WHEAT IS ONE OF THE MOST IMPORTANT CROPS FOR HUMAN NUTRITION IN THE WORLD, AND IT FEEDS AT LEAST ONE-THIRD OF THE WORLD'S POPULATION. IN ADDITION TO ITS POSITION AS ONE OF THE FOUNDATION CROPS OF AGRICULTURE, U.S. WHEAT ACCOUNTS FOR APPROXIMATELY 11% OF THE WORLD SUPPLY, AND NEARLY 35% OF WORLD EXPORTS. TO DEVELOP NOVEL WHEAT CULTIVARS IN THE GREAT PLAINS, IT IS CRITICALLY IMPORTANT TO MAINTAIN THE U.S.' ROLE AS A MAJOR GROWER AND EXPORTER OF WHEAT. HESSIAN FLY (HF, MAYETIOLA DESTRUCTOR SAY) IS ONE OF THE MAJOR INSECTS THAT FEED WHEAT PLANTS AND SIGNIFICANTLY AFFECT GRAIN YIELD AND END-USE QUALITY OF WHEAT IN THE U.S. AND WORLDWIDE. BIOTYPE GREAT PLAINS IS MOST PREVALENT IN THE SOUTHERN GREAT PLAINS. THIS INSECT ALSO BEHAVES LIKE A VECTOR TO TRANSMIT VIRUSES SUCH AS WHEAT STREAK MOSAIC VIRUS TO WHEAT PLANTS. ECONOMIC LOSSES TO WHEAT PRODUCTION FROM FREQUENTLY RECURRING HF HAS BEEN ESTIMATED $112-252 PER HA IN THE U.S. ALTHOUGH CHEMICAL INSECTICIDES ARE AVAILABLE TO ALLEVIATE THE INSECT STRESSES, GENETIC RESISTANCE IS THE MOST COST-EFFECTIVE AND ENVIRONMENTALLY FRIENDLY METHOD FOR CONTROLLING THE INSECTS. AT LEAST 37 GENES OR QUANTITATIVE TRAIT LOCI HAVE BEEN IDENTIFIED FOR RESISTANCE AGAINST HESSIAN FLY, AND MANY MORE GENETIC GENES HAVE BEEN REPORTED TO CONFER RESISTANCE AGAINST OTHER INSECTS, INCLUDING GREENBUG, RUSSIAN WHEAT APHID, AND WHEAT CURL MITE, BUT NONE OF THEM HAS BEEN CLONED SO FAR. THIS GAP RESULTS FROM A LACK OF UNDERSTANDING OF THE GENETIC BASIS OF THE GENES GOVERNING INSECT RESISTANCE IN THIS CRITICAL FOOD CROP. THIS KNOWLEDGE, IN TURN, HAS A DIRECT IMPACT ON OUR ABILITY TO DEVELOP NEW WHEAT CULTIVARS WITH IMPROVED INSECT RESISTANCE THAT ARE RESPONSIVE TO THE INCREASING CHALLENGES OF CLIMATE CHANGE AND GLOBAL FOOD SECURITY. THE POSITIONAL CLONING OF THE FIRST RESISTANCE GENE AGAINST HF, AS PROPOSED IN THE PROJECT, WILL ALLOW US TO HAVE A BETTER UNDERSTANDING OF THE MOLECULAR GENETIC MECHANISMS OF WHEAT-INSECT INTERACTIONS AND MORE EFFECTIVEAND EFFICIENT UTILIZATION OF THE RESISTANCE GENES IN WHEAT BREEDING.