Submitted to: Proceedings Washington State Potato Conference
Publication Type: Proceedings
Publication Acceptance Date: March 15, 2007
Publication Date: July 26, 2007
Citation: Munyaneza, J.E., Crosslin, J. 2007. Assessing the Impact of Purple Top Disease Pathogen on Potatoes in the Columbia Basin. Proceedings Washington State Potato Conference. pp. 75-80. Interpretive Summary: Since 2002, Columbia Basin potato growers in Washington and Oregon have experienced serious outbreaks of potato purple top disease that caused significant yield losses and reduction in tuber processing quality. Researchers from USDA-ARS Wapato and Prosser, WA, conducted studies to assess the impact of this disease on potato in the Columbia Basin. It was found that most of the potato cultivars grown in the Columbia Basin are susceptible to the disease and that younger potato plants are more vulnerable to the disease. Also, no differences in fry color were observed between tubers from infected and healthy potato plants, immediately after harvest and after 90 days in storage. Information from the present study will help growers in the Columbia Basin make effective management decisions to reduce losses to potatoes due to this disease by protecting susceptible varieties and younger potato plants against insect vectors of this potato disease.
Technical Abstract: Since 2002, Columbia Basin potato growers in Washington and Oregon have experienced serious outbreaks of potato purple top disease that caused significant yield losses and a reduction in tuber quality. The beet leafhopper-transmitted virescence agent (BLTVA) phytoplasma is the causal agent of the disease in the Columbia Basin and this pathogen is transmitted by the beet leafhopper. To increase the understanding of the impact of this potato disease in the Columbia Basin, the following objectives were addressed: 1) assess the susceptibility of important potato cultivars grown in the Columbia Basin to the BLTVA phytoplasma and purple top disease under field conditions; 2) assess the impact of the phytoplasma and purple top on tuber quality in different potato cultivars under field conditions; 3) determine susceptibility of different potato plant growth stages to the phytoplasma under laboratory and field conditions; 4) determine the incidence of the phytoplasma in beet leafhoppers collected from potatoes throughout the growing season; and 5) test selected weeds and other crop plants for presence of the phytoplasma, to determine the potential source of this pathogen. Results showed that most of the potato cultivars grown in the Columbia Basin are susceptible to the purple top phytoplasma; however, Russet Burbank appears resistant to or tolerant of this plant pathogen. Younger potato plants seem more vulnerable to the phytoplasma. BLTVA is effectively transmitted to daughter tubers at a very high rate. No differences in fry color between tubers from BLTVA infected and healthy potato plants were observed immediately after harvest and after 90 days in storage. A high proportion of beet leafhoppers in potatoes and nearby weeds were found to carry the BLTVA phytoplasma throughout the whole season. The BLTVA phytoplasma was detected for the first time in Russian thistle samples collected in the field late in the season.