The purpose of the studies carried out in the years 1996-1998 was to establish the composition of bacteria and fungi communities in the potato rhizosphere and non-rhizosphere soil. Besides, in the examined samples the studies established the proportion of bacteria and fungi antagonistic towards soilbome pathogens. The microbiological analysis of 1 g of dry weight of soil coming from the rhizosphere of potato revealed from 3.96 x 10' to 7 .26 x 10 6 bacteria colonies and from 51.38 x 103 to 69.96 x 103 fungi colonies. In the case of nonrhizosphere soil of 1 g of dry weight of soil revealed from 3.50 x 10' to 4.75 x 106 bacteria colonies and from 16.16 x 103 to 34.1 0 x 103 fungi colonies. Moreover, potato cultivation had a positive effect on the increase of numbers of antagonistic bacteria (Bacillus spp. and Pseudomonas spp.) and fungi (Gliocladium spp., Penicillium spp., Trichoderma spp.). A larger number of the communities of bacteria and fungi, including antagonistic ones, in the root area of potato, indicates considerable biological activity, which contributes to a better phytosanitary condition of the soil.

The purpose of the studies carried out in the years 1996-1998 was to establish the composition of bacteria and fungi communities in the soil of spring wheat and winter wheat. Besides, the studies provided the information on quantitative and qualitative composition of amino acids as well as the amount of water soluble sugars in roots exudates of these cereals. The microbiological analysis of I g of dry weight of soil coming from the rhizosphere of spring wheat revealed the mean number of 4.94 x I O' bacteria colonies and 45.08 x 1 O 3 fungi colonies. In the case ofwinter wheat, in Ig of dry weight of the rhizosphere soil 5.07 x 10 'bacteria colonies and 28.59 x l O 3 fungi colonies (mean of three year studies) were found. Besides, winter wheat, through the proper composition of root exudates, created positive nutritional conditions for the growth of microorganisms showing antagonistic effect towards pathogenic fungi. The rhizosphere soil of winter wheat contained 1.5 times more antagonistic bacteria and more than twice antagonistic fungi as compared to spring wheat.