Innovative grafting and metabolomics research unlock salt tolerance in tomatoes

Grafting has become a promising technique in agriculture to enhance the salt tolerance of crops, a critical issue as salt stress affects around 20% of irrigated land globally, severely reducing crop yields. Specifically, grafting in crops like tomatoes has yielded significant results, with certain rootstocks leading to improved scion tolerance to salt stress. However, the underlying mechanisms by which rootstocks influence scion response to salinity remain largely unknown, particularly in terms of metabolic responses in plant leaves under stress conditions. Recent research suggests that metabolomics-assisted breeding, using metabolic markers to predict phenotypic traits, could be a promising avenue. Yet, the challenge lies in comprehensively understanding the interaction between scion and rootstock, and how it affects plant yield traits, which is crucial for advancing grafting techniques and crop salt tolerance.

In March 2022, Horticulture Research published a research article entitled by “Leveraging a graft collection to develop metabolome-based trait prediction for the selection of tomato rootstocks with enhanced salt tolerance”.  

In this study, researchers examined how 254 tomato rootstock accessions affect the morphological and metabolic traits of cv. M82 tomato plants under saline conditions. The results revealed a wide range of phenotypes when tomatoes were grafted onto different rootstocks under saline conditions. Variations in morphological traits and malondialdehyde (MDA) content were observed. A coefficient of variation (CV) was calculated for each trait to assess the extent of variation, with MDA content showing the highest variability. Most grafts (98.4%) produced fewer branches than the standard graft SG-M82, and over 200 grafts showed better overall performance than SG-M82 in terms of higher dry weight and longer main inflorescence length. Correlation analysis revealed significant relationships among seven morphological traits, including fresh and dry weights. The strong correlation between total fresh weight (TFW) and fruit fresh weight (FFW) resulted in a stable FFW/TFW ratio across the population. Additionally, the study found a consistent correlation between plant fresh weight (PFW) and FFW, indicating an intrinsic trait of M82 of productive efficiency. There were significant differences in productive ability between grafts with wild and domesticated rootstocks. There were significant differences in productive ability between grafts with wild and domesticated rootstocks.

Metabolite analysis identified 54 metabolites across the grafts, showing significant variability in levels of metabolites like malate, citrate, and aspartate. A notable trend was observed in the accumulation of amino acids like proline, suggesting a response to salt stress. Further analysis showed three distinct patterns of associations between morphological traits and metabolites, indicating varying responses to saline conditions. It identifies clusters of positive and negative correlations between metabolites, such as TCA cycle intermediates and amino acids, and a set of metabolites including threitol and caffeate.  Correlation analysis between morphological traits and metabolites highlighted relationships with four yield-associated traits and six metabolites. The LASSO method was employed to predict the yield-associated traits, revealing effective predictions with high accuracy.

In summary, this study underscores the significant impact of rootstock on the morphological and metabolic traits of tomato scions under saline conditions. The findings highlight the complexity of the interaction between scion and rootstock and the potential for using metabolic markers in breeding for improved salt tolerance.

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References

Authors

Chao Song¹, Tania Acuña², Michal Adler-Agmon³, Shimon Rachmilevitch², Simon Barak² and Aaron Fait^2,*

Affiliations

¹The Albert Katz International School for Desert Studies, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel

²Albert Katz Department of Dryland Biotechnologies, French Associates Institute for Agriculture and Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, 8499000, Israel

³R&D Southern Arava, Hevel Eilot, 8882000, Israel

About Aaron Fait

He investigates seed metabolism and development by using metabolomics and bioinformatics tools. He leads few projects on grapevine, focusing on grape berry development and the impact of regulated water deficit on plant physiology and metabolism.