Successful Modification of a Commercial Wheat Variety, Lunxuan 13, for Pre-Harvest Sprouting Resistance Through Editing of the TaQsd1 Gene

Wheat is a globally important food crop, and its yield is crucial for ensuring food security. Lunxuan 13 is an elite wheat variety developed by the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences. It has high yield potential and outstanding agronomic traits, such as excellent seed setting rate, plump kernels, and good lodging resistance. However, this variety is highly susceptible to pre-harvest sprouting (PHS) when exposed to rain during the maturation period, leading to premature grain germination on the spike, which causes yield losses and quality deterioration, severely restricting its popularization. This study focused on addressing the PHS susceptibility of Lunxuan 13 by employing CRISPR/Cas9 technology for the targeted knockout of the three homoeologous copies (A, B, and D subgenomes) of TaQsd1, a key gene regulating seed dormancy. A total of 41 transgenic plants were obtained, achieving a transformation efficiency of 52.6%, among which 27 plants exhibited edits at the target sites, resulting in an editing efficiency of 65.9%. Phenotypic analysis of homozygous T2 edited lines revealed significant functional redundancy among the three TaQsd1 homoeologs: a significant extension of the seed dormancy period and a substantial increase in PHS resistance were achieved only when all three A, B, and D copies underwent loss-of-function mutation (aabbdd genotype). After-ripened seeds from these mutants showed normal germination ability, indicating enhanced dormancy rather than loss of germination capacity. Importantly, all of the edited lines exhibited no significant differences compared to the wild type in key agronomic traits such as plant height, spike length, and grains per spike, thus retaining the excellent characteristics of Lunxuan 13. This study successfully optimized Lunxuan 13 for significantly enhanced PHS resistance while retaining its superior agronomic traits. This work provides an effective approach for improving PHS resistance in white-grained wheat and removes a key barrier to the potential commercialization of this variety.