addressing taxonomic problems and in
determining degrees of inter- and intraspecifi c
genetic variation. Polymorphism studies have
contributed to our understanding of the genetic
diversity and population structures of fungi and have
provided information that can be very important to
programs of biological control. Molecular biological
techniques have important roles in our understanding
of the genes involved in host infection processes,
such as the adhesion steps, appressorium formation,
and the degradation of the host cuticle. Measures
of the persistence of entomopathogenic fungi in
the soil and any possible effects of their application
on the structural and functional diversity of soil or
rhizosphere microbial communities are essential
ecological aspects that must be understood in
agrosystems, as these microorganisms represent a
signifi cant fraction of the soil biota in terms of its
species diversity and the multiplicity of metabolic
activities occurring in that milieu. Metarhizium is