Journal of Environmental Biology

Characterization and screening of antifungal activity of bacteria associated with entomopathogenic nematodes from Mizoram, North-Eastern India

M. Lalramchuani^1,2, H.C. Lalramnghaki^1,2, R. Vanlalsangi³, E. Lalhmingliani², Vanramliana¹ and Lalramliana¹* 

¹Department of Zoology, Pachhunga University College, Aizawl-796 001, India

²Systematics and Toxicology Laboratory, Department of Zoology, Mizoram University, Aizawl-796 004, India

³Department of Biochemistry, Government Zirtiri Residential Science College, Aizawl-796 001, India

*Corresponding Author Email : lrl_zoo@yahoo.co.in

Paper received: 19.12.2019??????? ?????????????????????????????????????? Revised received: 02.07.2020? ??????????? ?????????????????????????????????? Accepted: 10.07.2020

Abstract

Aim: The present study was conducted to isolate and characterize symbiotic bacteria of the genera Xenorhabdus and Photorhabdus associated with entomopathogenic nematode isolated from Mizoram, North-Eastern India and screening of their antifungal activity against Fusarium oxysporum.

Methodology: Symbiotic bacteria were isolated by macerating infective juveniles of entomopathogenic nematode (EPN) and subsequently plated on nutrient agar supplemented with 0.0025% bromothymol blue and 0.004% triphenyltetrazolium chloride (NBTA). 16S rRNA gene was further sequenced for molecular characterization of isolated bacteria. Screening of antifungal activity was conducted by placing 4 mm of fungal mycelium on petri-plate consisting of spread bacterial suspensions adjusted to 3 ? 107 CFU ml^-1.?????     

Results: The morphological and molecular characterization (16S rRNA) revealed that three species of symbiotic bacteria were isolated, Xenorhabdus vietnamensis from Steinernema sangi, Xenorhabdus stockiae from S. surkhetense and Photorhabdus luminescens akhurstii from both Heterorhabditis indica and H. baujardi. The maximum likelihood tree showed that X. vietnamensis was a sister species of X. japonica; X. stockiae formed a sister group with X. doucetiae, X. nematophila, X. magdalenensis, X. cabanillasii and X beddingii whereas Phototorhabdus luminescens akhurstii formed a sister group with P. luminescens hainanensis and P. luminescens thracensis. The screening of antifungal activity revealed that all the isolated bacterial symbionts successfully inhibited the growth of Fusarium oxysporum showing the potential of entomopathogenic bacteria as biological control of pathogenic fungi.      

Interpretation: The present study constitutes the first report of symbiotic bacteria, X. stockiae and P. luminescens akhurstii from Mizoram which contributes to the regional diversity of bacteria. The results emphasized significant toxicity of bacterial isolates against F. oxysporum to a great extent, conveying the prospective of isolates as a sustainable biological control agent in future. 

Key words: Biological control, Entomopathogenic nematodes, Infective juveniles, Integrated pest management, Photorhabdus, Xenorhabdus

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