Functional marker-assisted selection for bacterial leaf blight resistance genes in rice (Oryza sativa L.)

P>Evolving high yielding rice genotypes with durable resistance to bacterial leaf blight (BLB) is pertinent considering the extensive damage caused by the disease in most of the rice growing regions. Two high yielding BLB susceptible indica rice cultivars, 'ADT43' and 'ASD16' popular among farmers and consumers across South India have been introgressed with three BLB resistance genes xa5, xa13 and Xa21 from isoline IRBB60 using functional markers. The F(2) populations of 500 plants from ADT43 x IRBB60 and 806 plants from ASD16 x IRBB60 crosses were screened for the presence of all the three resistance genes. Thirty genotypes with three genes in homozygous and 55 genotypes with two genes in homozygous and one gene in heterozygous condition were identified. These pyramided genotypes with two or three resistance genes exhibited high levels of resistance against two predominant Xanthomonas oryzae isolates of South India. Among the 30 pyramided genotypes (xa5 + xa13 + Xa21), 12 were found to be significantly high yielding with desirable agronomic characteristics and the selection efficiency of the present markers was hundred percent.