Vesicular–arbuscular mycorrhizae in the Chenopodiaceae and Cruciferae: do they occur?

Abstract

A sparse vesicular (chlamydospore) infection by Glomus fasciculatus was found in 4 spp. of Chenopodiaceae [Chenopodium album, C. amaranticolor, C. quinoa and spinacia oleracea] and 2 spp. of Cruciferae [Brassica nigra and Raphanus sativus] but only when grown in the presence of a mycorrhizal companion plant, citrus or onion. No arbuscules were obserbed in infected roots. C. album had the highest incidence of infection (5%). Infection was restricted to older tissue and penetration of the vascular cylinder was common, which is atypical of VA[vesicular-arbuscular] mycorrhizae. As hyphae from mycorrhizal companion plants grew through the soil, they encountered older roots of the test plants which probably offered little or no resistance to infection. In documenting the occurrence of VA mycorrhizae in any speices, it is important to observe whether the plant is growing by itself or there are mycorrhizal plants closely associated with it. Also, care should be taken not to confuse common root parasites for the fungal strucures of VA mycorrhiza.