Effect of five Bacillus strains on seed germination of Pisum sativum and plant growth of Origanum vulgare subsp. hirtum (oregano)

This study aims to investigate the effect of PGP-strains from genus Bacillus on seed germination of Pisum sativum and plant growth of Origanum vulgare subsp. hirtum in comparison with two growth plant regulators. Bacterial cell free supernatants (CFS) from five Bacillus strains were used in two different concentrations – 100 and 500 fold dilutions. The growth regulators (gibberellic acid and indole acetic acid) were used to determine optimal concentration to Pisum sativum seeds germination and plant growth, and were compared with the bacterial CFS. PGP-activities of CFS and plant regulators were evaluated by morphometric data of sprouted seeds and plants. Bacterial CFS increase the number of lateral root branching and the average number of leaves compared with the tested growth regulators. The growth regulators had positive effect on plant growth, although their accumulation in the soils has been shown to cause soil erosion and pollution. The treatment of Origanum vulgare subsp. hirtum with bacterial CS from B. subtilis 8VR, B. pumilus 9VR and B. thuringiensis 13VR, resulted in significant increase in the root length compared to the control. The maximum length of the main root was measured after treatment with CS from B. thuringiensis 13VR. Bacterial CS from genus Bacillus had no effect of stem length of Origanum vulgare subsp. hirtum, while CS from B. cereus 7VR and B. subtilis 8VR increased the number of leaf trichomes compared to the control.