LAUSR

Two greenhouse experiments were conducted with the new species of root-lesion nematode, Pratylenchus dakotaensis, discovered in North Dakota, USA in 2017 and named in 2021. Experiment 1 was conducted to ascertain resistance levels of soybean [Glycine max (L.) Merr.] cultivars to the new species P. dakotaensis and Experiment 2 was conducted to evaluate the population levels of P. dakotaensis in roots versus soil. A total of 20 soybean cultivars, and the positive control, cv. Barnes, accompanying a non-planted control were evaluated in both experiments each with five replicates and experiments were repeated. Among the 20 soybean cultivars evaluated, a cultivar with the ID# 13 consistently produced the greatest population densities of P. dakotaensis across all the experiments and therefore it was selected as the susceptible check. The ratio of the final nematode population density of a test cultivar relative to the final population density of the susceptible check was used to scale resistance rating. Combined results of all the trials indicated that seven of the cultivars were moderately resistant, nine of the cultivars plus Barnes were moderately susceptible, and four of the cultivars were susceptible. However, none of the cultivars tested were classified as resistant. Analysis of P. dakotaensis population levels revealed that above or close to 50% of the population resided in the root habitat and the remaining nematodes were recovered from soil at nine weeks after planting for a majority of the cultivars tested. These results provide an insight into the virulence of P. dakotaensis on commercial soybean cultivars.