Evaluation location: North Dakota, United States
A commercial field site near St. Thomas, ND was selected to screen thirty-six Beta germplasm entries for potential host plant resistance to sugarbeet root maggot. All entries were planted on 1 May, 2015 into single-row plots 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. Thirty entries were accessions obtained from the NPGS Beta collection, courtesy of the USDA-ARS Western Regional Plant Introduction Station (Pullman, WA). Six additional entries (i.e., ACH-817, PI-179180, PI-269309, PI-285590, PI-608437, and PI-658654) were included for comparative purposes. ACH-817, a commercial hybrid shown in previous testing as susceptible to SBRM feeding injury, served as the susceptible control. On 4 August, SBRM larval feeding injury was rated on up to ten roots per plot in accordance to a 0 to 9 scale (0 = no damage and 9 = 75% or more of root surface blackened with feeding scars or a dead plant). High levels of SBRM fly activity developed in the plot area, and activity peaked at 140 flies/stake/day on 12 June. As a result, SBRM feeding pressure in the plots was high. Entries that sustained the least amounts of SBRM root feeding injury included PI-608437 (F1016) and PI-658654 (F1024), which averaged 3.10 and 3.08, respectively, on the 0 to 9 scale. Other entries that incurred relatively low levels of feeding injury included PI-179180, PI-269309, PI-518308, PI-518312, PI-518313, PI-518321, PI-518343, PI-546442, PI-546443, and PI-546523. Root injury sustained by all of these entries was significantly lower than that observed in the susceptible control (ACH-817).