Calli growth patterns and 1-dimensional protein profiles of resistant (PI 137739) and susceptible (‘Stephens’) genotypes of wheat, Triticum aestivum L., were examined after treatment with extract fractions from the Russian wheat aphid, Diuraphis noxia (Mordvilko). Growth of resistant calli were consistently higher than susceptible calli after treatment. Expression of several polypeptides were altered specifically in susceptible calli exposed to D. noxia extracts. Use of these polypeptides in in vitro genotype selection is discussed.