The haplotype-phased genome assembly facilitated the deciphering of the bud dormancy-related QTLs in <i>Prunus mume</i>

Bud dormancy is a vital physiological process in woody perennials, facilitating their adaptation to seasonal environmental changes. Satisfying genotype-specific chilling requirements (CR) and heat requirements (HR) through exposure to specific chilling and warm temperatures is essential for dormancy release and the subsequent resumption of growth. The genetic mechanisms regulating bud dormancy traits in Prunus mume remain unclear. In this study, we first assembled the genome of 'Nanko', the leading P. mume cultivar in Japan, in a haplotype-resolved manner. Using an F1 segregating population from a cross between 'Nanko' (high-chill) and 'SC' (low-chill), a cultivar adapted to subtropical conditions, we identified quantitative trait loci (QTLs) for vegetative bud dormancy traits on chromosome 4 (LG4 QTLs) in the 'Nanko' genome and for CR and HR on chromosome 7 (LG7 QTL) in the 'SC' genome. A notable 5.6 Mb chromosome inversion was overlapped with LG4 QTL interval in one of the 'Nanko' haplotypes. We also identified candidate genes based on haplotyping, differential expression between the parents or the presence of trait-correlated variants in coding regions. Notably, genes such as PmuMAIN, PmuNAC2, PmuDOG1, PmuSUI1, PmuATG8CL, PmubZIP44, and PmuSAUR50 were identified. This study provides valuable insights into the genetic regulation of vegetative bud dormancy in Prunus species.