Genomics control of biostimulant-induced stress tolerance and crop yield enhancement

Abstract

Biostimulants are changing modern agriculture, as they have the potential to secure healthy and sustainable food production while preserving the environment. They have two main biological effects: growth promotion and stress protection. Both effects can lead to enhancement of the yield and improvement of the marketable grade of the produce in crops, without compromising crop quality. Their use increased exponentially in the past decade, as they are highly efficient, ecologically friendly (non-toxic, biodegradable), and applicable to all major crops. While exponential data on the physiological mechanisms of stress protection is accumulating in recent years, the information as to how biostimulants act at the molecular level is still rather limited. Here we review the growing evidence of the biostimulants role in stress protection and yield enhancement of crops, as well as the recent transcriptomic and metabolomic data, which indicate biostimulants' molecular mode of action. In particular, we outline the role of genes encoding signaling components, plant hormones (abscisic acid, brassinosteroids, and ethylene), genes encoding transcription factors from ERF, WRKY, NAC, and MYB families, and genes related to growth, photosynthesis, and stress response. Finally, we describe strategies to study the genetic and genomics control of biostimulants mode of action, with foci on stress tolerance and yield enhancement. In Arabidopsis, established systems for biostimulants-induced protection against drought and oxidative stress will allow both forward and reverse genetics approaches to identify key genes from the biostimulants network. Mutations in such genes compromise the stress-protective effect of biostimulants. In major crops such as pepper and tomato, large Genome Wide Association Studies (GWAS) panels can be utilized to study crops responses to biostimulants in terms of drought tolerance, fruit qualities, and yield in order to pinpoint genes controlling biostimulants-induced stress protection and yield enhancement. The combination of these approaches allows identification and verification of important genes involved in the pathways of biostimulant-induced stress protection and yield enhancement, as well as deciphering parts of the intricate biostimulant-signaling network.

Keywords: Arabidopsis; abiotic stress; biostimulants; drought; oxidative stress; tomato.

Figure 1

Mutant screening to identify genes, which are part of the biostimulant network. (a) Forward genetics approach utilizing either gene inactivation by T‐DNA/transposons to inactivate unknown positive regulators (gene 1) or activation tag construct to identify negative regulators (gene 2) of the biostimulant network. (b) Reverse genetic approach, in which genes regulated by biostimulants (e.g., SuperFifty, SF) are mutated or CRISPR‐Cas9 genome edited. If a gene is involved in the biostimulant pathway, its inactivation will result in a sensitive phenotype upon SF‐drought exposure (mutant 1), as opposed to the inactivation of a gene which is not part of the biostimulant pathway (mutant 2).

Figure 2

GWAS analysis pipeline for identification and verification of genes modulating the biostimulant pathway in vegetable crops. Genetic resources: hundreds of pepper and tomato lines and cultivars will be primed with biostimulants and evaluated under normal and stress (e.g., drought) conditions. Agronomically important traits such as growth, stress tolerance, fruit nutritional properties (metabolites, essential elements, vitamins, and yield) will be studied, and candidate genes identified by GWAS analysis will be verified using CRISPR‐Cas9 genome editing.