Characterization and genetic identification of a low-temperature-sensitive wheat apical spike aberrance mutant

A low-temperature-sensitive wheat mutant exhibiting apical spike aberration, designated as lwasa-B1 , was identified and comprehensively characterized. Integrated analyses of BSE-Seq, gene mapping, transcriptomic, and metabolomic data revealed TraesCS4B02G023800 as a key candidate gene associated with the lwasa-B1 mutant phenotype. Spike development is a key factor in determining wheat yield, and cold tolerance during the spike's vulnerable stages is essential for preserving both fertility and productivity. This study presents a comprehensive characterization of the apical spike aberrance mutant lwasa-B1 , which was generated through ethyl methanesulfonate mutagenesis of the wheat cultivar Chuannong 16, and its response to low-temperature stress. The mutant lwasa-B1 exhibited reduced cold tolerance, with a critical temperature threshold identified between 13-15°C. Under low-temperature stress, lwasa-B1 showed delayed growth, increased tillering, and varying degrees of spike degradation. Compared to the wild type, lwasa-B1 demonstrated significantly lower enzymatic activities of catalase, peroxidase, and auxin, while levels of malondialdehyde and gibberellin were markedly higher. Integrated metabolomic and transcriptome analyses suggest that lwasa-B1 may be implicated in plant hormone signal transduction and phenylpropanoid metabolic regulation pathways. A target gene was mapped to the chromosome arm 4BS, within a 2.07 Mb region, bounded by the markers k_sau_4B_17478331 and k_sau_4B_19541181 . The integrated analysis, encompassing BSE-Seq, transcriptomics, and metabolomics, has identified TraesCS4B02G023800 as a potentially key gene associated with lwasa-B1 . This research delineates the phenotypic and physiological responses of lwasa-B1 to low-temperature stress and nominates a candidate gene potentially responsible for spike degradation. The study provides a preliminary dissection of the regulatory mechanisms underlying spike degradation in wheat under low-temperature stress, contributing significant insights for wheat breeding programs. 1