Isolation and identification of Bacillus cereus strains from the rhizosphere zone of Artemisia absinthium L. and their effect on biochemical indices of Artemisia absinthium L. under salinity stress

Artemisia absinthium (L.) is known as wormwood and grand wormwood. The use of growth-promoting bacteria reduces environmental stress and improves plant growth. Some Bacillus spp. found in the rhizosphere of plants, which can produce auxin hormone and have phosphate dissolution ability, which improves plant growth. This study aimed to isolate Bacillus spp. from the rhizosphere of A. absinthium L. and to evaluate the ability of the isolated strains for auxin production and phosphate dissolution as well as their effect on biochemical indices of A. absinthium L. under salinity stress. Soil samples were collected from the rhizosphere of A. absinthium L. and Bacillus spp. were isolated and purified from them, utilizing an initial heat shock for bacterial spore selection and then cultivation of spores on nutrient agar. In the next step, quantitative measurements of auxin production capacity and inorganic phosphate dissolution were performed on the purified isolates, and then the selected isolates that had more auxin production and phosphate dissolution were biochemically and molecularly identified. Finally, the effect of selected bacteria on some biochemical characteristics of the A. absinthium plant under salt stress was investigated. The effect of four levels of inoculation (no inoculation, inoculation with B. cereus B strain, B. cereus E strain, and co-inoculation with B. cereus B strain and B. cereus E strain) was investigated on the biochemical indices of A. absinthium under three levels of salinity stress (control, ۷۵ mM, and ۱۵۰ mM). The production of malondialdehyde (MDA), protein, proline, superoxide dismutase enzyme (SOD), catalase (CAT), peroxidase (POX), and total phenol increased with increasing salinity. The results showed that the inoculation of Bacillus bacteria under salinity stress decreased proline and MDA and increased the amount of protein, total phenol and antioxidant enzymes (superoxide dismutase, catalase, and peroxidase). The best results were obtained by the combined inoculation of rhizosphere bacteria, B. cereus B and E strains, under salinity stress (۷۵ mM NaCl), in which the greatest decrease in proline (۹۰%) and MDA (۹۰%) as well as the greatest increase in protein (۹%), total phenol (۱۸۰%), and antioxidant enzymes including superoxide dismutase (SOD) (۵۰%), catalase (CAT) (۴۰%), and peroxidase (POX) (۷۰%) was obtained compared to the control.

کلیدواژه ها:

Artemisia absinthium ، Antioxidant enzymes ، Rhizosphere bacteria ، Auxin hormone ، Salinity stress ، Artemisia absinthium ، Antioxidant enzymes ، Rhizosphere bacteria ، Auxin hormone ، Salinity stress