Rhizobium laguerreae Improves Productivity and Phenolic Compound Content of Lettuce (Lactuca sativa L.) under Saline Stress Conditions.

Miguel Ayuso-Calles,Alejandro Jiménez-Gómez,M. Teresa Escribano-Bailón,Ignacio García-Estévez,Raúl Rivas,José D. Flores-Félix

doi:10.3390/foods9091166

Miguel Ayuso-Calles, Alejandro Jiménez-Gómez + Show 4 more

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https://doi.org/10.3390/foods9091166

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Abstract

Lettuce (Lactuca sativa L.) is a widely consumed horticultural species. Its significance lies in a high polyphenolic compound content, including phenolic acids and flavonols. In this work, we have probed the ability of Rhizobium laguerreae HUTR05 to promote lettuce growth, under in vitro and greenhouse conditions (both non-saline and saline conditions). This strain has shown several in vitro plant growth promotion mechanisms, as well as capacity to colonize lettuce seedlings roots. We have analyzed the effect of the rhizobacterium inoculation on mineral and bioactive compounds in lettuce, under greenhouse conditions, and found a rise in the content of certain phenolic acids and flavonoids, such as derivatives of caffeoyl acid and quercetin. The genome analysis of the strain has shown the presence of genes related to plant growth-promoting rhizobacteria (PGPR) mechanisms, defense from saline stress, and phenolic compound metabolism (such as naringenin-chalcone synthase or phenylalanine aminotransferase).

Highlights

The current trend of consumers to maintain a healthy and balanced diet has led to an increase in the consumption of fresh vegetables in recent years, due to their low caloric content and richness in bioactive compounds, which are the secondary metabolites with remarkable effects on human health [1,2,3].Lettuce (Lactuca sativa L.) is a species belonging to the Asteraceae family, widely cultivated in temperate areas around the globe, more than 21 million tons are produced annually [4]
The two housekeeping genes, recA and atpD, were analyzed in the phylogenetic relationships in Rhizobium genus [24], in this case, the analysis of the concatenated gene sequences showed that HUTR05 had a 100% similarity with R. laguerreae
The effects of the inoculation with a Rhizobium laguerreae strain in lettuce are analyzed for the first time

Summary

Introduction

Lettuce (Lactuca sativa L.) is a species belonging to the Asteraceae family, widely cultivated in temperate areas around the globe, more than 21 million tons are produced annually [4]. It is traditionally consumed fresh, as in a Mediterranean diet. Lettuce stands out for its content of fiber, folate, vitamins, and bioactive compounds such as phenolic acids and flavonoids, mainly flavonols [1,2,5]. Several studies indicate that these polyphenolic compounds have beneficial effects on human health, conferring protection against cardiovascular diseases and various

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