Glycine-betaine in wilted barley reduces the effects of gramine on aphids

Abstract

The gramine content in different barley cultivars was not changed under water stress. Proline and glycine-betaine increased as plant water potential decreased. The population growth rate of the aphids Schizaphis graminum and Rhopalosiphum padi were increased in plants with higher glycine-betaine/gramine ratio. When the aphids were fed with artificial diets with different ratios of glycine-betaine/gramine, the survival of aphids increased in proportion to the glycine-betaine content in the diets. Proline had no effect on the survival of aphids. The LD50 of gramine was 0.8 and 4.1 mM when 0 and 12 mM glycine-betaine were added to the diets. These results suggest that glycine-betaine accumulation due to water stress may reduce the harmful effects of gramine on the aphids S. graminum and R. padi