The CYP51C gene, a reliable marker to resolve interspecific phylogenetic relationships within the Fusarium species complex and a novel target for species-specific PCR.

Early diagnosis and control of different Fusarium species is essential for successful management of plant disease and subsequent prevention of toxins entering the food chain. This issue can be addressed using phylogenetic analyses and other molecular techniques, including the design of species-specific primers and corresponding PCR assays. In practice, only a few genes are sequenced for most species and insights into the evolutionary mechanisms at the species level usually stem from phylogenetic analyses of only one or a small number of genetic loci. This poses the question of whether the recovered tree accurately reflects the relationships among species or rather more local interrelationships particular to the genetic marker employed. This study examined if the Fusarium-specific CYP51C gene can be used to establish evolutionary relationships between Fusarium species and enable species-specific detection. The resolving power of the CYP51C gene was studied for 46 Fusarium isolates representing 18 different species. The resulting phylogeny analysis showed clear and well-structured separation of the isolates according to their species rank, synthesised toxin and Fusarium section. Moreover, a comparison between the individual CYP51C phylogeny and a reference tree (inferred from the concatenation of ITS, CYP51C, β-tubulin and TEF-1α sequences) indicated superior resolution of CYP51C relative to ITS and β-tubulin sequences. In addition to its suitability as a reliable marker for diagnosis of different toxigenic Fusarium species, we also show that the CYP51C gene is a promising target for development of species-specific PCR. This was demonstrated by the specific detection of Fusarium cerealis in grain samples of wheat.