Genome-Wide Identification and Expression Analysis of the WAK Family in Vitis davidii Reveals VdWAK19 Confers Resistance to Grape Ripe Rot

Grapes are among the most widely cultivated fruit crops globally, yet their growth and yield are severely compromised by Colletotrichum viniferum, which causes a devastating disease that affects grape berries. The wall-associated kinase (WAK) gene family, a unique subfamily of receptor-like-kinases (RLKs), plays important roles in mediating plant responses to both abiotic and biotic stresses. However, the expression patterns and biological functions of grape WAKs in response to C. viniferum infection remain largely uncharacterized. In this study, a total of 57 VdWAK genes were identified and phylogenetically classified into twelve subgroups. Chromosomal localization and collinearity analyses further revealed that tandem duplication and segmental duplication events contributed to the expansion of the VdWAK gene family. Transcriptomic profiling identified VdWAK19 as a key responsive gene. It was predominantly expressed in mature berries but transcriptionally repressed upon C. viniferum infection. Virus-induced gene silencing assays in grape berries demonstrated that knockdown of VdWAK19 significantly reduced fruit resistance to C. viniferum infection. Overall, these findings advance our understanding of the functional roles of VdWAK genes during C. viniferum infection and provide a theoretical basis for the potential application of VdWAK19 in breeding grape varieties with enhanced resistance to ripe rot.