INHERITANCE OF RUSSIAN WHEAT APHID RESISTANCE IN SPRING BARLEY

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a devas tating 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 19 93. Genetic analysis was performed on the parents, F-1, reciprocal F-1 , F-2, and backcross (BC) populations, as well as 231 F-2-derived F-3 Families. Segregation in the F-2 and BC populations indicated multiple gene control. Fourteen F-3 families were found to be homozygous resis tant and 16 were homozygous intermediate, indicating that two genes co ntrol RWA resistance in STARS-9301B, Analysis of data from the F-2 and BCs to both parents suggested recessive epistasis of a dominant gene (Dnb2) on an incompletely dominant gene (Dnb1). This type of genetic c ontrol will necessitate screening for RWA resistance after each cycle of selection in a breeding program.