Effects of Non-Stop Farming on Milkvetch Root Microbes and Secretions

Jim Crocker
27th April, 2024

Effects of Non-Stop Farming on Milkvetch Root Microbes and Secretions

Image Source: Natural Science News, 2024

Key Findings

  • In China, continuous cropping of Mongolian milkvetch reduces plant growth and quality
  • The study found harmful fungi increased and beneficial bacteria decreased in the plant's root zone
  • Certain chemicals from the plant's roots, meant to defend against pathogens, also hindered plant growth
Astragalus mongholicus, commonly known as Mongolian milkvetch, is a herb used in traditional medicine, valued for its health-promoting properties. However, when grown repeatedly in the same soil—a practice known as continuous cropping—its quality notably declines. Scientists from the Chinese Academy of Sciences[1] have conducted a study to understand the underlying reasons for this decrease in quality, focusing on the plant's root environment and the microscopic life that thrives there. The study examined two distinct fields: one virgin soil (Field I), which had never been used to cultivate A. mongholicus, and a field where the plant had been continuously cropped (Field II). The research revealed that plants in Field II had lower fresh and dry weight, indicating that continuous cropping was detrimental to the plant's growth. The root environment, or rhizosphere, is a hotbed for interactions between plants and microorganisms. In Field II, high-throughput sequencing techniques showed a shift in the fungal community, with an increase in fungi that could potentially harm the plant. This is in line with previous findings that continuous cropping can lead to a build-up of pathogens in the soil[2], altering the balance of the soil's microbial community and making plants more susceptible to disease. Additionally, the study delved into root exudates—compounds secreted by plant roots into the surrounding soil. These exudates can affect microbial communities and play a role in plant health. Metabolomic analysis, which identifies the chemical fingerprints of these compounds, found 20 distinct substances that varied between the two fields. Of these, four were found to inhibit the growth of either A. mongholicus, the disease-causing fungus Fusarium oxysporum, or both. This suggests that the plants might be attempting to defend themselves against pathogens by altering the chemical composition of their root exudates. This comprehensive analysis by the Chinese Academy of Sciences not only sheds light on the microbial and chemical changes associated with continuous cropping but also builds upon earlier studies. For instance, consistent with the findings that bioorganic fertilizer can help manage Fusarium wilt in watermelon by maintaining beneficial microbial populations[3], the current study suggests that managing the soil microbiome could be crucial for sustaining A. mongholicus cultivation. The study also echoes the observation that continuous cropping affects microbial diversity in soil, as seen with cotton and ginseng [3, 4]. The adaptation of microbial communities over time can lead to a new equilibrium that may either benefit or harm the crop. Furthermore, the research aligns with previous work on Panax notoginseng, which found that continuous cropping impacts both rhizospheric and root endophytic fungal communities[4]. The significance of this study lies in its potential applications. By understanding the root-associated microbiome and root exudates, farmers and scientists can develop strategies to mitigate the negative effects of continuous cropping. This could involve crop rotation, use of bioorganic fertilizers, or the introduction of beneficial microbes to the soil. Such interventions could lead to healthier plants and more sustainable agricultural practices, contributing to food security. In conclusion, the Chinese Academy of Sciences' research has provided valuable insights into the decline in plant quality due to continuous cropping. By studying the complex interactions between A. mongholicus, its root exudates, and the surrounding microbial community, the study opens the door to developing new agricultural practices that can ensure the health and productivity of this important medicinal plant.

BiochemPlant ScienceAgriculture

References

Main Study

1) Impacts of continuous cropping on the rhizospheric and endospheric microbial communities and root exudates of Astragalus mongholicus

Published 26th April, 2024

https://doi.org/10.1186/s12870-024-05024-5

Related Studies

2) Diversity and composition of the Panax ginseng rhizosphere microbiome in various cultivation modesand ages.

https://doi.org/10.1186/s12866-020-02081-2

3) Variation of rhizosphere bacterial community in watermelon continuous mono-cropping soil by long-term application of a novel bioorganic fertilizer.

https://doi.org/10.1016/j.micres.2013.10.004

4) Rhizospheric soil and root endogenous fungal diversity and composition in response to continuous Panax notoginseng cropping practices.

https://doi.org/10.1016/j.micres.2016.09.009


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