Plant growth-promoting bacterial endophytes have been increasingly used in sustainable agriculture. Previous studies reported the isolation of Pseudomonas putida Pt12 with plant growth-promoting properties associated with the roots of Piper tuberculatum, a Piperaceae from the Amazon region. Thus, this study aimed to evaluate the effect of P. putida Pt12 on promoting the growth of cowpea (Vigna unguiculata L.), a legume crop with economic importance in developing countries, where its production can be affected by biotic and abiotic factors. Experiments were arranged in a completely randomized design using two methods of inoculation (seed bacterization and seedling irrigation). In seed bacterization, cowpea seeds were surface-sterilized, followed by inoculation with the Pt12 suspension (OD600= 0.3, 3×108 cells/mL). For irrigation, 8-day-old seedlings were inoculated with the P12 suspension (OD600= 0.1, 1x108 cells/mL and OD600= 0.3, 3×108 cells/mL) through soil irrigation.
Plant growth was monitored over a period of 25 days, which the parameters of biomass were assessed. The data were subjected to analysis of variance using the Scott-Knott test at 5% significance. Plants inoculated with Pt12 exhibited significantly higher growth compared to non-inoculated plants. Enhanced growth of both roots and the aerial part of the plant was observed, resulting in 206% and 59% increases in total dry biomass of plants inoculated by seed bacterization and soil irrigation, respectively. No significant differences were observed between plants irrigated with the two inoculum concentrations.
