Preference of Root‐Lesion Nematode for Alfalfa and Forage Grasses Growing in Binary Mixtures

Abstract

Most forage crops are hosts for the root‐lesion nematode, Pratylenchus penetrans (Cobb) Filipjev & Schur‐Stekhoven. The objective of this research was to compare the preference of P. penetrans for two alfalfas (Medicago sativa L.) and 14 forage grasses or small grains when grown in binary (two species) mixtures. The two alfalfas included the susceptible cultivar Baker, and MNGRN‐16, an experimental population with field resistance to P. penetrans. The grasses included 12 species: barley (Hordeum vulgare L,), Kentucky bluegrass (Poa pratensis L.), smooth bromegrass (Bromus inermis Leyss.), oat (Avena sativa L.), orchardgrass (Dactylis glomerata L.), pearl millet (Pennisetum glaucum L.), perennial ryegrass (Lolium perenne L.), quackgrass [Elytrigia repens (L.) Nevski], reed canarygrass (Phalaris arundinacea L.), tall fescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), and wheat (Triticum aestivum L.). Two seedlings of each grass entry and one alfalfa seedling were planted into a polyethylene tube containing a 1:1 sand/soil mixture. Eight tubes (replicates) were each inoculated with 90 nematodes; non‐inoculated tubes were used as controls. Six weeks after inoculation, fresh root weight and dry shoot weight were recorded and numbers of nematodes in the roots were determined by staining with acid fuchsin. Among the grasses, the oat, reed canarygrass, and quackgrass had the greatest number of nematodes, whereas pearl millet, perennial ryegrass, tall fescue, and timothy had the least. Alfalfa was the preferred host of P. penetrans when grown in combination with grasses. Baker and MNGRN‐16 alfalfa each supported 75% of the total number of nematodes compared with all grass‐alfalfa combinations. These results suggest possibilities for developing cropping systems including forage species that can tolerate or reduce root‐lesion nematode populations.