The effect of psychrotrophic bacteria isolated from the root zone of winter wheat on selected biotic and abiotic factors

The roots of winter wheat plants, cv. Mikon, grown in 45-year monoculture, were analysed in the study. Twenty-two bacterial isolates obtained from the rhizosphere, rhizoplane, and endorhizosphere that were capable of growth at 8°C and at 28°C, were selected for further analysis. The isolated psychrotrophs accounted for 25% of all bacteria present in the wheat rhizosphere and capable of growth at 8°C. Psychrotrophic bacteria were analysed at a temperature of 10°C and 28°C to determine their ability to inhibit the growth of pathogenic fungi, solubilise mineral phosphates, and to determine their ability to degrade chitin and cellulose. Similarity between the isolates was determined by Enterobacterial Repetitive Intergenic Consensus – Polymerase Chain Reaction (ERIC-PCR) and Random Amplification of Polymorphic DNA – Polymerase Chain Reaction (RAPD-PCR). The majority of isolated psychrotrophs inhibited the growth of pathogenic fungi and solubilised mineral phosphates at both incubation temperatures. Psychrotrophic bacteria exerted a two-fold stronger inhibitory effect on mycelial growth at 10°C than at 28°C. The growth of Fusarium culmorum and F. oxysporum was inhibited to the highest extent at 10°C and at 28°C, respectively. Phosphate solubilisation rates were higher at 28°C, particularly in the rhizosphere. Regardless of temperature, the bacteria exhibited low chitin-degrading potential, and none of the isolates was capable of degrading cellulose. A high similarity between the selected psychrotrophs was revealed by ERIC-PCR and RAPD- -PCR analyses. Based on RAPD-PCR, the analysed population was divided into a group of isolates obtained from the rhizosphere, and two groups comprising representatives of both the rhizoplane and the endorhizosphere. Due to their ability to grow over a wide temperature range and increase phosphorus availability to plants, and their antagonism against pathogens, psychrotrophic bacteria can be used to improve the growth and yield of cereal crops.