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Title: POTATO GERMPLASM RESISTANT TO CORKY RINGSPOT DISEASE

Author
item Brown, Charles
item MOJTAHEDI, H - WSU IAREC, PROSSER WA
item SANTO, G - WSU IAREC, PROSSER WA
item HAMM, P - OSU, HERMISTON OR
item PAVEK, J - USDA ARS, RETIRED ID
item Corsini, Dennis
item LOVE, S - UNIV OF IDAHO,ABERDEEN ID
item Crosslin, James
item Thomas, Peter

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/1999
Publication Date: 1/15/2000
Citation: BROWN, C.R., MOJTAHEDI, H., SANTO, G.S., HAMM, P., PAVEK, J.J., CORSINI, D.L., LOVE, S., CROSSLIN, J., THOMAS, P.E. POTATO GERMPLASM RESISTANT TO CORKY RINGSPOT DISEASE. AMERICAN JOURNAL OF POTATO RESEARCH. 77:23-27. 2000.

Interpretive Summary: It costs about 2,400 dollars per acre to grow potatoes in the Columbia Basin. About 300 dollars of this are spent to apply strong pesticidal chemicals to the soil. These chemicals are called soil fumigants. They are designed to reduce or eliminate soil-borne pathogens or pests such as nematodes. Nematodes are microscopic worms that attack plant roots. One kind of nematode is the stubby root nematode. In about ten percent of the field in the Columbia Basin stubby root nematodes transmit a virus into developing potato tubers. The tubers have a strong reaction to this virus and tuber flesh dies and turns brown. This disease is called corky ringspot. Even a slight amount of the brown tissue is considered unacceptable for fresh market or for potatoes that are processed into French Fries or other pre-cooked products. The research reported here describes field screening of diverse breeding clones and varieties of potato and the identification of particular clones that are resistant to corky ringspot. In addition to the identification of resistance, this research presents evidence that the potatoes that resist this disease are resistant to the virus and not the nematode. The nematode reproduces well on all the potato clones and varieties studied. The identification of resistant parents for breeding could lead to the release of corky ringspot resistant varieties in the future. Resistant varieties could facilitate the reduction of the amount of soil fumigant used, a reduction in production costs, and less contamination of the ground water and the environment resulting from use of soil fumigants. It is also likely that green manures or natural plant by-products applied as soil amendments that have nematicidal activity would replace soil fumigants altogether if

Technical Abstract: Potato germplasm was assessed for resistance to corky ringspot disease (CRS) incited by transmission of tobacco rattle virus (TRV). TRV is transmitted by the stubby root nematode, Paratrichodorus allius, in the Pacific Northwest, and characterized by necrotic areas in the tuber. Four tests were conducted at two different problem fields in Umatilla, OR and Pasco, WA. The fields differed in the virulence of the virus isolates. Some clones and named varieties showed resistance only in the field with the relatively mild Umatilla isolate, while others remained symptomless at both sites. The host suitability of test potatoes to three P. allius populations from the region was determined in greenhouse pot tests, and expressed as reproductive values [Rf = (final population of nematode at 55 days)/ (initial population)]. The Rf values for the nematodes were not correlated with resistance ratings based on visual scoring of CRS symptoms in field grown potatoes. Thus, it appears that CRS resistance is based on reaction of potato genotypes to virus and not the vector. The availability of resistant clones in in vitro form is indicated.