Intimate interactions of Enterobacter, Aspergillus and Enterobacter-Aspergillus biofilm with strawberry, tomato and rice: early plant growth under glass house conditions

The host specificity of biofertilizers poses many challenges at large scale production and usage. The present study investigated the versatility of a fungal-bacterial biofilmed biofertilizer (FBB) in comparison to its monoculture bacterial (BB) and fungal (FB) biofertilizers using three crops. The FBB was formulated using selected strawberry (Fragaria ananassa) rhizosphere-associated bacterial (Enterobactor sp.) and fungal (Aspergillus sp.) strains. Strawberry, rice and tomato were grown in hydroponics under similar conditions and the liquid biofertilizers (FBB, BB and FB) were applied at a ratio of biofertilizer: hydroponic medium in 1:90 (in volume). A control was maintained without any biofertilizers. The treatments were triplicated and arranged according to completely randomized design. The growth medium collected at different time intervals were analyzed for polysaccharides, amides and lipids by Fourier Transform Infra-red (FTIR) spectroscopy. Plant height and dry mass were recorded after a month. Data were analyzed by ANOVA and correlation. After 30 days, root-FBB interactions of all three crops observed significantly improved polysaccharides, amides and fatty acids concentrations in the hydroponic medium over the control. Total plant biomass and height of strawberry and rice were significantly (p < 0.05) increased with FBB over its monoculture biofilms (BB, FB) and the control. In tomato, FBB-treated seedlings showed an improved growth over their counterparts treated with monoculture biofertilizers, though the differences were not significant (p > 0.05). The growth of strawberry and rice showed a significant (p < 0.05) positive correlation with functional polysaccharides and amides, while tomato showed a similar correlation with all three functional biomolecules tested. The findings clearly indicate that the FBB developed from strawberry root-associated microbes nullify the crop specificity, and show the potential to improve growth of rice and tomato. Therefore, mixed-culture biofertilizers seem to possess a universal potential in improving crop growth in comparison to conventional monoculture biofertilizers. Further studies with other crops are imperative to confirm their potential universality.