A comparison of polypeptides from the wheat bunt fungi Tilletia laevis, T. tritici, and T. controversa

Phenol-soluble polypeptides were extracted from teliospores of six races of each of Tilletia laevis and T. tritici, and eight collections of T. controversa. The polypeptides were separated by two-dimensional isoelectric focusing – polyacrylamide gel electrophoresis and the resulting patterns compared. Although the races and collections had the morphological and physiological features of their respective species and possessed different combinations of virulence genes, they all gave similar polypeptide patterns. There were 359 polypeptides common to all 20 races and collections. Another 56 polypeptides were found in only some races and collections, but none of these variable polypeptides were species specific, i.e., found in every race or collection of one species but absent from every race or collection of one or both of the other species. Therefore, no polypeptide could be correlated to a morphological or physiological feature typical of any one species. Furthermore, no correlation was found between the polypeptides and virulence. However, previous studies on interspecific hybridization, the overlap in spore morphology and germination requirements, and the high number of common polypeptides and absence of species-specific polypeptides demonstrated here prove a closer genetic relationship among the three fungi than is indicated by their current taxonomic designation. It is, therefore, proposed to treat them as varieties of one species: T. tritici var. laevis, T. tritici var. tritici, and T. tritici var. controversa.