108(4)_str 44

 

ISSN 1392-3196 / e-ISSN 2335-8947
Zemdirbyste-Agriculture, vol. 108, No. 4 (2021), p. 347–354
DOI 10.13080/z-a.2021.108.044

Autochthonous plant growth-promoting rhizobacteria enhance Thymus vulgaris growth in well-watered and drought-stressed conditions

Dragana STAMENOV, Simonida DJURIC, Timea HAJNAL-JAFARI, Snežana ANDJELKOVIĆ

Abstract

The use of plant growth-promoting rhizobacteria (PGPR) in the production of medicinal plants is crucial, because agricultural chemicals are no longer acceptable in their production. This paper discusses the results of a recent study undertaken to isolate and characterize PGPR isolates of Bacillus, Pseudomonas and Azotobacter from common thyme (Thymus vulgaris L.) rhizospheric soil and monitor the effect of their application on seed germination and plant growth. The effect of selected isolates on seed germination and initial growth of common thyme was examined in controlled conditions. The impact of the isolates on the content of biochemical stress markers (total phenols and lipid peroxidation intensity) in germinated seeds was determined. The influence of the isolates on the plant growth under well-watered conditions (watered to 80% of water holding capacity (WHC)) and under water deficit stress (watered to 40% of WHC) was evaluated by measuring plant root and stem length in semi-controlled conditions.

This study confirmed that indigenous rhizospheric bacteria of common thyme have multiple plant growth-promoting (PGP) properties. Among Bacillus 10 isolates, Pseudomonas 12 isolates and Azotobacter 9 isolates, only Pseudomonas isolate (P53) had all the tested PGP properties. The applied isolates had a positive effect on the examined plant growth parameters. The highest percentage of germination was determined in the treatment with P53 isolate (96%). The highest response for vigour index was observed with isolate A1 (3807%). All isolates, except B58 and B60, reduced stress by lowering the amount of both or at least one stress related molecules. The results of the experiment led to the conclusion that isolates Azotobacter sp. A1 and Pseudomonas sp. P53, both ACC-deaminase-producing bacteria, have the best effect on plant growth under well-watered and drought-stressed conditions, which indicates their potential to be used as a biofertiliser for promoting common thyme growth.

Key words: common thyme, medicinal plants, drought, biofertiliser, ACC-deaminase.

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