Diversidad y control biológico de insectos - CyberTesis UACh ...

act as single locus (France et al., 1999). Therefore, both kinds of genes differ in their rates
of evolution and modes of inheritance.
The genetic structure arises from the interaction of several factors, some of which
(mutations, genetic drift and, in some cases, selection) increase variation, while other like
gene flow tend to homogenisation. This balance also can be influenced by species life
traits, for example the fungus mating system. The species belonging to the Beauveria genus
reproduce by two asexual spores: the yeast-like spores are produced into the host during the
pathogenesis process, while conidia are produced over the host surface after the host death.
Sexual reproduction is a very rare event and when it has been observed, the resulting fruit
bodies have shown similarity with the genus Cordyceps, but some genetic material is
exchanged by other ways such as the parasexual cylce, in which two compatible hyphae
fuse temporally. In brief, the limited genetic exchange and dispersal capability of B.
bassiana sensu lato allow supposing a strongly structured population.
The growing importance of integrated pest management (IPM) and biological pest control
have triggered efforts to use native entomopathogenic organisms in Chile. In the late 1990s,
the Entomopathogenic Organisms Collection arose from a nation-wide prospecting and
collecting effort, including nematodes and fungi such as Metarhizium, Verticillium,
Cordyceps and Beauveria spp. About 300 B. bassiana isolates were collected from
agricultural and natural systems, different regions and hosts. Consequently, the potential of
this entomopathogenic fungus is being evaluated and so far, up to 30 insect hosts have been
identified, most of them important pests of main Chilean crops, confirming the wide host
range of the species and the extreme variability between genotypes, at least what
pathogenicity concerns. Nevertheless, pathogenic properties of genotypes are only partially
characterized and other relevant ecological and genetic traits remain unknown.
The Chilean Beauveria bassiana isolates were found in very contrasting environments and
ecological conditions, from the desertic areas through Mediterranean and temperate zones
until Patagonia, including Eastern Island. Such wide distribution of a clonal organism poses
a interesting fact from both basic and applied ecology. In consequence, this study was
conducted to determine genetic diversity of B. bassiana accross its observed range in Chile
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