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Title: Genetic Diversity of Sclerotinia species from Alaskan Vegetable Crops

Author
item WINTON, LORETTA
item LEINER, R - UAF
item KROHN, ANDREW

Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2006
Publication Date: 7/20/2006
Citation: Winton, L.M., Leiner, R.H., Krohn, A.L. 2006. Genetic Diversity of Sclerotinia species from Alaskan Vegetable Crops. Canadian Journal of Plant Pathology 28(3):426-434.

Interpretive Summary: White mold diseases are prevalent and poorly managed on vegetable crops in the Matanuska Valley, the main agricultural region of Alaska. Prior research on Sclerotinia sclerotiorum, the primary white mold pathogen throughout the world, has shown it to be predominantly clonal in cool temperate regions, while sexual recombination contributes to the population structure in milder climates. We examined the population structure of the fungus in the boreal forest region of Alaska to determine whether the trend towards clonality holds up at more extreme latitudes. DNA markers revealed that S. sclerotiorum populations in Alaska are predominantly, if not exclusively, comprised of non-recombining clonal lineages. Surprisingly, many diseased plants were found to be infected by the unnamed and closely related Sclerotinia “species 1”, previously found on wild plants from Norway. In some fields “species 1” was the only pathogen involved in disease. However, white mold in most fields was caused by both “species 1” and S. sclerotiorum together. The results of this study are important to vegetable growers in Alaska because efforts to develop management strategies to control white mold in Alaska must account for both of the species involved in this disease complex. These results will also be of interest to plant pathologists and mycologists interested in fungal population biology in natural and managed systems.

Technical Abstract: White mold diseases are prevalent and poorly managed on vegetable crops in the Matanuska Valley, the main agricultural region of Alaska. Prior research on Sclerotinia sclerotiorum, the primary white mold pathogen throughout the world, has shown it to be predominantly clonal in cool temperate regions, while sexual recombination contributes to the population structure in milder climates. We examined the population structure of the fungus in the boreal forest region of Alaska to determine whether the trend towards clonality holds up at more extreme latitudes. Microsatellite and ribosomal DNA markers revealed that S. sclerotiorum populations in Alaska are predominantly, if not exclusively, comprised of non-recombining clonal lineages. Surprisingly, many diseased plants were found to be infected by the cryptic Sclerotinia sp. 1, previously found on wild plants from Norway. In some fields Sclerotinia sp. 1 was the only pathogen involved in disease. However, white mold in most fields was caused by both Sclerotinia sp. 1 and S. sclerotiorum in sympatry.