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

Abstract

The flavonoids 5,6,7,8,9-hydroxy chalcone, 3,7-hydroxy-4?methoxy flavone, 5,6,7,8-hydroxy-4?-methoxy flavone and 3,5,6,7,4?-hydroxy flavone can be detected only in non-mycorrhizal roots of white clover, but not in mycorrhizal roots, whereas the flavonoids acacetin, quercetin and rhamnetin are only present in mycorrhizal roots. We tested the effect of several concentrations of these compounds on spore germination, hyphal growth, hyphal branching, formation of clusters of auxiliary cells and of secondary spores of the arbuscular mycorrhizal fungi Gigaspora rosea , Gigaspora margarita , Glomus mosseae and Glomus intraradices . Our results indicate that depending on the flavonoid, the tested compounds are involved at different stages in the regulation of mycorrhization. This hypothesis is strengthened by their differing effect on several AM fungal growth parameters. Furthermore, our study provides more data on the AM fungus genus/species specificity of flavonoids.

Flavonoids and Strigolactones in Root Exudates as Signals in Symbiotic and Pathogenic Plant-Fungus Interactions

“…Interestingly, similar to the effect of flavonoids on different pre-symbiotic stages of AMF [18][19][20], the alterations of the flavonoid pattern in roots produced by different AMFs also exhibit a certain AMF fungal genus-and species specificity [21,22]. Larose et al [22] and Harrison and Dixon [23] linked the alterations of the flavonoid pattern in mycorrhizal roots to the developmental stage of the AM symbiosis.…”

“…Interestingly the stimulatory effect of the flavonoids has been shown to be even more pronounced in presence of CO 2 at concentrations similar to those found in the rhizosphere [14,15,17]. In most recent studies it has been reported that during pre-symbiotic growth and when applied to plants inoculated with AMF, flavonoids exhibit an AMF fungal genus-and species specific effect [18][19][20].…”

“…A hyphal branching effect has been reported for a number of flavonoids [16,18,19,73,74], however, as the flavonoids inducing branching can only be found in a limited number of plants, their role as general signaling compounds for hyphal branching as a pre-requisite for a successful AM root colonization seems questionable.…”

O-coumaric acid ester, a potential early signaling molecule in Pinus pinea and Pisolithus arhizus symbiosis established in vitro

“…In AM symbioses, flavonones, flavones, and isoflavones are capable of stimulating spore germination, hyphal elongation, and hyphal branching (Graham 1991;Siqueira et al 1991;Tsai and Phillips 1991;Harrison & Dixon 1993;Scervino et al 2005aScervino et al , 2005b. In the case of legumerhizobia symbiosis, other phenolic acids like hydroxybenzoic and hydroxycinnamic acids that are derived from the general phenylpropanoid pathway act as signaling molecules in the initiation of the symbioses and as agents in the plant defense (Mandal et al 2010).…”

Biologically active secondary metabolites in white clover (Trifolium repens L.) – a review focusing on contents in the plant, plant–pest interactions and transformation

“…Luteolin is toxic to the insect Heliothis zea (Elliger et al, 1980). In contrast, acacetin shows an inhibitory effect on many AM fungal parameters (Scervino et al, 2005a; Table 5), but shows no insecticidal behaviour (Elliger et al, 1980).…”