The role of vesicular–arbuscular mycorrhizal fungi in the growth of Kansas winter wheat

Abstract

In field experiments, fall-planted hard red winter wheat plants failed to become mycorrhizal until May or June just prior to harvest. No benefit to yield was evident from this late-season colonization, and in-furrow infestation with Glomus mosseae or Glomus epigaeum failed to provide earlier colonization or any increased yield. Neither were these mycorrhizal fungi successful in reducing the soil-borne diseases Cephalosporium stripe and take-all in the field. All eight wheat cultivars tested became mycorrhizal under greenhouse conditions whether nonsterile field soil was amended or not with a vesicular–arbuscular (VAM) fungus. Volunteer wheat plants collected from the field during summer also showed some limited level of colonization. Plants grown at 10 °C failed to be colonized, but plants grown at 25 °C were mycorrhizal after 10 weeks. Therefore, the observed failure of winter wheat in the field to become mycorrhizal until late in the growing season could not be explained by cultivar resistance or insufficient inoculum levels in field soils but may be attributed to low fall soil temperatures which may inhibit spore germination or root colonization. Thus, under field conditions it appears that mycorrhizal fungi have little or no effect on winter wheat in Kansas, but the isolation of cold-tolerant, highly efficient isolates should be pursued.