Molecular Microbiology Research 2024, Vol.14, No.3, 153-161 http://microbescipublisher.com/index.php/mmr 156 towards multiple fungicides and conferred growth-promoting abilities to rice, indicating their potential role in disease suppression (Shen et al., 2019). The modulation of rhizospheric microbial communities by non-rhizobial endophytes can enhance the plant's resistance to pathogens (Debnath et al., 2023). 3.3 Growth promotion The growth-promoting effects of non-rhizobial endophytes in rice are well-documented. These microbes enhance various growth parameters, including plant height, root length, leaf area, and chlorophyll content. For instance, the co-inoculation of endophytic and rhizosphere bacteria has been shown to significantly increase root and stem height, root fresh weight, and shoot dry weight in rice plants (Etesami and Alikhani, 2016). The endophytic colonization by nitrogen-fixing bacteria, such as Azotobacter sp. strain Avi2, has also been associated with higher photosynthetic rates and improved yield. Moreover, the production of phytohormones like indole-3-acetic acid (IAA) by endophytic bacteria further promotes plant growth and development. Non-rhizobial endophytic microbes enhance nutrient uptake, suppress diseases, and promote growth in rice plants through various mechanisms, including nitrogen fixation, phosphorus solubilization, and modulation of rhizospheric microbial communities. These beneficial effects highlight the potential of non-rhizobial endophytes as sustainable alternatives to chemical fertilizers and pesticides in rice cultivation. 4 Benefits in Rice Cultivation 4.1 Improved yield and quality The application of non-rhizobial endophytic microbes in rice cultivation has shown significant improvements in yield and quality. For instance, a consortium of endophytic microbes isolated fromTypha angustifolia was found to enhance nitrogen metabolism in rice, leading to increased biomass, shoot length, and chlorophyll content under both nitrogen-sufficient and nitrogen-deficient conditions (Saha et al., 2016; Jhuma et al., 2021). Microbial inoculants have been shown to improve photosynthetic efficiency and root architecture, which are critical for better nutrient uptake and overall plant health. 4.2 Enhanced stress tolerance 4.2.1 Abiotic stress resistance Endophytic microbes play a crucial role in enhancing rice tolerance to abiotic stresses such as drought and salinity. Streptomyces albidoflavus OsiLf-2, for example, produces osmolytes like proline and soluble sugars, which help rice plants adjust osmotically under drought and salt stress conditions. This leads to improved physiological and biochemical responses, ultimately raising rice yields even under adverse conditions (Niu et al., 2021). Similarly, endophytic bacteria such as Bacillus haynesii and Bacillus safensis have been shown to alleviate salinity stress by modulating antioxidant enzyme activities and enhancing root architecture (Gupta et al., 2023). 4.2.2 Biotic stress resistance Endophytic microbes also contribute to biotic stress resistance by suppressing pathogen virulence and deterring herbivores. For instance, endophytic bacteria have been shown to produce various enzymes and secondary metabolites that inhibit the growth of fungal pathogens and reduce disease incidence in rice (Shahid et al., 2022). These microbes can also induce systemic resistance in plants, making them more resilient to pest attacks. 4.2.3 Hormonal regulation under stress conditions Endophytic microbes influence hormonal regulation in rice plants under stress conditions. For example, certain bacterial endophytes have been found to reduce the levels of abscisic acid (ABA) while increasing glutathione (GSH) and sugar content in rice under salt stress. This hormonal modulation helps in better stress management and promotes growth (Khan et al., 2020). These microbes can enhance the expression of stress-responsive genes, further aiding in the plant's ability to withstand adverse conditions (Gupta et al., 2023).
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