Beet curly top resistance in USDA-ARS Kimberly germplasm lines, 2015

Curly top caused by Beet curly top virus is a widespread disease problem vectored by the beet leafhopper in semiarid sugar beet production areas. Host resistance is the primary defense against this problem, but resistance in commercial cultivars is only low to intermediate. In order to identify novel sources of curly top resistance, 14 sugar beet lines were screened in a disease nursery in 2015. The lines were arranged in a randomized complete block design with six replications. A curly top epiphytotic was created by releasing six viruliferous beet leafhoppers per plant at the four-to six-leaf growth stage on 24 Jun. Foliar symptoms were evaluated on 13 and 20 Jul using a scale of 0-9 (0 = healthy and 9 = dead) in a continuous manner. 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. Based on the overall visual rating, KDH13 and KDH4-9 performed the same as the resistant check and were better than all other entries. Additionally, ELISA data also indicated that these two lines had significantly lower virus titer than all other entries including the resistant check. These germplasm lines will be released to the general public, so they can be utilized to improve resistance in commercial cultivars