Distinct electrophoretic isozyme profiles of Fusarium graminearum and closely related species

Cellulose-acetate electrophoresis (CAE) was used to investigate isozyme polymorphisms among different isolates of Fusarium cerealis, F. culmorum, F. graminearum and F. pseudograminearum from around the world. After initial testing of 22 enzymes in three buffer systems for activity and resolution of bands, 12 proved to be appropriate for analysis of the full sample set. Remarkably uniform isozyme patterns were obtained intraspecifically, irrespective of the geographical origin of the isolates or the host/substratum from which they were isolated. This result indicated that isolates within a given species are descendant from a same ancestral population. Comparing the different electrophoretic types (ETs), adenylate kinase (AK), NADP dependent glutamate dehydrogenase (NADP GDH), peptidase B (PEP B), peptidase D (PEP ID) and phosphoglucomutase (PGM) proved to be diagnostic for at least one species examined. However, only PEP D was useful alone as a marker to distinguish the four taxa studied providing a rapid and simple CAE based diagnostic protocol. Cluster analysis of band sharing coefficients grouped the isolates into four distinct groups corresponding to the 4 species studied. Isolates of F. cerealis were clustered between those of F. culmorum and F. graminearum corroborating their known close relationship to both species. For common ETs, the similarity values between F. cerealis and F. culmorum and between F. cerealis and F. graminearum were the same. Furthermore, the similarity values and the resulting phenogram indicated that F. graminearum is more closely related to F. cerealis and F. culmorum than to F. pseudograminearum, thus the morphological similarity of F. graminearum and F. pseudograminearum does not reflect their generic relationship. This fact supports the species status of F. pseudograminearum.