The effect of plant growth-promoting rhizobacteria on yield, water use efficiency and Brix Degree of processing tomato

Abstract

Open field experiments were conducted to investigate the effects of plant growth-promoting rhizobacteria (PGPR) (Phylazonit MC®) as a biofertilizer on processing tomato cultivar var. Uno Rosso F₁, grown under three different regimes of water supply. Field effectiveness of rhizobacteria inoculation on total biomass production, yield and water use efficiency, were examined in 2015 and 2016. Seedlings were inoculated with 1% liquid solution of Phylazonit MC® (Pseudomonas putida, Azotobacter chroococcum, Bacillus circulans, B. megaterium; colony-forming unit: 10⁹ CFU/mL) at sowing and planting out by irrigation. There were three different regimes of water supply: rain-fed control (RF); deficit water supply (WS50) and optimum water supply (WS100); the latter was supplied according to the daily evapotranspiration by drip irrigation. Total aboveground biomass (shoot and total yield) and red fruits yield were measured at harvest in August, in both years. Total biomass changed between 32.5 t/ha and 165.7 t/ha, the marketable yield from 14.7 t/ha to 119.8 t/ha and water use efficiency (WUE) between 18.5 kg/m³ to 32.0 kg/m³. The average soluble solids content of the treatment combinations ranged from 3.0 to 8.4°Brix. Seasonal effects were significant between the two years with different precipitation, which manifested in total biomass and marketable yield production. PGPR increased WUE only in WS50 in both years, while under drought stress and higher water supply, the effect was not clear. The effect of PGPR treatment on marketable yield, total biomass and WUE was positive in both years when deficit irrigation was applied and only in the drier season in the case of optimum water supply.