Phytoalexins clover

Fig. 1. Biosynthetic pathway for alfalfa and clover phytoalexins. SAM, S-adenosyl methionine.

Many compounds with phytoalexin activity are also implicated in allelopathy between plants (Rice, 1984). For example, isoflavonoids are important phytoalexins (Ingham, 1982 Paxton, 1981 Dakora and Phillips, 1996) and allelochemicals (Tamura et al. 1967 1969) from the Leguminosae. Parbery et al. (1984) found that the isoflavonoids biochanin A, formononetin and genistein increased in subterranean clover by 62%, 123% and 75% respectively following infection by pepper spot (Leptosphaerulina trifolii). In comparison, Tamura et al. (1967 1969) isolated a succession of isoflavonoids (including biochanin A, formononetin and genistein) from the shoots of red clover (Trifolium pratense) that inhibited its own germination by 50% at concentrations of 50 ppm. 

Brassica oleracea (Brassicaceae), Spinacia oleracea (Chenopodiaceae), Medicago spp., Pisum sativum, Trifolium spp. (clover) (Fabaceae) induced phytoalexin in Glycine max, Phaseolus lunatus, P. vulgaris, Vigna unguiculata (Fabaceae)... 

GUSTINE Phytoalexin Levels in Ladino Clover Callus... 

The phytoalexin response of callus cultures derived from Ladino clover to various substances Is shown In Table III. Most of the ellcltors listed for the callus system have also shown ellcltor activity in other plant phytoalexin-producing systems. However, most of the abiotic and biotic non-ellcltors for the callus system (Table III) are ellcltors In whole plant systems (see 1 and references therein). 

Both pathogenic and nonpathogenic fungi may detoxify phytoalexins either in vivo or in vitro (Barz and Welle, 1992 Friend, 1979 Kuc, 1992). Red clover Trifolium pratense) produces primarily, medicarpin (96) and maackiain (97) [formononetin (82) is an intermediate] when inoculated with Helminthosporium carbonum, but only the nonfungitoxic... 

Higgins, VJ. and Smith, D.G. (1972) Separation and identification of two pterocarpanoid phytoalexins produced by red clover leaves. Phytopathology 62, 235-238... 

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