Variation among Fusarium species and isolates infecting wheat ears based on aggressiveness, mycotoxin production and RAPD-PCR analysis

Abstract

Fusarium species from Germany and Kenya were investigated for the variation in mycotoxin production, aggressiveness on wheat ears and PCR-based DNA fingerprints in order to characterize the Fusarium species and isolates involved in the head scab complex of wheat in different regions. Nineteen isolates of F. graminearum from Kenya were screened for aggressiveness and trichothecene production on wheat ears and in vitro-mycotoxin production on autoclaved cracked corn. Two isolates of each Fusarium species, F. avenaceum, F culmorum, F. graminearum and F poae, respectively, were compared for their virulence and aggressiveness on four winter wheat cultivars. Twenty isolates belonging to various Fusarium species differing in mycotoxin production and aggressiveness in wheat were characterized by random amplified polymorphic DNA (RAPD-PCR). The Fusarium species were differentiated by cluster analysis of the PCR products using decamer random primers. Isolates of F. graminearum markedly varied in aggressiveness and mycotoxin production. Variation among isolates was also evident in RAPD-PCR profiles, indicating that it is genetically inherited. For F. culmorum isolates from Germany, RAPD-PCR profiles did not clearly differentiate between nivalenol- and deoxynivalenol-producing isolates, for F. graminearum however, the two chemotypes could be discriminated. Therefore, most of the F. culmorum isolates may be capable of producing both trichothecenes, as was demonstrated by a few isolates of this species. Differences in aggressiveness of isolates of F. graminearum and F. culmorum isolates, however, could not be related to the variation in RAPD patterns. The high genetic variability for aggressiveness and mycotoxin production among isolates of Fusarium species within small regions considerably complicates the forecasting of the effects of head scab on yield quantity and quality.