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Incorporated Biochar-Based Soil Amendment and Exogenous Glycine Betaine Foliar Application Ameliorate Rice (Oryza sativa L.) Tolerance and Resilience to Osmotic Stress.

ABSTRACT: Osmotic stress is a major physiologic dysfunction that alters the water movement across the cell membrane. Soil salinity and water stress are major causal factors of osmotic stress that severely affect agricultural productivity and sustainability. Herein, we suggested and evaluated the impact of integrated biochar-based soil amendment and exogenous glycine betaine application on the growth, physiology, productivity, grain quality, and osmotic stress tolerance of rice (Oryza sativa L., cv. Sakha 105) grown in salt-affected soil under three irrigation intervals (6, 9, or 12 days), as well as soil properties and nutrient uptake under field conditions during the 2019 and 2020 seasons. Our findings showed that dual application of biochar and glycine betaine (biochar + glycine betaine) reduced the soil pH, electrical conductivity, and exchangeable sodium percentage. However, it enhanced the K⁺ uptake which increased in the leaves of treated-rice plants. Additionally, biochar and glycine betaine supplementation enhanced the photosynthetic pigments (chlorophyll a, b, and carotenoids) and physiological attributes (net photosynthetic rate, stomatal conductance, relative water content, and electrolyte leakage) of osmotic-stressed rice plants. Biochar + glycine betaine altered the activity of antioxidant-related enzymes (catalase, ascorbate peroxide, and peroxidase). Moreover, it improved the yield components, biological yield, and harvest index, as well as the nutrient value of rice grains of osmotic-stressed rice plants. Collectively, these findings underline the potential application of biochar and glycine betaine as a sustainable eco-friendly strategy to improve plant resilience, not only rice, but other plant species in general and other cereal crops in particular, to abiotic stress, particularly those growing in salt-affected soil.

SUBMITTER: Hafez EM

PROVIDER: S-EPMC8471834 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Application of biochar, a pyrolyzed biomass from organic sources, to agricultural soils is considered a promising strategy to sustain soil fertility leading to increased plant productivity. It is also known that applications of biochar to soilless potting substrates and to soil increases resistance of plants against diseases, but also bear the potential to have inconsistent and contradictory results depending on the type of biochar feedstock and application rate. The following study examined the effect of biochar produced from maple bark on soybean resistance against Rhizoctonia foliar blight (RFB) disease caused by Rhizoctonia solani, and examined the underlying molecular responses of both soybean and R. solani during interaction with biochar application. Soybean plants were grown in the presence of 1, 3, or 5% (w/w) or absence of maple bark biochar for 2 weeks, and leaves were infected with R. solani AG1-IA. At lower concentrations (1 and 3%), biochar was ineffective against RFB, however at the 5% amendment rate, biochar was conducive to RFB with a significant increase in disease severity. For the first time, soybean and R. solani responsive genes were monitored during the development of RFB on detached leaves of plants grown in the absence and presence of 5% biochar at 0, 6, 12, and 24 h post-inoculation (h.p.i.). Generally, large decreases in soybean transcript abundances of genes associated with primary metabolism such as glycolysis, tricarboxylic acid (TCA) cycle, starch, amino acid and glutathione metabolism together with genes associated with plant defense and immunity such as salicylic acid (SA) and jasmonic acid pathways were observed after exposure of soybean to high concentration of biochar. Such genes are critical for plant protection against biotic and abiotic stresses. The general down-regulation of soybean genes and changes in SA hormonal balance were tightly linked with an increased susceptibility to RFB. In conjunction, R. solani genes associated with carbohydrate metabolism were up-regulated, while genes involved in redox reactions and detoxification had varying effects. In conclusion, this study presents strong evidence that maple bark biochar increased susceptibility of soybean to a foliar disease. This condition is partly mediated by the down-regulation of soybean genes leading to reduced immunity and also affecting R. solani gene expression.

Project description:Salt stress is a common abiotic stress that limits the growth, development and yield of maize (Zea mays L.). To better understand the response of maize to salt stress and the mechanism by which exogenous glycine betaine (GB) alleviates the damaging effects of salt stress, the morphology, physiological and biochemical indexes, and root transcriptome expression profiles of seedlings of salt-sensitive inbred line P138 and salt-tolerant inbred line 8723 were compared under salt stress and GB-alleviated salt stress conditions. The results showed that under salt stress the growth of P138 was significantly inhibited and the vivo ion balance was disrupted, whereas 8723 could prevent salt injury by maintaining a high ratio of K+ to Na+. The addition of a suitable concentration of GB could effectively alleviate the damage caused by salt stress, and the mitigating effect on salt-sensitive inbred line P138 was more obvious than that on 8723. Transcriptome analysis revealed that 219 differentially expressed genes (DEGs) were up-regulated and 153 DEGs were down-regulated in both P138 and 8723 under NaCl treatment, and that 487 DEGs were up-regulated and 942 DEGs were down-regulated in both P138 and 8723 under salt plus exogenous GB treatment. In 8723 the response to salt stress is mainly achieved through stabilizing ion homeostasis, strong signal transduction activation, increasing reactive oxygen scavenging. GB alleviates salt stress in maize mainly by inducing gene expression changes to enhance the ion balance, secondary metabolic level, reactive oxygen scavenging mechanism, signal transduction activation. In addition, the transcription factors involved in the regulation of salt stress response and exogenous GB mitigation mainly belong to the MYB, MYB-related, AP2-EREBP, bHLH, and NAC families. We verified 10 selected up-regulated DEGs by quantitative real-time polymerase chain reaction (qRT-PCR), and the expression results were basically consistent with the transcriptome expression profiles. Our results from this study may provide the theoretical basis for determining maize salt tolerance mechanisms and the mechanism by which GB regulates salt tolerance.

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Incorporated Biochar-Based Soil Amendment and Exogenous Glycine Betaine Foliar Application Ameliorate Rice (Oryza sativa L.) Tolerance and Resilience to Osmotic Stress.

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