Marker-assisted selection of two-line hybrid rice for disease resistance to rice blast and bacterial blight

Here, we report the pyramiding of the blast resistance gene Pi9 and the bacterial blight resistance gene Xa23 in GZ63S and its derived hybrid, Liangyou6326, by marker-assisted selection (MAS). The improved sterile line and its derived hybrid showed high levels of resistance to all eight tested Xanthomonas oryzae pv. oryzae strains. Moreover, they demonstrated high levels of resistance to leaf blast at the seedling stage and to neck blast in most natural sites at the maturity stage. The improved GZ63S and its derived hybrid had maintained elite agronomic traits of original variety under normal growth conditions. When exposed to disease stresses, the improved hybrid represented much better agronomic traits than the original variety. Our results indicate that pyramiding the Pi9 and Xa23 genes by MAS is useful for breeding blast- and bacterial blight-resistant hybrids.