Antifungal compounds from the roots of mycotrophic and non‐mycotrophic plant species

SUMMARY The roots of twelve plant spades From bath mycotrophic (hosts of YAM fungi) and non‐mycotropic (non‐hosts) families were examined for their ability to produce antifungal compounds. A TLC bioassay was used with the fungus Cladosporium cucumerimun Ellis & Arch. Of the non‐mycotrophic species, five species from the Brassicaceae [ Brassica kaber (DC.) Wheeler, Brassica napus L., Brassica campestris L., Thlaspi arvense L., Rhaphanus raphasnistrum L.] had detectable antifungal compounds in extracts from roots, while two species from the Chenopodiaceae ( Spinacea oleracea L., Beta vulgaris L.) and one species from the Amaranthaceae ( Amaranthus retroflexus L.) did not. One mycotrophic species ( Daucus carota L.) also had a detectable antifungal compound in root extracts, while three other mycotrophic species ( Lactuca sativa LK., Abutilon theophrasti Medic., sorghum bicolor L.) did not. Chloroform extracts of B. kaber roots appeared to have the greatest quantity of extractable antifungal compounds as detarmined by the TLC bioassay. In a separate experiment, chloroform extracts from B. kaber roots greatly inhibited the germination of spores of Glomus etunicatum Becker and Gerd., while extracts from a number of other mycotrophic and non‐mycotrophic plant roots were only marginally inhibitory. Three antifungal compounds in chloroform extracts from B. kaber roots were shown to be derived from glucosinolates. The predominant antifungal compound was identified as +‐hydroxybenzyl isothiocyanate, the isothiocyanate produced by the action of myrosinase on glucosinalbin. The data provide evidence of a possible role for glucosinolates in determining the non‐mycotrophic status in B. kaber.