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    Evaluation of elite native strawberry germplasm for resistance to anthracnose crown rot disease caused by Colletotrichum species
    (American Society for Horticultural Science, 2007) Lewers, K.S.; Turechek, W.W.; Hokanson, S.C.; Maas, J.L.; Hancock, J.F.; Serçe, S.; Smith, B.J.
    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.
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    Taxonomic variation among North and South American subspecies of Fragaria virginiana Miller and Fragaria chiloensis (L.) Miller
    (2004) Hancock, J.F.; Serçe, S.; Portman, C.M.; Callow, P.W.; Luby, J.J.
    A morphometric comparison was done in the greenhouse of 220 genotypes representing all the American taxa of octoploid strawberries. Only two groups of Fragaria virginiana Miller (Staudt) and Fragaria chiloensis (L.) Miller were well separated in both principle component and cluster analyses: a group composed primarily of F. chiloensis subspecies plus some F. virginiana ssp. glauca (Wats.) Staudt and F. virginiana ssp. platypetala (Rydberg) Staudt and another group composed primarily of F. virginiana ssp. virginiana Duchesne; and F. virginiana ssp. grayana (E. Vilmorin ex Gay) with some F. virginiana ssp. glauca and F. virginiana ssp. platypetala. Among the individual traits examined, only hair orientation reliably distinguished F. chiloensis ssp. lucida (E. Vilmorin ex Gay) from F. chiloensis ssp. pacifica Staudt, and F. virginiana ssp. grayana from F. virginiana ssp. virginiana. Little separation was observed between North and South American F. chiloensis in our principle component and cluster analyses, although these groups did show significant individual discontinuities for a number of traits. Individuals representing the cultivated race of F. chiloensis were in a relatively tight cluster within the scatter of native F. chiloensis. Taken together, these data indicate that F. virginiana and F. chiloensis may be extreme forms of the same biological species and that many of the subspecies designations currently employed in F. virginiana and F. chiloensis should not be recognized. We suggest, however, that there is sufficient morphological and geographical separation to warrant the species designations F. chiloensis and F. virginiana. Fragaria chiloensis ssp. pacifica and Fragaria chiloensis ssp. lucida do not appear to deserve distinct subspecies rank, nor do F. virginiana ssp. virginiana and F. virginiana ssp. grayana. North and South American F. chiloensis are morphologically quite similar, but probably deserve subspecies rank, based on their isolation from each other and the fact that they are evolving separately. Fragaria virginiana ssp. glauca and F. virginiana ssp. platypetala should probably be joined as a single subspecies and retained within F. virginiana until further investigations more definitively determine affinity to other F. virginiana and F. chiloensis subspecies.