The Ph-3 gene from Solanum pimpinellifolium encodes CC-NBS-LRR protein conferring resistance to Phytophthora infestans.
Key message
Ph-3is the first cloned tomato gene for resistance to late blight and encodes a CC-NBS-LRR protein.
Abstract
Late blight, caused by
Phytophthora infestans, is one of the most destructive diseases in tomato. The resistance (
R) gene
Ph-
3, derived from
Solanum pimpinellifolium L3708, provides resistance to multiple
P. infestans isolates and has been widely used in tomato breeding programmes. In our previous study,
Ph-
3 was mapped into a region harbouring
R gene analogues (RGA) at the distal part of long arm of chromosome 9. To further narrow down the
Ph-
3 interval, more recombinants were identified using the flanking markers G2-4 and M8-2, which defined the
Ph-
3 gene to a 26 kb region according to the Heinz1706 reference genome. To clone the
Ph-
3 gene, a bacterial artificial chromosome (BAC) library was constructed using L3708 and one BAC clone B25E21 containing the
Ph-
3 region was identified. The sequence of the BAC clone B25E21 showed that only one RGA was present in the target region. A subsequent complementation analysis demonstrated that this RGA, encoding a CC-NBS-LRR protein, was able to complement the susceptible phenotype in cultivar Moneymaker. Thus this RGA was considered the
Ph-
3 gene. The predicted Ph-3 protein shares high amino acid identity with the chromosome-9-derived potato resistance proteins against
P. infestans (Rpi proteins).