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

Abstract

Mesorhizobium contains species widely known as nitrogen-fixing bacteria with legumes, but their ability to promote the growth of non-legumes has been poorly studied. Here, we analyzed the production of indole acetic acid (IAA), siderophores and the solubilization of phosphate and potassium in a collection of 24 strains belonging to different Mesorhizobium species. All these strains produce IAA, 46% solubilized potassium, 33% solubilize phosphate and 17% produce siderophores. The highest production of IAA was found in the strains Mesorhizobium ciceri CCANP14 and Mesorhizobium tamadayense CCANP122, which were also able to solubilize potassium. Moreover, the strain CCANP14 showed the maximum phosphate solubilization index, and the strain CCANP122 was able to produce siderophores. These two strains were able to produce cellulases and cellulose and to originate biofilms in abiotic surfaces and tomato root surface. Tomato seedlings responded positively to the inoculation with these two strains, showing significantly higher plant growth traits than uninoculated seedlings. This is the first report about the potential of different Mesorhizobium species to promote the growth of a vegetable. Considering their use as safe for humans, animals and plants, they are an environmentally friendly alternative to chemical fertilizers for non-legume crops in the framework of sustainable agriculture.

A Degeneration Gradient of Poplar Trees Contributes to the Taxonomic, Functional, and Resistome Diversity of Bacterial Communities in Rhizosphere Soils

“…In terms of prokaryotes, Proteobacteria , Actinobacteria and Acidobacteria are the dominant phyla, as well as the rhizosphere of many other hosts [ 35 , 36 ]. At the genus level, Bradyrhizobium and Mesorhizobium contains species widely known as nitrogen-fixing bacteria with legumes, and they have an outstanding ability to promote the growth of non-legumes through the production of indole-3-acetic acid (IAA) and siderophores, the solubilization of potassium and phosphate [ 37 ]. Members of the Sphingomonas genus increased Arabidopsis thaliana growth rate, alter rhizosphere microbial community structure of plant under drought stress [ 38 ], and alleviate Cd stress in oilseed rape through regulation of the GSH-AsA cycle and antioxidative enzymes [ 39 ].…”

Siderophore and indolic acid production by Paenibacillus triticisoli BJ-18 and their plant growth-promoting and antimicrobe abilities

“…Siderophores are low molecular weight compounds (500-1,500 Da) possessing a high affinity for Fe 3+ (K f > 10 30 ) (Haas & Defago, 2005) and they are synthesized by bacteria through non-ribosomal pathways (Hutchins et al, 1999;Khan et al, 2020). Many PGPB have been reported to produce siderophores, such as Bacillus subtilis, Paenibacillus polymyxa SK1, Mesorhizobium sp., Brevibacillus brevis GZDF3 (Franco-Sierra et al, 2020;Khan et al, 2020;Menéndez et al, 2020;Sheng et al, 2020). The chelate of siderophores and ferric iron can be directly absorbed by plants and are called mechanism III, which is thought to be used by plants to resist iron stress (Shenker et al, 1992;Yehuda et al, 1996;Chen, Dick & Streeter, 2000).…”

“…When grown under iron-limiting conditions, mung bean plants by inoculation with the siderophore-producing Pseudomonas strain GRP3 showed reduced chlorotic symptoms and an enhanced chlorophyll level compared to uninoculated plants (Sharma et al, 2003). Tomato seedlings inoculation with these two Mesorhizobium strains that produce siderophores and IAA showed significantly higher plant growth traits than uninoculated seedlings (Menéndez et al, 2020). In addition, siderophores secreted by PGPB can suppress plant pathogens by competing for trace amounts of iron in the environment (Glick, 2012).…”

Peer Review #1 of "Siderophore and indolic acid production by Paenibacillus triticisoli BJ-18 and their plant growth-promoting and antimicrobe abilities (v0.1)"

“…Siderophores are low molecular weight compounds (500-1500 Da) possessing a high affinity for Fe 3+ (K f > 10 30 ) (Haas & Defago, 2005) and they are synthesized by bacteria through non-ribosomal pathways (Hutchins et al, 1999;Khan et al, 2017). Many PGPB have been reported to produce siderophores, such as Bacillus subtilis, Paenibacillus polymyxa SK1, Mesorhizobium sp., Brevibacillus brevis GZDF3 (Franco-Sierra et al, 2020;Khan et al, 2020;Menéndez et al, 2020;Sheng et al, 2020). The chelate of siderophores and ferric iron can be directly absorbed by plants and are called mechanism III, which is thought to be used by plants to resist iron stress (Shenker et al, 1992;Yehuda et al, 1996;Chen, Dick & Streeter, 2000).…”

“…When grown under iron-limiting conditions, mung bean plants by inoculation with the siderophore-producing Pseudomonas strain GRP3 showed reduced chlorotic symptoms and an enhanced chlorophyll level compared to uninoculated plants (Sharma et al, 2003). Tomato seedlings inoculation with these two Mesorhizobium strains that produce siderophores and IAA showed significantly higher plant growth traits than uninoculated seedlings (Menéndez et al, 2020). In addition, siderophores secreted by PGPB can suppress plant pathogens by competing for trace amounts of iron in the environment (Glick, 2012).…”