Identification of bacterial blight resistance gene in hybrid rice (BC1F5)

Identification of xa5 gene was done using RG556 marker in 14 hybrid rice (BC 1 F 5 ) lines derived from the cross between KDML 105 rice and IRBB5 (a bacterial blight resistant variety having xa5 gene), backcrossed to KDML 105 followed by selfing for 4 generations. It was found that all BC 1 F 5 lines carried 1,600 bp DNA band. Upon treating the PCR amplicon with restriction enzyme Hpy CH4 IV, all BC 1 F 5 lines gave DNA fragments of 1,000 bp and 300 bp similar to those of bacterial blight resistant line (IRBB5). These results indicated that the tested BC 1 F 5 lines had resistance xa5 gene, in homozygous condition. The level of bacterial blight resistance was also determined by inoculation with Xanthomonas oryzae pv. oryzae race 0701 on 45 day young seedling leaves. All BC 1 F 5 lines showed resistant to the bacteria. Using AFLP technique, B1, B3, B5, B6, B13 and B14 of BC 1 F 5 lines showed 99.06% genetic similarity to KDML105. These six selected lines will be further used for quality and yield testing.