STUDY OF HYDROGEN CYANIDE PRODUCTION AS A MECHANISM OF ANTIFUNGAL ACTIVITY OF FLUORESCENT PSEUDOMONAS SPECIES AGAINST PHYTOPATHOGENIC PYTHIUM AND FUSARIUM SPECIES
*Balkrishna M. Sandikar
ABSTRACT
Among 150 Pseudomonas isolates obtained from rhizosphere of
healthy crop plants, nine isolates showed good in vitro antagonistic
activity against phytopathogenic Pythium and Fusarium species. These
Pseudomonas isolates were tested for ability to produce HCN by
inverted plate technique on nutrient sucrose agar (NSA) supplemented
with glycine and FeCl3, in Petri plates with picric acid discs fixed
inside the lid. Among the nine Pseudomonas isolates, three were found
to produce hydrogen cyanide as a metabolic product. Study of
morphological, cultural, biochemical and genetic characters identified
these isolates as Pseudomonas aeruginosa 13, P. aeruginosa58, and P.
fluorescens 106. A direct correlation between the extent of HCN
production and fungal growth inhibition was observed. These three
HCN producing Pseudomonas isolates also showed other mechanisms
of antifungal activity such as production of antibiotics and siderophores. Other
six isolates which did not produce HCN showed good antifungal activity. This indicated that,
HCN production is one of the important mechanisms of antifungal activity by Pseudomonas
species but not always involved in inhibition or killing of phytopathogenic fungi. These
Pseudomonas isolates were also found more effective to control fungal Infections of crop
plants, in pot culture experiments.
Keywords: Pseudomonas, Phytopathogenic fungi, Antifungal activity, Hydrogen cyanide.
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