Foliar Application of Vegetal-Derived Bioactive Compounds Stimulates the Growth of Beneficial Bacteria and Enhances Microbiome Biodiversity in Lettuce

Abstract

Many studies on plant biostimulants and organic fertilizers have been focused on the ability of these products to increase crop productivity and ameliorate crop tolerance to abiotic stresses. However, little information is available on their effect on plant microbiota, whereas it is well known that microorganisms associated with plant play crucial roles on the health and productivity of their host. The aim of this study was to evaluate the effect of a vegetal-derived protein hydrolysate (PH), a vegetal-derived PH enriched with copper (Cu-PH), and a tropical plant extract enriched with micronutrients (PE) on shoot growth and the epiphytic bacterial population of lettuce plants and the ability of these products to enhance the growth of beneficial or harmful bacteria. The three plant-derived products enhanced shoot biomass of lettuce plants indicating a biostimulant effect of the products. Data obtained using culture-independent (Terminal Restriction Fragment Length Polymorphism and Next Generation Sequencing) and culture-dependent approaches indicated that foliar application of commercial products altered the composition of the microbial population and stimulated the growth of specific bacteria belonging to Pantoea, Pseudomonas, Acinetobacter, and Bacillus genus. Data presented in this work demonstrated that some of these strains exhibited potential plant growth-promoting properties and/or biocontrol activity against fungi and bacteria phytopathogens including Fusarium, Trichoderma, and Erwinia species. No indication of potential health risks associated to the enrichment of human or plant bacterial pathogens emerged by the analysis of the microbiota of treated and no-treated plants. Overall, the findings presented in this study indicate that the commercial organic-based products can enhance the growth of beneficial bacteria occurring in the plant microbiota and signals produced by these bacteria can act synergistically with the organic compounds to enhance plant growth and productivity.

Biostimulant Application with a Tropical Plant Extract Enhances Corchorus olitorius Adaptation to Sub-Optimal Nutrient Regimens by Improving Physiological Parameters

“…Higher photosynthetic activity, SPAD index, and enhanced leaf nutritional status, reflected by higher K and Mg and lower Na concentrations, were observed in PE-treated jute plants, indicating a more efficient accumulation and translocation of assimilates to photosynthetic sinks irrespective of macronutrient concentration in the nutrient solution, thus allowing improved crop performance. Our results are in line with the previous findings on the effect of commercial vegetal-derived biostimulant produced through water extraction and fermentation of tropical plant biomass (Auxym ® ) on tomato [1], spinach [16], and lettuce [45]. A presumed direct mechanism behind the stimulation of jute fresh yield production in response to foliar application of PE under both half-and quarter-strength NS could involve the increased presence of signaling molecules, such as amino acids (glutamic and aspartic acids involved in the stimulation of C and N metabolism), peptides (root-promoting hair peptides), and phytohormones (auxins and cytokinins), which are typical compounds in the commercial PE Auxym ® .…”

Appraisal of Biodegradable Mulching Films and Vegetal-Derived Biostimulant Application as Eco-Sustainable Practices for Enhancing Lettuce Crop Performance and Nutritive Value

“…The greater SPAD index and chlorophyll content of lettuce leaves corroborated this, thus confirming the better photosynthetic efficiency that leads to better plant performance. Similar results on the stimulation of the physiological and biochemical status of biostimulant-treated plants were also previously observed in greenhouse tomato [18], spinach [34], lettuce [35], and jute [28].…”

Yield and Nutritional Quality of Vesuvian Piennolo Tomato PDO as Affected by Farming System and Biostimulant Application

“…In other experiments, Lactuca sativa L. sprayed with PE or PH showed a 11% higher biomass In other experiments, Lactuca sativa L. sprayed with PE or PH showed a 11% higher biomass than non-treated control, which may be as a consequence of both the stimulation exerted by the most represented substances such as amino acids and key peptides and of enhancement of cultivable epiphytic bacteria as well as their species richness and diversity [46]. Overall, the direct and/or indirect mode of actions of the applied biostimulants may have boosted both growth and crop productivity of treated cherry tomato plants compared to the non-treated control treatment.…”