Resistance in Durum Wheat Sources to Hessian Fly (Diptera: Cecidomyiidae) Populations in Eastern USA

Damage from Hessian fly, Mayetiola destructor (Say), infestation of soft red winter wheat, Triticum aestivum L, in the eastern USA has been reduced by the deployment of genes for resistance in commercial cultivars. Hessian fly populations in the eastern USA have developed virulence to previously deployed genes for resistance except for H13, deployed in 1998. Durum wheat, Triticum durum Desf., is an important source of resistance to Hessian fly. Four populations of Hessian fly, believed representative of the eastern USA, were selected for seedling tests of 26 durum genotypes which had shown resistance to Hessian fly biotypes B, D, or L in earlier laboratory tests. The putative number of genes conditioning resistance to laboratory biotype L was determined in backcross segregation analysis of 11 PI selections of unknown genotype. The number of genes for resistance to Hessian fly was also recorded of other durum genotypes in the test from observed segregation or published data. Some common wheat genotypes were included in tests with the four populations. Most of the 26 durum genotypes were resistant to the four eastern USA Hessian fly populations. The four Hessian fly populations were similar in avirulence to most durum germplasm lines but with differences in virulence to a few lines. The four populations were virulent to the previously deployed resistances provided by H3, H5, and H6. The northern two Hessian fly populations were virulent and the southern two populations were avirulent to the previously deployed resistance of H7H8. Resistance to laboratory biotypes D or L of the 26 durum genotypes was conditioned by one, two, or three genes, depending upon line.