Abstract
Consistent with their reported abundance in soils, several Burkholderia sensu lato strains were isolated from the rhizosphere of maize plants cultivated at different sites in central México. Comparative analysis of their 16S rRNA gene sequences permitted their separation into three distinctive clades, which were further subdivided into six other clusters by their close resemblance to (1) Trinickia dinghuensis; (2) Paraburkholderia kirstenboschensis, P. graminis, P. dilworthii and P. rhynchosiae; (3) B. gladioli; (4) B. arboris; (5) B. contaminans, or (6) B. metallica representative species. Direct confrontation assays revealed that these strains inhibited the growth of pathogenic Fusarium oxysporum f. sp. radicis-lycopersici, and F. verticillioides within a roughly 3–55% inhibition range. The use of a DIESI-based non-targeted mass spectroscopy experimental strategy further indicated that this method is an option for rapid determination of the pathogen inhibitory capacity of Burkholderia sensu lato strains based solely on the analysis of their exometabolome. Furthermore, it showed that the highest anti-fungal activity observed in B. contaminans and B. arboris was associated with a distinctive abundance of certain m/z ions, some of which were identified as components of the ornbactin and pyochelin siderophores. These results highlight the chemical diversity of Burkholderia sensu lato bacteria and suggest that their capacity to inhibit the Fusarium-related infection of maize in suppressive soils is associated with siderophore synthesis.
Highlights
Maize is extensively cultivated in the world, with a production rate of about 990.6 Mt/year, ranking as the third most important cereal for human consumption
This study identified rhizobacteria associated with suppressive soils able to reduce the incidence of highly damaging fungal infections of cultivated maize in central Mexico
Fusarium verticillioides is frequently reported as the causative agent of severe maize plant diseases characterized by extensive stalk, ear or root decay that may lead to reduced grain quality [58,59]
Summary
Maize is extensively cultivated in the world, with a production rate of about 990.6 Mt/year, ranking as the third most important cereal for human consumption. The production of maize is conditioned by various biotic and abiotic factors. Fusarium spp. is a ubiquitous soil-borne plant pathogenic fungus that can cause highly damaging infections characterized by severe decay of seeds, roots, stems, ears or kernels [1,2]. Wineland) is the prevalent species of Fusarium in distinct landscapes [3,4], and the losses caused by this fungus can vary from 7% to 38% [5]. Certain bacterial components of this root microbial community, known as plant growth promoting rhizobacteria (PGPR), are known to enhance plant growth and fitness [6]. Plant growth promotion can take place indirectly when PGPR prevent or diminish the damage caused by pathogenic microorganisms, an effect frequently produced through the production of secondary metabolites
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