Biotype determination and a study of the selective interaction between the Hessian fly, Mayetiola destructor (Say), and wheat, Triticum aestivum L. em Thell

Fifteen collections of Hessian fly from the northern portion of the soft winter wheat region were used to determine the biotype composition and frequency. Biotypes J and L were found to have replaced biotype B as the prevalent biotypes in Indiana since wheat cultivars carrying the H5 and the H6 genes have been grown. Biotype GP, the least virulent of the known biotypes of Hessian fly, was identified in New York indicating that cultivars with no genes for resistance are still being grown there. Experiments were conducted to determine the interaction between wheats having the H6 gene and Hessian fly biotype M. By definition, biotype M should not survive on wheats having the H6 gene. Auburn, Caldwell, Fillmore, and Knox 62, cultivars all having the H6 gene for resistance, were exposed to Hessian fly biotype M. Reactions to biotype M were significantly different among the cultivars. The selection experiments showed that resistance of Auburn and Fillmore could be easily overcome. Selection on wheats having the H6 gene resulted in a biotype derived from biotype M, capable of surviving on wheats having the H6 gene. This new biotype selected on specific cultivars with the H6 gene differed depending on the cultivar used for selection. Results showed that Knox 62 was consistently different from the other three cultivars used in this study because it probably possesses the H6, the H7H8 and Kawvale genes. Therefore, Knox 62 should not be used as the H6 gene source as a differential cultivar. The responses of this new biotype to wheats having the H9, H9H10, H12, and H13 genes were determined. Results showed that this new biotype possesses virulence on wheats having the H9, H12, and H13 genes. The flies have linked virulence for the H6, H9, H12, and H13 genes