Evaluation of elite native strawberry germplasm for resistance to anthracnose crown rot disease caused by Colletotrichum species

Anthracnose crown rot of cultivated strawberry (Fragaria xananassa Duchesne ex Rozier) has been a major disease problem in the strawberry producing regions of the southeastern United States since the early 1970s. Chemical controls are often inadequate, but use of resistant cultivars is seen as a credible option for managing this disease. Only a small portion of Fragaria L. germplasm has been screened for resistance to anthracnose crown rot. A core subset of the Fragaria collection maintained at the U.S. Department of Agriculture National Clonal Repository in Corvallis, OR, has been constructed to contain an elite group of native F. virginiana Mill. and F. chiloensis (L.) Mill. This collection, referred to as the "core collection," has been characterized for many horticultural traits, including reactions to several common foliar diseases, resistance to black root rot (causal organisms unknown), and resistance to northern root-knot nematode (Meloidogyne hapla Chitwood) and root-lesion nematode [Pratylenchus penetrans (Cobb) Filipjev & Shuurmans Stekhoven]. Our objective was to evaluate the core collection for resistance to a selection of isolates of three Colletotrichum Corda species known to cause strawberry anthracnose, Colletotrichum fragariae A.N. Brooks, Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. [teleomorph Glomerella cingulata (Stoneman) Spauld. & H. Schrenk], and Colletotrichum acutatum J.H. Simmonds (teleomorph Glomerella acutata J.C. Guerber & J.C. Correll). No Fragaria subspecies or geomorph was more resistant than any other; rather, individual genotypes within these groups were identified as sources from which resistance can be obtained. Collecting germplasm in areas of intense disease pressure may not be as beneficial as one might assume, at least where anthracnose crown rot disease is concerned.