BIOLOGICAL PROPERTIES OF A RED PIGMENT PRODUCED BY THE NEMATOPHAGOUS FUNGUS VERTICILLIUM SUCHLASPORIUM
Verticillium suchlasporium, a parasite of eggs of the cereal cyst nematode Heterodera avenae, produced diffusible pigments on the nutrient-rich media potato dextrose agar and malt extract agar but not on the nutrient poor medium corn meal agar. V. suchlasporium (isolate 10, CBS 464.88, ATCC no. 76547) produced a red pigment on potato dextrose agar when the fungus was plated together with Arthrobotys amerospora and Cylindrocarpon destructans, the pigment being produced in the interaction zones between the colonies. The red pigment which was extracted from the agar using glacial acetic acid or chloroform, absorbed light at 510 nm, 355 nm and especially 200 nm. Four main spots with RFs 0.54, 0.31, 0.14 and 0.084 were resolved by thin layer chromatography using toluene/ethyl acetate/formic acid. The red pigment which inhibited the growth of Cladosporium cucumerinum spores in bioautographs, revealed the presence of mycotoxic compounds. Cysts of Globodera rostochiensis were placed on paper discs impregnated with potato root diffusate, sterile distilled water, acetic acid and an extract of the red pigment in acetic acid. After five days, significantly (P<0.05) fewer second-stage juveniles of G. rostochiensis were found hatched outside the discs treated with the pigment than in the rest of the treatments. The extract of the red pigment also significantly (P<0.001) reduced the mobility of G. rostochiensis juveniles compared with both untreated controls and acetic acid treated discs suggesting that the red pigment had a nematicidal role.