The term "biodiversity" is nowadays one of the most often used words, both, in biological and in social sciences. However, a generally accepted definition of this term is lacking. In biological sciences the concept becomes a catchall and is mostly understood in the categories of taxonomy and systematics. The understanding is obvious and necessary and yet, very unsatisfactory. Apart from the occurrence of various taxons on an area, the important elements are also: their frequency, distribution, interactions, etc., which are most often omitted or unmeasurable. When they are all considered - in the concept at least- it seems obvious that phytopathology, dealing with diseased plants, is involved in the objects reflecting the biodiversity in a very distinct way.
Results of research carried out within 1995-1998 on application of molecular methods to identify the fungal pathogens of cereals were reviewed in the paper. Results of studies on fungal genome of Fusarium species - the number and size of chromosomes were presented. Available information concerning the possibilities of fungal pathogens identification with the use of RFLP, RAPD-PCR, SCAR and AFLP methods, based on the analysis of extracted fungal DNA and PCR (polymerase chain reaction) procedure were described.