We screened 108 cultivars of grapevine (Vitis spp.) for resistance to grape ripe rot, caused by Colletotrichum acutatum and C. gloeosporioides. We evaluated the resistance to ripe rot of berries and vine leaves from grape cultivars by measuring the lesion size after inoculation with C. acutatum and C. gloeosporioides. ‘Aki Queen’ (Table grape) and ‘Cabernet Sauvignon’ (Wine grape) were shown to be moderate resistant against inoculation of C. acutatum both in berries and leaves. ‘Emperatriz’, ‘Honey Red’, ‘Honey Venus’, ‘Izumo Queen’, and ‘Rosario Rosso’ in table grapes, and ‘Cabernet Sauvignon’, ‘Chancellor’, ‘Chardonnay Decoupe’, and ‘Ventura’ in wine grapes, were shown to be resistant to C. gloeosporioides both in berries and leaves of them. Grape cultivars were classified into four classes based on its level of resistance to C. acutatum and C. gloeosporioides. The present data for determining ripe rot resistance will be very useful in developing effective disease management strategies in the vineyards and selecting grape genetic resources to be used in disease resistant grape breeding programs.

It is necessary to evaluate the resistance to disease among genetic resources for development of disease resistant grapes. This study was conducted to screen the resistance to crown gall in muscadine and Florida hybrid bunch grapes by pathogen inoculation. In order to compare the responses to infection with different pathogen strains, muscadine and Florida hybrid grapes were inoculated with 3 strains of Agrobacterium vitis. Although there were different levels crown gall formation among grape cultivars, there little variation in response to inoculated strains. Among 29 muscadine cultivars tested by inoculation of A. vitis ‘C4612’, most of them were shown to be susceptible, and ‘Gold Isle’ and ‘Africa Queen’ were highly susceptible, and two cultivars, ‘Welder’ and ‘Jumbo’ were found to be resistant to crown gall disease. Among Florida hybrid grapes, ‘Daytona’, ‘Stover’, and ‘Swanee’ were susceptible and ‘Blanc du Bois’ was moderately susceptible to crown gall. Because muscadine grapes have been actively utilized as useful genetic resources for development of new grape varieties by intersub-genus cross, this result from the screening of resistance among muscadine grapes can provide valuable information in breeding programs of grape resistant to crown gall.