Soybean resistance to stink bugs ( N ezara viridula and P iezodorus guildinii ) increases with exposure to solar UV ‐ B radiation and correlates with isoflavonoid content in pods under field conditions

Solar UV ‐ B radiation (280–315 nm) has a significant influence on trophic relationships in natural and managed ecosystems, affecting plant–insect interactions. We explored the effects of ambient UV ‐ B radiation on the levels of herbivory by stink bugs ( N ezara viridula and P iezodorus guildinii ) in field‐grown soybean crops. The experiments included two levels of UV ‐ B radiation (ambient and attenuated UV ‐ B ) and four soybean cultivars known to differ in their content of soluble leaf phenolics. Ambient UV ‐ B radiation increased the accumulation of the isoflavonoids daidzin and genistin in the pods of all cultivars. Soybean crops grown under attenuated UV ‐ B had higher numbers of unfilled pods and damaged seeds than crops grown under ambient UV ‐ B radiation. Binary choice experiments with soybean branches demonstrated that stink bugs preferred branches of the attenuated UV ‐ B treatment. We found a positive correlation between percentage of undamaged seeds and the contents of daidzin and genistin in pods. Our results suggest that constitutive and UV ‐ B ‐induced isoflavonoids increase plant resistance to stink bugs under field conditions.