Soil Protozoa: Research Methods and Roles in the Biocontrol of Soil-Borne Diseases

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Supported by the National Natural Science Foundation of China(No. 41922053) and the National Key R&D Program of China (No. 2018YFD1000800)

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    Protozoa are a type of protists that act as consumers in the soil food web preying on other microorganisms such as bacteria and fungi, even nematodes. Soil protozoa are known to have an important impact on soil microbial communities and elements cycling. Recent studies reveal that soil protozoa might act, together with some soil microorganisms, such as bacteria, fungi, etc. forming a biological network barrier and playing an important role in defending plant roots from invasion of soil borne pathogens. Relative to the researches on beneficial bacteria and fungi, much less have been done on effects and mechanisms of soil protozoa controlling soil-borne diseases, either abroad or at home. Therefore, this paper calls for more scholars to pay attention to and to study soil protozoa and their functions in the ecosystem, and to explore their important values in soil health and sustainable agriculture. To achieve this goal, this paper first introduces soil protozoa and their ecological functions, and especially reports on their roles in controlling soil-borne plant diseases. In the next section, this paper summarizes potential mechanisms of soil protozoa preventing and controlling soilborne diseases. 1) Soil protozoa can not only prey direct on pathogens but also secrete secondary metabolites that will inhibit growth of pathogen, thus lowering pathogen density and disease incidence; 2) Their predation of soil microorganisms could induce the preys to generate more antagonistic compounds, which could help guard them from predation and indirectly inhibit growth of pathogens; and 3) Their predation can alter the structure and function of indigenous microbial communities. For instance, the highly selective predation behavior of protozoa could form a highly competitive microbial community, thus leading to a higher inhibiting effect on invading pathogens. The traditional method of studying soil protozoa depends mainly on isolation, culture and morphological observation. With development of the modern molecular technology, the research method has changed dramatically. In order to better study protozoa in the soil food chain from multiple angles, the third section of this paper summarizes the main methods used in studying biomass, diversity, community structure, and ecological functions of soil protozoa, including culturological/morphological methods, identification with biochemical methods, modern molecular technology, and screening and counting of protozoa with flow cytometry. Although protozoa play an important role in preventing and controlling soil-borne diseases, they have just made their debut on the stage of scientific research, waiting for more in-depth researches, as compared to other soil microorganisms. Then, the last section of this paper lists some future research topics related to soil biology researchers. 1) Explore diversity and structure of the soil protozoan community and their relationships with occurrence of soil-borne diseases; 2) establish technologies for identification, isolation, and culture of crop health related protozoa; 3) investigate effects of soil protozoa and other soil organisms on crop health; and 4) strengthen the research and development of technologies for collection and exploitation of protozoan resources.

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WEI Zhong, SONG Yuqi, XIONG Wu, XU Yangchun, SHEN Qirong. Soil Protozoa: Research Methods and Roles in the Biocontrol of Soil-Borne Diseases[J]. Acta Pedologica Sinica,2021,58(1):14-22.

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  • Received:February 01,2020
  • Revised:May 08,2020
  • Adopted:May 26,2020
  • Online: October 30,2020
  • Published: January 11,2021