PRODUCTIVITY OF BARLEY INFESTED WITH RUSSIAN WHEAT APHID [DIURAPHIS-NOXIA (KURDJUMOV)]

Resistance to Russian wheat aphid, [Diuraphis noxia (Kurdjumov)], was studied in barley, (Hordeum vulgare L.), based on maintenance of plant height, spike number, straw weight, grain yield and kernel weight. The experiments comprised small plots artificially infested with the aphid, plots naturally infested, and plots regularly sprayed with insecticide. Seven symptomatically resistant and five symptomatically susceptible barleys were compared. Mature plant height of the resistant barleys, compared with the susceptible barleys, was better maintained in the artificially infested plots. Spike number, straw weight, grain weight and kernel weight were also better maintained in the resistant accessions than in the susceptible ones. Gloria/Come, symptomatically resistant, did not perform well over the parameters measured. The susceptible varieties Esperanza and Shyri were severely affected by the aphid in terms of the measured traits. Grain yield of infested plots as a percentage of control plots ranged between 50 and 77 %; spike number between 66 and 96 %; straw weight betwen 62 and 78 %, and kernel weight between 70 and 84 %. Genotypes Barberousse/Rumorosa//Gloria/Come and Barberousse/3/ASE/2CM//B76BB/4/Gloria/Come were the most resistant accessions. Selection of barley genotypes based on visual assessment of symptoms in artificially infested hill plots facilitates selection of genotypes that maintain their yield in artificially infested plots sown at commercial rates. These D. noxia resistant barleys are widely adapted and of good agronomic type, and will be useful to barley growers where the aphid is a pest.