This study screened superior variant types through phenotypic trait analysis and measurement of nutritionally valuable components in the fruits of Docynia delavayi, providing a theoretical basis for the breeding of high-quality Docynia delavayi cultivars.

Taking the fruits of Docynia delavayi from Lancang County as the subject of study, twelve variant types were classified based on fruit size, shape, and color. Seven nutritional components—total acidity, total sugars, tannins, flavonoids, crude protein, vitamin C, and crude fiber—were measured. Comprehensive evaluation of the twelve types was conducted using principal component analysis, correlation analysis, score assignment method, and integrated scoring method.

Based on the variation characteristics of fruit phenotypic traits (fruit size, fruit shape, fruit color), these are categorized into 12 variation types: small globular yellow type, small globular red-yellow type, small oval yellow type, small oval red-yellow type, medium globular yellow type, medium globular red-yellow type, medium oval yellow type, medium oval red-yellow type, large globular yellow type, large red-yellow type, large oval yellow type, large oval red-yellow type). Analysis of fruit constituents (total acidity, total sugars, tannins, flavonoids, crude protein, vitamin C, crude fiber) revealed significant variation across all traits. The coefficients of variation were as follows: flavonoids (39.92%)>total sugars (27.25%)>crude fiber (20.83%)>vitamin C (18.42%)>crude protein (12.50%)>total acidity (10.39%)>tannin (2.31%). Correlation analysis revealed extremely significant positive correlations between flavonoid, vitamin C, and total sugar content with fruit transverse diameter, longitudinal diameter, individual fruit weight, and fruit shape index. Principal component analysis further indicated that individual fruit weight, transverse diameter, longitudinal diameter, total sugar, and flavonoids were the primary indicators influencing fruit morphological variation, cumulatively accounting for 70.795% of the variance. Principal component-based ranking revealed that PC1 and PC2 clearly distinguished the ‘large, medium, and small’ fruit size categories, with high internal clustering and distinct classification boundaries within each category. The quality ranking obtained using the score assignment method—‘large fruit>medium fruit>small fruit’—was consistent with the PCA analysis conclusions.

The fruits of Docynia delavayi exhibit rich phenotypic variation and nutritional bioactive compounds. Twelve types were identified and screened, yielding four superior types. This provides a scientific basis for the breeding of high-quality Docynia delavayi cultivars and the development and utilization of its resources.

The R2R3-MYB genes, as one of the largest transcription factors (TFs) families in the plant kingdom, play a significant role in the regulation of pigment accumulation. The aim of this study was to screen the candidate R2R3-MYB genes involved in peel coloration, as there are remarkable variations in the pericarp's color of Docynia delavayi (Franch.) Schneid.

The pericarp of three D. delavayi types was used as the material, the R2R3-MYB genes were identified based on the transcriptomic data and subsequently analyzed for their physicochemical properties, phylogeny, conserved domains, conserved motifs and expression patterns.

A total of 99 R2R3-MYB genes were identified, and most of them were hydrophilic proteins with an amino acid sequence varying from 86 to 881aa, molecular weight between 10.21 and 99.63 kDa, an isoelectric point between 5.01 and 11.44, and an aliphatic index between 55.77 and 91.78. The phylogenetic tree showed that 4 R2R3-MYBs of D. delavayi (DdR2R3-MYB) and MdMYB10 were co-clustered in the subgroup 6, suggesting a possible association with anthocyanin biosynthesis. Additionally, 8 DdR2R3-MYBs were clustered in subgroup 22, indicating that they might be related to carotenoid biosynthesis. Each DdR2R3-MYB contained 2 R domains, which displayed high conservation in the evolutionary process. Conserved motif analysis showed that motif 1 ～ motif 4 were located at the N terminus of most members, which was similar to the R2 and R3 conserved domains. Expression pattern analysis showed that the 48 differentially expressed DdR2R3-MYB genes exhibited 5 expression patterns, indicating diverse functions of DdR2R3-MYBs. RT-qPCR analysis showed that DdR2R3-MYB2/16/18 was significantly up-regulated in the red pericarp, and DdR2R3-MYB47/48 was accumulated in the yellow pericarp.

Based on the phylogenetic and expression pattern analyses, three candidate genes have been screened for anthocyanin biosynthesis regulation and two candidate genes were obtained for carotenoid biosynthesis regulation, which laid a theoretical foundation for the mining of the genes related to peel coloration in D. delavayi.