Ornamental cherry tolerance of flooding and Phytophthora root rot

Abstract

Seedlings of eight Prunus taxa were evaluated for variation in susceptibility to a single, 4- or 5-day flooding period and root rot caused by Phytophthora cryptogea Pethybr. and Lafferty. Survival, plant defoliation, disease severity index, root necrosis, and net photosynthesis indicated that the combination of flooding and pathogen was significantly more severe to all taxa than either individual treatment. Most response variables reflected early plant dysfunction but were not correlated with long-term survival. Long-term survival was 70% in the combination treatment compared to 99% in the control group. Flooding injured seedlings more than the pathogen in most taxa. Taxa differed only slightly in tolerance to the treatments, as measured by survival rate. Prunus takesimensis Nakai had the highest survival rate of 100% and along with P. mahaleb L. and P. yedoensis Matsum, showed some tolerance to flooding and the pathogen. Prunus sargentii Rehd, had the lowest survival rate of 81% and appeared to be least tolerant to the pathogen.