Characterization of a novel wheat (Triticum aestivum L.) mutant with reduced seed dormancy

A novel wheat (Triticum aestivum L.) mutant with reduced seed dormancy, RSD32, was isolated from a NaN₃-treated population of a dormant cultivar, Norin61. Results show that RSD32 reduced not only the seed dormancy but also sensitivity to abscisic acid (ABA) on germination. The segregation ratio in the F₂ population of a cross that had been derived from Norin61 and RSD32 suggested that the reduced dormant phenotype was inherited as a recessive trait. At 30 days after pollination (DAP30) and later developmental stages, ABA-insensitivity of RSD32 was observed, but the seeds were sensitive to ABA at DAP20. Defects of ABA sensitivity depended upon seed development. Auxin acted synergistically for sensitivity to ABA in germination of Norin61, but the effects of auxin on ABA sensitivity were diminished in RSD32. The expression of TaABF, a bZIP class transcription factor associated with ABA signal transduction in seed, was lower in embryos of RSD32 than those of Norin61. TaDOG1 is a wheat orthologue of Arabidopsis DOG1, which is identified as a quantitative trait locus (QTL) for the regulation of seed dormancy. Moreover, RSD32 showed lower expression of TaDOG1 in embryos. Both TaABF and TaDOG1 have potential functions for regulation of wheat seed dormancy.