EFFECTS OF NACL ON GLYCINE-BETAINE AND ON APHIDS IN CEREAL SEEDLINGS

The effect of NaCl on the aphid Schizaphis graminum was studied on seedlings and with artificial diets. Wheat and barley seedlings irrigated with saline Hoagland solution (0-700 mM NaCl) accumulated ions in their leaves. Glycine-betaine, also accumulated in wheat and barley seedlings with increasing salt levels. The population growth rate of the aphid S. graminum in wheat decreased with the amount of salt accumulated by leaves. In barley, however, population growth rate of aphids reached a minimum at 50 mM NaCl, increasing at higher NaCl concentration. Survival of aphids feeding from artificial diets with NaCl decreased (LD50 = 65 mM). Glycine-betaine, however, increased both survival and reproduction in salt treated and untreated aphids. In addition, ingestion time of aphids feeding in artificial diets also decreased (ED50 = 105 mM). These results show that accumulation of NaCl by cereals is more deleterious to aphids in wheat than in barley. This could be partly explained by the higher glycine-betaine accumulation in barley leaves.