Influence of Plant Interactions on Vesicular‐arbuscular Mycorrhizal Infections. I. Host and Non‐host Plants Grown Together

Abstract

Summary Mycorrhizal infections formed by different endophytes were examined in 10 crop species grown separately and in pairs in sterilized and unsterile soils. No infection was observed in cabbage, kale, rape or swede (in the supposedly non‐mycorrhizal family Cruciferae) and only traces were seen in sugar beet (supposedly non‐mycorrhizal Chenopodiaceae) when these plants were grown alone. However, slight (< 5 %) infection (cortical mycelium and vesicles, but no arbuscules) developed in some when a mycorrhizal host plant was present and there were many clumps of endophyte mycelium on their root surfaces, usually attached to entry points which had often aborted. Glomus fasciculatus‘E3’ was a more infective endophyte than Gigaspora margarita. Infection was usually well developed in the host plants barley, lettuce, maize, potato and onion. It was depressed only in a few pairs but no more by the presence of a ‘non‐host’ plant than by a host plant. The results suggest that the barriers to mycorrhizal infection in ‘non‐hosts’ are intrinsic and more probably related to characteristics of the root cortex or epidermis than to any infection‐inhibiting factors that might be released in root exudates.

Influence of intergeneric grafts between host and non‐host legumes on formation of vesicular–arbuscular mycorrhiza

“…Evidence for such shoot control comes also from recent experiments on decapitated lupin seedlings by Giovannetti et al (personal communication (Trinick, 1977;Ocampo et al, 1980;Plenchette & Trouvelot, 1986). Under these conditions non-host roots still, however, show resistance to VA mycorrhizal fungi in that abortive entry points are frequent and, where roots become colonized, only intercellular hyphae form and arbuscules do not develop.…”

Influence of Plant Interactions on Vesicular‐arbuscular Mycorrhizal Infections.

“…Previous observations (Ocampo et al 1980) showed that VA fungal hyphae can make some growth around the roots of 'non-hosts'. The present study suggests that these hyphae are more active in infecting roots than is fresh inoculum added at the same rate as before.…”

“…The same two soils were used as before (see Ocampo et al 1980, for full details), one from a fallow area at Woburn and the other from a maize field at Rothamsted | (Long Hoos). The Woburn soil (Tables 1, 4, 5 and 6) was sterilized with y-irradiation (1 Mrad), mixed 1:1 with sterilized sand, and inoculated with soil from stock plant cultures of either Glomus fasciculatus ' E3 ' or Gigaspora margarita which contained spores, mycelium and infected root fragments, at the rate of 5 g soil inoculum mixed with 5 g sand per 75 mm pot.…”

“…OcAMPO AND D. S. HAYMAN under controlled conditions in pot experiments than in the field. We did this using conditions and plant combinations similar to those in previous experiments (Ocampo, Martin and Hayman, 1980).…”

Suppression of clubroot formation in Chinese cabbage by the root endophytic fungus,Heteroconium chaetospira

“…Plant diseases caused by soilborne fungi are usually affected by the formation of mycorrhizas, and mycorrhizas are known to be effective in inhibiting the development of pathogens and reducing incidence of the disease (Dehne, 1982;Caron, 1989;Perrin, 1990). Although most plant species, including a large number of crops, can develop mycorrhizas, Cruciferae is an exceptional plant family, with few or no mycorrhizas (Ocampo et al, 1980). In some species of Cruciferae, however, the presence of an endophytic dark-septate fungus was reported and it appeared that the functional relationship between the fungus and plants might be mutualistic rather than parasitic (Vare et al, 1992).…”