Variation in abscisic acid responsiveness at the early seedling stage is related to line differences in seed dormancy and in expression of genes involved in abscisic acid responses in common wheat

• A wide genetic variation in ABA responsiveness was found in 186 wheat accessions.
• Higher ABA responsiveness was observed in wheat cultivars with dormant seeds.
• ABA responsiveness was correlated to germination index and α-amylase activity.
• Two QTLs for ABA responsiveness were found on chromosomes 2A and 4A.
• The 2A QTL for ABA responsiveness regulates WABI5 and Cor/Lea genes.

Abiotic stresses and pre-harvest sprouting reduce grain yield and quality. ABA plays important roles in regulation of abiotic stress tolerance and seed dormancy. We show wide genetic variation in ABA responsiveness evaluated as root growth inhibition under exogenous ABA treatment using a core collection of hexaploid wheat with 186 accessions. Significantly higher ABA responsiveness was observed in Japanese wheat cultivars, which included some dormant seed-producing cultivars. Transcript accumulation of a WABI5 transcription factor and its downstream Cor/Lea genes was more abundant in the highly ABA-responsive lines than in the less responsive lines after ABA treatment. The germination index and α-amylase activity tended to be higher in seeds of the low ABA-responsive lines than in those of highly ABA-responsive lines for 30–50 days post-anthesis. Significant correlations among ABA responsiveness, germination index and α-amylase activity were confirmed for the KU-3162/Chinese Spring mapping population. Two QTLs for ABA responsiveness were found on chromosomes 2A and 4A in this population. The 2A QTL could regulate WABI5 expression and accumulation of its downstream COR/LEA proteins through TaAFP, a putative negative regulator of WABI5. The core collection of hexaploid wheat is thus useful for identification and functional characterization of QTLs for ABA responsiveness.