Biotype composition of Hessian fly (Diptera : Cecidomyiidae) populations from the southeastern, midwestern, and northwestern United States and virulence to resistance genes in wheat

Twenty-three Hessian fly, Mayetiola destructor (Say), populations collected in the southeastern (Alabama and Mississippi), midwestern (Indiana), and n orthwestern (Idaho and Washington) United States from 1995 to 1999 were eva luated for biotype composition based on response to Hessian fly resistance genes H3,H5, H6, and H7H8 in wheat, Triticum aestivum L. Biotypes L and O, combined, mode up at least 60% of all Alabama populations. Biotype L was pr edominant in the northern third of Alabama and biotype O in the southern tw o-thirds of the state. Based on biotype data, wheat cultivars with H7H8 res istance should he highly effective in central and southern Alabama. Fifty-f our percent of the Mississippi population consisted of biotype L, and the r emaining virulent biotypes (B, D, E, G, J, and O) ranged in frequency from 1 to 17%. The Mississippi population also contained 4% of the avirulent bio type GP. Only biotypes D and L were found in Indiana populations, but bioty pe L was predominant. Hessian fly populations from Idaho and Washington con tained one or more of the virulent biotypes D-H, J, and L-O; however, only biotypes E, F, and G occurred at frequencies >12%. The avirulent biotype GP made up 25-57% of Idaho and Washington populations, a much higher percenta ge than found in populations from the eastern United States. Although the h ighest level of virulence in Idaho and Washington populations was found to resistance genes H3 and H6, the frequency of biotype GP would indicate that the currently deployed gene H3 would provide a moderate to high level of r esistance, depending on location. Nine of the populations, plus populations collected from the mid-Atlantic state area in 1989 and 1996, also were tes ted against the wheat cultivar 'INW9811' that carries H13 resistance to Hes sian ny biotype L and two Purdue wheat lines with unidentified genes for re sistance. The H13 resistance in INW9811 was highly effective against all po pulations tested from the eastern and northwestern U.S. wheat production ar eas, except Maryland and Virginia. population studies also indicated that w heat line CI 17960-1-1-2-4-2-10 likely carries the H13 resistance gene, bas ed on the similarity of its response and that of INW9811 to eight flp popul ations. Continued monitoring of biotype frequency in Hessian ny populations is required for optimal deployment and management of resistance genes in a ll wheat production areas.