Biopesticide synergy when combining plant flavonoids and entomopathogenic baculovirus

Authors: Hay, William; Behle, Robert; Berhow, Mark; MILLER, ANDIE - Bradley University; Selling, Gordon

Submitted to: Nature
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2020
Publication Date: 4/22/2020
Citation: Hay, W.T., Behle, R.W., Berhow, M.A., Miller, A.C., Selling, G.W. 2020. Biopesticide synergy when combining plant flavonoids and entomopathogenic baculovirus. Nature. 10:6806. https://doi.org/10.1038/s41598-020-63746-6.
DOI: https://doi.org/10.1038/s41598-020-63746-6

Interpretive Summary: This research has identified three naturally occurring compounds in soybean which increase the potency of a natural viral bioinsecticide. The use of insect specific viruses for crop protection is an environmentally friendly management strategy which does not broadly impact beneficial insects in the treated location. We found that the AfMNPV baculovirus was far more potent in protecting against the insect pest Trichoplusia ni when it was applied to soybean (compared to cotton cabbage or the closely related green bean). Three plant flavonoid compounds were isolated and identified in soybean: daidzein, genistein, and kaempferol. These compounds were not found in any of the other tested plant species. When incorporated into an artificial insect diet at leaf level concentrations, the diet did not cause any insect mortality. Once the AfMNPV baculovirus was applied to the insect diet with the incorporated flavonoids, we observed a dramatic increase in virus potency similar to that observed with virus treatments on soybean leaves. Increasing the concentration of the defense compounds in the artificial diet increased the virus potency against the insect pest Trichoplusia ni. This research informs plant breeders and farmers and allows for the improvement of plant insect resistance using environmentally friendly bioinsecticides within an integrated pest management system.

Technical Abstract: Four crop plants known to be hosts for the lepidopteran Trichoplusia ni (soybean, green bean, cotton, and cabbage) were treated with AfMNPV baculovirus in a dosage response assay. Treated soybean had, on average, a 6-fold increase in virus activity compared with the other crops. Leaf trichomes on soybeans were not found to be responsible for the observed increase of insecticidal activity. Three flavonoid compounds (daidzein, genistein, and kaempferol) were uniquely found only in the soybean crop, and were not detected in cotton, cabbage, or green bean plant matter. The individual flavonoid compounds did not cause T ni. mortality in no-virus assays when incorporated into artificial insect diet. The combination of the three flavonoid compounds at leaf level concentrations significantly increased baculovirus activity in diet incorporation assays. When the daidzein, genistein, and kaempferol were added to artificial diet, at 3.5-6.5 × leaf level concentrations, virus activity increased 1.5, 2.3, and 4.2-fold for each respective flavonoid. The soybean flavonoid compounds were found to synergistically improve baculovirus activity against T. ni.