Phenotype responses to abiotic stresses, asexual reproduction and virulence among isolates of the entomopathogenic fungus Cordyceps javanica (Hypocreales: Cordycipitaceae)

Authors: MASCARIN, GABRIEL - Embrapa; JUNIOR, RONALDO ALVES - Federal University Of Goias; FERNANDES, EVERTON KORT - Federal University Of Goias; QUINTELA, ELIANE - Embrapa; Dunlap, Christopher; ARTHURS, STEVEN - Texas A&M University

Submitted to: Microbiological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2018
Publication Date: 11/1/2018
Citation: Mascarin, G.M., Junior, R.P., Fernandes, E.K., Quintela, E.D., Dunlap, C.A., Arthurs, S.P. 2018. Phenotype responses to abiotic stresses, asexual reproduction and virulence against whiteflies among strains of the entomopathogenic fungus Cordyceps javanica (Hypocreales: Cordycipitaceae). Microbiological Research. 216:12-22. https://doi.org/10.1016/j.micres.2018.08.002.
DOI: https://doi.org/10.1016/j.micres.2018.08.002

Interpretive Summary: An important challenge in developing beneficial fungi for insect control is identifying fungi that can survive environmental stress and still provide the desired biological activity. In this study, we characterized the essential traits in strains of an important insect killing fungus to determine how these traits affect each other. The results demonstrate there are trade-offs between stress tolerance and insect virulence. These results will be used to identity strains with improved traits for crop protection applications. This research benefits farmers and consumers impacted by insect crop pests.

Technical Abstract: Selecting entomopathogenic fungal strains with resilience to environmental stresses, stable mass production characteristics, and high virulence to target pests favors the development mycopesticides. Isaria javanica is an environmentally friendly alternative to chemical insecticides against various agricultural insect pests and, more specifically, has been extensively investigated to control whiteflies worldwide. We screened and phenotypically characterized 11 native strains of I. javanica from distinct geographic regions of Brazil for tolerance to heat-shock, UV-B radiation, osmotic and oxidative stresses, as well as conidial production on cereal grain and insecticidal activity with spores against the whitefly Bemisia tabaci in the laboratory. All tested strains killed whitefly nymphs, and the median lethal concentration significantly differed among the strains at magnitude up to 2.75-fold. However, more pronounced differences among strains were found for stress factors and conidial production. Using principal component analysis, our results revealed three major clusters formed by strains (i) resistant to osmotic and oxidative stress, (ii) resilient to UV-B, and (iii) with high virulence, conidial-production and heat tolerance. Overall, strain CG1228 performed best based on multi-stress resistance, mass production and virulence attributes in the laboratory. This study highlights the importance of exploring natural variation in I. javanica for selection of appropriate fungal strains for effective biocontrol of whiteflies.