COMPARATIVE INOCULUM POTENTIAL OF SPORES OF SIX VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI

Abstract

Using the most probable number method, differences in inoculum potential between six vesicular‐arbuscular (VA) mycorrhizal fungal isolates were demonstrated. Inoculum of Glomus mosseae had the highest inoculum potential while G. constrictus, and G. fasciculatus isolate 92, and isolate 0–1 were approximately 1/5, 1/6 and 1/12 as effective. G. fasciculatus isolate 185 and G. epigaeus were approximately 1 /50 as effective. These differences were not correlated with differences in spore viability or germinability since approximately 75 % germination occurred in all species after 3 weeks. While G. mosseae has the largest spore size and had the highest inoculum potential, no further correlation between spore size and inoculum potential was observed. The rate of increase of infection by these six VA mycorrhizal fungi differed more when equal spore numbers were used as inoculum than when equalized inoculum potentials were used. The percentage root infection, subjected to the multiple infection correction, was regressed against log of inoculum density and yielded slopes of 063 to 070 for all VA mycorrhizal fungi tested. The inoculum density‐infection relationships of mycorrhizal fungi are discussed with respect to Baker's epidemiological models. Copyright © 1981, Wiley Blackwell. All rights reserved