EFS12- Book of abstracts - Contact
EFS12- Book of abstracts - Contact
EFS12- Book of abstracts - Contact
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SESSION 3: PATHOGENESIS – EPIDEMIOLOGY AND POPULATION<br />
GENETICS<br />
Fusarium graminearum: Species or Clade?<br />
J. F. Leslie¹, R. L. Bowden²<br />
¹Department <strong>of</strong> Plant Pathology, Throckmorton Plant Sciences Center, Kansas State University,<br />
Manhattan, Kansas 66506, USA; ²Plant Science and Entomology Research Unit, USDA-ARS,<br />
Throckmorton Plant Sciences Center, Kansas State University, Manhattan, Kansas 66506, USA.<br />
E-mail: jfl@ksu.edu<br />
Fusarium graminearum is a common cause <strong>of</strong> disease and mycotoxin<br />
contamination <strong>of</strong> grains such as maize, wheat, barley and rice. Within F.<br />
graminearum there are a number <strong>of</strong> phylogenetic lineages that some researchers<br />
recognize as distinct phylogenetic species. This hypothesis brings with it the<br />
expectation <strong>of</strong> other significant differences between the lineages. Yet, there is no<br />
significant difference in the quantitative ability <strong>of</strong> the strains from any <strong>of</strong> the tested<br />
lineages to form perithecia or ascospores when crossed with female-fertile tester<br />
strains that were designed for making controlled crosses. Physical and<br />
recombinational maps <strong>of</strong> F. graminearum are co-linear and similar for members <strong>of</strong><br />
at least the tested phylogenetic lineages, and there is no evidence for large<br />
numbers <strong>of</strong> chromosomal rearrangements segregating in field populations. In<br />
general, biological and phylogenetic species concepts group strains similarly and<br />
into a larger number <strong>of</strong> groups than those identified on the basis <strong>of</strong> morphology<br />
alone. In F. graminearum, however, the number <strong>of</strong> morphological and biological<br />
species is the same, i.e., one. These results could be explained in at least two<br />
ways. The explanation voiced the loudest is that the lineages are incipient species<br />
and that the phylogenetic analysis has caught this group in the act <strong>of</strong> evolving<br />
from a single species into many. Alternatively, the phylogenetic lineages may be<br />
separate populations that have evolved independently for some time but are still a<br />
part <strong>of</strong> a single common species, much as Eskimos and Australian aborigines are<br />
in humans. Identifying natural populations where “hybrids” between lineages may<br />
occur under field conditions remains a key to the competitive evaluation <strong>of</strong> these<br />
hypotheses, with populations <strong>of</strong> F. graminearum in South America and South<br />
Korea <strong>of</strong>fering, perhaps, the best opportunities to do so.<br />
Keywords: biological species, sexual fertility<br />
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