Identification of New Sources of Resistance to Black Rot in a Collection of Vitis Species.

Black rot caused by Phyllosticta ampelicida is a notable example of a recent re-emerging disease of grapevine (Vitis vinifera). The pathogen infects young, actively growing plant parts and it may have a large effect on yield even at low incidence. A strategy to control grapevine black rot is to develop resistant varieties through breeding programs aimed at introducing the resistance into the susceptible V. vinifera. However, a complete picture of the existing sources for resistance in the Vitis species is missing. In this work, we evaluate a collection of Vitis species for resistance to black rot in the vineyard in natural conditions of infection over a three-year period and validate the results using a bio-assay for the evaluation of resistance in semi-controlled conditions. Our results confirmed the resistance to black rot previously reported for several species and identified new sources of resistance. The majority of the species identified as resistant come from America, while almost all species of Asian origin are susceptible. Because they displayed strong resistance, under field conditions and after artificial inoculation, the new sources of resistance reported here have a high potential to be used in future breeding programs.