Fine mapping of a panicle blast resistance gene Pb-bd1 in Japonica landrace Bodao and its application in rice breeding

Rice blast caused by Magnaporthe oryzae is the most devastating disease in rice production. Compared with seedling blast, panicle blast is considered to be more destructive, which can occur without being preceded by severe seedling blast. However, panicle blast resistance research is rarely reported. Bodao, a japonica landrace from Taihu Lake region, showed a high level of panicle blast resistance. In this study, a mapping population of 212 recombination inbreeding lines (RILs) was developed from a cross of Bodao and the susceptible cultivar Suyunuo, and the RILs were evaluated for panicle blast resistance in three trials. Two quantitative trait loci (QTLs) qPb11-1 and qPb6-1 for panicle-blast resistance were identified, including a major QTL qPb11-1 (Pb-bd1) on chromosome 11 of Bodao explaining from 55.31% to 71.68% of the phenotype variance, and a minor QTL qPb6-1 on chromosome 6 of Suyunuo explaining from 3.54% to 6.98% of the phenotype variance. With the various segregation populations, Pb-bd1 was fine mapped in a 40.6 Kb region flanked by markers BS83 and BS98, and six candidate genes were identified within this region, including one gene encoding NAC domain-containing protein, one gene encoding unknown expression proteins, two genes encoding nucleotide binding site-leucine rich repeat (NBS-LRR) type disease resistance proteins, and two genes encoding von Willebrand factor type A (VWA) domain containing proteins. For application in rice breeding, three introgression lines of Pb-bd1with significantly enhanced panicle blast resistance were developed by using molecular assisted method (MAS) from the commercial variety Nanjing46 (NJ46). Two QTLs, qPb11-1(Pb-bd1) and qPb6-1 conferring panicle blast resistance, were identified from japonica landrace Bodao and Suyunuo.qPb11-1(Pb-bd1) was fine mapped in a 40.6 Kb region flanked by marker BS83 and BS98. Three introgression lines of Pb-bd1with significantly enhanced panicle blast resistance were developed by MAS method from the commercial variety NJ46. It indicated that Pb-bd1 would be useful gene source in panicle blast resistance breeding.