A Microbial-Based Biostimulant Enhances Sweet Pepper Performance by Metabolic Reprogramming of Phytohormone Profile and Secondary Metabolism.

Paolo Bonini,Luigi Lucini,Mariateresa Cardarelli,Begoña Miras-Moreno,Veronica Cirino,Youssef Rouphael,Giuseppe Colla,Byungha Lee,Gorka Erice

doi:10.3389/fpls.2020.567388

Abstract

Microbial-based biostimulants can improve crop productivity by modulating cell metabolic pathways including hormonal balance. However, little is known about the microbial-mediated molecular changes causing yield increase. The present study elucidates the metabolomic modulation occurring in pepper (Capsicum annuum L.) leaves at the vegetative and reproductive phenological stages, in response to microbial-based biostimulants. The arbuscular mycorrhizal fungi Rhizoglomus irregularis and Funneliformis mosseae, as well as Trichoderma koningii, were used in this work. The application of endophytic fungi significantly increased total fruit yield by 23.7% compared to that of untreated plants. Multivariate statistics indicated that the biostimulant treatment substantially altered the shape of the metabolic profile of pepper. Compared to the untreated control, the plants treated with microbial biostimulants presented with modified gibberellin, auxin, and cytokinin patterns. The biostimulant treatment also induced secondary metabolism and caused carotenoids, saponins, and phenolic compounds to accumulate in the plants. Differential metabolomic signatures indicated diverse and concerted biochemical responses in the plants following the colonization of their roots by beneficial microorganisms. The above findings demonstrated a clear link between microbial-mediated yield increase and a strong up-regulation of hormonal and secondary metabolic pathways associated with growth stimulation and crop defense to environmental stresses.

Highlights

Three major current global challenges are food security, environmental degradation, and climate change
The total number of Trichoderma colonies estimated by Quantitative Real-Time PCR (qPCR) in the rhizosphere of inoculated pepper plants was significantly (P < 0.01) higher than that recorded for the untreated control (2.2 × 105 ± 0.6 × 105 vs. 1.2 × 103 ± 0.4 × 103 colony forming unit (CFU) g−1, respectively)
Relative to the uninoculated control, inoculation with arbuscular mycorrhizal fungi (AMF) and Trichoderma koningii significantly increased fruit yield at single harvests (139, 174, 272 days after transplanting (DAT)) and as a total (Table 1); the biostimulant-mediated yield increase was more pronounced during the first part of the reproductive cycle, namely, early yield (139 and 174 DAT) (Table 1)

Summary

Introduction

Three major current global challenges are food security, environmental degradation, and climate change. Several studies reported that certain Trichoderma spp. including T. atroviride, T. koningii, T. harzianum, and T. virens are other plant biostimulants that boost crop performance (Colla et al, 2015) and nutrient use efficiency and/or endue plants with abiotic stress tolerance (Saia et al, 2020). The direct and indirect mechanisms of the biostimulant action of Trichoderma strains include (i) improvement of lateral root development, (ii) induction of plant mitogen-activated protein 6, and (iii) production and rhizosphere excretion of auxins and secondary metabolites such as volatile and non-volatile substances that stimulate various plant responses and enhance crop nutrient uptake, resilience, and productivity (López-Bucio et al, 2015)

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Results

Conclusion