Leaf disk infection by Colletotrichum acutatum and its relation to fruit rot in diverse blueberry germplasm

Response to foliar infection by Colletotrichum acutatum Simmonds ex Simmonds was assayed in a diverse group of 149 blueberry cultivars and selections using a detached leaf-disk assay. Disks were inoculated and incubated for one week, then were digitally imaged, and images analyzed for percent leaf decay. Infection percentages across cultivars averaged 32%, and ranged from 8% to 79%. The lowest levels of foliar infection were seen in the cultivars, Burlington, Sharpblue, and Berkeley. Foliar responses were compared to anthracnose fruit-rot susceptibility data from a previous study. Several clones were observed to have low levels of both foliar and fruit infection. Cultivars with particularly good resistance to both phases included 'Sharpblue', 'Sunshine Blue', 'Legacy', 'Little Giant', 'Flordablue', 'Elliott', 'Blue Ridge', 'Blue Rose', and 'November Glow'. Little correlation was observed between foliar response and fruit response to anthracnose infection (r = 0.15). Since C acutatum overwinters primarily in vegetative tissue, breeding new cultivars with foliar resistance may assist in reducing inoculum levels of this disease under field conditions.