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Ryegrass Cultivars and Endophyte in Tall Fescue Affect Nematodes in Grass and Succeeding Soybean

USDA-ARS, Dep. of Agronomy, Univ. of Kentucky, Lexington, KY 40546-0091

R. Rodriguez-Kabana and R. A. Shelby

Dep. of Plant Pathology, Auburn University, Auburn, AL 36849

^* Corresponding author.

Annual ryegrass (Lolium multiflorum Lam.) is often double cropped with soybean [Glycine max (L.) Merr.] in much of the southeastern United States to provide winter grazing and ground cover. Little is known about the effect of annual ryegrass cultivars on nematodes associated with the grass, and with subsequent soybean crops. In several other taxonomically similar grasses, including tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.), the presence of endophytic fungi imparts pest resistance to the grass. No information is available on the effect of these endophytic fungi on nematodes associated with the grass. Therefore, the objectives of this study were to determine: (i) the effect of annual ryegrass cnltivars on nematodes in the grass and in succeeding soybean, and (ii) the effect of Acremonium coenophialum Morgan-Jones and Gams in tall fescue on nematodes. Thirteen annual ryegrass cultivars, ‘Kentucky 31" tall fescue with and without A. coenophialum infection, and a nematode-susceptible soybean check were grown for 7 wk in pots in the greenhouse in a Malibis sandy loam (fine-loamy, siliceous, thermic Plinthic Palendults) soil known to be infested with high numbers of phytonematodes. Plants were then removed from the soil, and the soybean was seeded into the pots and grown for 7 wk. Significant differences among nematode populations in the annual ryegrass cultivars occurred, and the nematode numbers were generally higher in the soybean that followed. However, these increased numbers did not affect soybean performance. Therefore, it does not appear that the use of annual ryegrass-soybean doublecropping systems will be effective in controlling most nematodes when using nematode-susceptible soybean cultivars. In tall fescue, lower spiral [Helicotylenchus dihystera (cobb) Sher.] and stubby root [Paratrichodorus minor (culbran) Siddiqi) nematode numbers were associated with A. coenophialum in the grass. Since nematode damage has previously been associated with stand decline in tall fescue, breeders working in nematode-infested areas should be aware that decreased pest resistance may be associated with the removal of A. coenophialum from tall fescue.

Received for publication February 10, 1987.