Protein composition of wheat apoplastic fluid and resistance to the Russian wheat aphid

The protein composition of intercellular fluids from three different wheat cultivars (Triticum aestivum L. cvv. Tugela DN, Molopo DN and Betta DN) with resistance to the Russian wheat aphid, Diuraphis noxia (Mordvilko) and the corresponding near-isogenic susceptible cultivars (Tugela, Molopo and Betta) were studied under conditions of infestation and non-infestation. The aim was to gain information on the mechanism of resistance and the possible presence of molecular markers of resistance. Aphid infestation induced the accumulation of specific corresponding proteins in the intercellular fluids of resistant cultivars only. The infestation-related proteins were of different molecular mass ranges (28-33; 22-24; 18.5-19.5 and 15.5-17 kDa). Some were serologically related to PR proteins. We suspect that the infestation-related proteins are involved in resistance to the Russian wheat aphid. Although not particularly time saving, the intensified bands of infestation-related proteins on SDS-PAGE gels may be useful for determining resistance.