Abstract
This work aimed to study the effects in tomato (Solanum lycopersicum L.) of foliar applications of a novel calcium-based biostimulant (SOB01) using an omics approach involving transcriptomics and physiological profiling. A calcium-chloride fertilizer (SOB02) was used as a product reference standard. Plants were grown under well-watered (WW) and water stress (WS) conditions in a growth chamber. We firstly compared the transcriptome profile of treated and untreated tomato plants using the software RStudio. Totally, 968 and 1,657 differentially expressed genes (DEGs) (adj-p-value < 0.1 and |log2(fold change)| ≥ 1) were identified after SOB01 and SOB02 leaf treatments, respectively. Expression patterns of 9 DEGs involved in nutrient metabolism and osmotic stress tolerance were validated by real-time quantitative reverse transcription PCR (RT-qPCR) analysis. Principal component analysis (PCA) on RT-qPCR results highlighted that the gene expression profiles after SOB01 treatment in different water regimes were clustering together, suggesting that the expression pattern of the analyzed genes in well water and water stress plants was similar in the presence of SOB01 treatment. Physiological analyses demonstrated that the biostimulant application increased the photosynthetic rate and the chlorophyll content under water deficiency compared to the standard fertilizer and led to a higher yield in terms of fruit dry matter and a reduction in the number of cracked fruits. In conclusion, transcriptome and physiological profiling provided comprehensive information on the biostimulant effects highlighting that SOB01 applications improved the ability of the tomato plants to mitigate the negative effects of water stress.
Highlights
Biostimulants are increasingly important in agriculture, being considered environmentally sustainable and economically favorable answers to optimize crop productivity (Rouphael and Colla, 2020)
Transcriptomics and physiological analyses have provided a detailed description of the different modes of action exerted by the biostimulant product compared to a classic fertilizer both in water stress and well-watered conditions
The modulation of different genes categories both in terms of up-regulation and down-regulation by the biostimulant compared to the standard calcium-chloride fertilizer suggests a peculiar activity exerted by the novel product
Summary
Biostimulants are increasingly important in agriculture, being considered environmentally sustainable and economically favorable answers to optimize crop productivity (Rouphael and Colla, 2020). Biostimulants are derived from a broad variety of compound classes that include mainly humic and fulvic substances, seaweed extracts, beneficial microorganisms, protein hydrolyzates and other nitrogen-containing compounds, carbohydrates, and inorganic compounds (Rouphael and Colla, 2020). They are increasingly studied and used to mitigate the negative effects of environmental stresses such as lack of water and nutrients on cultivated plants (Van Oosten et al, 2017). The physiological responses induced by water stress include decreased cell turgor (Le Gall et al, 2015), leaf rolling (Kadioglu et al, 2012), inhibited CO2 exchange, decreased photosynthetic efficiency and chlorophyll contents (Mao et al, 2015), and, a drop in overall crop performance
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