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ARS Home » Research » Publications at this Location » Publication #103896


item O`donnell, Kerry
item Nirenberg, Helgard
item Aoki, Takayuki
item Cigelnik, Elizabeth

Submitted to: Mycoscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The Gibberella fujikuroi species complex is one of the largest and most important groups within the filamentous fungus Fusarium, a genus noted for many agriculturally important plant pathogens and toxigenic species. The purpose of this investigation was to use molecular genetic techniques to characterize newly discovered plant pathogenic strains within this complex isolated from several economically important crops. Based on molecular genetic analyses of DNA sequence data from multiple regions, 10 new morphologically cryptic species were discovered from the following areas: two from Asia and four from both Africa and South America. Results of this study illustrate the importance of using molecular genetic data to diagnose agronomically important species so that their host range, geographic distribution, and mycotoxin potential can be accurately documented. This information is critical to fully evaluate the potential risk these plant pathogenic and toxigenic species pose to plant, human, an animal health.

Technical Abstract: Phylogenetic relationships within the Gibberella fujikuroi species complex were extended to newly discovered strains using nucleotide characters obtained by sequencing polymerase chain reaction (PCR) amplified DNA from four loci used in a previous study [nuclear large subunit 28S rDNA, nuclear ribosomal internal transcribed spacer (ITS) region, mitochondrial small subunit (mtSSU) ribosomal DNA, and Beta-tubulin] together with two newly sampled protein-encoding nuclear genes, translation elongation factor EF-1alpha, and calmodulin. Sequences from the ribosomal ITS region were analyzed separately and found to contain two highly divergent, nonorthologous ITS2 types. Phylogenetic analysis of the individual and combined datasets identified 10 new phylogenetically distinct species distributed among the following three areas: two within Asia and four within both Africa and South America. Hypotheses of the monophyly of Fusarium subglutinans and its two formae speciales, f. sp. pini and f. sp. ananas, were strongly rejected by a likelihood analysis. The results further indicate that the protein-encoding nuclear genes provide considerably more phylogenetic signal than the ribosomal genes sequenced.