ABSTRACT
This chapter examines the existence and great physiological significance of mycorrhizae in Allium. Alliums possess but one type of mycorrhiza: vesicular-arbuscular (VA) mycorrhiza. The fungal partner is a species of the Endogonaceae and these fungi are ubiquitous in soils from an extremely wide range of habitats from deserts to the tundra. The fungal partner of VA mycorrhizae has not yet been cultured axenically. Hyphae from a propagule of a VA mycorrhizal fungus appear to show little chemotropism when approaching a root. At the point of contact between hypha and root an appressorium forms and this may be preceded by branching of the hypha to form a fan-like structure. In many studies on mycorrhizae the extent of colonization is expressed as fractional infection, and this is recorded at a single arbitrary date of harvest only. Another great problem in the potential use of inoculum of VA mycorrhizal fungi is the technology of production and application of inoculum.
