Isolation of ABA-responsive mutants in allohexaploid bread wheat (Triticum aestivum L.): Drawing connections to grain dormancy, preharvest sprouting, and drought tolerance
Schramm, Elizabeth C. | Abellera, Jorgen C. | Strader, Lucia C. | Campbell, Kimberly Garland | Steber, Camille M.
This paper describes the isolation of Wheat ABA-responsive mutants (Warm) in the Chinese Spring background of allohexaploid Triticum aestivum L. Because the hormone abscisic acid (ABA) is required for the induction of seed dormancy, stomatal closure, and drought, cold and salt tolerance, ABA-hypersensitive wheat mutants were expected to show increased seed dormancy and decreased leaf transpiration in drying soils. Lack of wheat grain dormancy is associated with a propensity for preharvest sprouting (PHS), the germination of seed on the mother plant when moist conditions persist before harvest. PHS tolerance correlates with higher seed dormancy resulting from red grain color, higher ABA accumulation and sensitivity. Wheat grain loses dormancy and sensitivity to ABA inhibition of seed germination with after-ripening. Warm lines maintained higher ABA sensitivity when partially after-ripened. The Warm1 and Warm4 mutants showed the strongest and most reproducible increase in ABA sensitivity, accompanied by a requirement for more prolonged after-ripening to break dormancy. Warm2, Warm3, Warm5, and Warm6 showed normal germination without ABA but increased sensitivity to inhibition of germination by applied ABA. The Warm4 mutant showed decreased whole plant transpiration in drying soil, consistent with the role of ABA in inhibiting vegetative leaf transpiration.Show more [+] Less [-]