Resistance of Strawberry Cultivars and the Effects of Plant Ontogenesis on and Causing Crown Rot.

Phytophthora crown rot (PhCR) is an important disease of strawberry worldwide. is the most common causal agent, however, was also recently reported causing PhCR in the U.S. Therefore, the goals of this study were to evaluate the resistance of strawberry cultivars from Florida and California, and to study the etiology of the two species causing PhCR. Sixteen strawberry cultivars were evaluated over three Florida seasons for susceptibility to , and . Inoculations at different days after transplanting (DAT) were also carried out to evaluate the ability of both species to cause PhCR at different phenological stages of the plant. Plant wilting and mortality were assessed weekly, and disease incidence, and the area under the disease progress curve were calculated. Cultivars Sensation 'Florida127', 'Winterstar FL 05-107', and 'Florida Radiance' were susceptible, whereas 'Florida Elyana', 'Camarosa', 'Fronteras', 'Sweet Charlie', and 'Strawberry Festival' were highly resistant to both species. However, some cultivars exhibited stronger resistance to one species over the other. caused more PhCR when plants were inoculated at transplanting, 45, and 60 DAT, whereas only caused disease when inoculated at transplanting. These results emphasize the importance of screening for disease resistance to guide management recommendations in commercial strawberry production as well as the need for proper pathogen identification since cultivar susceptibility might differ. Varying susceptibility to and at different growth stages emphasizes the importance of considering both plant and pathogen biology when making management recommendations.