Biocontrol Activities of Gamma Induced Mutants of against some Soilborne Fungal Pathogens and their DNA Fingerprinting.

BACKGROUND

Random induced mutation by gamma radiation is one of the genetic manipulation strategies to improve the antagonistic ability of biocontrol agents.

OBJECTIVES

This study aimed to induce mutants with more sporulation, colonization rate leading to enhanced antagonistic ability ( assay) comparing to wild type (WT) and the assessment of genetic differences (in situ evaluation) using molecular markers. The superior mutants could be appropriate biocontrol agents against soil borne fungal diseases.

MATERIALS AND METHODS

In this research sampling and isolation of isolates were performed from soils with low incidence of soil borne disease. 65 was selected and irradiation was conducted with gammacell at optimal dose 250 Gray/s. Mutants (115) were obtained from the WT. The antagonistic abilities of twenty-four mutants were evaluated using dual culture and culture filtrate tests.

RESULTS

The results of assays revealed that and mutants exhibited stronger growth inhibition (GI) and colonization rate on and AG4 compared to the wild type. and mutants exhibited stronger GI and colonization rate on in dual culture and culture filtrate tests and and mutants exhibited stronger GI on in culture filtrate test. The DNA fingerprinting was carried out using RAPD and rep-PCR markers. Two ( and ) out of the 24 mutants categorized distantly from the rest based on different polymorphism obtained by molecular markers. However, was different in GI% from . RAPD analysis separated WT from mutants, from and also phenotypically superior mutants from other mutants. Meanwhile, rep-PCR analysis categorized WT isolate and mutants according to their antagonistic properties.

CONCLUSIONS

The latter marker (rep-PCR) appeared to be reproducible and simple to distinguish mutants from a single isolate of . Mutants (3 isolates) were phenotypically and genotypically distinct from WT. These mutants demonstrated a pronounced biocontrol activities against soilborne fungal phytopathogens.