Abstract

SCREENING OF CHITINOLYTIC ACTINOBACTERIA FOR BIOLOGICAL CONTROL OF FUSARIUM OXYSPORUM: A PATHOGEN CAUSING DAMPING-OFF AND BASAL ROT DISEASES IN ONION

*G. Vaijayanthi and R. Vijayakumar

ABSTRACT

Thirteen strains of actinobacteria were isolated from mangrove soils from Muthupet province using Actinomycetes isolation agar and starch casein agar media (SCA). All the strains were screened for chitinolytic activity and eleven strains gave significant clear zone on chitinase mineral agar medium. The selected strains were assayed for in vitro antagonistic activity against Fusarium oxysporum on potato dextrose agar media (PDA), and the result showed that seven isolates had notable inhibitory action on the growth of the fungus. Of which three remarkable antagonistic actinobacterial strains namely VMK1, VMK4 and VMK9 were selected for further studies. The result indicated that these actinobacteria produce chitinase which catalyze the degradation of chitin, resulting in growth inhibition of F. oxysporum. These three antagonists reduced the disease development up to 80%. All the selected strains were identified as Streptomyces spp. according to morphological and microscopic characteristics. The study suggested that these chitinolytic actinobacteria could be developed to be potential biological control agents, and they could be included as a complement with organic fertilizers in order to manage basal rot and damping off diseases and promote growth of onion.

Keywords: Streptomyces spp., basal rot, damping off, Fusarium oxysporum, biocontrol.