Occurrence of phytoalexins and phenolic compounds in endomycorrhizal interactions, and their potential role in biological control

Abstract

This paper will review work mainly done during the last twenty years on the involvement of phytoalexin and phenolic compounds in mycorrhizal interactions. It has been observed that phytoalexins and associated molecules accumulate in roots after mycorrhizal infection, but less intensively and more slowly than in pathogenic interactions. Following mycorrhizal infection, enzymes of phenylpropanoid metabolism have been shown to be activated differentially. Some flavonoids and isoflavonoids have been reported to stimulate in vitro germination of mycorrhizal fungi or in vitro mycorrhizal infection, but their biological significance in signalling between the two symbiotic partners, and in biocontrol of plant disease by arbuscular mycorrhizal fungi, have not yet been elucidated.

Flavonoids exclusively present in mycorrhizal roots of white clover exhibit a different effect on arbuscular mycorrhizal fungi than flavonoids exclusively present in non-mycorrhizal roots of white clover

“…The flavonoid concentrations 0.5, 2 and 8 mM of were selected for showing significant effects on different steps of the AM fungal development with other flavonoids (Morandi 1996, Vierheilig et al 1998.…”

“…A number of studies on the effect of flavonoids on AM spore germination, fungal growth and root colonization are available , Kape et al 1992b, Morandi et al 1992, Morandi, 1996, Vierheilig et al 1998, Juge et al 2002, however, data on the effect on other important parameters such as hyphal branching and the formation of auxiliary cells or secondary spores are scarce (Gianinazzi-Pearson et al 1989, Bécard et al 1992, Phillips & Tsai 1992. In a recent study Ponce et al (2004) showed that the flavonoid pattern in white clover is altered after colonization by the AM fungus Glomus intraradices.…”

Interactions of Arbuscular Mycorrhizal Fungi With Plants and Soil Microflora

“…The formation of the mycorrhizosphere modifies growth conditions for microorganisms in the root zone of plants (mechanisms of competition and selection in the rhizosphere) and the plants are protected against harmful microorganisms [Cordier et al 1998, Amer and Abou-El-Seoud 2008, Al-Askar and Rashad 2010. Root colonization by AMF can also cause defense reactions of plants by inducing the accumulation of phytoalexins and production of antioxidant enzymes in plants [Morandi 1996, Yang et al 2015. Another mechanism of the protection of the mycorrhizal plant from fungal pathogens can be an increase of the accumulation of non-soluble polysaccharides and lignins in the cell walls of plant roots as well as the very presence of the mycorrhizal fungus hyphae in the root tissue, which can constitute a physical barrier for the infection of fungal pathogens [Amer and Abu-El-Seoul 2008].…”

Effects of climatic factors on native arbuscular mycorrhizae and Meloidogyne exigua in a Brazilian rubber tree (Hevea brasiliensis) plantation

“…Mycorrhizal rubber tree roots are more lignified than nonmycorrhizal ones (results not published). When AM fungi penetrate into roots, they increase cell wall lignification and protect the roots from penetration by other pathogens (Morandi, 1996). However, no curative effect was shown and nematode life cycles appeared to be complete (eggs in roots and second-stage juveniles in soil were observed at infected sites throughout the year).…”