relationships between closely related taxa and their SM biosynthetic abilities are
frequent in Fusarium genus and are presented and discussed in this chapter. Main
Fusarium-produced mycotoxin pathways were reviewed in terms of genetic divergence and biochemical and chemotypic population shifts. We also summarized the
data on genetic and biochemical diversity occurring in the studies of main secondary
metabolites produced by Fusaria differing in origin and ecology.
2
Fusarium: Clades and Species
First description of Fusarium was reported in 1809 by Link and since than more than
a thousand species have been identified, of which 70 is well-known. The first
taxonomic classifications have been created based on morphological characters of
species and test crosses [14]. Later, thanks to the genetic and bioinformatic tools,
species became classified using phylogenetic analyses. Aoki et al. in 2014 divided
Fusarium species into four complexes based on RNA polymerase II subunit gene
sequences (Fusarium fujikuroi species complex (FFSC), Fusarium graminearum
species complex (FGSC), Fusarium oxysporum species complex (FOSC), and
Fusarium solani species complex (FSSC)), but some well-known species were not
assigned to any of these [15]. In 2011, Watanabe et al. used maximum likelihood
method for reconstruction of the phylogenetic relationships using the following
genetic markers: rDNA cluster region, β-tubulin (β-tub), translation elongation
factor 1α (EF-1α), and aminoadipate reductase (lys2). Based on the resulting phylogenetic tree, they proposed a new classification divided into seven clades (Table 1)
[16].
Obviously, this classification contained some flaws, related to the limited number
of strains used, but mainly followed earlier dividing Fusarium into “sections” which
is no longer used. More detailed studies allowed to discriminate closely related
species inside the clades, and currently, many reports describing new species or
chemotypes are becoming available, particularly concerning trichothecene producers from the FGSC and fumonisin producers from the FFSC.
3
Ecological Niches: From Saprotrophs to Human Pathogens
As a worldwide occurring genus, Fusaria are adapted to survive and spread in a wide
spectrum of environmental conditions. The genus is known at best as a plant
pathogen that causes yearly huge economic losses in yields of almost all crops
cultivated all over the world. Spores of Fusarium infect plants and then develop
hyphae within plant organs (e.g., leaves, stems, seeds, flowers, roots) which cause
changes in host cells’ metabolism, tissue destruction, and, eventually, the development of numerous diseases.
Some Fusarium species complexes are still classified as specialized groups within
the species, so-called formae specialis (f.sp.) based on specific host that they are
able to infect. F. oxysporum is the species with the largest number of formae
214
Ł. Stępień et al.
frequent in Fusarium genus and are presented and discussed in this chapter. Main
Fusarium-produced mycotoxin pathways were reviewed in terms of genetic divergence and biochemical and chemotypic population shifts. We also summarized the
data on genetic and biochemical diversity occurring in the studies of main secondary
metabolites produced by Fusaria differing in origin and ecology.
2
Fusarium: Clades and Species
First description of Fusarium was reported in 1809 by Link and since than more than
a thousand species have been identified, of which 70 is well-known. The first
taxonomic classifications have been created based on morphological characters of
species and test crosses [14]. Later, thanks to the genetic and bioinformatic tools,
species became classified using phylogenetic analyses. Aoki et al. in 2014 divided
Fusarium species into four complexes based on RNA polymerase II subunit gene
sequences (Fusarium fujikuroi species complex (FFSC), Fusarium graminearum
species complex (FGSC), Fusarium oxysporum species complex (FOSC), and
Fusarium solani species complex (FSSC)), but some well-known species were not
assigned to any of these [15]. In 2011, Watanabe et al. used maximum likelihood
method for reconstruction of the phylogenetic relationships using the following
genetic markers: rDNA cluster region, β-tubulin (β-tub), translation elongation
factor 1α (EF-1α), and aminoadipate reductase (lys2). Based on the resulting phylogenetic tree, they proposed a new classification divided into seven clades (Table 1)
[16].
Obviously, this classification contained some flaws, related to the limited number
of strains used, but mainly followed earlier dividing Fusarium into “sections” which
is no longer used. More detailed studies allowed to discriminate closely related
species inside the clades, and currently, many reports describing new species or
chemotypes are becoming available, particularly concerning trichothecene producers from the FGSC and fumonisin producers from the FFSC.
3
Ecological Niches: From Saprotrophs to Human Pathogens
As a worldwide occurring genus, Fusaria are adapted to survive and spread in a wide
spectrum of environmental conditions. The genus is known at best as a plant
pathogen that causes yearly huge economic losses in yields of almost all crops
cultivated all over the world. Spores of Fusarium infect plants and then develop
hyphae within plant organs (e.g., leaves, stems, seeds, flowers, roots) which cause
changes in host cells’ metabolism, tissue destruction, and, eventually, the development of numerous diseases.
Some Fusarium species complexes are still classified as specialized groups within
the species, so-called formae specialis (f.sp.) based on specific host that they are
able to infect. F. oxysporum is the species with the largest number of formae
214
Ł. Stępień et al.