Soil Microorganisms Quantitative Dynamic Characterizing the Overall Biological State in Rhizosphere of Tobacco and Tomato Plants Infected by Broomrape

Abstract

The quantitative dynamics of soil microorganisms in the rhizosphere of tobacco and tomato plants infected by broomrape /Phelipanche ramosa L./ were investigated. Parallel pot experiments with the two hosts of the parasite - Oriental type of tobacco and tomato were presented. The variants were: by introducing contamination into the soil - seeds by broomrape and control pots - without the seeds by broomrape. Experiments were carried out under controlled conditions. Soil samples for microbiological analyzes were taken from the rhizosphere, in dynamics. The microbiological analyses were executed according to Koh’s, in three replications (MPN/g a.d.s), with confidence level 0.05. The surveyed set of soil microorganisms has been comprised two indicators groups characterizing the overall biological state of the microbial communities: Autochthonous (on soil extract agar) and Oligotrophic (on diluted soil extract agar). Diversity indexes Shannon (H) and Simpson (D) and the distribution evenness (EH) in the microbial communities were determined. A statistical analysis has been made. The obtained results showed that the quantities of the two groups of microorganisms begun to change visibly around and after 20th day, compared to the amount at the rhizosphere of uninfected by broomrape plants. There was an increase at the population density of autochthonous microorganisms between 20 and 60 days and reduced significantly after this period. The trend was reversed at oligotrophic microorganisms, but the quantities were higher throughout the study period. These dynamics coincide with the phases of broomrape development - germination, formation of a haustorium (about 10-20th day) and attachment to the root of the host (up to about 40-60 days) and the above-ground phases (80-100 days). The analysis showed that microbial communities formed in rhizospheres in the presence of a broomrape had been an oligotrophic character. The relative share of oligotrophic microorganisms in these microbial communities was over 50% at both host rhizospheres.