ARS | Publication request: Species Identification and Variation in the North American Cranberry Fruit Rot complex

Submitted to: International Society for Horticultural Science Meeting
Publication Type: Proceedings
Publication Acceptance Date: February 8, 2008
Publication Date: March 1, 2009
Citation: Polashock, J.J., Caruso, F.L., Oudemans, P.V., Mcmanus, P., Constanelos, C., Crouch, J. 2009. Species identification and variation in the North American cranberry fruit rot complex. In: Proceedings of the International Society for Horticultural Science 9th International Vaccinium Symposium, July 13-16, 2008, Corvallis, Oregon. p. 395-399.

Technical Abstract: Complex mixtures of pathogenic fungi cause cranberry fruit rot, with the contribution by any given fungus to the disease varying from bed to bed, cultivar to cultivar, season to season, and across regions. Furthermore, population variability within the individual fungal species across growing regions is unknown. This fundamental uncertainty about pathogen diversity makes the recommendation and implementation of effective control measures unpredictable. Because cranberry vines are shipped long distances between growing regions we hypothesized that a concurrent migration of fungi might have a homogenizing effect upon cranberry fruit rot pathogen populations, resulting in a convergence of genotypes across North America. To test this theory, we assessed the morphological and genetic variation of the five major cranberry fruit rot pathogens: Phyllosticta vaccinii, Coleophoma empetri, Colletotrichum acutatum, Colletotrichum gloeosporioides, and Physalospora vaccinii. Representative samples of each species were isolated from rotted cranberry fruit in the major growing areas of NJ, MA, WI, and British Columbia (BC). In general, fungal morphological characteristics were similar across all sample sites. However, atypical non-pigmented cultures of Phys. vaccinii and C. acutatum were isolated. Molecular analysis of ribosomal ITS sequence data showed a low level of variability (98-100% nucleotide similarity) for most of the pathogen species, with the exception of the morphologically distinct isolates. Phylogenetic analysis of the ITS sequence showed that the atypical, non-chromogenic C. acutatum formed a distinct, but closely related clade, to the normal pink-pigmented isolates. In contrast, the atypical white Phys. vaccinii strains possessed an entirely distinct ITS sequence from the morphologically standard strains suggesting that the white isolates are a different species.