Beet curly top resistance in USDA-ARS plant introduction lines of sugar beet, 2020

Authors: Dorn, Kevin; Fenwick, Ann; Strausbaugh, Carl

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2021
Publication Date: 3/9/2021
Citation: Dorn, K.M., Fenwick, A.L., Strausbaugh, C.A. 2021. Beet curly top resistance in USDA-ARS plant introduction lines of sugar beet, 2020. Plant Disease Management Reports. 15.

Interpretive Summary: Thirty sugar beet (Beta vulgaris L.) USDA-ARS Plant Introduction (PI) lines and three commercial control cultivars 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 in 2020. The field was plowed and then fertilized and roller harrowed on March 27th, and the sugar beets were planted on May 18th. Plants were inoculated at the four-to six-leaf growth stage on June 23rd with approximately six viruliferous (containing the following BCTV strains: California/Logan and Severe) beet leafhoppers (Circulifer tenellus Baker) 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 on July 7th to kill the beet leafhoppers. Plots were rated for foliar symptom development on July 13th using a scale of 0 to 9 (0 = healthy and 9 = dead), with the scale treated as a continuous variable for statistical analysis. Data were rank transformed and analyzed in SAS using the general linear model procedure, and Fisher’s protected least significant difference (LSD; a = 0.05) was used for comparing means. 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. Statistically, 13 of the entries contain at least some minor resistance since their visual ratings were significantly lower than those for both susceptible checks. However, only entry 28 was not significantly different from the resistant check. Entry 28 along with entries with similar levels of resistance will be retested and, if resistance is confirmed, these lines will be considered for incorporation into the USDA-ARS germplasm improvement program as a source of resistance to BCTV.

Technical Abstract: Thirty sugar beet (Beta vulgaris L.) USDA-ARS Plant Introduction (PI) lines and three commercial check cultivars 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 2019. The field was plowed and then fertilized and roller harrowed on 27 Mar. The germplasm was planted on 18 May. The plots were two rows 10-ft long with 22-in. row spacing and treatments were 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 about 23,760 plants/A on 17 Jun. Plants were inoculated at the four- to six-leaf growth stage on 23 Jun with approximately six viruliferous (containing the following BCTV strains: California/Logan and Severe) beet leafhoppers (Circulifer tenellus Baker) 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 on 7 Jul to kill the beet leafhoppers. Plots were rated for foliar symptom development on 13 Jul using a scale of 0 to 9 (0 = healthy and 9 = dead), with the scale treated as a continuous variable. Data were rank transformed and analyzed in SAS using the general linear model procedure (Proc GLM), and Fisher’s protected least significant difference (LSD; a = 0.05) was used for mean comparisons. The non-transformed means are presented in the table. Only results for 26 lines are reported in the table since 4 lines (6, 19, 20, and 21) did not grow. 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. Statistically, 13 of the entries contain at least some minor resistance since their visual ratings were significantly lower than those for both susceptible checks. However, only entry 28 was not significantly different from the resistant check. Entry 28 along with entries with similar levels of resistance will be retested and, if resistance is confirmed, these lines will be considered for incorporation into the USDA-ARS germplasm improvement program as a source of resistance to BCTV.