Download Comparison of Bipolaris isolates using molecular and

Comparison of Bipolaris isolates using molecular and biochemical markers
Author: Krisztina KRIZSÁN, 5th
Supervisor: Dr. Tamás PAPP, senior lecturer
Institution: University of Szeged, Faculty of Science, Department of Microbiology, Szeged
Members of the genus Bipolaris (Ascomycota, Euascomycetes, Pleosporales, Pleosporaceae)
are dematiaceous, filamentous fungi cosmopolitan in nature associated primarily with grasses,
but they can be isolated from plant debris and soil also. The plant pathogenic species cause
diseases in a wide range of gramineaceous hosts. A few species have also significants as
human and animal pathogenic fungi: Bipolaris is one of the causative agents of
phaeohyphomycosis.
Traditionally, examination of the conidial morphology (including colour, shape, size,
numbers and distribution of septa) has been used to circumscribe many species. However,
identification of the species within the genus is relatively difficult due to the possible
inconsistencies within isolates, variable cultural conditions, or loss of ability to produce
conidia.
In the present study, isolates of B. maydis, B. zeycola, B. oryzae, B. sorokiniana, B.
sacchari and B. nodulosa from different origins were compared using various methods, such
as analyses of rDNA sequences, secondary metabolite production and carbon source
assimilation.
The complete ITS (internal transcribed spacer) region coding the ITS1, the ITS2 and
the 5.8S rDNA were amplified by PCR. Sequences of the amplified DNA fragments were
determined and analysed.
Carbon source assimilation of the studied isolates was also tested. Utilization of
almost 70 compounds was analyzed; carbon sources differentiating among the strains at
species- or intraspecific level were determined. Some species show typical morphological
(shape, colour, size) divergences on certain carbon sources. Secondary metabolite spectrum
analysis was also performed. Antimicrobial effect of these metabolites against various fungi
and bacteria was also tested in agar diffusion assay.
Keywords: Bipolaris, ITS region, carbon assimilation, antimicrobial evaluation