The fungus Macrophomina phaseolina is the causal agent of charcoal rot in many crops, such as strawberries and beans. Symptoms include stem and root rot and chlorotic foliage. This disease’s management is complicated because the pathogen forms resistant microsclerotia. This work aimed to obtain bacterial isolates for the biocontrol of M. phaseolina in arid regions. Two strains that grew well under low pH and high salinity, named BsA3MX and BsC11MX, were isolated and identified as B. amyloliquefaciens, based on their morphology and analysis of the 16S ribosomal RNA. Both strains inhibited M. phaseolina up to 66.8% in vitro through the combined action of volatile and diffusible compounds. Furthermore, they produce siderophores and indole-3-acetic acid (IAA), have ACC-deaminase activity, solubilize phosphate and zinc, and decrease microsclerotia germination. Moreover, in greenhouse assays using cowpea plants (Vigna unguiculata L.), strain BsA3MX reduced lesions caused by M. phaseolina and induced a significant increase in foliage and root biomass. Overall, these results suggest B. amyloliquefaciens BsA3MX and BsC11MX can be used as biological control agents against M. phaseolina in arid zones.
Plant growth-promoting rhizobacteria are often utilized to improve crop health and productivity. Nevertheless, their positive effects can be hindered if they fail to withstand the environmental and ecological conditions of the regions where they are applied. An alternative approach to circumvent this problem is a tailored selection of bacteria for specific agricultural systems. In this work, we evaluated the plant growth promoting and pathogen inhibition activity of rhizobacteria obtained from the rhizosphere of Mariola (Solanum hindsianum), an endemic shrub from Baja California. Eight strains were capable of inhibiting Fusarium oxysporum in vitro, and thirteen strains were found to possess three or more plant-growth-promotion traits. Molecular identification of these strains, using 16 s rRNA partial sequences, identified them as belonging to the genera Arthrobacter, Bacillus, Paenibacillus, Pseudomonas, and Streptomyces. Finally, the effect of selected plant growth-promoting rhizobacteria (PGPR) strains on the growth and suppression of Fusarium wilt in tomato was evaluated. Results showed that these strains improved tomato plants growth under greenhouse conditions and reduced Fusarium wilt effects, as reflected in several variables such as length and weight of roots and stem. This work highlights the potential of native plants related to regionally important crops as a valuable source of beneficial bacteria.
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