Evaluation of Xa7 Introgressed Lines Against Bacterial Leaf Blight (BLB) Disease and Their Agronomic Performances
Abstract Bacterial leaf blight (BLB) is one of the major rice diseases in Malaysia. The disease can potentially cause a 30 to 50% yield loss to the rice crop. Hence, the utilization of resistant rice varieties to BLB is a crucial approach to prevent potential yield loss and to ensure the sustainability of the rice industry in Malaysia. This study aims to incorporate BLB resistant trait into a susceptible, high yielding, popular commercial variety MR219. The identified donor parent is IRBB7, harboring Xa7, a broad-spectrum BLB resistant gene which closely linked to two STS markers, the ID7 and ID15. Backcrossing was initiated, using IRBB7 as the donor and MR219 as the recurrent parents. Marker-assisted selection (MAS) was applied to monitor and confirm the introgression of Xa7 in the progenies of the cross based on alleles produced by the markers. We managed to generate 19 BC3F4 lines harboring homozygous Xa7 gene that were phenotypically resistant when challenged with Xanthomonas oryzae pv. oryzae through an artificial inoculation. The improved lines exhibited similar morphological and yield performance of the recurrent parent. Two lines, PB-2-107 and PB-2-34 were identified for their outstanding performances which are comparable to MR219. This study demonstrates the advantage of MAS application in the improvement of disease resistance traits in the elite rice cultivars.