SUGARBEET.CURLYTOP.2018.STRAUSBAUGH

Thirty sugar beet (Beta vulgaris L.) Plant Introduction (PI) Lines from the USDA-ARS National Plant Germplasm System (NPGS) and three commercial check cultivars [SV2012RR (susceptible), Detroit Dark Red (susceptible), and HM PM90 (resistant)] were screened for resistance to Beet curly top virus (BCTV). 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 barley in 2017. In the spring, the field was plowed and then fertilized (60 lb N and 110 lb P2O5/A) and roller harrowed on 5 Apr. Planting at a density of 142,560 seeds/A was done on 29 May. The plots were two rows 10 ft long with 22-in. row spacing and arranged in a randomized complete block design with six replications. The field was sprinkler irrigated, cultivated, and hand weeded as necessary. Plant populations were thinned to approximately 47,500 plants/A on 22 Jun. Plants were inoculated at the four- to six-leaf growth stage on 25 Jun with approximately six viruliferous (contained the following BCTV strains: California/Logan and Severe) beet leafhoppers per plant. The beet leafhoppers were redistributed three times a day during the first two days and then twice a day for five more days by dragging a tarp through the field. The plants were sprayed with Lorsban 4E (1.5 pints/A) on 9 Jul to kill the beet leafhoppers. Plots were rated for foliar symptom development on 10 Jul using a scale of 0 to 9 (0 = healthy and 9 = dead), with the scale treated as a continuous variable (Plant Dis. 90:1539-1544). Data were rank transformed and analyzed in SAS using the general linear models procedure (Proc GLM), and Fisher’s protected least significant difference (LSD; α = 0.05) was used for mean comparisons. Curly top symptom development was uniform and no other disease problems were evident in the plot area. The resistant and susceptible checks performed as expected for the visual ratings. Based on the visual rating, there were five lines (entries 18, 22, 26, 27, and 29) that were not significantly different from the resistant check. These five lines will be reevaluated and considered for incorporation into future germplasm.