The purpose of the studies conducted in the years 1996-1998 was to determine the quantitative and qualitative composition of bacterial and fungal communities in rhizosphere of soybean cultivated in monoculture and non-rhizosphere soil. Besides, the proportion of bacteria and fungi, which were distinguished by their antagonistic effect towards soil-borne pathogens was established. A microbiological analysis of lg of dry weight of soil from rhizosphere of soybean resulted in 3.21 x I ()6 to 8.70 x 106 bacterial colonies and from 70.51 x I 03 to 123.74 x 103 fungal colonies. In the case of non-rhizosphere soil, 3.50 x 106 to 4.75 x 10" bacterial colonies and 16.16 x 10' to 51.38 x 10' fungal colonies were obtained. Besides, soybean cultivation in monoculture had a negative effect on the number of antagonistic isolates of bacteria (Bacillus spp., Pseudomonas spp.) and fungi (Gliocladium spp., Penicillium spp., Trichoderma spp.). Smaller numbers of antagonistic bacteria and fungi in rhizosphere soil of soybean cultivated in monoculture as compared to non-rhizosphere soil, can prove little biological activity, which results in a worse phytosanitaty 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 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.

Ability of five strains of Trichoderma pseudokoningii (antagonists) to suppress radial growth of Fusarium verticillioides (Sacc.) Nirenberg (= Fusarium moniliforme Sheldon) was examined in vitro These were T. pseudokoningii strai n1 (IMI 380933), strain 2 (IMI 380937), strain 3 (IMI 3809 39), strain 4 (IMI 380940) a nd strain 5 (IMI 380941). Each strain was paired with pathogen by inoculating at opposite ends of 9 cm petri plates using three pairing methods. Gradings were assigned to varied growth inhibition of pathogen by antagonists and analysed using GLM procedure (SAS). Growth suppression of F. verticillioides by all strains of T. pseudokoningii was significantly different (R² = 0.98, p = 0.05) from control in all pairing methods. It differed significantly (p > 0.0003) among the strains in all pairing methods. Growth suppression also differed significantly among (p>0.0001) and within (p > 0.018) pairing methods. Growth suppression was best when antagonists were inoculated before pathogen. Suppression mechanisms include mycoparasitism and competition for space and nutrients. T. pseudokoningii strains 3 and 4 had the best (p = 0.05) growth suppression of F. verticillioides and could be used as biocontrol agents for endophytic F. verticillioides in maize plant. This experiment was conducted in the search for resedent microorganisms that might be capable of checking F. verticillioides within maize plant by competitive exclusion in subsequent experiment.

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.