Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/1996
Publication Date: N/A
Interpretive Summary: The Hessian fly is the most important insect pest of wheat in the eastern U.S. Although fly populations are suppressed by resistant wheat varieties, the insect has been able to evolve new strains, or biotypes, over time, that can live on wheat plants with resistance genes, thus reducing effectiveness of control. This study describes research to determine the frequency of resistance-breaking (virulent) biotypes in Hessian fly populations in the eastern U.S. and their response to improved wheat lines with 11 resistance genes that are being investigated in the Purdue/USDA program. Laboratory research identified the major Hessian fly biotypes in populations collected from Arkansas, Florida, Indiana, Michigan Pennsylvania and South Carolina and determined shifts in virulence to resistance genes in these populations. Although most of the Hessian fly populations were virulent to resistance genes presently utilized in wheat varieties, many of the newer genes under investigation were effective against a range of fly populations. The most effective genes or gene combinations were identified for use against Hessian fly populations in specific areas of the eastern U.S. This information is vital to researchers developing wheat varieties for these areas and will aid entomologists and wheat breeders in determining the most effective way to use resistance genes in the future to prolong their effectiveness in controlling the Hessian fly.
Technical Abstract: Ten Hessian fly, MAYETIOLA DESTRUCTOR (Say), populations from the eastern United States were evaluated for biotype composition and response to 15 Hessian fly resistance genes. The biotype composition of populations was estimated by confining individual gravid females on four wheat differentials with resistance genes H7H8, H3, H5 and H16. The response of Hessian fly populations and biotypes to resistance genes was evaluated in replicated tests with wheat lines homozygous for genes H9, H10, H11, H12, H13, H14, H15, H16, H17, H18 and H19. Hessian fly populations from northwestern Florida and southwestern South Carolina were predominantly biotypes E, G, M and O and were avirulent to genes H7H8. Fly populations from northeastern and northwestern South Carolina contained H7H8-virulent biotypes J and L in varying frequency. Populations from north central Arkansas and Indiana were predominantly biotype L. In tests with genes H9-H19 to laboratory-reared biotypes GP, B-E and L, H9 was susceptible to biotype C, H12 to biotype E, and H11 and H15 to biotype L. Genes H16 and H17 were resistant to all Hessian fly biotypes and populations, while the remaining genes varied in response to fly sources. The overall effectiveness of genes H9-H19 to the 10 fly populations, in descending order of effectiveness, was H16=H17>H9=H13=H14>H10=H18>H12=H15=H19>H11. The number of Hessian fly populations virulent to the respective genes were H16, H17=0; H9, H13, H14=1; H10, H18=2; H12, H15, H19=3; H11=7.