Inheritance of Russian Wheat Aphid Resistance in Spring Barley Germplasm Line STARS‐9577B

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has become a major pest of barley ( Hordeum vulgare L.) in the western USA. STARS‐9577B (PI 591617), a six‐rowed, spring barley germplasm line with a high level of resistance to RWA, was recently released to barley breeders for barley improvement. Understanding the inheritance of RWA resistance in this germplasm line is necessary for breeders to develop an effective strategy for utilization of this germplasm in their breeding programs. This greenhouse study was conducted to determine the genetic control of RWA resistance in STARS‐9577B. Crosses were made between ‘Morex’, a susceptible, six‐rowed, malting barley cultivar, and STARS‐9577B. Genetic analyses were performed on reaction to RWA of parents, F 1 , reciprocal F 1 , F 2 , backcrosses (BC 1 F 1 ) to both parents, and F 2 ‐derived F 3 families. Reaction was based on a visual rating scale of 1 to 9 (1 = no damage, 9 = dead plant). Segregation in the F 2 and BC 1 F 1 populations indicated multiple gene control. Seventy‐seven F 3 families were found to be homozygous resistant and 18 homozygous susceptible, indicating two gene control of RWA resistance in STARS‐9577B. Analysis of data from F 2 and BC 1 F 1 populations suggested RWA resistance in STARS‐9577B is controlled by dominant alleles at two loci, with alleles at one locus conferring a high level of resistance and alleles at the other locus conferring an intermediate level of resistance only when recessive alleles are present at the first locus.