Role of reactive oxygen species and isoflavonoids in soybean resistance to the attack of the southern green stink bug

Abstract

Southern green stink bugs (Nezara viridula L.) are one of the major pests in manysoybean producing areas. They cause a decrease in yield and affect seed quality byreducing viability and vigor. Alterations have been reported in the oxidative responseand in the secondary metabolites in different plant species due to insect damage.However, there is little information available on soybean-stink bug interactions.In this study we compare the response of undamaged and damaged seeds by Nezaraviridula in two soybean cultivars, IAC-100 (resistant) and Davis (susceptible), grownunder greenhouse conditions. Pod hardness, H2O2 generation, enzyme activities inguaiacol peroxidase (GPOX), catalase (CAT) and superoxide dismutase (SOD) aswell as lipoxygenase expression and isoflavonoid production were quantified.Our results showed a greater resistance of IAC-100 to pod penetration, a decrease inperoxide content after stink bug attack, and higher GPOX, CAT and SOD activities inseeds due to the genotype and to the genotype-interaction with the herbivorytreatment. Induction of LOX expression in both cultivars and higher production ofisoflavonoids in IAC-100 were also detected. It was then concluded that the herbivorystink bug induces pathways related to oxidative stress and to the secondarymetabolites in developing seeds of soybean and that differences between cultivarshold promise for a plant breeding program.