Abstract
Greenhouse studies were conducted to evaluate the susceptibility of cover crop species to infection by Fusarium virguliforme (Fv), a soilborne fungus that causes sudden death syndrome (SDS) of soybean (Glycine max [L.] Merr.), and the soybean cyst nematode (SCN; Heterodera glycines), both important soybean pathogens. In the SDS experiments, cover crops were planted in Fv-infested soil, and plants were assessed for fresh biomass, root rot severity, foliar symptoms, and amount of Fv DNA in roots. Inoculated alfalfa (Medicago sativa L.), crimson clover (Trifolium incarnatum L.), red clover (Trifolium pratense L.), and pea (Pisum sativum L.) had more root necrosis than the noninoculated controls, and Fv DNA quantities in roots did not differ from those found in soybean roots. Inoculated alfalfa, corn (Zea mays L.), crimson clover, oat (Avena sativa L.), red clover, sorghum (Sorghum bicolor L.), and turnip (Brassica rapa L.) plants had lower biomass compared to noninoculated controls, although corn, oat, and turnip had no root necrosis. Biomass reduction and root necrosis were not observed in inoculated hairy vetch (Vicia villosa Roth), false flax (Camelina sativa [L.] Crantz), millet (Pennisetum glaucum [L.] R.Br.), mustard (Brassica juncea L.), rye (Secale cereale L.), ryegrass (Lolium multiflorum Lam.), triticale (Triticale hexaploide Lart.), and wheat (Triticum aestivum L.), and Fv DNA quantity in the roots of these species was lower than in soybean. These results suggest that the legume species tested are hosts of Fv whereas grasses and Brassicas spp. are nonhosts or poor hosts. In the SCN experiment, select leguminous and nonleguminous cover crop plants were grown in soil naturally infested with SCN, and the number of females formed per root after 30 days was determined. There were very few (zero to five) SCN females on the roots of multiple varieties of leguminous cover crop species studied. No females were recovered from the roots of any of the nonleguminous species studied, except for a single female on four plants from three different species. None of the cover crop plants studied were susceptible hosts for SCN. With the increasing interest in using cover crops as a soil conservation practice in corn–soybean production systems, it is important to understand how this practice would impact major soybean diseases. Knowing the impact that cover crops may have on SDS and SCN is important to help farmers make better decisions when planting cover crops in areas with history of these diseases.
- © 2017 by the Soil and Water Conservation Society
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