Given the problems associated with the use of synthetic chemicals in agriculture, the use of plant growth-promoting rhizobacteria (PGPR) in agriculture is gaining in importance and acceptance worldwide, and appears to be a trend for the future. Among strains that show growth-promoting activity, there are species belonging to the genera Pseudomonas and Bacillus.

The principal growth promotion mechanisms of Bacillus strains regards the production of growth stimulating phytohormones, phosphate solubilization and mobilization, siderophore production, antibiosis (including the production of antibiotics, the inhibition of plant ethylene synthesis and the induction of plant systemic resistance to pathogens).

Italian and Spanish scientists have investigated the effect of substrate disinfection and Bacillus subtilis application on the yield, quality and safety of watercress (Nasturtium officinale R. Br.) grown in floating system that is a soilless growing system. For the study, two factors were considered, disinfection of the substrate and inoculation with B. subtilis.

Substrate disinfection was carried out in a flow steam at 100°C for 45 min, inoculation was performed twice: one day before sowing and 11 days after sowing. For bacterial inoculation (BI), the commercial product Larminar® (1012 CFU/g of B. subtilis strain AP-01; Agrimor, Agricultura Moderna S.A., Madrid, Spain) was used at a dose of 0.5 kg/m3

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Scientists found that the disinfection of the substrate had a positive effect on the development of the watercress because it increased the shoot antioxidant capacity and general plant growth and decreased the CFU of moulds. Inoculation with B. subtilis had a less pronounced effect because it increased the antioxidant capacity and decreased the contents of chlorophyll and carotenoids.

The full study is available online since October 9th 2015 at:

Source: Giuseppe Pignata, Diana Niñirola, Manuela Casale, Paolo E. Lo Turco, Catalina Egea-Gilabert, Juan A. Fernández, Silvana Nicola, 'Inherent quality and safety of watercress grown in a floating system using Bacillus subtilis', 2015, The Horticulture Journal Preview, doi: 10.2503/hortj.MI-091.


Silvana Nicola
Vegetable Crops & Medicinal and Aromatic Plants, VEGMAP, Department of Agricultural, Forest and Food Sciences, DISAFA,
University of Turin
10095 Grugliasco (Turin), Italy