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.

In Neotropical regions, plantations and remnant forest populations of native trees coexist in a highly fragmented matrix and may be affected by isolation and reduction in population size, leading to genetic structure, inbreeding, and genetic bottlenecks that reduce the population’s genetic diversity. Tabebuia rosea variability in the Mayan Forest was studied by genotyping 30 trees from three plantations and three remnant natural populations using simple sequence repeats (SSRs) and inter-simple sequence repeats (ISSRs). H_o-SSR estimates were lower than H_e; the mean inbreeding coefficient was 0.07 and did not differ among populations, but was eight times higher in plantations than in remnant populations. Using ISSR data, the individuals were assigned to k = 5 and k = 4 clusters under admixture without and with geographic information used as priors in Bayesian analysis assignments. Genetic differentiation estimated with the Bayesian estimator II (0.0275 ± 0.0052) was significantly different from 0, but F_ST was not (0.0985 ± 0.1826), while paired F_ST among populations ranged from 0.05 up to 0.16. Only one remnant population displayed evidence of a genetic bottleneck. T. rosea displays a genetic structure in which the isolated remnant forest populations show moderate inbreeding levels.

During domestication, the selection of cultivated plants often reduces microbiota diversity compared with their wild ancestors. Microbiota in compartments such as the phyllosphere or rhizosphere can promote fruit tree health, growth, and development. Cordia dodecandra is a deciduous tree used by Maya people for its fruit and wood, growing, to date, in remnant forest fragments and homegardens (traditional agroforestry systems) in Yucatán. In this work, we evaluated the microbiota’s alpha and beta diversity per compartment (phyllosphere and rhizosphere) and per population (forest and homegarden) in the Northeast and Southwest Yucatán regions. Eight composite DNA samples (per compartment/population/region combination) were amplified for 16S-RNA (bacteria) and ITS1-2 (fungi) and sequenced by Illumina MiSeq. Bioinformatic analyses were performed with QIIME and phyloseq. For bacteria and fungi, from 107,947 and 128,786 assembled sequences, 618 and 1092 operating taxonomic units (OTUs) were assigned, respectively. The alpha diversity of bacteria and fungi was highly variable among samples and was similar among compartments and populations. A significant species turnover among populations and regions was observed in the rhizosphere. The core microbiota from the phyllosphere was similar among populations and regions. Forests and homegarden populations are reservoirs of the C. dodecandra phyllosphere core microbiome and significant rhizosphere biodiversity.