The impact of plant residues on the soybean cyst nematode, Heterodera glycines

The potential of plant residues and plant root exudates, from a range of traditional and nontraditional crop species, to protect soybean (Glycine max (L.)) plants against Heterodera glycines (Ichinohe) was examined in vitro and under greenhouse conditions. Plant residues from nonhosts Lespedeza capitata Michx, Lespedeza intermedia (S. Wats.) Britt, Lespedeza hirta (L.) Hornem, Lolium multiflorum (Lam.), Lolium perenne (L.), Lupinus perennis (L.), Melilotus officinalis (L.) Lam., Medicago sativa (L.), Trifolium pratense (L.), Fairway B Lawngrass mixture, and Pisum sativum (L.) reduced the number of H. glycines juveniles in the soil prior to planting soybeans and subsequently in the roots of soybeans. Root exudates of nonhosts Lespedeza capitata, Trifolium hybridum (L.), Trifolium repens (L.), Lolium multiflorum, Lupinus perennis, Echinochloa crusgalli (L.) Beauv., Vicia villosa (Roth), Medicago sativa, and of the host G. max increased the egg hatching rate of H. glycines in comparison to the water control. In addition, root exudates of Trifolium repens and Lolium multiflorum increased egg hatching by 37.9 and 46.6%, respectively, compared to root exudates of soybeans. Root exudates of Trifolium repens, Lolium multiflorum, E. crusgalli, Lupinus perennis, Trifolium hybridum, Medicago sativa, and G. max significantly increased neutral lipid utilization of H. glycines juveniles in comparison to the control. Overall, Lolium multiflorum was the most effective of all species tested for reducing populations of H. glycines, by increasing egg hatching: of the nematode in the absence of a host, depleting lipid reserves of the juveniles, and inducing the lowest nematode parasitism of all nonhost residues studied.