The influence of two factors - "broomrape" and "soil type" on quantities of seven trophic groups of soil microorganisms (Autochthonous; Oligotrophic; Actinomycetes; Microscopic fungi; Ammonifying; Assimilating mineral nitrogen; Aerobic nitrogen-fixing bacteria of the genus Azotobacter) were determined. Soil samples for microbiological analysis were taken from the rhizosphere zone of plants in sunflower crops from two soil types (Haplic Vertisols and Chromic Cambisols), in phenological phases of sunflower and of broomrape - "flowering". Reduction the quantities on all investigated groups of microorganisms in the system (sunflower + broomrape) were observed. The average population density as a whole in the microbial communities with presence of broomrape decreased by over 65% compared with the density in the microbial communities at uninfected plants, in both soil types. The power of influence of the factor "broomrape" was less than that of factor "soil type", but distinctly and statistically proven. The presence of broomrape had the strongest impact to the group of microscopic fungi (50% of total variance). Structural changes in the distribution between the different trophic groups of microorganisms in the microbial communities have been established - an increase the shares of oligotrophic microorganisms, of assimilating mineral nitrogen microorganisms and of microscopic fungi. | Changes at the rhizosphere microbiota of the sunflower Orobanche cumana wallr pathosystem
