Identification and Fine-mapping of a New Bacterial Blight Resistance Gene, Xa47(t), in G252, an Introgression Line of Yuanjiang Common Wild Rice (Oryza rufipogon)

Bacterial blight (BB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is a common, widespread, and highly devastating disease that affects rice yield. Breeding resistant cultivars is considered the most effective measure for controlling this disease. The introgression line G252 derived from Yuanjiang common wild rice (Oryza rufipogon) was highly resistant to all tested Xoo strains, including C5, C9, PXO99, PB, T7147Y8, Hzhj19, YM1, YM187, YJdp-2, and YJws-2. To identify the BB resistance gene(s) of G252, we developed an F2 population from the cross between G252 and 02428. A linkage analysis was carried out between the phenotype and genotype in the population. A segregation ratio of 3:1 was observed between the resistant and susceptible individuals in F2 progeny, indicating a dominant resistance gene, Xa47(t), in G252. The resistance gene was mapped within an approximately 26.24 kb physical region on chromosome 11 between two InDel markers, R13I14 and 13rbq-71; and moreover, one InDel marker, Hxjy-1, co-segregated with Xa47(t). Three genes were predicted within the target region, including a promising candidate gene encoding a nucleotide-binding domain and leucine-rich repeat (NLR) protein (LOC_Os11g46200) by combining the structure and expression analysis. Physical mapping data suggested that Xa47(t) was a new broad-spectrum BB resistance gene.