Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2010
Publication Date: 11/20/2010
Publication URL: http://hdl.handle.net/10113/47577
Citation: Otero-Colina, G., Rodriguez-Alvarado, G., Fernandez-Pavia, S., Maymon, M., Ploetz, R.C., Aoki, T., O Donnell, K., Freeman, S. 2010. Identification and characterization of a novel etilogical agent of mango malformation disease in Mexico, Fusarium mexicanum sp. nov. Phytopathology. 100(11):1176-1184. Interpretive Summary: This research was conducted to identify and characterize pathogens responsible for the economically devastating mango malformation disease (MMD) in México. Based on a survey of diseased mango in eight geographically diverse Méxican states conducted from 2002 through 2007, 142 isolates of the filamentous fungus Fusarium were recovered. Genetic and morphological data used to characterize these isolates indicated that a novel Fusarium species was the primary MMD pathogen in México. Results of the genetic studies further indicate that this novel pathogen is native to México and moved from some unknown host plant onto mango after it was introduced to México from Asia. The results of pathogenicity experiments demonstrated that the novel Fusarium was capable of inducing typical MMD symptoms. Moreover, the novel MMD pathogen was recovered from symptomatic mango plants that had been inoculated, thereby clearly establishing that it is a pathogen of this host. Detailed morphological analyses of the pathogen in pure culture identified several characters that can be used to identify and distinguish it from other MMD pathogens. The results of this study will be of interest to and benefit plant pathologists and plant breeders interested in controlling this economically devastating disease and developing cultivars with broad based resistance to MMD. Furthermore, the results will be of interest to quarantine officials charged with preventing the spread of and inadvertent introduction of this novel pathogen into non-indigenous areas.
Technical Abstract: The primary objective of this study was to characterize fusaria associated with the economically devastating mango malformation disease (MMD) in México. One hundred and 42 fusaria were isolated from symptomatic mango inflorescences and vegetative tissues in eight geographically diverse Méxican states from 2002 through 2007. Initially, all the Méxican isolates were screened for genetic diversity using ap-PCR and RAPD DNA markers and were grouped into seven distinct genotypes. Based on results of these analyses, evolutionary relationships and species limits of the genetically diverse MMD-associated fusaria were investigated using multilocus DNA sequence data and phylogenetic species recognition. Maximum parsimony analyses of a five-locus dataset comprising 5.8 kb of aligned DNA sequence data indicated that at least nine phylogenetically distinct fusaria within the Gibberella fujikuroi species complex are associated with MMD, including one species within the African clade (F. pseudocircinatum), two species within the Asian clade (F. mangiferae and F. proliferatum) and at least six species within the American clade (F. sterilihyphosum and five undescribed fusaria). Molecular phylogenetic analyses indicate that a novel genealogically exclusive lineage within the American clade was the predominant MMD associate in México. This new Fusarium species caused MMD and could be distinguished from all other known species morphologically by the production of mostly sterile, coiled hyphae which are typically associated with sporodochial conidiophores together with unbranched or sparsely branched aerial conidiophores. Koch’s postulates were completed for isolates of the new species on nucellar seedlings of mango cv. Ataulfo. This pathogen is formally described herein as Fusarium mexicanum.