Lettuce Soil Microbiome Modulated by an L-<i>α</i>-Amino Acid-Based Biostimulant

Maintenance of soil health is of foremost importance to sustain and increase crop productivity, while meeting the demand of a rising global population. Soil microbiome is gaining increasing attention as a modulator of soil health. Microbial communities confer traits to the soil as a living organism, which functions holistically and conforms part of the plant holobiont, reassembling the human-gut axis. Novel strategies in biostimulant development advocate for modulation of the native soil microbiome and the reinforcement of microbial networking to outpace pathogen inclusion. Consequently, we hypothesize that Terramin^® Pro may promotes beneficial microorganisms, depending on the native microbiota of soil, which would lead to an improvement of crop performance indicators. We proposed a soil microbiome-based approach to characterize the effect of an L-<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>α</mi></semantics></math></inline-formula>-amino acid based biostimulant (Terramin^® Pro) on resulting plant phenotypes in lettuce cultivars (<i>Lactuca sativa</i> L.) to address our hypothesis. First, product application promoted Actinobacteria group in assorted soils with different track of agronomic practices. Secondly, biostimulant application improved chlorophyll content in particular soils deviating from standard conditions, i.e., sick or uncultivated ones. Specially, we observed that product application at 30 L ha<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula> improved lettuce phenotype, while potentially promoted entomopathogenic fungi (<i>Beauveria</i> and <i>Metarhizium</i> spp.) and suppressed other lettuce disease-related fungi (<i>Olpidium</i> spp.) in nematode-infested soils. Further investigations could deepen into Terramin^® Pro as a sustainable prebiotic strategy of soil indigenous microbiota, through in-house microbiome modulation, even in additional crops.