Submitted to: Journal of Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/8/1999
Publication Date: N/A
Citation: Interpretive Summary: Species of Fusarium collectively represent the single most important genus of plant pathogens and toxin-producing molds. Because many genetically distinct species look identical, molecular methods have proven to be essential in order to rapidly detect and accurately identify these deleterious filamentous fungi so as to prevent or minimize their negative impact on human health and food safety. The purpose of this study was to compare two molecular methods for rapidly distinguishing between and identifying species isolated from moldy corn. Results of these studies indicate that the DNA sequencing method proved to be a statistically better source of molecular genetic data. In addition, these molecular genetic data provide a basis for developing species-specific molecular diagnostics and an objective framework within which toxin profiles can be accurately developed for all species of Fusarium for the first time. Also with this molecular data it is now possible for the first time to accurately record the host range and geographic distribution of these agronomically-important pathogens.
Technical Abstract: Phylogenetic relationships of several strains within the Fusarium oxysporum species complex and two related species from maize were used to test whether phylogenies inferred from nuclear encoded translation elongation factor EF-1alpha and mitochondrial small subunit (mtSSU) ribosomal RNA gene sequences are concordant with one derived from random amplified polymorphic DNA (RAPD) characters. Results of a partition- homogeneity test (PHT) indicated that the EF-1alpha and the mtSSU rDNA datasets are highly homogeneous (P = 1.00) and could be analyzed as a combined dataset. Based on the results of the PHT, the three RAPD partitions were also analyzed as a combined dataset. Results of a t-test showed that the consistency, retention, and rescaled consistency indices obtained with the nucleotide sequence data were significantly higher than those obtained with the RAPD data. T-tests of the RAPD data also showed that these indices were significantly higher when using the 15-mer M13 RAPD primer compared with the two decamers. Phylogenies inferred from the combined DNA sequence data, RAPD primer M13, and the combined RAPD data were mostly concordant and identified a phylogenetically distinct species (Fusarium sp.) intermediate between the F. oxysporum complex and F. redolens. These preliminary results demonstrate, at least for a small dataset, that RAPD data can be used to recover a phylogenetic structure that converges on one inferred from DNA sequence data.