Stimulatory effects of growth-promoting bacteria on growth, nutritional composition, and yield of kale plants

Plant growth promotion using beneficial bacteria is an eco-friendly approach to meet the worldwide need for raising crop yields. This research was done in a greenhouse during 2017 and 2018 seasons to investigate the effect of bacterial biofertilization using three strains, AP-28 of Pseudomonas koreensis, AP-29 of Ralstonia pickettii, and AP-51 of Bacillus cereus on kale plants. Seeds of kale plants were soaked in bacterial solutions for three hours and compared with untreated seeds. Our results exhibited that the highest significant differences in vegetative growth, including plant length (16.76 and 15 cm), leaf number (14.33 and 14.00), and leaf area (100.52 and 99.73 cm2) were obtained from AP-51 treatment compared with control (11.33 and 10.67 cm), (10 and 11.67) and (100.52 and 99.73 cm2) in both seasons, respectively. In both seasons, seed treatment with AP-51 produced the highest significant ascorbic acid (1.373 and 1.309 mg/g) compared with control (6.82 and 8.23 mg/100g, respectively). The highest phenolic contents in both seasons were produced by AP-51 (1.83 and 2.10 mg/g) compared to untreated plants (1.31 and 1.46 mg/g, respectively). AP-51 recorded the highest yield (95.81 and 94.75 g/plant) compared with control (72.92 and 82.76 g/plant) in both seasons, respectively. Macronutrients (N, P, K, Ca, and Mg), as well as microelements (Fe, Cu, and Zn), were examined. The treatment with plant growth-promoting bacteria has been recognized as an environmentally sustainable approach to reduce the inputs of chemical fertilizers and to increase crop productivity, phytochemical composition, and mineral contents.