Adverse Effects of Raw Soybean Extract in Artificial Diet on Survival and Growth of Lygus hesperus Knight

Bioassays were conducted to examine the effects of raw soybean extract in artificial diet on the development, survival, adult weight and biomass accumulation of Lygus hesperus Knight. The diet containing raw soybean extract significantly reduced survival of L. hesperus. Total biomass per rearing unit and survival from eggs to adults were significantly less for L. hesperus fed diet containing raw soybean extract than it was for those fed heat-treated extract, diet with extraction buffer but no extract, or control (standard) diet. Development period, weight of individual adults, and egg production were not significantly different among the four treatments. However, development time was greater for the L. hesperus exposed to raw soy extract, and egg production, as well as individual adult weights, were consistently lower than those fed on the other treatments. Raw and autoclaved soy extracts were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), revealing differences in protein banding patterns, including those from total protein and glycoprotein profiles. Activity of soy trypsin inhibitor (STI) also was measured in raw and heated samples, and it was determined that autoclaving greatly decreased the inhibition activity of this protein. The heat-based deactivation of STI, and the disappearance of most protein bands are most likely associated with the denaturation of proteins and formation of large aggregates that fail to migrate in an electrophoretic field.