Tomatoes are one of the most important crops worldwide and also play a central role in the human diet. Microbial consortia are microorganism associations, often employed as bioinoculants, that can interact with the native rhizosphere microbiota. The aim of this study was to evaluate the impact of a bacterial-based biostimulant (Pseudomonas fluorescens and Bacillus amyloliquefaciens) (PSBA) in combination, or not, with a commercial inoculum Micomix (Rhizoglomus irregulare, Funnelliformis mosseae, Funnelliformis caledonium, Bacillus licheniformis, Bacillus mucilaginosus) (MYC) on the native rhizosphere communities and on tomato production. The trial was carried out using Solanum lycopersicum in an open field as follows: control full NPK (CFD), control reduced NPK (CRD), MYC, PSBA, PSBA + MYC. Bacterial population in the different samples were characterized using a next generation sequencing approach. The bioinocula effect on the native rhizosphere microbiota resulted in significant variation both in alpha and beta diversity and in a specific signature associated with the presence of biostimulants, especially in the presence of co-inoculation (PSBA + MYC). In particular, the high initial biodiversity shifts in the community composition occurred and consisted in the increase in the abundance of genera correlated to the soil acidification and in an enhanced density of nitrogen-fixing microbes. The results also highlighted the well-known rhizosphere effect.

Biostimulants are gaining increasing interest because of their ability to provide a green and effective strategy towards sustainable crop production. Nonetheless, their mode of action remains often unknown. The object of this work was to unravel the mechanisms through which 4-Vita, a biostimulant plant extract, can mitigate drought stress in tomato. To this aim, tomato plants were treated with two foliar applications of 4-Vita and drought stress imposed to both treated and control plants. Phenomics investigations were coupled to mass spectrometric untargeted metabolomics, and raw data were elaborated by multivariate statistics and pathway analysis. The biostimulant elicited a broad reprogramming of the tomato’s secondary metabolism, including its phytohormones profile, corroborating an improved ability to cope with drought stress. A series of mechanisms could be identified in response to the biostimulant treatment under drought, pointing to the preservation of photosynthetic machinery functionality. The modulation of thylakoid membrane lipids, the increase in xanthins involved in ROS detoxification, and the modulation of chlorophylls synthesis could also be observed. Overall, a series of coordinated biochemical mechanisms were elicited by the biostimulant treatment, supporting the increased resilience to drought stress in tomato.

Downy mildew, caused by Plasmopara viticola in grapevine, is one of the most devastating and widespread fungal disease on causing serious harm to grape production. The heavy use of chemical pesticides, necessary to control the pests and pathogens, has caused issues with the resistance, resurgence and residues in food, as well as creating diffuse environmental pollution. In the last decade, biological control started to offer an alternative safe(r) and effective method to control diseases. In this paper, we investigate the potential activity of a plant extract to protect grapevine from downy mildew when used in strategy with a reduced dosage of the conventional fungicides (PPP). Four strategies were tested, with two of them giving the best results. Indeed, the use of LL017 increased the tolerance of the vine against P. viticola compared to its control with the same dosage of PPP, and with an efficacy closer to the full dosage of the PPP. In the tests where the yield was evaluated, the treatment with LL017 always resulted in a higher yield than the respective control with the same dosage of PPP and, in some cases, it gave a higher yield than even the positive control.