Tagging of Blast Resistance Genes in Oryza Sativa Using Rapd And Scar Markers

Abstract

Rice is the second most important cereal crop of developing countries and a staple food of about 65% world population. Increase threat of rice blast calls for serious efforts to develop resistant rice varieties against this pathogen. In this endeavors, it is important to identify resistant gene (s) with help of markers. Once a gene is tagged with molecular marker, it can be transferred selectively into different genetic backgrounds by marker assisted selection. A slow progress in breeding resistance to blast disease has been observed due to non-availability of reliable markers I traits associated with qisease resistance that can be used in marker assisted breeding. For this purpose, hundred and five elite Indian and exotic rice genotypes were evaluated for resistance to blast disease under an induced epiphytotic condition obtained in the field at Meerut (North West Plains Zone, India, 28.99°N and 77.70°E) in the year 2005-06 and 2006-07. The disease severity(%) and AUDPC was less than 45% and 1000, respectively in all the resistant genotypes, while it was around 85% and higher than 2000 in the case of susceptible genotypes. Substantial variability was present among rice genotypes for resistance toP. oryzae. Genotypes IR- 72107-4-159-1-3-3-3, IR-74886-55-2-3-2, PSBRC-80-1, IR-75298-59-3-1-3 and IR-71527-44-1-1 showed considerably less disease severity (%) and AUDPC. Ten RAPD and two SCAR primers were used to identify blast resistant genes. Markers OPA-05, OPF-06, OPF-09, OPF 17, OPG-17, OPG- 18, OPG-19, OPH-18, OPK-12, P-265-.550 and P-286-350 linked to blast resistance in most of the resistant genotypes, could be considered as potent molecular markers in the selection of blast resistant genotypes. Amplification with RAPD and SCAR primers revealed non-allelic relationship among resistant g~notypes and thus, there is good p~ssibility of obtaining enhanced resistance through gene pyramiding.