WILD GRASSES OF THE GENUS AEGILOPS AS HOSTS FOR CEREAL APHIDS

Over a 3 year period, 213 accessions of 20 Aegilops species were evalu ated for their suitability as hosts for cereal aphids under field cond itions. Three aphid species, Metopolophium dirhodum, Sitobion avenae a nd Rhopalosiphum padi were observed on Aegilops species. Their proport ion and density on the plants varied among years. The highest variabil ity in infestation among years was found in M. dirhodum, and the lowes t in S. avenae. According to positive and negative differences from th e average plant infestation, the number of unsuitable species prevaile d over suitable ones in all three aphid species. Greater differences b etween the number of unsuitable and suitable species were observed in 1989 and 1990, i.e., in the years with the lower aphid occurrence. Bet ween results of these 2 years, a significant positive correlation (P < 0,05) was found for all three aphid species. There was also a positiv e correlation among aphid species in their choice of Aegilops, especia lly between M. dirhodum and R. padi (P < 0.001) in all 3 years. The re sults are discussed from the point of view of virus transmission and c ereal resistance to aphids.