Evaluation location: North Dakota, United States
A grower-owned field site near St. Thomas, ND was chosen to evaluate Beta germplasm accessions for potential resistance to SBRM feeding injury. The experiment was planted on 14 May, 2010. No chemical insecticide protection was applied to any plots. Individual treatment plots were single rows that were 11.5 ft (3.5 m) long and spaced 55.9 cm (22 inches) apart. Experimental design was a randomized complete block with four replications of 36 treatments. Treatments included 30 accessions of B. vulgaris maritima that were obtained from the NPGS Beta collection, courtesy of the USDA-ARS Western Regional Plant Introduction Station (Pullman, WA). Six additional entries (i.e., PI-605413, PI-608437, PI-658654, Crystal R761, Beta 1125R, and Hilleshög 2467RZ) were included for comparative purposes. The commercial hybrid Crystal R671 served as the susceptible control. Larval feeding injury was assessed on five sugarbeet roots per plot and rated in accordance with a 0 to 9 scale (0 = no damage and 9 = 75% or more of root surface blackened with feeding scars or a dead plant) on 19 August. Sugarbeet root maggot fly activity in the area began in late-May, and peaked early on 3 June at 60 flies per trap per day. Levels of root maggot feeding injury observed for most entries were low to moderate when compared to other years of testing. The lowest levels of feeding injury in the test were recorded in plots seeded with PI-605413 (F1015) and PI-608437 (F1016), in which ratings averaged 0.70 and 1.00 on the 0 to 9 SBRM root injury rating scale; however, root-feeding injury means for the following entries also were not statistically different from the mean for PI-605413 (ranked in ascending order of root injury sustained): PI-658654 (F1024), Hilleshög 2467RZ, PI-540621, PI-540622, PI-540601, PI-540688, PI-540586, PI-540648, PI-540587, PI-546405, PI-540691, PI-546392, PI-540634, Crystal R761, PI-540593, PI-540668, PI-540675, PI-599350, PI-540671, and PI-540682. Heavy rains saturated the plot area during the SBRM fly activity and egg-laying period in 2010, and could have been a factor in the relatively low number of statistical differences between entries in this experiment.