Genotyping the Heading Date of Male-Sterile Rice Line II-32A

II‐32A, an elite male‐sterile line of rice (Oryza sativa L.), has been widely used for the production of hybrid rice seed in China. Heading date in most combinations using II‐32A shows transgressive inheritance or similarity to the latter parent, but the genotype of II‐32A with respect to major genes for heading time is unknown. This limits the further exploitation of this sterile line in breeding and hybrid seed production. Using a number of major gene heading date isogenic lines and heading date QTL near‐isogenic lines, we genetically analyzed II‐32B under both long‐ and short‐day conditions. We show that II‐32B carries two photoperiod‐sensitive genes, E1 and E3, a recessive late‐heading gene, ef‐1, and a photoperiod‐sensitive allele, Se‐1^u. In addition we identified in II‐32B a recessive inhibitor for E1 or Se‐1ⁿ and other modified photoperiod‐sensitive genes. The heading‐date constitution of II‐32A was determined to be E₁e₂E₃Se‐1^uef‐1i‐Se‐1. (Managing editor: Li‐Hui Zhao)