MONOSOMIC ANALYSIS OF RUSSIAN WHEAT APHID (DIURAPHIS-NOXIA) RESISTANCE IN TRITICUM-AESTIVUM LINE PI137739

The Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphid idae), has become an important pest of wheat (Triticum aestivum L.) in the United States. The aphid causes a phytotoxemic reaction in wheat evidenced by local and systemic chlorosis and rolling of infested leav es. Developing resistance in wheat cultivars to D. noxia is an essenti al factor in controlling the damage caused by this pest. Several sourc es of genetic resistance to D. noxia have been identified in wheat ger mplasm. Monosomic analysis of the monogenic resistant T. aestivum acce ssion PI137739 has shown that the gene (Dn1) for resistance is carried on chromosome 7D. It appears that chromosome 7B may carry a second re sistance gene for D. noxia that might be a source of minor or compleme ntary gene action for resistance.