with multiple number of blast resistant genes can be developed that can be an efficient solution for this disease. Hence, this studywas designed to gain insights into the resistance spectrum of commercially usedrice varieties of Pakistan. For this purpose 5 BR gene with functional markers ofi.e., Pita, Pib, Pit, Pi54, Pik-p and one PR gene i.e., RCC2 was studied using Polymerase Chain Reacton (PCR) method in 23 rice germ plasm i.e., Dilrosh, Sarshar, Jajai 77, Shandar, IR 09, JP 5, IR 06, Sada Hayat, Basmat 198,Supreme Basmat, Basmat 383, Fakhr e Malakand, Basmat 385, KSK 133, DR82, KS 282, DR 83, Shua 92, Shua, Kangani torh, Khushbo 95, KSB 282, andKanwal 95. The results revealed that the PR gene RCC2 was ubiquitous in all the studied rice varieties, whereas Pi54, Pita, Pik-p, and Pib genes wascollectively present in only Jajai 77, which is a wild type variety. More over, Basmat 198 variety was found with only one broad-spectrum gene i.e., Pita. However, the Pita gene was predominant in 22 out of 23 rice varieties. In addition to that, most of the varietes were naturally present with the 3 BR gene,i.e., Dilrosh, IR 09, IR06, Shua 92, DR 83, DR 82, Kangani torh, KS 282,KSK133, Fakhr e Malakand, Khusnoo 95, Basmat 385, Shandar, JP5, Sadahayat, Sarshar, Supreme Basmat, and Shaheen Basmat. However, Sarshar ,Kanwal 95, Basmat 370, and basmati 383 was found with 2 BR genes. The result depicts that Pakistani rice germ plasm is naturally abundant with the broad-spectrum blast resistant and pathogenesis related genes that are highly useful in breeding programs. A successful gene pyramiding can be done invarious commercial rice varieties to increase their resistance status. This study served as the first step towards the resistant spectrum of rice crop for rice blast disease.