A derivative of the plant family Musaceae (Musa), the commercial banana has enjoyed international success as a popular dessert item in the modern developed world. Understandably, the advent of an uncontrolled banana blight would certainly have major repercussions on the world market; moreover, it would spell doom for the millions of subsistence farmers across the globe for whom bananas are still a staple food. This frightening scenario is not wholly unrealistic – in the 1890s, Gros Michel, the former predominant banana cultivar, was all but wiped to extinction by a race of fungi dubbed Fusarium Oxysporum sp. cubense race 1, or simply Foc 1 (Hwang and Ko, 2004). The fungus operates by entering via the rhizomes of the banana plant, subsequently
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Regardless, F. Oxysporum has continued to evolve, and once again threatens to plague the banana industry. Race 4, a relatively recent and morphologically distinct strain of F. Oxysporum, has evolved to be pathogenic to Cavendish (Hwang and Ko, 2004). Since its initial discovery in 1967, Foc 4 has spread from the eastern hemisphere, where it is thought to have originated, at a frightening pace; this revitalized global threat has been documented from the Americas extending as far as Australia and regions lying between. Current research efforts are underway to find ways to combat the tenacity of Foc, whose persistence exemplifies the Red Queen’s dilemma as described by evolutionary biologists. To better understand this crucial dynamic is to understand the molecular basis for the evolution of Foc in relation to its host plant, to identify the genomic elements of the two as they interact, and to consider how methods involving genetic reengineering and artificial selection can help pioneer …show more content…
Oxysporum is described as having no sexual stage. More recent studies have sought to piece together the genetic relatedness between different Vegetative Compatibility Groups, or VCGs, of F. Oxysporum. VCGs are exclusive networks of fungal strains capable of heterokaryosis via the fusion of somatic nuclei, and their interactions are the primary mode of genetic recombination in F. Oxysporum (Fourie et al. 2009). It has been postulated that heterokaryosis is the mechanism through which virulence is conferred. To shed insight on these speculations, Fourie et al. compiled even more comprehensive phylogenetic trees using the same loci from O’donnell et al.’s studies, in addition to another rRNA locus and a mitochondrial DNA locus, for 70 F. Oxysporum isolates representing 20 VCGs; regional data was also noted (Fourie et al. Table 1.) The phylogenetic trees, which were compiled according to the criteria of maximum parsimony, Bayesian inference, and maximum likelihood were congruent to those of O’donnell et al., but displayed even more diversity in Foc, showing the same two distinct clades, albeit with a total of 8 distinct lineages. The three additional lineages contained strains which had evolved independently in different regions, with some including different formae specialis entirely. For example, Isolate CAV 1020 represented a new Foc VCG from Vietnam, though it was shown to be more related to non-pathogenic isolates than to pathogenic Foc VCGs (Fourie et al. 2009). This
Regardless, F. Oxysporum has continued to evolve, and once again threatens to plague the banana industry. Race 4, a relatively recent and morphologically distinct strain of F. Oxysporum, has evolved to be pathogenic to Cavendish (Hwang and Ko, 2004). Since its initial discovery in 1967, Foc 4 has spread from the eastern hemisphere, where it is thought to have originated, at a frightening pace; this revitalized global threat has been documented from the Americas extending as far as Australia and regions lying between. Current research efforts are underway to find ways to combat the tenacity of Foc, whose persistence exemplifies the Red Queen’s dilemma as described by evolutionary biologists. To better understand this crucial dynamic is to understand the molecular basis for the evolution of Foc in relation to its host plant, to identify the genomic elements of the two as they interact, and to consider how methods involving genetic reengineering and artificial selection can help pioneer …show more content…
Oxysporum is described as having no sexual stage. More recent studies have sought to piece together the genetic relatedness between different Vegetative Compatibility Groups, or VCGs, of F. Oxysporum. VCGs are exclusive networks of fungal strains capable of heterokaryosis via the fusion of somatic nuclei, and their interactions are the primary mode of genetic recombination in F. Oxysporum (Fourie et al. 2009). It has been postulated that heterokaryosis is the mechanism through which virulence is conferred. To shed insight on these speculations, Fourie et al. compiled even more comprehensive phylogenetic trees using the same loci from O’donnell et al.’s studies, in addition to another rRNA locus and a mitochondrial DNA locus, for 70 F. Oxysporum isolates representing 20 VCGs; regional data was also noted (Fourie et al. Table 1.) The phylogenetic trees, which were compiled according to the criteria of maximum parsimony, Bayesian inference, and maximum likelihood were congruent to those of O’donnell et al., but displayed even more diversity in Foc, showing the same two distinct clades, albeit with a total of 8 distinct lineages. The three additional lineages contained strains which had evolved independently in different regions, with some including different formae specialis entirely. For example, Isolate CAV 1020 represented a new Foc VCG from Vietnam, though it was shown to be more related to non-pathogenic isolates than to pathogenic Foc VCGs (Fourie et al. 2009). This