Formulation and testing of biofertilizers obtained from native soil microbiota associated with strategic crops from arid zones of northern Mexico
Guardiola Marquez, Carlos Esteban
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Agriculture is a major contributor to environmental and soil degradation. Currently, crop areas are expanding to arid zones generating the challenge to maintain or increase plant production under drought conditions in a sustainable manner. The correct formulation and use of biofertilizers is a sustainable strategy to overcome this problem. Microorganisms play a fundamental role in improving nutrient uptake efficiency and increasing plant stress-tolerance. Therefore, the objective of this study was to characterize and isolate native plant growth-promoting (PGP) microorganisms associated to six economically relevant crops in arid zones of northern Mexico, for the formulation and testing of crop-specific biofertilizers. Isolates were screened for different PGP attributes (N-fixation, P and K solubilization, and indole acetic acid (IAA) production) and candidates with the best performance were selected for MALDI-TOF mass spectrometry identification. Moreover, to understand the overall microbial community composition, MiSeq Illumina sequencing was used for bacteria and arbuscular mycorrhizal fungi (AMF) identification (Chapter 1). From the isolates, several Penicillium and Pseudomonas species were identified and described as potential candidates for arid zone biofertilizer formulation. Formulation and testing of self-made and commercial biofertilizers were conducted under seedbeds, to assess early plant response, and greenhouse and field conditions, to analyze plant yield (Chapter 2). Molasses was found to be a cheap culture media supplement for bacteria and vermicompost leachate, combined with PGP bacteria and AMF, achieved higher plant growth yields under 35% chemical fertilizer reduction. Early plant response to different microbial consortia was evaluated in maize where fungal consortia had greater effects on root development, while bacteria showed better results in shoot growth. Finally, a commercial biofertilizer based on the model AMF species Rhizophagus irregularis was tested on jalapeño pepper under 35% drought stress; a significant increase in fruit production was observed when plants were inoculated with the highest spore dose (1500 spores). In conclusion, the strategies applied in this study were useful to isolate and characterize soil microorganisms with PGP attributes from arid zones. Tests of commercial and self-made biofertilizers revealed that they can be implemented to reduce chemical fertilizer and water usage. These findings represent a starting point for the formulation of crop-specific biofertilizers and implementation of sustainable agricultural practices.