Marker assisted improvement of super fine grain rice variety, VGD 1 for bacterial blight resistance 

Abstract Background Super fine grain rice variety, VGD 1 (ADT 43 x Seeragasamba) is land mark variety in India for its grain quality traits. However, it is highly susceptible to bacterial blight (BB) disease. It is pertinent to improve the disease resistance without altering grain quality traits and high yielding capacity. We introgressed broad spectrum BB resistance genes, xa5, xa13 and Xa21 into VGD1 through marker assisted selection. Genome wide SSR markers were used to recover the recurrent genome contribution. Foreground selection was carried out at BC1F1, BC2F1, BC2F2 to BC2F4. Background screening was performed for RPG recovery at BC1F1, and BC2F1 generations. Results True breeding lines in BC2F4 were confirmed for targeted genes; screened for bacterial blight disease; and they were evaluated for agronomic and grain quality traits. Foreground selection of BC1F1 revealed four positive plants (Plant-7, plant-18, plant-36, and plant-58) for targeted bacterial blight R genes which were subjected to background selection and genotype (Plant-18) with high RPG (78.44%) was backcrossed to obtain BC2F1. In BC2F1 generation, two positive plants (Plant 10 and Plant 12) were screened for polymorphic SSR markers where plant-12 with RPG of 86.20% was advanced to BC2F2. Phenotypic screening of BC2F4 breeding lines for bacterial blight disease revealed that the seven lines with three genes pyramided were resistant showing the mean lesion length ranging from 0.76 ± 0.18 to 2.26 ± 0.04. Conclusion The superfine variety, VGD 1 was enhanced with xa5, xa13 and Xa21 genes for bacterial blight resistance. Seven pyramided lines were identified with high resistant to BB and grain quality similar to VGD1. The line 56 is promising with all desired agronomic and quality traits with improved resistance and higher yield than VGD1 was identified.