Rhizobium as a biofertilizer for non-leguminous plants

Utilising biofertilizers is a sustainable alternative of integrated nutrient management in plants. Commercialized biofertilizers for non-legumes include Azotobacter and Phosphate Solubilizing Bacteria (PSB), without reported adverse effects on human health, including consumption of raw salad vegetables. However, no commercial biofertilizers for non-legumes are based on rhizobia, despite proven human safety from decades of legume inoculation research. A comparative analysis investigating the yield of tomatoes (Solanum lycopersicum), and content of Lycopene, Vitamin C and antioxidants was undertaken to assess the potential commercial viability of Rhizobium as a biofertilizer for non-leguminous plants. Rhizobium amendment gave a lesser yield of tomatoes (3 +/- 1) compared to Azotobacter (4 +/- 1), but was better than the control (2 +/- 1), and PSB (2 +/- 1). It showed highest lycopene content (0.7 +/- 0.02 mg/100 g) compared to other amendments. The Vitamin C (32.4 +/- 0.01 mg/100 g) with Rhizobium amendment surpassed that of Azotobacter (24.9 +/- 0.09 mg/100 g) and control (12.84 +/- 0.03 mg/100 g). Antioxidant activity of cherry tomatoes grown in Rhizobium-amended soil, was 1.34 times higher than chemically-fertilized plant yield. This study therefore affirms the suitability of rhizobia as a biofertilizer for stimulating the growth and productivity of non-leguminous plants such as tomato (S. lycopersicum) and its potential to be commercialized for use in non-leguminous plants.