A 5′-end based Molecular Marker Enables Identification and Deployment of a Functional Rpi-vnt1.1 Allele for Durable Late Blight Resistance in Potato

Potato (Solanum tuberosum) is a globally important food crop, yet its production is severely threatened by late blight, caused by Phytophthora infestans. Deploying resistance (R) genes in breeding programs offers a sustainable approach for disease management. Rpi-vnt1.1 is a broad-spectrum R gene cloned from wild Solanum species Solanum venturii. Here, we developed a PCR marker targeting the 5′-end extension of Rpi-vnt1.1, which enables efficient and specific detection of the resistant alleles. Screening of advanced breeding lines from the International Potato Center (CIP) identified line C1848, which carries a functional Rpi-vnt1.1 allele. Inoculation assays confirmed C1848 confers strong resistance to P. infestans. Subsequent functional assays, including RNAi-mediated silencing in C1848 and heterologous expression in Nicotiana benthamiana, demonstrated that this resistance is specifically mediated by the Rpi-vnt1.1 allele. This specific marker provides a rapid, low-cost tool for marker-assisted breeding, facilitating the deployment of potato cultivars carrying Rpi-vnt1.1.