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Hyoscyamine and scopolamine production of black henbane (Hyoscyamus niger) infected with Pseudomonas putida and P. fluorescens strains under water deficit stress
Twenty plant growth promoting rhizobacteria (PGPR) strains belonging to Pseudomonas putida and P. fluorescens with different abilities for auxin production were screened based on their effects on vigor index of Hyoscyamus niger plants. Seedlings radicles and culture media were inoculated with these bacteria (109 CFU/ml) and grown under in vitro and growth room conditions. Thereafter, two strains namely PP-168 and PF-187 were selected, which had the highest values of VI. Subsequently, the effects of these two strains on Hyoscyamine (HYO) and Scopolamine (SCO) production in root and shoot tissues were investigated under three water deficit stress levels as 30, 60 and 90% water depletion of field capacity during the vegetative stage (45 to 90 days after planting) in pot experiment. Results indicated that the highest alkaloid content values in root (HYO: 0.268% DW; SCO: 0.122% DW) and shoot (HYO: 0.855% DW; SCO: 0.480% DW) were achieved in PF-187 treated plants grown under severe water stress conditions. By contrast, the maximum alkaloid yield in root (HYO: 1.927mg.plant–1; SCO: 0.835mg.plant–1) and shoot (HYO: 5.887mg.plant–1; SCO: 3.067mg.plant–1) were obtained in PP-168 treated plants under low water stress conditions (W1). Furthermore, the maximal total alkaloids yield (11.716mg.plant–1) in whole plant and 63% increase of shoot SCO yield were observed in the W1PP treatment compared with the respective uninoculated control. PGPR inoculation highly increased the roots and shoots dry matter and decreased severe negative effects of water stress on fine root growth, chlorophyll and relative water content.