Methylotrophic Actinobacteria Boost Rice Growth and Cut Methane Emissions

New microbial allies help rice thrive while reducing methane emissions

Researchers at the ICAR–Indian Agricultural Research Institute, New Delhi, have identified a group of methylotrophic actinobacteria and bacteria capable of boosting rice productivity and potentially mitigating methane emissions from flooded paddy fields. The study, published in the World Journal of Microbiology and Biotechnology (2025), demonstrates how bioinoculants that utilize methanol carbon can enhance plant growth, photosynthesis, and yield in Basmati rice (Oryza sativa cv. PB1121).

Background

Methane (CH₄), a potent greenhouse gas, is the second largest contributor to global warming after carbon dioxide. Flooded rice fields are one of the major agricultural sources of methane. Conventional use of chemical fertilizers to increase yields not only worsens soil health but also contributes indirectly to greenhouse gas emissions. As an alternative, the study explores methylotrophic microbes—organisms that consume single-carbon compounds like methanol—as sustainable agents to promote plant growth while reducing methane output.

Experimental approach

Thirty-three microbial isolates were obtained from the rhizosphere of rice plants cultivated across diverse agro-climatic zones in India. These isolates were screened for plant growth-promoting traits such as nitrogen fixation, phosphorus and potassium solubilization, and indole-3-acetic acid production. Based on their methanol carbon use efficiency, six promising strains were selected—three efficient and three inefficient methanol utilizers—for detailed testing.

Basmati rice seeds were inoculated with these strains and grown under controlled pot conditions. Researchers evaluated germination rate, root and shoot growth, chlorophyll and carotenoid content, nutrient uptake, and grain yield.

Key findings

Seed inoculation with methylotrophic actinobacteria and bacteria significantly enhanced all growth parameters compared to the uninoculated control.

Germination rates increased by up to 30%.
Leaf chlorophyll a and b levels nearly quadrupled.
Phosphorus and potassium contents rose by 45% and 13%, respectively.
Grain yield improved by up to 75%, with Rhizobium pusense MB4 recording the highest production.

Root imaging and analysis revealed that treated plants had denser and longer root systems, facilitating superior nutrient absorption. Correlation and path coefficient analyses confirmed strong positive relationships between grain yield, shoot length, and grain number per plant.

Implications

The study provides strong experimental evidence that methylotrophic actinobacteria—particularly Streptomyces tritici KA11 and Rhizobium pusense MB4—function as powerful plant growth-promoting rhizobacteria (PGPR). These strains not only enhance rice productivity but also have the potential to lower methane emissions by efficiently utilizing methanol in the rhizosphere.

The authors suggest that integrating these microbial bioinoculants into rice cultivation systems could significantly reduce dependence on chemical fertilizers while aligning with global climate mitigation goals.

Conclusion

This work highlights methylotrophic actinobacteria and bacteria as dual-function bioinoculants—improving crop performance and contributing to methane reduction. As the demand for sustainable agriculture intensifies, such microbial technologies could play a crucial role in achieving eco-efficient food production and climate resilience.

Reference

Kavya, T., Singh, G., Govindasamy, V., Reddy S., B., & Patted, P. S. (2025). Influence of Methylotrophic actinobacteria and bacteria with varying methanol carbon use efficiency on rice growth and development. World Journal of Microbiology and Biotechnology, 41(10), 367. https://doi.org/10.1007/s11274-025-04567-5