Submitted to: Journal Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/1996
Publication Date: N/A
Interpretive Summary: Stem blight is one of the most serious diseases of rabbiteye blueberry. Severe losses result when young plants are infected and die one or two years after planting. Infection of older plants usually results in the loss of several canes; however, mature plants sometimes die. There is no chemical control for this disease. Cultural controls, such as pruning out infected canes, are often not effective. Resistant cultivars are needed; however, procedures for screening blueberry germplasm for resistance are often time-consuming and expensive. The laboratory procedures described in this paper can be used by plant geneticists to rapidly screen large numbers of blueberry seedlings for resistance without sacrificing the entire plants and without fear of introducing new strains of the pathogen into the environment. The procedures can easily be adapted by plant pathologists to evaluate chemicals for control of this disease and to evaluate cultivars for resistance.
Technical Abstract: The susceptibility of five rabbiteye blueberry cultivars to stem blight (Botryosphaeria dothidea) was compared using field, greenhouse and laboratory inoculations. In each test, succulent, partially-hardened stems were wounded by scraping away a 2 x 4 mm section of bark 50 mm from the tip of the stem and inoculated by securing against the wound a 2 mm mycelial square cut from a 14-day-old potato dextrose agar culture of the pathogen. For the detached stem assay, 150 mm shoots were cut from the plants, and all leaves except the terminal three were removed. The stem was inoculated, inserted into moistened, sterilized sand in a 150 x 25 mm tissue culture tube, and incubated at 20 C. In each test there were significant differences in lesion length among cultivars 20 days after inoculation. Relative cultivar susceptibility was similar in each assay procedure with 'Tifblue' being the most susceptible of the cultivars tested. The detached stem assay can be used in a breeding program to efficiently identify resistant genotypes.