Screening of Azotobacter, Bacillus and Pseudomonas Species as Plant Growth-Promoting Bacteria

In this study, bacteria from the genus of Azotobacter, Bacillus and Pseudomonas were isolated from the roots of Phaseolus vulgaris and used as plant growth-promoting bacteria for Sinapis alba L., Brassica napus L., Amaranthus retroflexus L., Linum usitatissimum L., Panicum miliaceum L. and Rumex patientia L. plants. The results showed that all three bacteria had different effects on plants growth considering both sterile and non-sterile soil. Bacillus sp. induced the greatest influence in terms of the root length of Sinapis alba L. grown in sterile soil (with 28%), while considering non-sterile soil, Pseudomonas sp. increased the root and shoot length by 11.43% and 25.15%, respectively, compared to the blank sample. Azotobacter sp. exerted the highest beneficial influence on Brassica napus L. growth in non-sterile soil, since the root and shoot lengths were stimulated with 27.64% and 52.60%, respectively, compared to uninoculated plants. Bacillus sp. had a positive effect on the growth of the shoot length of Amaranthus retroflexus L. (with 30.30% in sterile soil and 3.69% in non-sterile soil compared to the control). Azotobacter sp. stimulated the growth of the root length of Rumex patientia L. with 35.29% in sterile soil and also the shoot length of Panicum miliaceum L. in non-sterile soil by 20.51% compared to the control. Further, the roots and shoots of Linum usitatissimum L. grown in non-sterile soil and in the presence of Pseudomonas sp. increased by 178.38% and 15.08%, respectively, compared to the flax grown in sterile soil. Statistically, according to Tukey's Honestly Significant Difference (HSD) test results, not all observed differences in plants grown with the selected bacteria are significantly different compared to the control.

Automated summary

In this study, bacteria from the genus of Azotobacter, Bacillus and Pseudomonas were isolated from Phaseolus vulgaris roots and used as plant growth-promoting bacteria for various plants. The results showed that different bacteria had different effects on plant growth in both sterile and non-sterile soil. Bacillus had the most influence on Sinapis alba in sterile soil, while Pseudomonas had the greatest effect on root and shoot length in non-sterile soil. Azotobacter stimulated the growth of Brassica napus in non-sterile soil, while Bacillus had a positive effect on Amaranthus retroflexus. Azotobacter also promoted the growth of Rumex patientia and Panicum miliaceum, while Pseudomonas enhanced the growth of Linum usitatissimum in non-sterile soil. However, not all differences observed in plants with the selected bacteria were statistically significant compared to the control.