Browsing by Author "Hidalgo Bermeo, Nataly Eliseth"

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    Testing bacterial inocula isolated from the rhizosphere of Theobroma gileri trees as an alternative for biological fertilization of Theobroma cacao seedlings
    (PUCE - Ibarra, 2026) Hidalgo Bermeo, Nataly Eliseth; Mafla Andrade, Santiago Xavier
    We tested for the first time whether bacterial inocula isolated from the rhizosphere of Theobroma gileri trees—a wild relative of cacao—harbors diverse bacterial communities with potential to act as biofertilizers of Theobroma cacao seedlings, thus helping to reduce the overdrive of chemical fertilizers. Inocula enriched in N-fixing bacteria were prepared from the soil rhizosphere of T. gileri trees growing on primary forest soil (IPS replicates) and secondary forest soil (ISS replicates). Metagenomic analysis, based on 16S rRNA amplicon sequencing, revealed 175 genus-level clades in total, with 67 genus-level clades exclusive to IPS and 39 genus-level clades exclusive to ISS. In silico analyses designed to search for nif genes (known to express N-fixing function) recognized 47 genus-level clades as potential N-fixing bacteria; these included several species of Clostridium (anaerobic N-fixing bacteria relatively common in IPS replicates) and Azotobacter (aerobic N-fixing bacteria very common in ISS replicates). To assess the effect of bacterial inocula versus urea on the growth of cacao seedlings (CCN-51 variety), a 63-day greenhouse pilot experiment was set up using a two-way ANOVA design, with inoculum origin as first factor (three levels: IPS, ISS, and no-inoculum [control]) and urea fertilization as second factor (two levels: presence or absence [control] of urea). Response variables were plant survival (%), height change (mm/week), diameter change (mm/week), and chlorophyll index change (SPAD units/week). Seedlings under treatments with bacterial inocula had no mortality, while those with urea-only treatment exhibited 40% survival rate. Although no significant effects (at α=0.10) were detected for any response variable, the urea factor influenced almost significantly on height (F=2.41, P=0.14) and chlorophyll index (F=2.66, P=0.12). In conclusion, bacterial inocula isolated from the rhizosphere of T. gileri do not seem to have an evident effect on T. cacao seedlings growth, although may be beneficial to assure seedling survival.