WATER RELATIONS OF VARIOUS PEACH CULTIVARS IN RELATION TO PEACH CANKER DISEASE

Whole-shoot water potential, osmotic potential of the xylem fluid, and bark water potential were examined from late winter through early spring for six peach [Prunus persica (L.) Batsch.] cultivars varying in relative susceptibility to Leucostoma canker. There were significant differences among cultivars for whole-shoot water potential on all 11 dates tested in 1986, but not in 1985. The date effect was not consistent among cultivars, although when averaged across dates, the whole-shoot water potential of 'Loring' was significantly more negative than that of 'Candor' or 'Garnet Beauty'. There were significant differences among cultivars for xylem fluid osmotic potential on one of five dates tested in 1985 and three of 11 dates tested in 1986, although cultivar differences were not consistent between years. Cultivars exhibited differences in bark water potential on three of five dates tested in 1985, with 'Loring' exhibiting the least negative values when averaged across dates. There were only occasional significant correlations of the water status characteristics with relative susceptibility to Leucostoma canker or suberin accumulation. Measurements of plant water status among cultivars or genotypes in peach do not appear to be reliable indicators of susceptibility to Leucostoma spp. or wound response.