MAPPING RESISTANCE TO CEREAL APHIDS IN BARLEY

A set of 150 doubled-haploid (DH) barley (Hordeum vulgare L.) lines de rived from the cross of Harrington/TR306 was used to determine the num ber and chromosomal location of quantitative trait loci (QTLs) control ling resistance to cereal aphids. The experiments were conducted under natural infestation in the field during two growing seasons: 1994 and 1995. Aphid resistance was measured by counting the number of aphids per plot. Counts were made on a weekly basis. Each year at the time of maximum aphid density there was an obvious difference in reaction bet ween the parental genotypes. The DH lines showed continuous variation for aphid density. Simple interval mapping and simplified composite in terval mapping revealed that the principal QTL determining cereal aphi d resistance is on the distal region of the short arm of chromosome 1. This aphid-resistance QTL is linked with a heading-date QTL. At the t ime of highest aphid infestation, this QTL accounted for 31% and 22% o f the total variance of aphid density in 1994 and 1995, respectively. A QTL on chromosome 5 was also detected but only by simplified composi te interval mapping. However, the largest consistent effect was due to the QTL on the short arm of chromosome 1. This QTL may be a useful ta rget for marker-assisted selection for adult plant cereal aphid resist ance in barley.