Apolygus lucorum, a cosmopolitan Hemiptera insect, poses a significant threat to Ziziphus jujuba (jujube), causing symptoms such as mottled chlorosis. However, the mechanisms through which A. lucorum affects chlorophyll biosynthesis and degradation remain unclear. This study investigates the effects of A. lucorum infestation on chlorophyll metabolism and photosynthetic performance in winter jujube leaves. Results revealed a substantial reduction in chlorophyll a and b content, which was strongly correlated with decreases in key photosynthetic parameters, such as the Photochemical Performance Index (PI_ABS) and electron transport efficiency (ψ(Eo)). Infestation downregulated genes critical for chlorophyll biosynthesis, such as HEMA, HEMB, and chlG, leading to a bottleneck in chlorophyll production. Concurrently, chlorophyll degradation pathways were upregulated, with genes like PAO and RCCR driving increased chlorophyll catabolism. This imbalance between reduced synthesis and accelerated degradation exacerbated chlorophyll loss, impairing photosynthetic capacity. Furthermore, the application of exogenous H₂O₂ intensified chlorophyll degradation, particularly in A. lucorum-infested leaves. The accelerated degradation of chlorophyll, coupled with reduced light-harvesting efficiency, contributed to oxidative stress and further impaired the photosynthetic machinery, despite an increase in antioxidant enzyme activity. These findings underline the critical role of chlorophyll metabolism in maintaining photosynthetic efficiency in winter jujube under A. lucorum infestation. It underscores the need for targeted strategies to protect chlorophyll synthesis and limit its degradation in order to mitigate the detrimental effects of A. lucorum-induced stress.

To understand the anthocyanin characteristics of wine grape varieties, the anthocyanin composition and content of 31 wine grape varieties were analyzed to explore the use of anthocyanins as chemical fingerprints to distinguish varieties. Results showed that a total of 21 anthocyanins were detected in the skins, including cyanidin, delphinidin, petunidin, peonidin and malvidin 3-monoglucosides (or 3,5-diglucosides) along with the corresponding acetyl and p-coumaroyl derivatives. The highest and lowest total amount of anthocyanins were detected in ‘Ruby Cabernet’ and ‘Muscat Rouge’, respectively. In the 21 Vitis vinifera grapes, there were 3~11 monoglucoside anthocyanins detected, however, there were 4 to 9 monoglucoside anthocyanins and 1~7 diglucoside anthocyanins detected in the 10 other species of grapes. Except for ‘Zhesexiang’ ‘Seibel Noir’, ‘44-6-7-1’ and ‘Beibinghong’, the contents of diglucoside anthocyanins in the other six varieties accounted for more than 52% of the total anthocyanins. Except for ‘Zhesexiang’, ‘Muscat Rouge’ and ‘Beibinghong’, the content of methylated anthocyanins accounted for more than 75% of total anthocyanins. There were significant differences in the anthocyanin types and contents in the skins among V. vinifera and other grapes. The results of the principal component analysis and the cluster classification of 31 grape varieties (lines) were nearly consistent, which suggested that anthocyanins can be used as chemical fingerprints to distinguish wine grape varieties.

Grape downy mildew is a major grape disease that typically occurs when grape leaves are subjected to high temperature. In this study, downy mildew incidence in ‘Red Globe’ grape was investigated. To clarify the effects of grape downy mildew on grape leaves under high-temperature stress. Grape downy mildew infestation and high-temperature treatment alone or combinations were applied to ‘Red Globe’ grape. The gas exchange and chlorophyll fluorescence parameters of grape leaves were measured. The results showed that logistic growth period of grape downy mildew in the Jinzhong, China was from July 20 to August 10. After the combined stress of high temperature and grape downy mildew, photosynthetic rate (Pn), stomatal conductance (G_s), intercellular carbon dioxide concentration (C_i), maximum photochemical efficiency(Fv/Fm), actual photochemical efficiency(ΦPSII), and performance index on absorption basis (PI_ABS) of grape leaves were all decreased more than the sum of those indexes under the two stresses individually. At 28°C, the damage of downy mildew had no significant effect on the degree of photosystem closure of leaves, but it was significantly increased with the combined stresses. The electron transfer efficiency from photosystem II to photosystem I was decreased significantly under the combined stresses. Under 38°C high-temperature stress, the energy dissipated per active reaction center of the leaves affected by grape downy mildew was significantly increased. High temperature aggravated adverse effects of downy mildew on the structure and function of photosystem II (PSII) of grape leaves and then further exacerbated reduction of photosynthesis caused by heat stress.

Grapes, particularly wine grapes, are one of the most widely cultivated and consumed fruit crops worldwide, serving as a cornerstone of the agricultural economies of many countries and playing a vi...