Directed inoculum production – shall we be able to design populations of arbuscular mycorrhizal fungi to achieve predictable symbiotic effectiveness?

Abstract

Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with most terrestrial plants. They provide several important benefits including enhanced nutrition, drought tolerance, biocontrol of pathogens and tolerance of heavy metals and other pollutants. Maximising these benefits for agriculture to produce high quality plants more sustainably has in recent years been an important aim. Progress has been made in several areas. Notably, benefits have been achieved by inoculating in vitro cultivated plants during the weaning stage (Varma and Schuepp 1994) and seeds, seedlings, cuttings, or mature plants Chang 1994). Moreover, the introduction of AMF to target plants has been carried out successfully under greenhouse conditions (Miller et al. 1986), in nurseries (Nemec 1987) and in the field (Thompson 1994). From an inoculum formulation perspective it is advantageous that AMF do not generally exhibit a high degree of host specificity. Consequently, one single AMF species can often be used to inoculate dicotyledons, monocotyledons and ferns (Feldmann 1998a). Furthermore, the same AMF species can often be used in the humid tropics (Sieverding 1991) and in temperate climates (Baltruschat 1993).