The early-ripening peach industry has undergone rapid development in the Panxi region of the Sichuan Basin in recent years. However, after the introduction of some new peach varieties to the high-altitude peach-producing areas in Panxi, the titratable acid content in peach fruit has significantly increased. This study compared the fruit quality indicators of early-ripening peach varieties cultivated in Xide County (a high-altitude peach-producing area) and Longquanyi District (a low-altitude peach-producing area) in Sichuan Province and analyzed the differences in organic acid metabolism by combining primary metabolomic and transcriptomic approaches. The results showed that the ‘Zhongtaohongyu’ fruit from the high-altitude peach-producing area had a much higher accumulation of malic acid and, accordingly, a significantly higher organic acid content than the other samples. The lower annual average temperature and stronger ultraviolet radiation in high-altitude peach-producing areas may lead to the increased expression of genes (PpNAD-ME1, PpNADP-ME3, and PpPEPC1) in the organic acid synthesis pathway and the decreased expression of genes (PpACO2, PpNAD-MDH2/3/4/5, and PpPEPCK2) in the organic acid degradation pathway in peach fruit, ultimately resulting in the accumulation of more organic acids. Among them, the downregulation of the key genes PpNAD-MDH3/4/5 involved in malic acid metabolism may be the main reason for the higher malic acid accumulation in peach fruit from high-altitude peach-producing areas. Overall, this study elucidates the mechanism by which environmental factors enhance the accumulation of organic acids in peach fruit from high-altitude peach-producing areas from a multi-omics perspective, as well as providing a theoretical basis for screening key genes involved in organic acid metabolism in peach fruit.

GF677 is a widely used peach rootstock with resistance to chlorosis and continuous-cropping disease. Peach varieties grafted onto GF677 generally exhibit larger leaf area and deep green foliage in alkaline soils, demonstrating a higher nitrogen utilization efficiency (NUE) than other rootstocks. To elucidate the mechanism for the higher NUE of GF677, we grafted four peach varieties onto either GF677 or peach ( Prunus persica , the control rootstock) in alkaline soils. The results revealed that grafting of peach varieties onto GF677 resulted in larger leaf area and significantly higher total nitrogen content than grafting onto the control rootstock. Comparative transcriptomic analysis and WGCNA showed that the grafting onto GF677 significantly up-regulated 13 genes related to nitrogen uptake, transport, and reuse, while grafting onto the control rootstock up-regulated two monothiol glutaredoxin-encoding genes, in the leaves of different peach varieties. RT-qPCR further confirmed that four genes, including PpNRT1 , PpNRT4 , PpGLDH , and PpGRF9 , may play crucial roles in the nitrogen utilization of GF677. Additionally, PpMGrx2 may play an important role in the response of peach ( Prunus persica ) to alkaline stress. This study elucidates the mechanism underlying the efficient nitrogen utilization of GF677, providing an important basis for the application and improvement of peach rootstock varieties.

Kiwifruit canker disease, caused by different bacterial pathogens, was observed in Sichuan Province, China. Specifically, in the winter and spring seasons, Pseudomonas syringae pv. actinidiae (Psa) was identified as the primary pathogen, causing reddish-brown exudates, branch dieback, and phloem decay. In contrast, during the summer months, Pectobacterium carotovorum subsp. actinidiae (Pca) emerged as the primary causal agent of kiwifruit canker, exhibiting similar symptoms to those caused by Psa, such as exudates from leaf scars and lenticels, xylem necrosis, and branch desiccation. From 55 symptomatic samples, 34 bacterial isolates were obtained, with 28 identified as Psa and 6 as Pca. Pathogenicity tests revealed significant variation in virulence, with Psa isolate G5 and Pca isolate M5 showing the highest pathogenicity on leaves and branches, respectively. Both pathogens caused characteristic necrosis and lesion expansion, fulfilling Koch’s postulates. Phylogenetic analyses confirmed the distinct evolutionary relationships of Psa and Pca isolates. These findings highlight the seasonal variability of kiwifruit canker pathogens and emphasize the need for targeted disease management strategies.

Blood-fleshed peach is an important and distinctive peach species widely distributed in southwestern China. Here, we compared the main fruit intrinsic quality indicators and antioxidant capacity of five blood-fleshed peach varieties from Sichuan Province and one white-fleshed peach cultivar, and clarified cyanidin-3-O-glucoside, pelargonidin-3-O-glucoside, and total anthocyanin are the three most critical intrinsic indicators influencing the total antioxidant capacity of blood-fleshed peaches. Combined metabolomic and transcriptomic analysis as well as transient transformation experiments in peach flesh revealed that two novel MYB transcription factors (PpMYB121, PpMYB158) and one bHLH transcription factor (PpbHLH59) play crucial roles in anthocyanin accumulation in blood-fleshed peach. Additionally, we constructed a molecular regulatory network for anthocyanin accumulation in blood-fleshed peach, including 17 structural genes, three transcription factors, and nine major anthocyanin components, which provides an important theoretical basis for refining the mechanism of anthocyanin accumulation in blood-fleshed peaches. In summary, this study improves our understanding of the nutritional value of blood-fleshed peach and provide targets for the improvement of peach varieties with high anthocyanin content.