Evaluation location: North Dakota, United States
A field site near St. Thomas, ND was selected to evaluate Beta germplasm accessions for potential resistance to sugarbeet root maggot (SBRM) feeding injury. The experiment was planted on 8 May, 2003 without any insecticidal root protection into 32-ft (9.75 m) long single-row plots spaced 22 inches (55.9 cm) apart. Experimental design was a randomized complete block with four replications. A total of 32 entries were tested. Thirty B. vulgaris accessions were obtained from the NPGS Beta collection, courtesy of the USDA-ARS Western Regional Plant Introduction Station (Pullman, WA). Two additional entries (i.e., PI-605413 and PI-608437) were included in the experiment for comparative purposes. Root maggot larval feeding injury was assessed on up to ten sugarbeet roots per plot on 13 August. All root samples were 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 slightly later than average, with the first flies being detected in early June and activity peaking on 18 June at a moderate rate of 69 flies captured per trap per day. Sugarbeet root maggot feeding injury in this trial was low to moderate in most plots, as was evidenced by the highest mean root injury rating (RI) in the trial only reaching 4.41 on the on the 0 to 9 rating scale. Consequently, the low overall feeding pressure in the trial resulted in very few statistical differences among treatments. The lowest mean SBRM feeding injury rating in the test (RI = 1.78) was recorded for PI-608437 (F1016). Other entries that incurred low levels of SBRM feeding injury (i.e., mean RI < 3.22) that were not significantly different from those in plots planted with PI-608437 included PI-605413 ([F1015] RI = 2.08), PI-504215 (RI = 2.8), Ames 19161 (RI = 3.03), PI-504218 (RI = 3.17), and PI-504249 (RI = 3.22).