Inheritance and allelic relationships of resistances to the Russian wheat aphid in two Iranian wheat lines

Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is a serious pest of small grains in many countries. A previous study screened 70 genotypes, collected from different parts of Iran, for RWA resistance. Four crosses were made between two resistant lines (Shz.W-102 and Shz.W-104) and two susceptible lines (Shz.W-101 and Shz.W-103). Parents, F₁, F₂, and BCF₁ seedlings were screened for RWA resistance in the greenhouse by artificial infection. To determine allelism, the two resistant lines were intercrossed and F₁, and F₂ seedlings were evaluated. Resistance in Shz.W-102 and Shz.W-104, when crossed with Shz.W-101, was controlled by one dominant gene. However, resistance in Shz.W-102 and Shz.W-104, when crossed with Shz.W-103, was controlled by two dominant genes. Genes in two resistant lines segregated independently of each other. A three-gene system was proposed to govern resistance in the lines under study . This revised version was published online in July 2006 with corrections to the Cover Date.