Identification and Functional Analysis of the Ph-2 Gene Conferring Resistance to Late Blight ( Phytophthora infestans ) in Tomato

Late blight is a destructive disease affecting tomato production. The identification and characterization of resistance (R) genes are critical for the breeding of late blight-resistant cultivars. The incompletely dominant gene confers resistance against the race T of in tomatoes. Herein, we identified ( ) as a candidate gene for through the analysis of sequences and post-inoculation expression levels of genes located within the fine mapping interval. The was subsequently validated to be a gene through targeted knockout and complementation analyses. It encodes a CC-NBS-LRR disease resistance protein, and transient expression assays conducted in the leaves of indicate that is predominantly localized within the nucleus. In comparison to its susceptible allele ( ), the transient expression of can elicit hypersensitive responses (HR) in , and subsequent investigations indicate that the structural integrity of the protein is likely a requirement for inducing HR in this species. Furthermore, ethylene and salicylic acid hormonal signaling pathways may mediate the transmission of the resistance signal, with - and HR-related genes potentially involved in the -mediated resistance. Our results could provide a theoretical foundation for the molecular breeding of tomato varieties resistant to late blight and offer valuable insights into elucidating the interaction mechanism between tomatoes and .