Skip to main content
ARS Home » Pacific West Area » Logan, Utah » Poisonous Plant Research » Research » Publications at this Location » Publication #331727
Title: Production of destruxins from metarhizium spp. fungi in artificial medium and in endophytically colonized cowpea plants

Author
item GOLO, P - Universidade Federal Do Rio De Janeiro
item Gardner, Dale
item GRILLEY, M - Utah State University
item TAKEMOTO, J - Utah State University
item Krasnoff, Stuart
item PIRES, M - Universidade Federal Do Rio De Janeiro
item FERNANDES, EVERTON - Federal University Of Goias
item BITTENCOURT, VANIA - Universidade Federal Do Rio De Janeiro
item ROBERTS, DONALD - Utah State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2014
Publication Date: 8/15/2014
Publication URL: https://handle.nal.usda.gov/10113/63021
Citation: Golo, P.S., Gardner, D.R., Grilley, M.M., Takemoto, J.Y., Krasnoff, S., Pires, M.S., Fernandes, E.K., Bittencourt, V.R., Roberts, D.W. 2014. Production of destruxins from metarhizium spp. fungi in artificial medium and in endophytically colonized cowpea plants. PLoS One. 9(8):e104946.

Interpretive Summary: Destruxins (DTXs) are cyclic depsipeptides produced by certain fungi that have long been assumed to contribute to their toxicity or insecticidal activity. In this study the toxicity of 20 specific fungal isolates was tested against insect larvae and their concentration of DTXs A, B, and E produced were measured. Eight of the isolates did not produce DTXs A, B, or E. In the other fungal isolates destruxins were first detected at 2–3 days. The test insects showed considerable variation in their susceptibility to the toxic fungi and the concentration of DTXs produced in vitro did not correlate with percent or speed of insect kill. In a second study the fungi were found to be associated (endophytically) with two host plants,Vigna unguiculata (cowpeas) and Cucumis sativus (cucumber) plants. DTXs were detected in cowpeas colonized by the fungi 12 days after fungal inoculation, but DTXs were not detected in cucumber. This is the first instance of DTXs detected in plants endophytically colonized. This finding has implications for new approaches to fungus-based biological control of pest arthropods.

Technical Abstract: Destruxins (DTXs) are cyclic depsipeptides produced by many Metarhizium isolates that have long been assumed to contribute to virulence of these entomopathogenic fungi. We evaluated the virulence of 20 Metarhizium isolates against insect larvae and measured the concentration of DTXs A, B, and E produced by these same isolates in submerged (shaken) cultures. Eight of the isolates (ARSEF 324, 724, 760, 1448, 1882, 1883, 3479, and 3918) did not produce DTXs A, B, or E during the five days of submerged culture. DTXs were first detected in culture medium at 2–3 days in submerged culture. Galleria mellonella and Tenebrio molitor showed considerable variation in their susceptibility to the Metarhizium isolates. The concentration of DTXs produced in vitro did not correlate with percent or speed of insect kill. We established endophytic associations of M. robertsii and M. acridum isolates in Vigna unguiculata (cowpeas) and Cucumis sativus (cucumber) plants. DTXs were detected in cowpeas colonized by M. robertsii ARSEF 2575 12 days after fungal inoculation, but DTXs were not detected in cucumber. This is the first instance of DTXs detected in plants endophytically colonized by M. robertsii. This finding has implications for new approaches to fungus-based biological control of pest arthropods.