Swietenia macrophylla is a tropical timber species of ecological and economic importance. However, its slow vegetative growth and root development in nurseries strongly limit its production. This study evaluated the effect of 10 rhizobacteria strains during the early stages of production of S. macrophylla. Superficially disinfected seeds were inoculated with rhizobacteria under commercial nursery conditions. Inoculation was complemented by initial fertilization without growth regulators, fungicides, or bactericides. The results indicate that the rhizobacteria strains induce different responses in plants. Significant differences in plant biomass and root architecture were found. Treatments inoculated with Bacillus sp., Bacillus polyfermenticus, and Bacillus siamensis strains; showed an increase of up to 41% (dry weight). Plants increased root biomass by 30% when inoculated with S. siamensis. All inoculated strains were identified as members of the genus Bacillus spp., and their presence three months after inoculation was assessed by 16S rRNA gene-based amplicon massive sequencing. We found that Bacillus sp. genus was only present in inoculated treatments, suggesting that inoculated bacteria could establish themselves successfully as part of the microbiota. These results support the advantages of using PGPRs in commercial tropical tree production.
To explore the capability of soil mycobiota to degrade avocado peel waste and identify relevant successions and trophic guild shifts, fungal communities from three environments with different land uses were evaluated in a solid-state process. Soil samples used as inoculum were collected from a pristine mature tropical forest, a traditionally managed Mayan land, and an intensively managed monospecific avocado plantation. Soil-substrate mixes were evaluated for 52 weeks to evaluate organic matter decay and the carbon-to-nitrogen ratio. Amplicon-based high-throughput sequencing from internally transcribed spacer (ITS) analysis revealed significant differences in fungal communities widely dominated by Fusarium sp. and Clonostachys sp.; however, less represented taxa showed relevant shifts concomitantly with organic matter content drops. Trophic guild assignment revealed different behaviors in fungal communities between treatments over the 52 weeks, suggesting distinct preconditioning of fungal communities in these environments. Overall, the results lead to the identification of promising degradation moments and inoculum sources for further consortia enrichment or bioprospecting efforts.
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