Zinc Solubilizing Fluorescent Pseudomonads as Biofertilizer for Tomato (Solanum lycopersicum L.) under Controlled Conditions

Zinc solubilization by Plant Growth Promoting Rhizobacteria (PGPR) is relatively a newer strategy and can be a potential alternative for zinc-based chemical fertilizers to alleviate zinc deficiencies. The following study characterized the zinc-solubilization potential of fluorescent pseudomonads to observe their role in growth promotion of tomato. Nine strains of Pseudomonas spp. were screened to solubilize ZnO, ZnSO4 and ZnCO3 on tris-minimal agar plates. P. chlororaphis strain RP-4 solubilized ZnCO3 whereas, P. aurantiaca strains GS-4 and Type strain (NCIB 10068T) solubilized ZnCO3 and ZnO, only. Moreover, cotton isolate P. aurantiaca ARS-38, solubilized ZnO, however, rest of the strains could not solubilize ZnCO3 or ZnO. All bacterial strains were analyzed for their growth enhancement potential, at pot-scale plant experiments and effect was observed on growth parameters. Plant experiments were set-up in RCBD, conducted in triplicate and harvested after four weeks. Maximum fresh weights of shoots and roots were noted for the plants inoculated with P. aurantiaca PB-St2 (non Zn-solubilizer), however, maximum dry root weights were recorded for the Zn-solubilizer strain RP-4 (P. chlororaphis) inoculated plants. Likewise, substantial increase in root and shoot lengths and area were observed for the Zn-solubilizer strains GS-4, and ARS-38 (P. aurantiaca) inoculated plants in comparison of un-inoculated controls. These findings indicate the potential of Znbiofertilizer strains of Pseudomonas spp. in increasing bioavailability of zinc to plants for sustainable agriculture