Feeding on soybean crops decreased bacteria biodiversity in guts of the Southern green stinkbug (Nezara viridula)

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Virginia Medina, Biochemistry, School of Agronomy University of Buenos Aires, Buenos Aires, Argentina, Jorge A. Zavala, Catedra de Bioquimica, Facultad de Agronomia, UBA-CONICET, Argentina and Bruno Rosso, School of Agronomy University of Buenos Aires, Buenos Aires, Argentina

Background/Question
The southern green stink bug, Nezara virdula, is a mayor pest of soybean. The mechanism underlying stinkbug resistance to soybean antiherbivore defenses is yet ignored. However, gut bacteria could be having an essential role in insect-plant interactions.Although, laboratory rearing condition experiments are developed to analyze insect-plant-bacteria interactions, field conditions can generate more realistic results due to environmental factors affecting the system.
Methods and Results/Conclusions
Firstly, we identify gut bacteria of field collected and laboratory reared stink bugs trough metagenomic analysis. After that we performed lab and field conditions experiments with soybean pest Nezara viridula and indigenous bacteria Serratia sp and Yokenella We analyzed the effect of bacterial infection on nymph’s mortality, survivorship, weight gain, gut lipid peroxidation and digestive cysteine protease activity. Our results reveal that viridula feeding in field grown soybean eliminates midgut bacteria while laboratory reared conditions increased bacterial abundance in the insect’s gut. Also, Yokenella sp. caused early death of 2nd instar nymphs in lab conditions, while field soybean feeding resulted in stabilization of the mortality curve. Finally, cysteine protease activity and gut lipid peroxidation were also negatively affected by laboratory rearing conditions and the presence of bacteria in the insect’s gut, while under field conditions those parameters were not affected. These results suggest Nezara viridula needs natural environmental conditions to eliminate midgut bacteria and achieve gut homeostasis and therefor field experiment should be taken under consideration to support laboratory experiments.