Evaluation location: Idaho, United States
Thirty sugar beet (Beta vulgaris L.) Plant Introduction (PI) Lines from the USDA-ARS National Plant Germplasm System were screened for resistance to Beet severe curly top virus (BSCTV) and closely related Curtovirus species in 2013. The curly top evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID which has Portneuf silt loam soil and had been in alfalfa in 2012. The field was plowed in the fall and in the spring, it was fertilized (90 lb N and 110 lb P2O5/A) on 19 Apr 13, sprayed with Ethotron (2 pt/A) for weed control, and roller harrowed. The germplasm was planted (density of 142,560 seeds/A) on 20 May. The plots were two rows 10 ft long with 22-in row spacing and arranged in a randomized complete block design with three replications. The fields were sprinkler irrigated and hand weeded as necessary. Plant populations were thinned to about 23,760 plants/A on 14 June. Plants were inoculated at the four- to six-leaf growth stage on 27 June with approximately six viruliferous beet leafhoppers per plant. The beet leafhoppers were redistributed twice a day (immediately after sunrise and just before sunset) for one week by dragging a tarp through the field to disrupt settled/feeding leafhoppers. The plants were sprayed with Lorsban 4E (1.5 pints/A) on 2 July to kill the beet leafhoppers. The plots were rated for foliar symptom development on 16 July using a scale of 0-9 (0 = healthy and 9 = dead). Curly top symptom development was uniform and no other disease problems were evident in the plot area. The disease pressure in the test was moderately severe with good symptom development in the susceptible check.