Response of the antioxidative defence to flavonoid quercetin in two populations of Lymantria dispar L.

Abstract

Lymantria dispar L. a polyphagous herbivore is the most dangerous insect pest of forest and fruit trees. Its host range is estimated at more than 500 plant species from 73 families (Lance, I 983, Liebhold et al., 1995). 111e locust tree Robinia pseudoacaccia is a plant that the gypsy moth avoids as a food (Barbosa and Krischik, 1987). Locust tree leaves contain large quantities of alkaloids and flavonoids (Bagrbosa & Krischik 1987). Some of them may have toxic and prooxidant effects (Hodnick et al., 1986). Gypsy moth populations in locust tree forest are rare (Jankovic 1958). The ingestion of oxidizable flavonoids can exacerbate oxidative stress in herbivorous insects (Ahmad, 1992; Felton and Summers, 1995; Pardini, 1995). The flavonoid quercetin used in this experiment was chosen as test prooxidant plant allelochemical. Upon insect ingestion quercetin is metabollicaly activated by one-electron oxidation to a free radical (o­ semiquinone) which in turn reacts with 02 (oxygen) to generate 0{ (superoxide anion radical) and consequently H202 (hydrogen peroxide) and OH (hydroxyl radical) resulting in numerous destructive reactions in insect cell (Hodnick et al.,1986; Hodnick et al.,1989).