Implications on Engineering Rhizosphere Microbiomes for the Suppression of Soil-Borne Diseases by Compost in a Long-Term OrganicGreenhouse Experiment

The importance of rhizosphere microbiome on plant health and nutrient acquisition has been increasingly recognized, and it may serve as an avenue to the next green revolution. However, engineering rhizosphere microbiome for the suppression of soil-borne diseases is still very challenging due to the great complexity in rhizosphere, e.g. the simultaneous presence of hundreds to many thousands of bacterial species, and the dynamical influence from plants and its surrounding environments. We set up a long-term greenhouse experiment in 2002 at Quzhou experimental station, Hebei Province, China. It consists of organic, intermediate, and conventional farming systems. All three farming systems were under the same schemes of crop rotation, irrigation, and tillage, but they differed in compost fertilization and plant protection management. Previously, disease incidence, soil microbial communities, rhizobium were compared among different farming systems. To acquire an in-depth understanding of microbial ecological mechanisms associated, we analzyed both soil and microbial in a suite of different studies. Changes in soil microbiomes were mainly associated with mineralizing of organic matters and nitrogen-cycling. Climate chamber experiment further revealed that organic soil was suppressive to two disastrous soil-borne diseases caused by Phytophthora capsici and Ralstonia solanacearumis, which often damage greenhouse vegetable production. Analysis on microbial communities of pepper and tomato indicated that recruitment of antagonistic Bacillus may contribute to the suppression of both diseases. In summary, these studies provide insights into the microbial mechanisms associated with the suppression of soil-borne disease and a possible strategy for engineering rhizosphere microbial communities.