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Title: Partial Resistance to Potato Black Dot, Caused by Colletotrichum coccodes in Solanum tuberosum Group Andigena

item NITZAN, NADAV - Washington State University
item Quick, Rich
item Hutson, Will
item Bamberg, John
item Brown, Charles

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2010
Publication Date: 7/20/2010
Citation: Nitzan, N., Quick, R.A., Hutson, W.D., Bamberg, J.B., Brown, C.R. 2010. Partial Resistance to Potato Black Dot, Caused by Colletotrichum coccodes in Solanum tuberosum Group Andigena. American Journal of Potato Research. 87:502-508.

Interpretive Summary: The fungus Black Dot attacks the potato causing yield losses and blemishes on the tubers. It can be brought into the field as a contaminant on seed potatoes, but also lasts many years in the soil. Fungicide treatments are not effective enough and are too costly. Hence producing new varieties with greater resistance is the best option. In the geographic zone of origin of the potato, the Andes Mountains of South America, the most important, widespread and most productive potato type is called the Group Andigena. They are comprised by several thousand varieties of landraces grown by indigenous farmers mostly in the very high elevations above 3,000 meter above sea level. Collections of this type of potato are maintained in Sturgeon Bay, WI. For the purposes of this study forty accessions were selected from throughout the range of distribution. It was found in the end that three accessions demonstrated levels of resistance to black dot significantly greater than the standard cultivars grown in the Pacific Northwest . Incorporation of this level of resistance into new varieites could prevent yield losses of up to 25 per cent.

Technical Abstract: Black dot is caused by the fungus Colletotrichum coccodes (Wallr.) S.J. Hughes. The disease is prevalent in potato fields and can be of economic concern by itself, or as a part of the potato early dying syndrome. Little is known about resistance to this disease. In the present study resistance to potato black dot was tested in Solanum tuberosum Group Andigena. Forty accessions were chosen randomly from the core collection and screened. The accessions originated from Peru, Mexico, Bolivia, Columbia, Ecuador, Argentina and Costa Rica. Five accessions had less (P=0.05) disease on roots and stems than a set of commercial standards. These accessions were: PIs 189473, 230475, 161683, 243367 and 230470. They were retested to validate their partial resistance. Fifteen plants, each a unique genotype, were selected from each accession and were propagated into multiple clones that were inoculated with the pathogen. Three genotypes were identified with less (P=0.05) disease on roots and stems than the industry standard. These genotypes originated from the accessions PI-243367 and PI-230475. Clones of the resistant genotypes were added to the potato germplasm collection located at the Potato Improvement Laboratory of the USDA-ARS near Prosser, WA, to be used in the development of black dot resistant commercial varieties.