Relationship Between Grape Berry Epidermis and Cuticle Thickness and Resistance to Grape Ripe Rot

ABSTRACT

Vitis vinifera grapevine varieties are widely cultivated worldwide and are essential for viticulture. However, these varieties are susceptible to fungal diseases, such as grape ripe rot (GRR), which is incited by Colletotrichum spp. and causes major production losses in warm and humid climates. Among plant defence mechanisms against pathogens, structural barriers may make it difficult for pathogens to penetrate plant tissues. The present study aimed to evaluate the association with GRR severity of berry epidermal layer and cuticle thickness of different varieties of grapevine. Grape berry samples of 12 varieties were collected during the 2020/2021, 2021/2022 and 2022/2023 growing seasons and prepared for analysis of the epidermis and cuticle by scanning electron microscopy. The grapes were inoculated with conidia of an isolate from the Colletotrichum acutatum complex and monitored for 10 days. GRR severity was measured and analysed using generalized linear models. In addition, path correlation analysis between the thickness of the cell barriers and the severity of the disease was carried out. The results showed significant variations in berry cuticle and epidermis thickness among varieties and growing seasons. Cuticular and epidermal thickness and incubation period together explained 31.0% to 39.8% of the variation in disease severity. While PI4407, ‘Seibel 1077’ and ‘Sibera’ varieties showed greater cuticular and epidermal thickness as well as greater GRR resistance, ‘Bronner’ and ‘Sauvignon Blanc,’ with thinner cuticular and epidermal layers, were more susceptible to GRR.