Molecular Soil Biology 2024, Vol.15, No.4, 151-162 http://bioscipublisher.com/index.php/msb 155 5 Rhizosphere microbial communities 5.1 Role of rhizosphere microbes in plant health and growth Rhizosphere microbes play a crucial role in plant health and growth by facilitating nutrient acquisition, enhancing stress tolerance, and promoting overall plant vigor. These microbes, including bacteria and fungi, interact with plant roots to form a symbiotic relationship that benefits both parties. For instance, plant growth-promoting rhizobacteria (PGPR) such as Azotobacter vinelandii and Serendipita indica have been shown to significantly enhance rice growth by improving root-shoot biomass and chlorophyll content (Dabral et al., 2020). Additionally, the rhizosphere effect, driven by root exudates, shapes the microbial community, which in turn influences plant growth and productivity (Li et al., 2019). The presence of specific microbial taxa, such as Oxobacter and Lachnospiraceae, in the rhizosphere has been linked to improved plant health and biogeochemical cycling (Li et al., 2019). 5.2 Factors influencing rhizosphere microbial diversity Several factors influence the diversity and composition of rhizosphere microbial communities. Soil type and plant genotype are primary determinants, with different soil types harboring distinct microbial communities (Xu et al., 2019). For example, the microbial communities in the rhizosphere of indica and japonica rice varieties differ significantly, influenced by both soil type and rice genotype (Xu et al., 2019). Additionally, root exudates, which include organic acids and other metabolites, play a significant role in shaping the microbial community by attracting specific microbial taxa (Li et al., 2019). Environmental conditions, such as moisture and nutrient availability, also impact microbial diversity. For instance, nitrogen and phosphorus fertilization have been shown to affect the richness and composition of rhizosphere bacterial communities in maize (Ujvári et al., 2023). As one of the most important cultivated rice varieties in China, Yongyou 12 hybrid rice had similar endophytic microbiota to both indica and japonica rice cultivars (Feng et al., 2019). This result means that the hybrid not only exhibits strong heterosis but also shows a similar root bacterial community between indica and japonicarice types, which likely enhances its environ mental adaptation and defense potential, considering the im portance of microbiota to the host plant. 5.3 Methods for studying rhizosphere microbial communities Various methods are employed to study rhizosphere microbial communities, each providing unique insights into microbial diversity and function. High-throughput sequencing techniques, such as 16S rRNA gene sequencing, are commonly used to characterize microbial communities at a taxonomic level (Xu et al., 2019). These methods allow for the identification of core microbial communities and the assessment of their functional potential. Metagenomic profiling further enhances our understanding by revealing the functional capabilities of microbial communities, such as nutrient cycling and stress response pathways (Lu et al., 2018). Additionally, techniques like polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and amplicon sequencing are used to monitor changes in microbial community composition under different agricultural practices (Ujvári et al., 2023). Confocal microscopy and other imaging techniques provide visual insights into microbial colonization and interactions with plant roots (Dabral et al., 2020). By understanding the role, influencing factors, and methods for studying rhizosphere microbial communities, researchers can develop strategies to optimize dryland farming models for enhancing root growth and rhizosphere microbial functions in hybrid rice. This knowledge is crucial for improving crop health, productivity, and sustainability in agricultural systems. 6 Interaction between Root Growth and Rhizosphere Microbes 6.1 Mechanisms of root-microbe interactions The interaction between root growth and rhizosphere microbes is a complex and dynamic process that significantly influences plant health and productivity. Roots and their associated microbiomes co-evolve, forming intricate relationships that enhance plant fitness. Plants selectively recruit beneficial microbes through root exudates, which are chemical compounds secreted by roots into the rhizosphere. These exudates serve as signals
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