Breeding for Heat Tolerance Rice Based on Marker-Assisted Backcrosing in Vietnam

A total of six markers RM3586 and RM160 on chromosome 3 and RM3735, RM3471, RM3687 and RM3536 on chromosome 4 were used to select promising lines in backcrossing populations for heat tolerance at flowering stage in rice. Fifty lines selected in BC3F2, BC4F1, and BC4F2 and parents were planted in 2013, and 2014 dry seasons at the CLRRI field under natural heat stress and greenhouse to evaluate heat tolerance at the reproductive period. Heat tolerance scoring under field condition was based on percentage of unfilled grains. All selected lines exhibited their homozygous alleles with two heat tolerance germplasm N22 or Dular in QTL loci. Twelve lines harboring homozygous alleles to QTL loci RM3586 on chromosome 3 and RM3735 on chromosome 4, respectively were selected and evaluated to agronomic traits and yield potential. Four lines BC4-1-10-1 from OM5930/N22//4 *OM5930, BC4-5-8 from OM5930/Dular//4*OM5930, BC4-5-9-4 from AS996/N22//4*AS996, and BC4-6-3 from AS996/Dular//4 *AS996, respectively were finally selected to would be for regional adaptable test in Central Coast of Vietnam under heat stress condition to release to rice farmers.