Probiotic activities of Rhizobium laguerreae on growth and quality of spinach

Abstract

The growing interest in a healthy lifestyle and in environmental protection is changing habits regarding food consumption and agricultural practices. Good agricultural practice is indispensable, particularly for raw vegetables, and can include the use of plant probiotic bacteria for the purpose of biofertilization. In this work we analysed the probiotic potential of the rhizobial strain PEPV40, identified as Rhizobium laguerreae through the analysis of the recA and atpD genes, on the growth of spinach plants. This strain presents several in vitro plant growth promotion mechanisms, such as phosphate solubilisation and the production of indole acetic acid and siderophores. The strain PEPV40 produces cellulose and forms biofilms on abiotic surfaces. GFP labelling of this strain showed that PEPV40 colonizes the roots of spinach plants, forming microcolonies typical of biofilm initiation. Inoculation with this strain significantly increases several vegetative parameters such as leaf number, size and weight, as well as chlorophyll and nitrogen contents. Therefore, our findings indicate, for the first time, that Rhizobium laguerreae is an excellent plant probiotic, which increases the yield and quality of spinach, a vegetable that is increasingly being consumed raw worldwide.

Bacillus subtilis CBR05 for Tomato (Solanum lycopersicum) Fruits in South Korea as a Novel Plant Probiotic Bacterium (PPB): Implications from Total Phenolics, Flavonoids, and Carotenoids Content for Fruit Quality

“…Moreover, plant probiotic bacterium (PPB) could be used to reduce the use of chemicals (fertilizers, pesticides) in agriculture. This could lead to improved quality at reduced costs and could provide the basis for more sustainable agriculture [42]. Organic agriculture has been widely promoted and adopted to establish better sustainability in food production and crop protection.…”

Increase in phenolic compounds of Coriandrum sativum L. after the application of a Bacillus halotolerans biofertilizer

“…One of the main challenges is replacing chemical fertilizers with biofertilizers, which include plant root-associated beneficial microorganisms (PGPR) with several direct and indirect plant growth promotion mechanisms, such as phosphate solubilization, nitrogen fixation or phytohormones production. 10 Beginning many decades ago, researchers have focused on the use of PGPRs to increase growth and yield plants further mineral content. 11 However, the role of these bacteria in management of abiotic stress and quality food is becoming more and more important.…”

Plant Growth Promotion Abilities of Phylogenetically Diverse Mesorhizobium Strains: Effect in the Root Colonization and Development of Tomato Seedlings

“…Most of these mechanisms have been reported for rhizobia belonging to different genera and families [10][11][12]. In addition to their ability to fix atmospheric nitrogen with legumes [13], the production of the auxin IAA is probably the most common direct mechanism observed in strains from genera Rhizobium [14][15][16], Phyllobacterium [17] and Mesorhizobium [18,19], which can also synthesize and secrete siderophores [14][15][16]19]. Phosphate solubilization is a mechanism also widespread among PGP strains of Rhizobium [15,16], Phyllobacterium [17,20] and Mesorhizobium [19,[21][22][23]; nevertheless, the ability to solubilize potassium has been reported to date only for one Mesorhizobium strain [24].…”

“…In addition to having several in vitro plant growth promotion mechanisms, good PGPR must be able to colonize the plant roots because this is an essential step for growth promotion [25]. The ability to colonize the roots of different non-leguminous plants has been shown for Rhizobium strains in tomato and pepper [14], strawberry [26], lettuce and carrots [15] and spinach [16], for a Phyllobacterium strain in strawberry [17] and for Mesorhizobium strains in lettuce and carrots [27]. Within these vegetables, the tomato (Solanum lycopersicon L.) is highlighted, whose production exceeds that of the other mentioned vegetables worldwide (http://www.fao.org/faostat/en/#home).…”