Proposed system of nomenclature for biotypes of Hessian fly (Diptera: Cecidomyiidae) in North America

Twenty genes in wheat, Triticum spp., for resistance to Hessian fly, Mayetiola destructor (Say), have been previously designated H1 to H20. The location on wheat chromosomes of some of the genes is known, but several have not yet been assigned to specific chromosomes. Four wheat differential cultivars have been used to identify 16 possible biotypes of Hessian fly; biotypes were designated GP and A-O. If an additional differential host genotype were added, it is apparent that there are not enough letters in the alphabet to designate all of the biotypes. Therefore, a new system of biotype designation is proposed. Three differential cultivars or lines are assigned to a set. Sets are designated A, B, C, and so on. There are eight combinations of resistant and susceptible reactions within a set. These are coded 1 to 8 for each set. Three sets are proposed to begin biotype designation. A biotype avirulent to all differentials in three sets is coded 111. If set C were not used, a zero (untested) replaces the digit. In the above case, the biotype is designated 110. The biotype designation system provides flexibility for the addition of new sets as new genes are identified and for the deletion of sets no longer deemed useful