Origin, biogeography, genetic diversity and taxonomic affinities of the cacao (Theobroma cacao L.) fungus Moniliophthora roreri (Cif.) Evans et al. as determined using molecular, phytopathological and morpho-physiological evidence
The origin, genetic diversity, biogeography and taxonomic affinities of the neotropical cacao pathogen M. roreri were studied through the application of various molecular, morpho-physiological and phytopathological methodologies to 96 isolates collected from throughout its geographic range. AFLP, ISSR and ITS sequence analyses revealed that this fungus has a considerable genetic variation, although regions of comparative genetic uniformity were also identified in Central America, central Ecuador and Peru. The highest variability was observed in north-eastern Colombia indicating that this region represents the centre of diversity for the fungus. The pattern of declining variability outside this area also suggests that M. roreri originated in this country, possibly within or close to the Medium Magdalena. Five major subspecific groupings were identified, with each exhibiting a characteristic distribution: Bolívar and Co-West groups being widespread, whereas Co-Central and Co-jEast groups apparently endemic to Colombia and the Gileri group being restricted to Ecuador. ITS was useful to define two subspecific groups and to reinforce some of the AFLP/ISSR findings. The morpho-physiological variation of 88 isolates and the effect of three in vitro temperature regimes were studied by evaluating eleven variables for which significant divergence was noted. Significant differences were observed between genetic groups for most variables, suggesting the variability may have a genetic basis. The virulence of seven Colombian isolates representing four genetic groups was determined by artificially inoculating pods of five cacao clones in Colombia. Genetic variation detected between isolates was not matched by similar diversity in their virulence. There was apparently only limited variation in virulence between them. Phylogenetic analysis of three different portions of the M. roreri genome (ITS regions, nLSU-rDNA, mtSSU-rDNA) confirmed that this fungus is a Basidiomycete and strongly suggest that it belongs to the order Agaricales, possibly belonging to the family tricholomataceae. Sequences analysis also demonstrated that M. roreri is closely related to the witches' broom pathogen of cacao Crinipellis perniciosa.
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| Format: | biblioteca |
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Reading (RU)
2003
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| Subjects: | AMERICA CENTRAL, ECUADOR, PERU, COLOMBIA, THEOBROMA CACAO, MONILIOPHTHORA, ENFERMEDADES FUNGOSAS, MORFOLOGIA FUNGICA, PATOGENICIDAD, AISLAMIENTO, VARIACION GENETICA, BASIDIOMYCOTINA, CULTIVO IN VITRO, TEMPERATURA, AMERICA TROPICAL, |
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