Evaluation location: North Dakota, United States
This trial was planted on 16 May, 2001 in a grower-owned field site near St. Thomas, ND to evaluate Beta germplasm accessions for potential resistance to sugarbeet root maggot (SBRM) feeding injury. Individual treatment plots were single, 28-ft (8.5 m) long rows that were spaced 22 inches (55.9 cm) apart. Experimental design was a randomized complete block with four replications. A total of 25 entries were tested. Twenty accessions (i.e., nine accessions of B. vulgaris, four of B. v. maritima, and seven accessions of B. v. vulgaris) were obtained from the NPGS Beta collection, courtesy of the USDA-ARS Western Regional Plant Introduction Station (Pullman, WA). Five additional entries (i.e., PI-605413, PI-608437, Beta 3712, PI-590659, and 99N0015 [Yellow]) were included in the experiment for comparative purposes. Root maggot larval feeding injury was assessed on up to ten sugarbeet roots per plot on 8 August. Each root was washed, examined for SBRM feeding injury, 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). Root maggot fly activity in the plot area began in early June and peaked on 12 June (i.e., a very typical time for peak fly to occur) at about 67 flies per trap per day. A second activity peak of about 50 flies per trap occurred about one week later. Overall, SBRM feeding injury ratings (RI) in this trial were considered moderate, with the highest (RI = 6.1 on the 0 to 9 rating scale) being recorded for PI-174062. The lowest mean SBRM root feeding injury in the test (RI = 2.63) was recorded for PI-608437 (F1016). This entry, as well as PI-590659 (FC704; RI = 2.7), sustained significantly lower levels of SBRM feeding injury than the susceptible commercial hybrid (Beta 3712; RI = 5.1). Other entries that incurred relatively low levels of feeding injury included Ames 19022 (RI = 3.70), Yellow (RI = 3.73), PI-531254 (RI = 3.85), PI-590664 (RI = 3.95), Ames 3096 (RI = 4.03), PI-605413 (F1015; RI = 4.10), PI-518306 (RI = 4.11), and PI-612770 (RI = 4.35).