Induced response to insect damages can result in chemical alteration in plants. The ability of Nezara viridula to induce the production of flavonoids in seeds of soybean genotypes (‘BR-16’, ‘IAC-100’, PI 227687, PI 229358, PI 274454) was investigated at greenhouse conditions. Cages with four stink bugs were placed on soybean plants, during 18 hours. Soybean pods were collected 72 hours after stink bugs have been removed and the damaged parts were identified, cut out and ground. A sample of 0,100 mg from each genotype was homogenised with 0,5 ml of 80% methanol (MeOH). After centrifugation, the supernatant was dried in N2, redissolved in 100 ? L 80% MeOH and an aliquot of 20 ? L were injected in HPLC (High Performance Liquid Chromatograph) for flavonoid analysis. The genotype PI 227687 damaged by N. viridula presented the highest concentration (0.35 mg/ml) of daidzin (daidzein 7-O-glucoside); the lowest concentration of isoflavone was observed in PI 229358 (0.03 mg/ml). The same tendency was observed with genistin (genistein 7-O-glucoside); PI 227687 presented 0.14 mg/ml, PI 274454, 0.03 mg/ml and PI 229358, 0.04 mg/ml of genistin. In general, genotypes damaged by stink bugs, produced higher isoflavones contents (daidzin and genistin), compared to controls (without stink bug damage). However, after being damaged by stink bug, PI 274454 and PI 229358 produced less genistin than the other genotypes and no difference in concentration between damaged plants and non-damaged was observed. N. viridula increased concentration or induced daidzin and genistin productions in PI 227687 seeds. Therefore, further studies must be carried out to elucidate their role on soybean defence against stink bugs.

Index terms: resistance, green stink bug, daidzin, genistin.

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