Development of Heat Tolerant Two-Line Hybrid Rice Restorer Line Carrying Dominant Locus of OsHTAS

In order to create novel germplasm resources for breeding heat tolerant variety, we transferred a dominant allele OsHTAS, previously characterized and cloned from a high-temperature tolerant local variety HT54, which was collected from the rice production area of southern China, into a high- temperature sensitive intermediate breeding line HT13 through six rounds of successive backcross by using marker-assisted selection. The molecular analysis showed that the recovery of genetic background of a resultant near isogenic line (NIL), MHT13, was around 99.8%. The OsHTAS gene introduced in the MHT13 expressed normally in the HT13 genetic background, mediating heat tolerance and phenotype similar to those of the donor parent HT54. The major agronomic traits of MHT13 resembled those of the recurrent parent HT13. Moreover, MHT13 had high general combining ability and its rice quality reached the grade 3 standard of edible high-quality rice issued by Ministry of Agriculture of the People's Republic of China, which greatly improved its application value in rice production.