The genetic relationships of 56 isolates from the taxa traditionally grouped in Fusarium sections Fusarium (syn. Discolor) and Roseum
were studied using the Restriction Fragment Length Polymorphism (RFLP) technique, by Southern hybridisation with random
genomic and mitochondrial DNA probes originating from Fusarium species. Pairwise distances between taxa were calculated from the
957 RFLP bands scored on autoradiograms, using Dice's coefficient in the RAPDistance computer program. A strong genetic
relationship was observed between F. graminearum, F. culmorum and F. crookwellense. However, the morphologically similar taxon, F.
pseudograminearum shared only approximately 40% of genomic DNA RFLP bands with these taxa, demonstrating affinity, but less
direct genetic similarity. Of all taxa examined F. pseudograminearum and F. graminearum shared the greatest similarity in mitochondrial
DNA RFLP patterns. F. avenaceum subsp. avenaceum, subsp. aywerte and subsp. nurragi displayed very little genetic resemblance with
each other, or with F. heterosporum and the cereal infecting pathogens. F. torulosum was closest genetically to subsp. avenaceum, with
approximately 22% of genomic DNA RFLP bands in common. On the basis of these results F. avenaceum subsp. aywerte and subsp.
nurragi are elevated to species rank, as F. aywerte comb.. nov. and F. nurragi comb. nov., and F. avenaceum subsp. avenaceum is returned to
its former species status.