Fenugreek (Trigonella foenum-graecum L.) is a valuable medicinal plant, which is widely distributed throughout the world. It has been known that plant growth promoting rhizobacteria (PGPR) have positive effects on the quality and quantity of medicinal plants under different soil water levels. For this reason, a factorial experiment was conducted on the basis of a randomized complete block design (RCBD) to evaluate PGPR effects on the morphophysiological and phytochemical traits of fenugreek under different soil water levels. This study was conducted in two separate experiments: after the six-leaf stage and after the flowering stage. In the experiments, the treatments were plant growth promoting rhizobacteria (PGPR) including the control, Sinorhizobium meliloti, Pseudomonas fluorescens, a combination of S. meliloti and P. fluorescens, and different soil water levels (i.e. 100, 80, 60 and 40% of field capacity (FC) in three replications. The results showed that the highest seed weight per plant was obtained by inoculation with the S. meliloti and P. fluorescens combination at 100% FC after the two developmental stages. The maximum concentrations of nicotinic acid and trigonelline were observed for the combination of S. meliloti and P. fluorescens at the soil water content of 40% FC after the six-leaf stage and for S. meliloti at the soil water content of 40% FC after the flowering stage. The correlation and stepwise regression analyses showed positive effects of PGPR application on the morphophysiological and phytochemical traits of fenugreek plants under different soil water levels.
