Plant growth-promoting rhizobacteria affect growth and sulforaphane content in broccoli seedlings (Brassica.oleracea var. Italica)

In this study, the effect of inoculation with PGPR on growth, sulfur and DL-sulforaphane content of broccoli seedlings was evaluated. Rhizobacterial strains of Bacillus pumilus R44, Pseudomonas tolaasii P61 and P. tolaasii A46 were screened for total indole production and P solubilization. Broccoli seedlings were inoculated with these strains in order to establish a greenhouse experiment. Seedlings were harvested 30 days after inoculation to determine fresh weight, dry weight, root volume, height, and relative chlorophyll content, also S uptake and sulforaphane content. Treatment with PGPR resulted in an increase in almost all the variables evaluated compared to the control. Outstanding results were obtained with the A46 and R44 strains, being 18 and 49% higher for sulforaphane content. P61 was the strain with the best results related to indole production (384% higher than A46), phosphate solubilization (287% higher than A46), and root volume (44% higher than control). There were no significant differences in relative chlorophyll content and sulfur accumulation among the treatments. This is the first work that showed the positive effect of PGPR on sulforaphane content in broccoli seedlings, a compound reported with anticancer activity.