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ARS Home » Northeast Area » Kearneysville, West Virginia » Appalachian Fruit Research Laboratory » Innovative Fruit Production, Improvement, and Protection » Research » Publications at this Location » Publication #309069
Title: Black knot [Apiosporina morbosa (Schw.)] resistance in imported and domestic Prunus domestica L. germplasm and cultivars

Author
item Scorza, Ralph
item Demuth, Mark

Submitted to: Journal of the American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2014
Publication Date: 1/20/2015
Citation: Scorza, R., Demuth, M.A. 2015. Black knot [Apiosporina morbosa (Schw.)] resistance in imported and domestic Prunus domestica L. germplasm and cultivars. Journal of American Pomological Society. 69(1):45-50.

Interpretive Summary: Black knot is a fungus disease of wild, ornamental, and edible plum and cherry trees that is particularly important in the northern and eastern U.S., and eastern Canada. The disease produces black “knots” on tree branches that spread and cause fruit losses, stunted growth, and eventual tree decline. The disease is difficult to control and requires the application of fungicides and pruning-off of infected branches. There are few black knot resistant edible plum varieties. We tested the resistance to black knot of 43 plum varieties including 23 plant import selections that are part of the U.S. National Plant Germplasm System (NPGS) http://www.ars-grin.gov/npgs/. We found that many of the NPGS accessions and some named varieties including several released by the breeding program at USDA-ARS Appalachian Fruit Research Station are highly resistant to black knot. This study provides information to growers in selecting plum varieties to grow in areas where black knot is a problem and identifies important NPGS genetic resources for breeders to use as parents in developing new black knot resistant plum varieties.

Technical Abstract: Black knot (BK) Apisporina morbosa (Schw.) is an important fungal disease of Prunus domestica and other Prunus species in North America. BK causes economic losses in the plum growing regions of northern and eastern U.S. and eastern Canada. Relatively few P. domestica commercial cultivars are resistant to BK. Evaluation of resistance to BK in P. domestica plums was carried out over four years including an evaluation of infection of new shoot growth following pruning. The 43 genotypes evaluated included 23 accessions from the U.S. National Plant Germplasm System (NPGS), and cultivars and selections from the U.S., Canada, and Europe. Based on the evaluations, genotypes were classified as highly resistant, moderately resistant, susceptible, and highly susceptible. Highly resistant genotypes, without visible symptoms made up 42 percent of the germplasm evaluated, and of these, 67 percent were accessions from the US NPGS collection. While the inheritance of resistance remains to be determined, these evaluations indicate that sources of high level resistance are available in P. domestica that can be utilized in breeding highly resistant commercial cultivars.