Indian Journal of Science and Technology

Abstract

Background: Strain improvement in fungi is based on the knowledge of biochemical and molecular basis of pathogenicity. Successful application of genetic manipulation techniques relies on the formation of mutants. The present study aimed at strain improvement for enhancement of biocontrol efficiency of Verticillium lecanii. Methods: Two potent fungicides were developed as markers in the V. lecanii isolate: Benomyl and Ketoconazole. Chlorate Resistant Mutants (ChlR) of V. lecanii were isolated and classified according to their phenotype containing one of the four nitrogen sources: 10mM Nitrate, nitrite, ammonium, glutamate. Also, vegetative growth of the mutant isolates at different temperatures was checked. Also, pathogenicity assay was performed with varied doses of conidial suspension. The conidial germination rates of mutant and wild type strains were tested. Findings: It was concluded that V. lecanii was highly sensitive to Benomyl and its growth was strictly inhibited even at low concentration of 2 µg/ml whereas it could tolerate up to 20 µg/ml concentration of Ketoconazole. Of the five chlorate resistant mutants purified, two were unable to utilize nitrate, they were considered as niaD- mutants. Remaining three showed inability to utilize nitrite and were considered niiA mutants. Vegetative growth of the mutant isolates at different temperatures was found to be significantly faster as compared to that of wild type isolates. Also, wild type strain of V. lecanii was less virulent than the mutants. Rate of germination of spores from mutants of V. lecanii was faster and exhibited thermotolerance with respect to conidial germination as compared to that of wild type. Application: Hence, development of mutants in Verticillium lecanii could enhance its effectiveness as an improved biocontrol agent.

Keywords: Biological Control, Chlorate, Entomopathogenic, Mutants, Resistant