Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/19/2003
Publication Date: 4/5/2003
Citation: Smith, B.J. 2003. Susceptibility of southern highbush blueberry cultivars to stem blight. Meeting Abstract pg. 252.
Technical Abstract: Stem blight, caused by the fungus Botryosphaeria dothidea, is a widespread and destructive disease of rabbiteye blueberries (V. ashei Reade) in the southeastern United States. Plants that become infected may die within the first two years of planting. In older plants the initial infection of a stem is usually through a wound. Southern highbush cultivars are being released for production in the coastal plains of the southeastern U. S. because they produce fruit early in the growing season, but little is known about their susceptibility to stem blight and other diseases. Southern highbush cultivars are hybrids between V. corymbosum and various native "southern" blueberry species, for example the cultivar Gulfcoast has a genetic composition of 72% V. corymbosum, 25% V. darrowi, and 3% V. angustifolium. As acreage of southern highbush blueberry cultivars increases, so does the potential threat of losses due to stem blight. The susceptibility of 18 southern highbush cultivars (Biloxi, Bluecrisp, Cooper, Emerald, Georgia Gem, Gulf Coast, Jewel, Jubilee, Magnolia, Misty, O'Neal, Pearl River, Santa Fe, Sapphire, Sharpblue, South Moon, Star, Windsor) to stem blight was compared to that of a highly susceptible rabbiteye cultivar, Tifblue, using a detached stem assay. The inoculum for the study was a fresh isolate of B. dothidea obtained from an infected blueberry plant grown at Poplarville. Succulent, partially-hardened stems (150 mm long) were cut from field grown plants, and all leaves except the terminal three were removed. Each stem was surface disinfected by washing in 10% commercial bleach then rinsing in sterile distilled water. The stem was wounded by scraping away a 2 x 4 mm section of bark and inoculated by enclosing a 2 mm mycelial square cut from a a 14-day-old potato dextrose agar culture of the pathogen against the wound with parafilm. The stem was then inserted into moistened, sterilized sand in a 150 x 25 mm tissue culture tube and incubated at 25 C for 20 days. Relative cultivar susceptibility was determined by measuring lesion length.