Exploring the Distribution of Blast Resistance Alleles at the Locus in Major Rice-Producing Areas of China by a Novel Indel Marker.

Rice blast disease caused by the fungus damages cereal crops and poses a high risk to rice production around the world. Currently, planting cultivars with resistance () genes is still the most environment-friendly approach to control this disease. Effective identification of genes existing in diverse rice cultivars is important for understanding the distribution of genes and predicting their contribution to resistance against blast isolates in regional breeding. Here, we developed a new insertion/deletion (InDel) marker, Pigm/2/9InDel, that can differentiate the cloned genes (, , and /) at the locus. Pigm/2/9InDel combined with the marker Pi2-LRR for was applied to determine the distribution of these four genes among 905 rice varieties, most of which were collected from the major rice-producing regions in China. In brief, nine containing varieties from Fujian and Guangdong provinces were identified. All of the 62 -containing varieties were collected from Guangdong, and 60 varieties containing were from seven provinces. However, was not found in any of the Chinese varieties. The newly identified varieties carrying the alleles were further subjected to inoculation tests with regional blast isolates and field trials. Our results indicate that and alleles have been introgressed for blast resistance breeding mainly in the Fujian and Guangdong region, and is a valuable blast resistance resource to be introduced into China.