Genetic and phenotypic variation of Fusarium proliferatum isolates from different host species.

Fusarium proliferatum (Matsushima) Nirenberg is a common pathogen infecting numerous crop plants and occurring in various climatic zones. It produces large amounts of fumonisins, a group of polyketide-derived mycotoxins. Fumonisin biosynthesis is determined by the presence and activity of the FUM cluster, several co-regulated genes with a common expression pattern. In the present work, we analyzed 38 F. proliferatum isolates from different host plant species, demonstrating host-specific polymorphisms in partial sequences of the key FUM1 gene (encoding polyketide synthase). We also studied growth rates across different temperatures and sample origin and tried to establish the relationships between DNA sequence polymorphism and toxigenic potential. Phylogenetic analysis was conducted based on FUM1 and tef-1α sequences for all isolates. The results indicated the greatest variations of both toxigenic potential and growth patterns found across the wide selection of isolates derived from maize. Fumonisin production for maize isolates ranged from 3.74 to 4,500 μg/g of fumonisin B(1). The most efficient producer isolates obtained from other host plants were only able to synthesize 1,820-2,419 μg/g of this metabolite. A weak negative rank correlation between fumonisin content and isolate growth rates was observed. All garlic-derived isolates formed a distinct group on a FUM1-based dendrogram. A second clade consisted of tropical and sub-tropical strains (isolated from pineapple and date palm). Interestingly, isolates with the fastest growth patterns were also grouped together and included both isolates originating from rice. The sequence of the FUM1 gene was found to be useful in revealing the intraspecific polymorphism, which is, to some extent, specifically correlated with the host plant.