Genetic Analysis Of A Heading Delay Mutant AH(T) And Fine Mapping Of The Gene In Rice

Flowering is one of the most important traits in plant developmental process. Plant cultivation area and production are partially determined by the flowering time. As one of the world’s most important food crops, rice is one kind of typical short-day plants, which head early in short-day conditions and delay heading in the long-day conditions. In this study, we identified a Nanjing35mutant ah(t)(activate heading), which delays flowering in normal long-day conditions in Nanjing. Through map-based cloning method, the gene controlling this trait was located on the range of45kb on chromosome9.First, we got the mutant through screening the Nanjing35radiation mutagenesis mutants, and tentatively named ah(t). The mutant in Nanjing flowers later than the wild type by50days, and cannot bear seeds. Nanjing35and the mutant were treated in artificial short-day conditions and the mutant still flowered later than the wild type to some extent, which shows that the regulation of gene AH(t) about heading date is independent of the length of daylight. We identified the phenotype of the mutant, made it hybrid with indica9311to produce F2mapping generation. The mapping populations were planted in experimental bases in Nanjing and Hainan, from which late heading individuals were picked. Meanwhile, we analyzed these extreme individuals using laboratory exiting makers, which were distributed on the12chromosome of rice. We selected32extreme individuals from a group of400populations, located the gene AH(t) in the range of16.7cM on the chromosome9. The new polymorphic primers between indica and sativa were designed in this interval. We reduced the interval to547kb by using the designed makers and selected75individuals from700populations. In2012, we planted10000F2populations and picked out915extreme individuals and reduced the interval to45kb. Then,5and1ORFs were predicted respectively in the interval through the sites Gramene and RAP-DB. Through analyzing sequences, we found the gene AH(t), which presents the deletion of3bases in mutant comparing with the wild type, resulting in the traits change in the mutant.