Isozyme characterisation of Fusarium graminearum isolates associated with head blight of irrigated wheat in South Africa

Head blight, caused by certain species in the genus Fusarium, has become an economically important disease of wheat under centre pivot-irrigation along the Orange River region in :South Africa. Isozyme analysis, by means of starch gel electrophoresis, was employed to compare 73 Fusarium isolates, obtained from three farms in this region, with isolates of Fusarium acuminatum, F. chlamydosporum, F. compactum, F. crookwellense, F. culmorum, F. equiseti, F. graminearum Group I and Group II, F. moniliforme, F. oxysporum, F. solani, and F. subglutinans. For all 11 Fusarium species, nine loci were identified in eight enzyme systems and 19 electrophoretic phenotypes (EPs) were detected, each composed of isolates from one species only. The extent of isozyme polymorphisms found among these Fusarium spp. provides a potential method for delineating isolates at species level. Six EPs, of which the most common one comprised 36 isolates, were identified within isolates obtained from the three farms. These isolates clustered together with the F. graminearum Group II reference isolates. Based on perithecial production, their identity was confirmed as F. graminearum Group II.