09-08-2013, 03:17 PM
Development of bacterial leaf blight resistant doubled haploid lines in basmati rice genotypes
ABSTRACT
Rice (Oryza sativa L.) is the second most important food crop of the world. In order to meet the demand of increasing population in India and to sustain the self sufficiency in rice production, the current production level (95.98 million tonnes) needs to be increased to 120 million tonnes by the year 2020. To achieve the targeted levels of production, breeding rice varieties for major biotic and abiotic stresses constitutes one of the most important research strategies. Among biotic stresses, bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae is one of the most serious production constraints in almost all the rice growing ecologies of the world. The present study aimed at induction of double haploid BLB resistant basmati rice lines. Eleven BLB differential lines (IRBB50 to IRBB60) from IRRI, Philippines which had expressed resistant response against prevalent strains of Xanthomonas oryzae pv. oryzae, were crossed with four elite high yielding basmati rice varieties viz. Basmati 370, Ranbir Basmati, Saanwal Basmati and Basmati 564. Anthers at appropriate stage of pollen development from F1 crosses were used as explants in the study. Callus induction potential of anthers in different genotypes could be enhanced by supplementing amino acids, particularly a combination of cysteine and tryptophan, in the medium [N6 (3.97 g l-1) + Maltose (40 g l-1) + 2,4-D (2.5 mg l-1) + Kinetin (0.5 mg l-1) + tryptophan (25 mg l-1) + cysteine (40 mg l-1)]. High scores of callus and haploid regeneration frequencies were obtained in another amino acid supplemented medium [MS (4.41 g l-1) + Sucrose (30 g l-1) + BAP (2.0 mg l-1) + Kinetin (0.5 mg l-1) + NAA (0.5 mg l-1)] + tryptophan (25 mg l-1) + cysteine (40 mg l-1)]. The mean doubled haploid (DH) induction frequencies over all the genotypes were 76.34 per cent in colchicine (0.1%) treated and 41.56 per cent in spontaneously induced DHs. The DH lines from the crosses Ranbir Basmati x IRBB59, Ranbir Basmati x IRBB60, Basmati 370 x IRBB59 and Basmati 370 x IRBB60 expressed resistant reaction when screened against prevalent races of leaf blight causing bacterium. Most of the genotypes depicted moderately resistant (MR) response and clear effect of introgressed genes could be observed.