Genetic analysis of environment-sensitive genic male sterile rice under US environments

Two line hybrid rice ( Oryza sativa L.) breeding uses environment-sensitive genic male sterile (EGMS) lines to produce sterile or fertile pollen depending on daylength and/or temperature. There is limited information on the performance and genetic control of EGMS lines under U.S. environments. Therefore, genetic characterization of two F 2 and four BC 1 F 2 populations derived from EGMS line 2009S was conducted under Louisiana field conditions. Chi squared analyses in the F 2 and BC 1 F 2 populations indicated that pollen sterility under high temperature and long daylength field conditions was controlled by a single recessive gene. Sequence comparisons at locus LOC_Os02g12290 between 2009S, CL161 (USDA-AMS 2002 ) and published sequences of G63S and Nipponbare revealed a single nucleotide polymorphism (SNP) that has been detected previously in several EGMS lines. Due to high GC content, a CEL1 nuclease assay was used to detect SNPs associated with pollen sterility in 177 F 2 and 59 BC 1 F 2 sampled individuals. A high percentage of lines (90–100%) across all segregating populations were identified correctly as pollen sterile using the CEL 1 assay. Results from this study suggest that single-gene control of pollen sterility in EGMS line 2009S will be compatible with a two-line system for U.S. hybrid rice development.