A bacterial formula with native strains as alternative to chemical fertiliser for tomato crop

Global tomato productivity is threatened by biotic and abiotic stressors. To support and guarantee an adequate yield of tomato crops, agricultural practices have been based on the intensive use of fertilisers with negative impacts on the environment. This study presents a simple and effective strategy of functional bioaugmentation, suitable for different varieties, to replace chemical fertilisation. A tailored microbial formula composed by eight indigenous strains (including the genera Delftia, Pseudomonas, Paenarthrobacter, Phyllobacterium, Bacillus, and Acinetobacter) was developed as biofertilizer. Strains were selected from native soil for their plant growth-promoting (PGP) functions, and combined respecting the taxonomic composition of the original PGP heterotrophic community structure. The effect of the bio-fertilisation vs chemical fertilisation was tested in three successive field trials in the company greenhouse, with different tomato varieties (Camone, Oblungo, Cherry). When bio-fertilisation was applied only twice during the Camone's life cycle, tomato yield was significantly reduced (0.8 vs 2.1 kg per plant, p = 0.0003). However, monthly inoculation during plant growth led to a fruit yield comparable to that obtained with chemical fertilisers (about 1.5 kg per plant for Oblungo, and about 2 kg per plant for Cherry variety, p = 0.9999). Bio-fertilization did not significantly affect plant height; only during the last growing period of the Cherry variety, a significantly higher average plant height (p < 0.0001) was observed with chemical fertiliser. The results indicate that a knowledge-based bacterial formula and monthly inoculation during the plant growth can be a successful bio-fertilisation strategy. These findings may pave the way towards more sustainable tomato production, since farming practices are becoming increasingly crucial, in accordance with Agenda 2030 and the UE "Farm to Fork" strategy.[GRAPHICS]

Biocidal Activity of Phyto-Derivative Products Used on Phototrophic Biofilms Growing on Stone Surfaces of the Domus Aurea in Rome (Italy)

Hypogean or enclosed monuments are important cultural heritage sites that can suffer biodegradation. Many of the stone walls of the prestigious Domus Aurea are overwhelmed by dense biofilms and so need intervention. Room 93 was chosen as a study site with the aim to test the efficacy of phyto-derivatives as new biocides. Laboratory studies were performed comparing the effects of liquorice leaf extract (Glycyrrhiza glabra L.), lavender essential oil (Lavandula angustifolia Mill.) and a combination of both. In situ studies were also performed to test the effect of liquorice. The results were compared with those of the commonly used synthetic biocide benzalkonium chloride. The effects on the biofilms were assessed by microscopy along with chlorophyll fluorescence analysis. The phototrophs in the biofilms were identified morphologically, while the heterotrophs were identified with culture analysis and 16S gene sequencing. Results showed that the mixed solution liquorice/lavender was the most effective in inhibiting the photosynthetic activities of biofilms in the laboratory tests; while, in situ, the effect of liquorice was particularly encouraging as an efficient and low-invasive biocide. The results demonstrate a high potential biocidal efficacy of the phyto-derivatives, but also highlight the need to develop an efficient application regime

A rhizospheric Burkholderia cepacia complex population: genotypic and phenotypic diversity of Burkholderia cenocepacia and Burkholderia ambifaria

The Burkholderia cepacia‘complex’ (Bcc) presently comprises nine species and genomovars. In order to acquire a better comprehension of the species and genomovar distribution and of the genetic diversity among environmental Bcc bacteria, a natural population of 60 bacterial isolates recovered from the rhizosphere of maize and belonging to the Bcc has been characterised to assess the exact taxonomic position, the genetic polymorphism and the metabolic profiles of isolates. The identification of the different species and genomovars was accomplished by a combination of techniques including sodium dodecyl sulfate–polyacrylamide gel electrophoresis of whole-cell proteins and recA-based restriction fragment length polymorphism analyses. The genetic diversity among Bcc isolates was analysed by means of the random amplified polymorphic DNA and amplified fragment length polymorphism techniques; the analysis of molecular variance method was applied to estimate the genetic differences among the various species and genomovars identified within the bacterial population. Metabolic profiles based on carbon source utilisation were obtained by means of the Biolog GN assay and analysed by means of cluster analysis. Forty-four strains were identified as B. ambifaria, 11 as B. cenocepacia recA lineage III-B, four as B. pyrrocinia, and one as B. cepacia genomovar I. Marked genetic differences were observed between B. cenocepacia and B. ambifaria, whereas limited differences were found between B. pyrrocinia and B. ambifaria and between B. pyrrocinia and B. cenocepacia. No significant differences (P>0.05) were observed between the mean genetic distances of isolates belonging to B. cenocepacia, B. ambifaria, and B. pyrrocinia. Phenotypic analyses revealed that all isolates tested were able to utilise more than 75% of substrates. The highest variability in the number of utilised substrates was found among B. cenocepacia isolates, whereas the lowest was found among B. ambifaria isolates. Cluster analysis of metabolic profiles revealed pronounced differences between B. cenocepacia and B. ambifaria; in contrast, B. pyrrocinia could not be clearly separated either from B. cenocepacia or from B. ambifaria

Comparative analysis of the effects of locally used herbicides and their active ingredients on a wild-type wine Saccharomyces cerevisiae strain

Herbicides are released to the environment with potential ecotoxicological risks for mammals. Yeast is a good model to elucidate toxicity mechanisms. We investigated how three commercial herbicides (Proper Energy, Pointer, and Silglif) and their active ingredients (respectively, fenoxaprop-P-ethyl, tribenuron methyl, and glyphosate) can affect biological activities of an oenological Saccharomyces cerevisiae strain, which may be resident on grape vineyards of the same geographical areas where herbicides are used. The use of commercial grade herbicides employed in Italy allowed us to reproduce the same conditions applied in crops; at the same time, assaying pure single active compounds made it possible to compare the effects obtained with commercial formulations. Interestingly, we found that while pure active compounds affect cell growth and metabolism at a lower extent, commercial preparations have a significant major negative influence on yeast biology