P-444 - Suppression of reniform nematode (Rotylenchulus reniformis) in sweetpotato production following velvet bean cover crop

Velvet bean suppresses plant-parasitic nematodes in the soil, but the mechanism of suppression is unclear. In previous trials, notable suppression of reniform nematodes was observed in sweetpotatoes following a velvet bean cover crop where median soil population densities of reniform nematodes at sweetpotato harvest were 880 nematodes/250cm³ soil in plots previously planted with velvet bean compared to 3,285 nematodes/250cm³ in plots previously fallowed. An ongoing experiment aims to test the hypothesis that velvet bean can induce nematode suppression by altering the rhizosphere microbiome. The soil microbiome and suppression of reniform nematodes was monitored in sweetpotato cultivation following velvet bean, cowpea, and bare ground. The rhizosphere microbiome, nematode communities, and nematode suppressive activities were measured at cover crop planting, termination, and three months after sweetpotato planting. Nematode suppression was examined using nematode survival and reproduction bioassays through lab and greenhouse incubation. Initial results identified abundant enchytraeid worms and Cateneria fungus in plots with high nematode suppression, validating the protocol of these bioassays. The experiment is in progress to understand how velvet bean can be used to induce nematode-suppressive soils. Multivariate analyses will be used to compare similarities and differences between the soil microbial communities, nematode communities, and the results of the nematode suppression bioassay to determine the nematode suppressive agents in this soil.