Genomic Diversity of Bradyrhizobium from the Tree Legumes Inga and Lysiloma (Caesalpinioideae-Mimosoid Clade)

Abstract

We identified diverse bradyrhizobia having distinct ERIC-PCR genomic fingerprints from native American trees Inga vera and Lysiloma spp. In addition, two nodule isolates recovered from Lysiloma divaricatum seedlings inoculated with soil from the tropical house of a UK botanical garden were also identified as Bradyrhizobium. Genomes were obtained (with sizes around 9 Mb each) from nine Inga and Lysiloma bradyrhizobial isolates; plasmids were detected in two of the Inga strains analyzed. Average Nucleotide Identity of whole genomes revealed five novel Bradyrhizobium genomospecies from Mexican trees, while the UK isolates were identified as Bradyrhizobium cajani and Bradyrhizobium brasilense. Inga vera and Lysiloma isolates, despite their genetic distances and different hosts, shared a common set of nod genes that suggested that I. vera and Lysiloma bradyrhizobia produce fucosylated, methylated and carbamylated lipochitooligosaccharides. Uptake hydrogenase hup, hyp and secretion system genes were found in some of the isolates. Lysiloma strains were found to be ineffective on I. vera. Some of the isolates may be used as plant inoculants.

Identification of Rhizobia Isolated from Nodules of Mexican Commercial Soybean Varieties

“…The lack of a clear pattern in the association could be attributed to various factors, including the complex interactions between soybean varieties, soil conditions, and rhizobial populations. Such diversity is not uncommon in tropical environments, as reported in Mexico and Brazil, where symbiotic strains of the Bradyrhizobium genus have been isolated from various legumes, emphasizing the importance of cross-infectivity between legumes and its agricultural implications [42] [43]. The ability of certain isolates to nodulate soybean from legumes other than soybean underlines the potential for diverse rhizobial populations to contribute to soil fertility and plant growth.…”