Effect of chitosan on hyphal growth and spore germination of plant pathogenic and biocontrol fungi.
OBJECTIVE
To investigate the toxic effect of chitosan on important root pathogenic and biocontrol fungi (nematophagous, entomopathogenic and mycoparasitic).


RESULTS
We have used standard bioassays to investigate the effect of chitosan on colony growth and developed bioassays to test spore germination. The results showed that the root pathogenic and mycoparasitic fungi tested were more sensitive to chitosan than nematophagous and entomopathogenic fungi. Chitosanases (and perhaps related enzymes) are involved in the resistance to chitosan. Two fungi, one sensitive to chitosan, Fusarium oxysporum f. sp. radicis-lycopersici, and one less sensitive, Pochonia chlamydosporia, were selected for ultrastructural investigations. Transmission electron microscopy revealed differences in the ultrastructural alterations caused by chitosan in the spores of the plant pathogenic fungus and in those of the nematophagous fungus. Confocal laser microscopy showed that Rhodamine-labelled chitosan enters rapidly into conidia of both fungi, in an energy-dependent process.


CONCLUSIONS
Nematophagous and entomopathogenic fungi are rather resistant to the toxic effect of chitosan. Resistance of nematophagous and entomopathogenic fungi to chitosan could be associated with their high extracellular chitosanolytic activity. Furthermore, ultrastructural damage is much more severe in the chitosan sensitive fungus.


CONCLUSIONS
The results of this paper suggest that biocontrol fungi tested could be combined with chitosan for biological control of plant pathogens and pests.
Palma-Guerrero
J
J
Laboratory of Plant Pathology, Multidisciplinary Institute for Environmental Studies (MIES) Ramón Margalef, Department of Marine Sciences and Applied Biology, University of Alicante, Alicante, Spain.
Jansson
H-B
HB
Salinas
J
J
Lopez-Llorca
L V
LV
D048271:Chitosan / Q000378:metabolism / Q000494:pharmacology*; D005658:Fungi / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D006026:Glycoside Hydrolases / Q000378:metabolism; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D009181:Mycoses / Q000517:prevention & control; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D013172:Spores, Fungal / Q000187:drug effects
D048271:Chitosan; D006026:Glycoside Hydrolases; C019868:chitosanase