Marker-assisted pyramiding of Xa21 and Xa7 genes conferring resistance to bacterial leaf blight in indica cultivar Bacthom7

Bacterial leaf blight (BLB) of rice is one of the most destructive diseases affecting rice fields.Xanthomonas oryzae pv.oryzae (Xoo) is the causal agent of BLB.Two BLB resistance genes, Xa21 and Xa7, were transferred into the susceptible indica cultivar Bacthom7 (BT7) by using marker-assisted selection with markers pTA248 for Xa21 and ID7 for Xa7.Improved BT7 lines carrying the two resistance genes were inoculated with three isolates of the Xoo from Northern Vietnam and evaluated for agronomic traits.Artificial inoculation of 13 lines with three Xoo races identified nine highly resistant lines with wide-spectrum resistance to Xoo, including D1, D2, D3, D6, D7, D8, D9, D10 and D12.These lines were similar to recurrent parent BT7 with regard to external appearance, yield performance and grain quality.On the basis of agronomic traits and the level of resistance to BLB, two promising lines, D6 and D9 were further selected.These two lines could efficiently contribute to rice production for food security and food safety in northern Vietnam.