Influence of Inoculum Placement Depth on Endomycorrhizal Fungal Infection and Perennial Ryegrass Shoot Growth

Abstract

Abstract Effects of several vesicular-arbuscular mycorrhizal (VAM) fungi on shoot growth and mycorrhizal development in ‘Citation’ perennial ryegrass (Lolium perenne L.) were studied as a function of inoculum placement depth. Soil columns were layered with inoculum at 0, 5, 10, or 20 cm prior to seeding. Three inocula were tested: 1) chopped roots and soil from sorghum (Sorghum bicolor L.) plants previously infected with the VAM fungus Glomus macrocarpus Tul. and Tul. var. macrocarpus; 2) a mixed inoculum from plants infected with G. macrocarpus var. macrocarpus; G. mosseae (Nichol. and Gerd.), G. faciculatum (Thaxter) Gerd. and Trappe, Gigaspora margarita Becker and Hall; 3) roots and soil from noninoculated sorghum plants. Shoot growth was greatest when VAM inoculum was placed at the surface, and declined progressively with deeper placement. Greatest mycorrhizal fungal infection of the root system occurred at the site of inoculum placement regardless of depth. The effectiveness of the surface-applied inoculum on enhancing the initial shoot growth (70 days) of perennial ryegrass in this study suggests that inoculation with VAM fungi might prove useful in low maintenance turfgrass culture.