Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/1996
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 races (biotypes) over time, that can survive on and injure wheat plants with resistance genes, thus reducing effectiveness on control. This study describes research to determine the frequency of resistance-breaking (virulent) biotypes in Hessian fly populations in the mid-south and southeastern U.S. and their response to wheat germplasm lines with 11 resistance genes that are being investigated in the Purdue/USDA program. Laboratory research identified the major Hessian fly biotypes in 13 populations collected from Arkansas, Georgia, Illinois, North Carolina, and Virginia and determined shifts in virulence to resistance genes in these populations. Results demonstrated that all genes presently incorporated into soft winter wheat varieties grown in the eastern U.S. are ineffective except in the extreme southeast. Newer resistance genes varied in effectiveness to the Hessian fly populations, but 7 of the 11 genes were highly resistant to the populations studied. This information is vital to researchers developing wheat varieties for the mid-south and southeastern states, and will aid entomologists and wheat breeders in determining the most effective way to use resistance genes or gene combinations in the future to prolong their usefulness in controlling the Hessian fly.
Technical Abstract: Thirteen Hessian fly, Mayetiola destructor (Say), populations from Arkansas, Georgia, Illinois, North Carolina, and Virginia were evaluated for biotype composition and two Arkansas populations were tested for response to Hessian fly resistance genes H3, H5, H6, H7H8, and H9 to H19 in wheat, Triticum spp. Hessian fly populations from Arkansas were predominantly biotype L, with low levels of biotypes F, G, J, M, and O, depending upon population. Biotype L was predominant in the Illinois, North Carolina, and Virginia populations, although Biotype D ranged from 14 to 26% in populations from extreme southwestern Illinois and Virginia and North Carolina. Biotypes M and O were identified from the southwestern Georgia fly population. All fly populations were virulent to resistance genes H3, H5, and H6, while the Georgia population was avirulent to H7H8. Plants with single resistance genes H9 to H19 varied signficantly (P < 0.05) in their resistance to the Arkansas populations. Plants with single gene pairs H9, H10, H13, H14, and H16 to H19 conditioned resistance (88 to 100%) to both populations, while plants with single resistance genes H11, H12, or H15 were susceptible to one or both populations. Wheat germplasm lines developed in the Purdue/USDA program which carry single gene resistances H9, H13, H14, and H16 to H19 should provide excellent sources of resistance for developing improved wheat cultivars adapted to the mid-south and southeastern United States. Results also indicate continued effectiveness of the resistance gene combination H7H8 in the lower southeastern states.