Effect of 1Bx7null on Soft Wheat Cookie Quality Under Different Nitrogen Inputs and Its CAPS Marker Development

The role of HMW-GSs in soft wheat quality remains inadequately understood. In Chinese soft wheat variety Ningmai 9, a nonsense mutation (Glu-B1x, 1Bx7null) reduced dough tenacity while enhancing dough extensibility under both low (LN) and high nitrogen (HN) inputs. The improved extensibility in the NIL carrying 1Bx7null was primarily due to a reduced glutenin/gliadin ratio, with HN further increasing extensibility compared to LN. Notably, the NIL under HN exhibited better cookie quality than WT under LN without yield loss (p < 0.05). A CAPS marker was developed based on a C-to-T SNP at 514 bp in the CDS of 1Bx7null, reliably distinguishing 1Bx7 and 1Bx7null alleles. This allele-marker combination shows promising potential for soft wheat breeding. Future studies should explore the effects of allele 1Bx7null across diverse genetic backgrounds and soft wheat products.