<span lang="EN-GB">The impact of agroecological conditions on culturable bacterial <span lang="EN-GB">and fungal diversity and soil chemical properties in chili pepper

BACKGROUND AND OBJECTIVES: Chili pepper (Capsicum annuum L.) production in North Sumatra is constrained by anthracnose, which can alter plant-associated microbial communities and soil ecological processes regulating nutrient cycling, plant health, and ecosystem functioning. To develop environmentally sustainable crop management practices, it is crucial to understand the intricate relationships between soil properties, microbial diversity, altitude, and disease status. The study objectives were to inestigate the influence of agroecological conditions on chili-associated microbial diversity and soil chemical characteristics as baseline ecological indicators for sustainable agroecosystem management.METHODS: A comparative field study was conducted in twenty chili plots, comprising ten healthy and ten anthracnose-infected plots across four regencies in North Sumatra, Indonesia. Plant tissues (comprising roots, stems, and leaves) alongside corresponding soil samples were collected for subsequent microbial isolation and chemical characterization, which included evaluations of organic carbon, total nitrogen, available phosphorus, exchangeable potassium, and soil acidity. Bacterial and fungal isolates were characterized morphologically, and microbial diversity was evaluated using the Shannon diversity index. Statistical evaluations were performed utilizing independent t-tests, Pearson correlation coefficients, and simple linear regression analyses. FINDINGS: Across the sampled locations, healthy plots exhibited significantly higher mean values for soil organic carbon, total nitrogen, available Phosphorus, exchangeable Potassium, and Potential of Hydrogen compared to diseased plots. Soil chemical properties were strongly associated with stem fungal diversity, explaining ۸۴.۷ percent of its variation (R² = ۰.۸۴۷, probability < ۰.۰۵). ۲۱۸ bacteria and ۱۶ fungal isolates were recovered, including ۴۱ bacterial and ۱۰ fungal isolates for further characterization. The highest level of microbial diversity was observed in the root-associated tissues. Soil organic carbon and total nitrogen exhibited the strongest correlations with the fungal diversity of root-associated tissues, while the top-performing regression model accounted for ۸۴.۷ percent of the variation in stem fungal diversity.CONCLUSION: Soil fertility, altitude, and plant health collectively associated with the diversity and composition of chili-associated microbial communities. The outcomes of this study elucidate how microbial community ecology functions as a proxy for agroecosystem condition, delivering foundational insights necessary for sustainable soil and crop stewardship. This study advances the understanding of plant-soil-microbe interactions and provides a foundation for microbiome-based strategies to improve soil health and sustainable agricultural management.

کلیدواژه ها:

Capsicum annuum L ، Colletotrichum spp ، Microbial diversity ، soil chemistry ، agroecology ، Ecological indicators