Evaluation location: North Dakota, United States
A commercial field site near Auburn, ND was selected to evaluate Beta germplasm accessions for potential resistance to SBRM feeding injury. Plots were planted on 22 May, 2009 without any chemical insecticide protection. Individual treatment plots were single rows that were 28 ft (8.5 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 17 accessions of B. vulgaris maritima and 13 B. v. vulgaris 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, Tst-2, Crystal 817, and FC704) were included for comparative purposes. The parentage of Tst-2, an experimental hybrid, was comprised of PI-658654 as the pollinator and a SBRM-susceptible female. The commercial hybrid Crystal 817 served as a susceptible control in the experiment. Larval feeding injury was assessed on up to ten 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 13 August. Sugarbeet root maggot fly activity in the area began slightly later than normal, and peaked 16 d later than average on 29 June at 84 flies per trap per day. This was considered a moderate level of SBRM fly activity. Levels of root maggot feeding injury observed for most entries was also moderate when compared to other years of testing. The only accessions that sustained significantly less SBRM feeding injury than the susceptible commercial hybrid (i.e., Crystal 817; rating mean = 4.23) were PI-605413 (F1015), PI-658654 (F1024), and PI-357355. The lowest level of feeding injury (i.e., 1.43 on the 0 to 9 rating scale) in the test was recorded for PI-605413 (F1015); however, root-feeding injury means for PI-658654 and PI-357355 were not significantly different from that for PI-605413. Other entries that incurred relatively low levels of SBRM feeding injury (mean < 3.1) included PI-518373, PI-562599, PI-251042, FC704, PI-232888, and PI-608437 (F1016).