Abstract
Bacteria with positive properties on plant vitality are also called PGPB (Plant Growth Promoting Bacteria). Their presence can be observed not only in the root area but also in the above-ground parts of plants like endophytic bacteria. The aim of our study was to characterize promoting features of bacteria from Bacillus genus and compare them with Pseudomonas simiae WCS417 (plant growth promoting strain). The work was carried out in locality Kolíňany near Nitra (40°26´46´´N, 79°58´56´´W) and root samples were taken from 6 randomly selected plants of maize (Zea mays L.) in vegetative plant growth stage BBCH 14-15. Bacteria isolated from plant roots were identified and tested to biochemical parameters. From the biochemical features, we observed the detection of siderophores, determination of indole-3-acetic acid (IAA), monitoring the ability to dissolve phosphates and antifungal activity. Bacterial suspensions were applied to maize seeds and tested in vivo controlled conditions. Tested isolates were identified as Bacillus flexus, Bacillus megaterium and Bacillus subtilis. All 3 strains achieved the middle – class of phosphate solubilization index (2.00 ≤ SI ˂ 4.00), produced phytohormone IAA and showed positive production of siderophores and inhibited growth of Fusarium culmorum to more than 50%. All differences between tested strains and control strain P. simiae WCS417 were also statistically confirmed. All strains showed positive results in monitoring plant growth promoting properties. The effect of three Bacillus strains on maize seeds in vivo conditions showed significant differences in root length (P<0.0001) and weight of the young plant (P<0.001) compared to control.
Highlights
Bacterial strains that have beneficial effects on plant growth and vitality are characterized as beneficial plant-associated bacteria colonize the rhizosphere, the phyllosphere, and the inside of plant tissues (Kobayashi and Palumbo, 2000)
These types of bacteria were classified as PGPB - Plant Growth Promoting Bacteria and we can divide them to three main groups like rhizospheric bacteria, phyllospheric bacteria and endophytic bacteria (Kuan et al, 2016)
Studies on the diversity of rootassociated bacteria in maize revealed extensive colonization by Bacillus strains during the active vegetative plant growth stage of the plants (Lalande et al, 1989)
Summary
Bacterial strains that have beneficial effects on plant growth and vitality are characterized as beneficial plant-associated bacteria colonize the rhizosphere (rhizobacteria), the phyllosphere (epiphytes), and the inside of plant tissues (endophytes) (Kobayashi and Palumbo, 2000). Depending on their effect on the host plant, bacteria can be categorized into three groups: plant-growth promoting (PGPB), plant-growth inhibiting, and plant-growth neutral (Sturz et al, 2000). The beneficial effects of PGPBs are generally observed by the occurrence of an increase in germination rates, root growth, yield, leaf area, chlorophyll content, magnesium content, nitrogen content, hydraulic activity tolerance to drought, shoot and root dry weights. Recent studies showed that the direct mechanisms involve improved uptake of nutrients such as nitrogen and phosphorus, production of plant hormones such as indole-3-acetic acid (IAA), gibberellins and cytokinins
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