This study aims to explore the molecular mechanisms underlying the formation of Non-red ground color in Xinjiang local peach (Prunus ferganensis and P. persica), providing a theoretical basis for the breeding of new peach varieties with Non-red skin color.

A phenotypic survey of the skin color of 85 progenies of Xinjiang peach and three cultivated varieties was conducted. The activity of various lengths of the PpMYB10.1 promoter was assessed using β-glucuronidase (GUS) staining. Predictive analysis of the cis-acting elements of the PpMYB10.1 promoter from different materials was performed using the PlantCARE (https://bioinformatics.psb.ugent.be/webtools/plantcare/html/). Genotypes with a 5 243 base pairs (bp) transposon insertion and a 483 bp deletion in the PpMYB10.1 promoter of 88 materials were identified and cloned using polymerase chain reaction (PCR). The transcriptional activation of PpMYB10.1 by Pp.4G186800 was validated through dual-luciferase assays.

Based on skin color, 85 Xinjiang peach progenies were classified into Non-red and red types. The majority exhibited Non-red colors (green or light yellow) with minimal or no anthocyanin accumulation. Compared to the fully red variety Zhongtao Jinmi, these exhibited significantly lower levels of anthocyanins and reduced expression of PpMYB10.1. Using GUS staining to assess the effects of promoter mutations on activity, the results showed that a 5 243 bp insertion in the PpMYB10.1 promoter caused the fruit discs to display a lighter blue, indicating decreased activity. Conversely, a 483 bp deletion resulted in a darker blue, suggesting increased promoter activity. No such insertions or deletions were found in the PpMYB10.1 promoter of the Xinjiang peach progenies. The promoter sequences of PpMYB10.1 were cloned, and cis-acting elements were categorized into four groups: light-responsive, plant hormone-responsive, abiotic stress and growth development-responsive, and elements of unknown function. Due to the late maturation of the Xinjiang peach progenies, all were found to have a 0 bp/0 bp genotype for the maturity-regulating gene Pp.4G186800. Dual-luciferase assays showed that Pp.4G186800 could bind to the PpMYB10.1 promoter. Notably, when the promoter had a 483 bp deletion, Pp.4G186800 (+9 bp) formed a strong interaction, potentially enhancing early maturation and anthocyanin accumulation in the peach skin. However, in late-ripening peaches, Pp.4G186800 (-9 bp) had no enhancing effect on the promoter's activity; If the PpMYB10.1 promoter lacked the 483 bp deletion, its intrinsic activity was weak, even though Pp.4G186800 could still interact with it, the effect was minimal.

The presence of insertions and deletions in the PpMYB10.1 promoter is not directly related to the Non-red skin color of Xinjiang peach. In early and mid-ripening varieties, Pp.4G186800 can activate the transcription of PpMYB10.1, facilitating anthocyanin synthesis; however, its influence is reduced or absent in late-ripening peaches.