Inheritance of Russian Wheat Aphid Resistance in Spring Barley

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a devastating pest of barley (Hordeum vulgare L.). An excellent source of RWA resistance (STARS‐9301B) was recently released to the barley industry. This greenhouse study was conducted to determine the genetic control of RWA resistance in STARS‐9301B. Crosses were made between Morex, a susceptible malting barley cultivar and STARS‐9301B during 1992 and 1993. Genetic analysis was performed on the parents, F1, reciprocal F1, F2, and backcross (BC) populations, as well as 231 F2‐derived F3 families. Segregation in the F2 and BC populations indicated multiple gene control. Fourteen F3 families were found to be homozygous resistant and 16 were homozygous intermediate, indicating that two genes control RWA resistance in STARS‐9301B. Analysis of data from the F2 and BCs to both parents suggested recessive epistasis of a dominant gene (Dnb2) on an incompletely dominant gene (Dnbl). This type of genetic control will necessitate screening for RWA resistance after each cycle of selection in a breeding program.