Molecular Microbiology Research 2024, Vol.14, No.3, 153-161 http://microbescipublisher.com/index.php/mmr 158 This consortium increased biomass, shoot length, and chlorophyll content under both nitrogen-sufficient and nitrogen-deficient conditions, showcasing its potential as a plant probiotic (Saha et al., 2016). Another study highlighted the use of Azotobacter sp. strain Avi2, which enhanced rice yield and photosynthetic rates in both greenhouse and field conditions, indicating its effectiveness as a bio-formulation for sustainable rice production 6. The image shows that rice inoculated with Bacillus haynesii and Bacillus safensis exhibits significantly better growth under salt stress compared to the control group (T2). For example, the treatment groups T4 (inoculated with Bacillus haynesii) and T5 (inoculated with Bacillus safensis) displayed better plant growth in both CO51 and PB1 varieties, particularly in terms of leaf greenness, plant height, and root development. These treatments significantly mitigated the negative effects of salinity on rice. The study results indicate that endophytic bacteria enhance salt tolerance in rice by promoting antioxidant enzyme activity, regulating the accumulation of osmoregulatory substances (such as proline), and modulating the expression of genes related to salt stress. These bacteria not only improve rice growth and biomass accumulation but also reduce ionic imbalance and oxidative stress caused by salinity, thus enhancing the overall health and yield of the plants. Figure 2 Effect of inoculation of halotolerant endophytes and rhizobacteria on two rice varieties (A) CO51, and (B) Pusa Basmati 1 (Adopted from Gupta et al., 2023) Image caption: T1=Negative control, T2=Positive control (200 mM NaCl), T3 = 200 mM NaCl +Trichoderma viride, T4 = 200mM NaCl + Bacillus haynesii 2P2, T5 = 200 mM NaCl + Bacillus safensis BTL5, T6 = 200 mM NaCl + Brevibacterium frigoritolerans W19, and T7 = 200 mM NaCl +Pseudomonas fluorescens (Adopted from Gupta et al., 2023) 6.2 Comparative studies with conventional practices Comparative studies have shown that the use of non-rhizobial endophytic microbes can be as effective, if not more so, than conventional agricultural practices. For example, treatments with Azotobacter sp. strain Avi2 resulted in similar yield parameters when compared to the recommended dose of nitrogen fertilizer, suggesting that these endophytes can reduce the need for chemical fertilizers. Another study compared the effects of urea fertilizer and rhizobial biofertilizer on the root-associated microbiome of rice. The results indicated that biofertilizer treatments significantly restructured the endophyte-enriched communities, leading to positive synergistic impacts on rice growth (Jha et al., 2019). These findings suggest that endophytic microbes can offer a sustainable alternative to traditional agricultural inputs, potentially reducing the reliance on agrochemicals (White et al., 2019). 6.3 Long-term impact on soil health The long-term impact of non-rhizobial endophytic microbes on soil health has also been a subject of investigation. Long-term manure application, for instance, was found to alter the microbial community structure in the rice rhizosphere, increasing the abundance of beneficial bacteria such as Rhizobium and Burkholderia (Tang et al., 2021). These changes in microbial communities can enhance nutrient cycling and soil fertility over time. Additionally, the use of endophytic microbes has been shown to improve the resilience of rice plants to environmental stresses, such as salinity and oxidative stress, which can have positive long-term effects on soil
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