Virulence in different populations of Hessian fly to resistance genes in wheat

The Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), is a serious pest of wheat in the southeastern United States.  Resistant wheat is the most effective method for control of this pest.  Unfortunately, the deployment of resistance results in an increase in the frequency of genotypes of the pest that can overcome deployed resistance.  This necessitates evaluation of the efficacy of identified resistance (R) genes on a regular basis.  In 2010 we reported on the efficacy of identified R genes for protection of wheat.  These results documented that a limited number of the evaluated R genes would provide effective protection of wheat in the southeastern United States.  In the present study, we have evaluated the efficacy of the newest identified R genes as well as some of the previously evaluated R genes with field populations of Hessian fly from the southeastern United States.  Additionally, we compared virulence in populations from the southeastern United States with the virulent Indiana Biotype L and a population from the Middle East.  These data document that only a few of the 35 identified R genes will provide effective protection of wheat in the Southeast and compare differences in virulence between pest populations from the Southeast, the Upper Midwest, and the Middle East.  This study highlights the need to identify effective new native genes for resistance to Hessian fly as well as transgenic resistance that can be pyramided with native resistance to ensure durable protection of wheat.  Studies directed toward these needs will be summarized.