Rice bacterial blight resistance – Screening of mutant and breeding for recombinant inbred line

Rice bacterial blight (BB) resistance is caused by Xanthomonas oryzae pv. oryzae (Xoo), and leads over 50 % yield loss while severe damage. To explore the BB resistance genes for rice improvement, we chose three typical Xoo isolates (XM1, XF89b and XM42) collected in Taiwan to evaluate the BB resistance in rice lines including: 38 sodium azide induced mutants (SA lines) of TNG67, 26 IRBB lines with known Xa resistance genes, and 22 cultivars (lines). When separately challenge with three Xoo isolates, the IRBB lines showed differential responses to isolates indicated that various resistant genes may involve. Only IRBB5 (xa5) and IRBB7 (Xa7) carrying a single Xa gene were resistant (responsive score 1) or even very resistant (0) to three isolates. Rice IRBB lines carry more than three Xa genes were resistant to three isolates that was consistent with previous reports. However, the well known BB resistance line IRBB21 (Xa21) was susceptible (7) or moderate susceptible (5) to three isolates suggesting that Xoo in Taiwan were more virulent than other resources. The responses of 22 cultivars (lines) to three Xoo isolates wer