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

Abstract

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 (Nezara viridula and Piezodorus 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.

Solar UV light regulates flavonoid metabolism in apple (Malus x domestica)

“…This phenomenon has been observed in other crops, including an increase in the harvestable weight of lettuce exposed to UV‐B (Wargent et al, ). There is evidence for an increase in photosynthetic performance and an increase in secondary metabolism in plants treated with UV‐B and that acclimation to UV‐B may have positive effects on growth and plant immunity (Wargent, Nelson, McGhie, & Barnes, ; Zavala, Mazza, Dillon, Chludil, & Ballare, ). How this increase in fruit weight is elicited remains to be studied, although photosynthetic capacity and performance are likely contributors.…”

Isoflavone Malonyltransferases GmIMaT1 and GmIMaT3 Differently Modify Isoflavone Glucosides in Soybean (Glycine max) under Various Stresses

“…Soybean tissues infected with pathogens produce isoflavonoid phytoalexins (coumestrol and glyceollins) in site during defense responses to pathogen attacks (Zavala et al, 2015; Nakata et al, 2016; Yoneyama et al, 2016). The fluctuations of endogenous isoflavones in various forms, such as glucosides and malonates, are also detected under various conditions, although their coding physiological meanings barely are understood (Suzuki et al, 2007; Dhaubhadel et al, 2008; Farag et al, 2008; Zhao et al, 2011; Zhao, 2015).…”

“…Isoflavonoids play a vital role in plant defense response against different biotic and abiotic stresses, such as plant-pathogen by acting as precursors for phytoalexins biosynthesis (Graham and Graham, 1991; Dixon, 2001; Zhao et al, 2005;Akashi et al, 2009; Zhou et al, 2011; Ishiga et al, 2015; Yoneyama et al, 2016), plant-insects (Murakami et al, 2014; Zavala et al, 2015; Nakata et al, 2016), plant-symbionts by providing signals for Nod gene stimulation and nodule development (Subramanian et al, 2007; Zhang et al, 2009; Yasuda et al, 2016), and abiotic environmental stresses (Gutierrez-Gonzalez et al, 2010; Tripathi et al, 2016). They also contribute significantly to health beneficiary properties of legume seed foods for improving human health against heart disease, female breast cancer, and cardiovascular disease (Shin and Lee, 2013; Lee et al, 2016).…”

The Role of Specialized Photoreceptors in the Protection of Energy‐Rich Tissues

“…UV-B and inducible defenses: UV-B attenuation experiments in the field have clearly shown that natural herbivory is more severe on plants growing with attenuated levels of UV-B compared to those exposed to full sunlight [7,[71][72][73]. Most of the plants increase the accumulation of soluble phenolic compounds in green tissues in response to UV-B, where some of these compounds were shown to have a direct role on insect herbivore performance [51,74,75].…”