Mapping diploid wheat homologues of Arabidopsis seed ABA signaling genes and QTLs for seed dormancy.

Abscisic acid (ABA) sensitivity in embryos is one of the key factors in the seed dormancy of wheat. Many ABA signaling genes have been isolated in Arabidopsis, while only a few wheat homologues have been identified. In the present study, diploid wheat homologues to Arabidopsis ABA signaling genes were identified by in silico analysis, and mapped them using a population of diploid wheat recombinant inbred lines derived from a cross between Triticum monococcum (Tm) and T. boeoticum (Tb). Four diploid wheat homologues, TmVP1, TmABF, TmABI8 and TmERA1 were located on chromosome 3A(m) and TmERA3 was on the centromere region of chromosome 5A(m). In two consecutive year trials, one major QTL on the long arm of 5A(m), two minor QTLs on the long arm of 3A(m) and one minor QTL on the long arm of 4A(m) were detected. The 5A(m) QTL explained 20-27% of the phenotypic variations and the other three QTLs each accounted for approximately 10% of the phenotypic variations. Map positions of the loci of TmABF and TmABI8 matched the LOD peaks of the two QTLs on 3A(m), indicating that these two homologues are possible candidate genes for seed dormancy QTLs. Moreover, we have found two SNPs result in amino acid substitutions in TmABF between Tb and Tm. Comparison of the marker positions of QTLs for seed dormancy of barley revealed that the largest QTL on 5A(m) may be orthologous to the barley seed dormancy QTL, SD1, whereas there seems no orthologous QTL to the corresponding barley SD2 locus.