Elucidation of the genetic architecture stabilizing the heading time in barley (Hordeum vulgare L.)

QHd.ouj-4H and HvPHYC were first found to affect the heading time stability under changing climate in barley, modulated by HvCEN, offering insights for stable early-maturing breeding. Heading time stability is essential for stable production of barley under the recent changes in climate. In this study, we sought to identify QTLs regulating heading time and stability, using RILs derived from a cross between two Japanese cultivars, Kashimamugi and Ishukushirazu, both of which are early-heading cultivars with spring growth habit, but differ in heading time stability. QTL analysis was performed by detecting genome-wide SNPs and InDels by MIG-seq, and detected three heading time QTLs (QHd.ouj-2H, QHd.ouj-4H, and QHd.ouj-5H). Among these, HvCEN and HvPHYC were considered to be the causative genes for QHd.ouj-2H and QHd.ouj-5H, respectively, while the gene underlying QHd.ouj-4H remains unknown. QTL analysis failed to detect QTLs for heading time stability, but analysis of the three heading time QTLs revealed that heading time stability was affected by the QHd.ouj-4H and HvPHYC genotype with the late allele and the early allele causing instability, respectively. Furthermore, interactions were observed between QHd.ouj-4H and HvCEN, and between HvPHYC and HvCEN. In the HvCEN-e background, QHd.ouj-4H had no significant effect on stability, and in the HvCEN-l background, HvPHYC showed no significant effect, indicating that the combination of QTLs is crucial for heading time stability. Since early-maturing cultivars are widely cultivated to avoid abiotic stresses, these results facilitate the breeding of barley cultivars under the changing global climate.