INFLUENCE OF ROOTSTOCK ON THE RESPONSE OF SEYVAL GRAPEVINES TO FLOODING STRESS

St. George, Couderc 3309, Riparia Gloire, Kober 5BB, Seyval, and Cynth iana vines were subjected to soil flooding under greenhouse conditions . The rate of shoot elongation (RSE), net CO2 assimilation rate (A), s tomatal conductance (g(s)), transpiration (E), and water use efficienc y (WUE) were measured at one to four day intervals as an estimate of s ensitivity to flooded conditions. In general, RSE was the most sensiti ve and WUE the least sensitive parameter to flooding. St. George, Coud erc 3309, and Riparia Gloire were the most tolerant cultivars, while K ober 5BB, Seyval, and Cynthiana were the most susceptible cultivars to flooding. Symptoms of flooding were desiccation of the shoot apex, fl agging of leaves, necrotic areas on leaves, senescence of basal leaves and regeneration of roots near the water surface. The effect of roots tock on flooding tolerance of a susceptible scion was measured during an eight-day flooding period. Treatments were own-rooted Seyval and Se yval grafted on Seyval, Couderc 3309, and St. George. Flooding toleran ce of Seyval was increased slightly by grafting onto Couderc 3309.