Soybean drought-stressed plants impair Anticarsia gemmatalis (Lepidoptera: Erebidae) midgut proteolytic activity and survival

Soybean plants are exposed to multiple stresses during development. Co-occurring stresses can activate common defense pathways on plants, increasing end products concentrations, such as protease inhibitors (PIs). Here, we evaluated the impact of drought stress on soybean defense mechanisms regarding PIs. Furthermore, the midgut proteolytic activity and survival of A. gemmatalis larvae fed with drought-stressed and well-watered plants were assessed. The lipoxygenase activity remained similar on soybean exposed to moderate (−0.6 and − 1.0 MPa) and severe (−1.6 MPa) drought stresses, however were higher than the irrigated control. The PIs activity on soybean was only induced due to herbivory at those exposed to moderate stress (−0.6 and − 1.0 MPa). The total-proteases and trypsin- like reduced activities in the midgut of A. gemmatalis that fed on moderate-stressed plants reflected the effects of the PIs induced after herbivory. Furthermore, A. gemmatalis showed reduced survival on drought-stressed plants over those well-watered. The results add knowledge about factors that limit A. gemmatalis performance.