Cytological and metabolic mechanisms underlying grapevine resistance to Coniella vitis

Grape white rot caused by Coniella species is one of the most serious fungal diseases of grape, leading to yield losses and quality reduction. Utilizing or breeding white rot-resistant grapevine is an important disease management strategy. This study evaluated the Coniella vitis resistance of 53 grape genotypes from 13 grape species and two interspecific hybrids. Most genotypes were susceptible, and disease resistance did not depend on grape species. No correlation was found between the C. vitis resistance of grape fruit and leaves. The resistant genotype 'Shine Muscat' and susceptible genotype 'Manicure Finger' were selected for cytological and metabolic studies. Compared with the susceptible genotype 'Manicure Finger,' the resistant genotype 'Shine Muscat' exhibited lower conidial germination rates and fewer infective hyphae in its leaf and berry tissues after inoculation with C. vitis as revealed by microscopy observation. After inoculation with C. vitis, the susceptible grape genotype showed higher H₂O₂ content in its leaf and berry tissues than the resistant grape genotype. Polyphenolic metabolites substantially accumulated in the berries of the susceptible genotype 'Manicure Finger.' Protocatechuic acid, catechin, epicatechin, and hyperoside significantly inhibited the conidial germination of C. vitis in a concentration-independent manner and exhibited a significant control effect on the white rot in grape leaves and berries. The findings of this work lay the foundation for breeding C. vitis-resistant grapes and enhance the understanding of the defense responses to C. vitis in different grape varieties.