Introgression of bacterial blight resistance gene Xa7 into popular Indonesian rice varieties through backcross and molecular breeding

Abstract

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of major diseases in rice production. The BB resistance gene Xa7 is one of effective genes against Xoo strains in Indonesia. This study aimed to introgress BB resistance gene Xa7 into submergence tolerant rice variety Inpara 5 (IR64 Sub1) and brown plant hopper (BPH) resistant rice variety Inpari 13. Stable BB resistant rice lines have been successfully developed after three backcrossing and four generations of fixation (BC3F4). Screening for BB resistance were conducted in generative stage using Xoo strains IV and VIII. The reaction pattern of the backcross lines against these two Xoo strains were similar to the BB resistant parent Conde. The introgression of the Xa7 gene in Inpara 5 and Inpari 13 genome have been confirmed by using SSR markers RM20589 and RM20590; and Xa7 gene specific marker Xa7-LD34. Agronomic characters and grain quality properties of the backcross lines were comparable to the recurrent parents. Other desirable traits from recurrent parents including submergence tolerance and BPH resistance retained in the selected backcross lines. The BB resistance rice lines with popular rice varieties genetic background developed through this study have potential to be released for farmers adoption.