Characterization and Evaluation of Metarhizium spp. (Metsch.) Sorokin Isolates for Their Temperature Tolerance.

Viswakethu Velavan,Govindaraju Ramkumar,Sengottayan Senthil-Nathan,Sengodan Karthi,Eliningaya J Kweka,Osmund A Ndomba,Rajendran Dhanapal

doi:10.3390/jof8010068

Abstract

A field survey was done in teak (Tectona grandis F.) forests in South India to explore the entomopathogenic effect of Metarhizium anisopliae (Ascomycota: Sordariomycetes) against teak defoliator, Hyblaea puera (Lepidoptera: Hyblaeidae). About 300 soils and infected insect samples were collected during the survey and thirty-six fungal isolates were isolated from soil and insect samples and characterized. The fungi were cultured on PDAY with dodine and antibiotics. Generally, the EPF culture was incubated at 27 °C in darkness for 15 days. Virulence of the Entomopathogenic Fungi (EPF) ability to germinate under cold and heat temperatures was assessed in a culture impregnated with conidia. In the experiment, it was found that for the first time Metarhizium quizhouense, Metarhizium robertsii, and Metarhizium majus species caused significantly higher mortality to hosts. These isolates of M. anisopliae, M. robertsii, M. majus, and M. quizhouense were all considered to be effective virulent and environmentally adaptive. The Metarhizium isolates were recommended as effective bio-control agents through the field investigation of teak defoliator Hyblaea puera from South India forest. This study paves the way to utilize the indigenous isolates of EPF for the control of teak defoliator and to combat the pests thatare resistant to insecticide.

Highlights

Entomopathogenic fungi (EPF) are widely used as bio-agents against various insect pests in agriculture, forest, other crop pests, and aquatic invertebrates
Other entomopathogenic fungi were grown in culture medium but failed to infect the host insects and were, not taken for further study
The present study demonstrated that the isolates, viz., M. quizhouense (ArMz1W) and M. robertsii (ArMz6W), showed the highest significant on par protease activity compared with other isolates (22.4 ± 1.0 and 22 ± 0.7 U/mL), respectively, whereas the isolate of M. anisopliae (BgMz2S) showed the lowest protease activity

Summary

Introduction

Entomopathogenic fungi (EPF) are widely used as bio-agents against various insect pests in agriculture, forest, other crop pests, and aquatic invertebrates. For about 100 years, myco-insecticides have been established [1] as one of the most promising pest biocontrol options in important insects or other arthropods [2,3] It increases the low growth rate of opportunistic fungi [4,5,6]. The use of EPF as a pest management tool is affected by many biotic and abiotic factors. During conidia germination, they are affected by enhanced activity of the secondary metabolism [7,8,9,10,11]. The EPF tolerated heat temperature during mycelia growth, which induces the high-protein metabolism [15,16]

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Conclusion