RESISTANCE TO RUSSIAN WHEAT APHID IN WILD HORDEUM SPECIES

The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious pest of cultivated barley, Hordeum vulgare L., grown where the aphid is endemic. Russian wheat aphid resistance identified in several wild Hordeum spp. may provide genetic variation necessary to breed Russian wheat aphid-resistant cultivated barleys. Eighty-four accessions representing seven species and four subspecies of wild Hordeum were screened to identify resistance to the Russian wheat aphid. Resistance was measured by plant damage, aphid reproduction, and aphid survival when confined to the plant for 14 d. Thirty-six of the 84 accessions were killed in the initial screening. Of the remaining 48 accessions, the damage rating scores (1 = no injury, 9 = dead plants) ranged from 1.33 to 7.67. There were intra-and interspecific differences among accessions, with the highest levels of resistance in H. bulbosum L. and H. brevisubulatum (Trin.) Link subsp. violaceum Boiss. & Hohen. One accession of H. bogdani Wil. had an intermediate level of resistance. Several accessions of H. bulbosum and one accession of H. brevisubulatum subsp. violaceum had low damage ratings, low aphid reproduction, and low leaf-curling ratings compared with other wild Hordeum accessions and the cereal checks. Broadening the genetic base of cultivated barley by the introduction of resistant alien genes may provide additional protection from new virulent strains or biotypes of the Russian wheat aphid.