Plant growth-promoting rhizobacteria improved growth, nutrient, and hormone content of cabbage (Brassica oleracea) seedlings

A greenhouse experiment was conducted to observe the effects of Bacillus megaterium strain TV-91C, Pantoea agglomerans strain RK-92, and B. subtilis strain TV-17C inoculation on the growth, nutrient, and hormone content of cabbage seedlings. The seeds of cabbage were incubated in flasks by shaking at 80 rpm for 2 h at 28 degrees C to coat the seeds with the rhizobacteria. Plant growth-promoting rhizobacteria (PGPR) treatments increased fresh and dry shoot and root weight, stem diameter, seedling height, chlorophyll reading values, and leaf area of cabbage seedlings compared with the control. Among the strains, B. megaterium TV-91C gave the greatest seedling nutrient content and growth parameters, although the maximum values for leaf area, gibberellic acid, salicylic acid, and indole acetic acid (IAA) contents of seedlings were obtained with the P. agglomerans RK-92 treatment. Seed inoculation with B. megaterium TV-91C increased fresh and dry shoot and root weight by 32.9%, 22.6%, 16.0%, and 35.69%, respectively. Inoculations also increased the stem diameter, seedling height, and SPAD chlorophyll values by 47.5%, 27.2%, and 5.8%, respectively. Furthermore, compared to the control, P. agglomerans RK-92 increased gibberellic acid, salicylic acid, IAA, and leaf area by 13.9%, 70.9%, 38.5%, and 27.3%, respectively. PGPR treatments may improve seedling growth and quality in cabbages.