Inheritance of the Photoperiod Thermo-Sensitive Genetic Male Sterility in Rice and Evaluation of SNP-Based Markers in Two-Gene Recessive Model

Genetic male sterility has been used successfully in Asia to achieve high grain yields in hybrids vs. pure line varieties. Information is lacking concerning performance and inheritance of environmentally sensitive genetic male sterility under U.S. field conditions. The objectives of our research were to investigate inheritance of photoperiod, thermo-sensitive male sterility (PTGMS) under field plot conditions and to evaluate SNP-based markers for utility in hybrid rice breeding programs. A total of 540 F₂ plants derived from a cross of a PTGMS x fertile tropical japonica line were randomly sampled in three separate studies across two locations (LA, AR) in 2012-2013 to determine fertile: sterile plant segregation ratios. Based on seed fertility, segregation ratios fit a 15 fertile: 1 sterile two-gene recessive model across the three studies. Genotyping of SNP markers at pms1(t) and pms3 loci showed two-gene recessive segregation with significant interactions affecting pollen fertility across 2012-2013 at the LA location. Combined marker main effects and their interactions explained 54% of observed variation. No significant year or year x marker interaction was detected in 2012-2013 suggesting stable expression of PTGMS trait over time at LA location.  All results indicate that the two-gene recessive SNP-based markers may be used for hybrid development under U.S. field conditions, but other loci most likely did contribute to the observed variation for PTGMS in the F₂ population evaluated in this study.