Submitted to: American Journal of Potato Research
Publication Type: Abstract only
Publication Acceptance Date: 7/23/2006
Publication Date: 1/1/2007
Citation: Porter, L.D., Miller, J.S., Atallah, Z., and Stevenson, W. 2007. Crop and weed hosts of the pink rot pathogen. American Journal of Potato Research 84: 111-112. Interpretive Summary:
Technical Abstract: Phytophthora erythroseptica (Pe), cause of pink rot of potato, is known to infect at least 31 different host plants. Wheat and barley are two of these reported hosts that are grown almost exclusively in rotation with potato in eastern Idaho. Additionally, wheat,barley, and seed of other crops found in potato rotations are often treated with metalaxyl based treatments. Metalaxyl/mefenoxam insensitivity in some Pe populations has led some to question if metalaxyl based seed treatments contribute to the selection of mefenoxam-insensitive isolates of Pe found in potato rotations. The objectives of this study were to confirm the host status of small grains and other crops and weeds as hosts for Pe, and to determine if metalaxyl seed treatments could lead to the development of mefenoxam insensitivity in Pe. A total of 30 crops and weeds were sampled from agricultural fields in the growing season of 2005 and assayed for the presence of Pe using both a Pe semi-selective medium and PCR primer.. These same plants were grown in the greenhouse and evaluated for root infection by artificial inoculation. Pe was isolated from wheat and barley roots from growers’ fields. Hairy nightshade, kochia, tomato, and bell pepper werenotable hosts based on greenhouse inoculations. Infection of inoculated barley plants was confirmed using PCR. Notable non-hosts included sugarbeet, field corn, sweet corn, alfalfa, and onion. Roots grown from barley seed (cv. Harrington) treated with metalaxyl (2 g a.i./100 kg seed) were analyzed for metalaxyl content at 7 and 14 days after planting. Metalaxyl could not be detected at a threshold of 0.014 ug/g root tissue. Therefore,metalaxyl seed treatments of these crops do not appear to put significant selection pressure on the Pe population.