Identification of the causal mutation in early heading mutant of bread wheat ( L.) using MutMap approach.

Unlabelled: In bread wheat ( L.), fine-tuning the heading time is essential to maximize grain yield. () and () are major genes affecting photoperiod sensitivity and vernalization requirements, respectively. These genes have predominantly governed heading timing. However, and significantly impact heading dates, necessitating another gene that can slightly modify heading dates for fine-tuning. In this study, we developed an early heading mutant from the ethyl methanesulfonate-mutagenized population of the Japanese winter wheat cultivar "Kitahonami." MutMap analysis identified a nonsense mutation in the clock component gene () as the probable SNP responsible for the early heading mutant on chromosome 3D. Segregation analysis using F and F populations confirmed that plants carrying the allele headed significantly earlier than those with the functional . The early heading mutant exhibited increased expression levels of and circadian clock genes, such as and (). Notably, the transcript accumulation levels of and were influenced by the copy number of the functional gene. These results suggest that a loss-of-function mutation in is the causal mutation for the early heading phenotype. Adjusting the functional copy number of will be beneficial in fine-tuning of heading dates.

Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-024-01478-5.