Abstract
Plant biostimulants are “green” solutions to improve crop production. Trichoderma spp. and phosphites, ordinarily used as biocontrol agents, can trigger phytostimulation, also promoting endogenous mechanisms involved in plant growth and development. The present study aimed at assessing the efficacy of a phosphite-based formulation (Phosphit-One) and Trichoderma harzianum-T22 on the morpho-physiological response and modulation of the metabolomics profile in zucchini squash plants (Cucurbita pepo L.) cultivated in controlled growth conditions (Fitotron®). The highest values of fresh biomass production (390.9 g plant−1) and root dry weight (5.6 g plant−1) were obtained for Trichoderma-treated plants. This last treatment resulted in an improved physiological performance (SPAD index, CO2 assimilation rate, and Fv/Fm ratio) measured 30 days after transplanting. Both Trichoderma and phosphite treatments induced a broad metabolic reprogramming in leaves, evident also for the phosphite treatment that did not result in a growth promotion. The microbial and the non-microbial treatments showed distinctive signatures in secondary metabolism yet, common responses could be also highlighted. For instance, both Trichoderma and phosphite triggered ROS-mediated signaling processes, together with the accumulation of phenylpropanoids, glucosinolates, and phytoalexins. Furthermore, a significant alteration of phytohormones was observed, with terpenoid gibberellins and brassinosteroids showing the largest differences. The metabolomic signatures induced by Trichoderma and phosphite in zucchini squash provided molecular insights into the processes underlying elicitation of plant defense due to biostimulation. Interestingly, the modulation of plant secondary metabolism by both treatments did not impair plant growth.
Highlights
In recent decades, the word “sustainability” has made an extraordinary rise to fame.The Neolithic agricultural revolution has paved the way for modern society by establishing systematic processes to harness natural resources based on plant products [1]
The application of Trichoderma resulted in increased fresh biomass production (14.9%) and root dry weight (115.4%) compared to the non-treated control as well as the highest dry biomass value (47.2 g plant−1 ) compared to either the phosphite treatment or the control
The highest Soil Plant Analysis Development (SPAD) values, which is an indicator of chlorophyll content, were recorded in plants inoculated with Trichoderma (30 days after transplanting (DAT)) and correlated to the highest leaf magnesium content, as observed in lettuce [53]
Summary
The Neolithic agricultural revolution has paved the way for modern society by establishing systematic processes to harness natural resources based on plant products [1]. When a system becomes inefficient in operating within its environment, it consumes more available resources and produces more entropy or waste, making it unsustainable [4]. For these reasons, modern agriculture must move towards sustainability while feeding an ever-increasing population [5] and preserving non-renewable natural resources (e.g., water and soil) [6,7]. Biostimulants are among the most promising sustainable tools to improve yield and quality of horticultural products under sub-optimal growth conditions. The positive effects on crops seem to be related to the signaling mechanisms (stimulus-response) induced by the biostimulant-plant interaction, which triggers a defense response that can mitigate the effects of unfavorable environmental conditions [14]
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