Evaluation location: Idaho, United States
Thirty Plant Introductions (PIs) from the USDA-ARS National Plant Germplasm System (NPGS) (Garden Beet, Sugar Beet, Leaf Beet, Fodder Beet, and wild beet) were evaluated for resistance to the Beet curly top virus in an artificially inoculated nursery, managed by the Beet Sugar Development Foundation (BSDF) in Kimberly, ID. The field was planted on 11 through 12 June.
Planting was late to maximize the number of viruliferous leafhoppers available to transfer to the sugarbeets while they are in the 8-to 10-leaf stage. Plots were 12 ft long, two-rows with 22 in between rows and replicated twice. After the beets emerged, plots were trimmed to 8 ft long, thinned to one foot between beets, and cultivated. Viruliferous leafhoppers were released on 15 and 16 July to cause an artificial epiphytotic. One week before the leafhoppers were released in the nursery, they had been transferred onto curly top-infested beets to assure that they were viruliferous when placed in the field. Uniform infection was achieved by placing leaf hoppers uniformly throughout the field at a rate of approximately 1 leafhopper per plant, and then spreading the leafhoppers daily for the next week by dragging a 12-foot tarp across the field. Plants were sprayed on 23 August to kill the leafhoppers. Plots were visually evaluated and rated on a Disease Index (DI) scale of 0 to 9 (no symptoms to dead) on September 10. Leafhopper release was late, and the summer was hot and dry, and the epiphytotic was moderate.