Location of genes controlling resistance to greenbug (Schizaphis graminum Rond.) in Hordeum chilense

Wheat/Hordeum chilense disomic addition lines have been used to locate genes influencing resistance against greenbug (Schizaphis graminum Rond.) in specific chromosomes of H. chilense. H. chilense is a source of antixenosis, antibiosis and host tolerance to the greenbug, being resistant also to the Russian wheat aphid, the two key pests in wheat. For measuring antixenosis, the numbers of aphids per plant were recorded in a host free choice test; antibiotic resistance was determined by measuring the developmental time, the fecundity and the intrinsic rate of population increase of aphids reared on the different hosts, and host tolerance to aphids was evaluated by the leaf damage and the number of expanded leaves on the hosts after 3 weeks of infestation. The greenbugs belonged to a clone of biotype C. Plant genes with positive effects for antixenosis were located on chromosome 1Hch. Genes with positive effects for antibiosis were located on three different chromosomes and those that prolonged aphid developmental time were located on chromosomes 5Hch and 7Hch while those that reduced the total fecundity were on 4Hch. Chromosome 7Hch accounted for host tolerance to greenbug.