Field Crop 2024, Vol.7, No.2, 70-78 http://cropscipublisher.com/index.php/fc 71 and explore how these microorganisms can be effectively utilized under different environmental and production conditions to promote a more sustainable and efficient rice production model. Through case studies in various regions and ecosystems, this study aims to identify the optimal strategies for PGPM application, ensuring the effectiveness and feasibility of these biotechnological approaches while taking into account local agricultural practices and environmental factors. Through this comprehensive analysis, this study hopes to provide practical biotechnological solutions for rice production globally, thereby enhancing the health and productivity of agricultural ecosystems. 1 Types of Plant Growth-Promoting Microorganisms 1.1 Bacteria Plant Growth-Promoting Bacteria (PGPB) are a diverse group of bacteria that colonize plant roots and promote growth through various mechanisms. These include nitrogen fixation, phosphate solubilization, production of phytohormones, and enhancement of stress tolerance. PGPB such as Azospirillum brasilense and Pseudomonas fluorescens have been shown to increase nitrogen fixation and nutrient uptake in crops like maize, which can be extrapolated to rice cultivation (Salvo et al., 2018). Salt-tolerant PGPB like Bacillus pumilus strain JPVS11 enhance rice growth under salinity stress by improving biochemical and physiological attributes, such as chlorophyll content and antioxidant enzyme activities (Kumar et al., 2020). The combined application of PGPB and arbuscular mycorrhizal fungi (AMF) has been found to significantly improve soil fertility and rice production, indicating the synergistic effects of these microorganisms (Chen et al., 2023). 1.2Fungi Arbuscular Mycorrhizal Fungi (AMF) form symbiotic relationships with plant roots, enhancing nutrient uptake, particularly phosphorus, and improving plant resilience to environmental stresses. AMF improve the uptake of essential nutrients like phosphorus, potassium, and nitrogen, which are critical for rice growth. For instance, AMF inoculation has been shown to increase nutrient concentrations in rice tissues and improve overall plant productivity (Chen et al., 2023). AMF also help plants withstand abiotic stresses such as drought and salinity by enhancing root water uptake and altering plant physiology (Emmanuel and Babalola, 2020). 1.3Others Other microorganisms, including actinomycetes and yeasts, also contribute to plant growth promotion through various mechanisms. Actinomycetes are known for their ability to decompose organic matter and release nutrients in a form that plants can absorb. They also produce antibiotics that can protect plants from pathogens. Yeasts contribute to plant growth by producing growth-promoting substances such as vitamins and hormones. They also enhance soil health by improving its structure and water-holding capacity (Naik et al., 2019). In summary, the use of diverse PGPM, including bacteria, fungi, and other microorganisms, offers a sustainable approach to enhancing rice productivity. These microorganisms improve nutrient availability, enhance stress tolerance, and promote overall plant health, leading to increased yields and better crop quality. The synergistic effects of co-inoculation with different types of PGPM further amplify these benefits, making it a promising strategy for sustainable rice cultivation. 2 Mechanisms of PGPM Action 2.1 Nutrient solubilization and uptake Plant growth-promoting microorganisms (PGPM) enhance nutrient solubilization and uptake in rice plants, leading to improved growth and yield. For instance, Pantoea ananatis and Piriformospora indica have been shown to significantly increase the uptake of potassium and nitrogen in rice tissues, thereby enhancing nutrient use efficiency (NUE) and grain yield (Bakhshandeh et al., 2017; 2020). Additionally, the combined application of plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) has been found to increase the availability of essential nutrients such as nitrogen, phosphorus, and potassium in the soil, which in turn boosts rice plant growth and productivity (Chen et al., 2023).
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