Powdery mildew is an economic threat for viticulture because it not only affects grape yield, but also causes a series of impacts on the qualities of fruit and wine, especially the flavors and various metabolites. Different grape varieties may have different levels of powdery mildew resistance/tolerance and their components of their metabolome are also various. In this study, two wine grape varieties, Guipu No.6 (GP6) and Marselan (Mar) with different levels of powdery mildew tolerance, were used to compare the quality differences in metabolism level by using the widely targeted metabolomics method. The results show that GP6 has a better powdery mildew leaf tolerance than Mar. A total of 774 metabolites were detected by using a UPLC-QQQ-MS-based metabolomics approach, and 57 differential metabolites were identified as key metabolites that were accumulated after infection with powdery mildew in GP6 and Mar, including phenolic acids, flavonoids, terpenoids, stilbenes, lipids, nucleotides and derivatives, lignans and coumarins, and quinones. This finding indicates that the defense mechanisms of grape fruit are mainly associated with phenylpropane-flavonoid metabolism. Specifically, stilbenes had greater variations after powdery mildew infection in GP6; while in Mar, the variations of flavonoids, especially kaempferol-3-O-glucuronide and luteolin-7-O-glucuronide, were more remarkable. The above results demonstrate that stilbenes may play a more important role than flavonoids in resisting powdery mildew infection in GP6’s fruits, and the drastic variations of these phenolic compounds in different wine grapes after powdery mildew infection might also lead to quality difference in the flavors. This study can provide new insights into the understanding of the cause of powdery mildew tolerance in different grape varieties and the effects on the quality of wine grapes infected with the disease exerted by metabolism level.

Grapevine is a popular cultivated fruit throughout the world and heat stress is one of the most serious threats to viticulture. However, transcriptional responses, such as molecular properties of photosynthesis and abscisic acid biosynthesis, metabolism and signal transduction pathway of grapevine to heat stress, are still poorly understood. In this study, RNA-seq was carried out for thermostabilized grapevine ‘Kyoho’ leaves. Results showed that 685 and 469 genes were commonly down-regulated and up-regulated at three sampling time-points. The light-dependent reactions of photosynthesis was significantly enriched in up-regulated DEGs at 1 hpt and down-regulated DEGs at R24 hpt. Heat stress impaired the photosynthetic capacity of grapevine leaves, and there was a significant positive relationship between photosynthesis and stomatal conductance at short-term post-heat stress treatment, but the inhibition of HS on Pn was non-stomata limitation for a longer period. Photosystem (PS)Ⅱ was more sensitive to heat stress than PSⅠ, and PsbP, as well as Psb28, played important roles in response to heat stress. The abscisic acid (ABA) content in heat-stress-treated Kyoho plants was higher than that in the control at 1 hpt, but less in heat-stress-treated plants at 4 and R24 hpt, which was regulated by numerous genes involved in the ABA biosynthesis and catabolism pathways. These results help to understand the influence of heat stress on photosynthesis and ABA biosynthesis, metabolism and signal transduction pathway.

Heat stress damages the photosynthetic apparatus of grapevine leaves. It also restricts plant growth and reduces fruit yield and quality. However, natural variation in photosystem II (PSII) thermal stability under heat stress in grapevine and its genetic basis remain poorly understood. Here, we evaluated 404 genetically diverse grapevine accessions. We measured the maximum quantum efficiency of photosystem II (Fv/Fm) after treatment at 47 °C. Phenotypic analysis, cluster analysis and genome-wide association analysis were then used to investigate the genetic basis of PSII thermal stability. The coefficient of variation for Fv/Fm increased from 4.52% at 25 °C to 40.60% at 47 °C. Wild accessions generally retained higher Fv/Fm than interspecific hybrids and Vitis vinifera cultivars. We also identified 21 accessions with relatively high PSII thermal stability. A genome-wide association analysis of 5,074,860 high-quality SNPs detected a suggestive association signal on chromosome 4. The lead SNP was Chr4_1743280_G_A. We integrated gene annotations within the associated interval, putatively functional variants and diplotype–phenotype comparisons. This analysis prioritized seven candidate genes potentially associated with variation in PSII thermal stability. The Hap2/Hap2 diplotype of Vitvi005414 was associated with higher Fv/Fm. However, these associations should be regarded as candidate hypotheses for further validation rather than evidence of causal relationships. These findings provide candidate loci, genes and diplotypes for understanding the genetic basis of PSII thermal stability. They also support the use of germplasm with relatively high PSII thermal stability, validation of candidate variants and future breeding for improved heat resilience.

Tropical viticulture has reached a considerable scale worldwide. Driven by innovative production systems such as two-harvests-a-year cultivation and ripening regulation, tropical grape-growing regions have become dynamic and economically significant viticultural areas. Most grape varieties currently cultivated in the tropics were originally bred in traditional temperate zones. When introduced to tropical regions, they often suffer from poor dormancy release, high disease and pest pressure, and compromised fruit quality. Therefore, it is imperative to conduct localized breeding directly under tropical stress conditions (e.g., high temperature, high humidity) to develop varieties with key target traits, including low chilling requirement, heat tolerance, disease resistance, suitability for two-harvest cultivation, good flavor, and good storage and transport tolerance. This paper systematically reviews the current status and breeding progress of the grape industry in major tropical viticultural regions, such as India, Brazil, and China. It summarizes the advances made by breeding teams in these countries in germplasm collection, crossbreeding, bud mutation selection, and the breeding and release of new varieties. The review concludes that developing adapted varieties through targeted breeding in tropics is essential for the sustainable and high-quality development of the grape industry in tropical regions.