Mitigating effect of PGPR on abiotic stress in basil (Ocimum basilicum L.).

Having in mind food security and the fact that basil (Ocimum basilicum L.) is used as fresh seasoning, the development of innovative technologies for its cultivation is required. This study aimed to isolate and characterize plant growth-promoting rhizobacteria (PGPR) isolates from basil rhizospheric soil and monitor the effects of their application on basil growth under different water stress conditions. Isolation, determination of isolates biochemical and PGP properties, evaluation of isolates influences on seed germination and parameters of growth of basil plant, growing under well-watered conditions (70% water holding capacity, WHC), under water deficit stress (35% WHC), and flooded conditions (95% WHC), were done. A total of five representative bacterial isolates were selected: Two Azotobacter isolates (A13, A14), one Pseudomonas isolate (P57), and two Bacillus isolates (B79, B82). The results of this experiment revealed that rhizospheric bacteria of O. basilicum L. var. minimum have multiple biochemical and PGP properties. The most intensive reactions on tested abiotic stressors - drought (higher total phenolics, reduced glutathione, and malondialdehyde content) and flooding (higher superoxide dismutase activity) - were from basil plants inoculated with Pseudomonas sp. P57 isolate, yet along with Azotobacter sp. isolate A13. The highest number of germinated seeds was obtained with the A13 isolate (96.0%), while the highest response for vigour index was observed with Azotobacter isolates (7200.0% and 5628.0%). In well-watered conditions, basil mass inoculated with P57 was 34.2% higher than control. In drought-stressed conditions, plant mass inoculated with A13 isolate was 90% higher than control. In flooded-stressed conditions, the plant mass inoculated with Azotobacter and Pseudomonas isolates increased by more than 100%. [ABSTRACT FROM AUTHOR]