J. Hallmann et Ra. Sikora, TOXICITY OF FUNGAL ENDOPHYTE SECONDARY METABOLITES TO PLANT-PARASITICNEMATODES AND SOIL-BORNE PLANT-PATHOGENIC FUNGI, European journal of plant pathology, 102(2), 1996, pp. 155-162
Fungi isolated from the cortical tissue of surface sterilized tomato r
oots collected from field plots produced secondary metabolites in nutr
ition broth that were highly toxic to Meloidogyne incognita. Especiall
y strains of Fusarium oxysporum were highly active with 13 of 15 strai
ns producing culture filtrates toxic to nematodes. The mechanism of ac
tion of the toxic metabolites produced by the non-pathogenic F. oxyspo
rum strain 162 with proven biological control of M. incognita in pot e
xperiments was investigated. These metabolites reduced M. incognita mo
bility within 10 min of exposure. After 60 min, 98% of juveniles were
inactivated. Juveniles were initially inactivated within a few minutes
of exposure, but with exposure of 5 h 50% of the juveniles were dead
and 24 h exposure resulted in 100% mortality. In a bioassay with lettu
ce seedlings metabolite concentrations >100 mg/l reduced the number of
M. incognita juveniles on the roots comparing to the water control. T
he F. oxysporum toxins were highly effective towards sedentary parasit
es and less effective towards migratory endoparasites. Non-parasitic n
ematodes were not influenced at all. Metabolites of strain 162 also re
duced significantly the growth of Phytophthora cactorum, Pythium ultim
um and Rhizoctonia solani in vitro. Secondary metabolites of endophyti
c fungi on plant-parasitic nematodes and soil-borne fungi should be co
nsidered for control of plant parasitic nematodes and plant pathogenic
fungi. The results also show the need for proper selection of target
nematodes in in vitro bioassays.