Population Development of the Root-Lesion Nematode on Soybean Cultivars.

Two greenhouse experiments were conducted with the new species of root-lesion nematode, , discovered in North Dakota, USA in 2017 and named in 2021. Experiment 1 was conducted to ascertain resistance levels of soybean ( [L.] Merr.) cultivars to the new species and Experiment 2 was conducted to evaluate the population levels of in roots versus soil. A total of 20 soybean cultivars, and the positive control, cultivar Barnes, accompanying a nonplanted control, were evaluated in both experiments; they each had five replicates and the experiments were repeated. Among the 20 soybean cultivars evaluated, a cultivar with the ID# 13 consistently produced the greatest population densities of 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 population levels revealed that ≥50% of the population resided in the root habitat and the remaining nematodes were recovered from soil at 9 weeks after planting for a majority of the cultivars tested. These results provide an insight into the virulence of on commercial soybean cultivars.