Biochar and its coupling with microbial inoculants for suppressing plant diseases: A review

Recently, the use of biochar (BC) to control plant diseases induced by pathogens has attracted great attention. However, the control effect of BC on plant diseases is limited because BC cannot specifically kill pathogens, and its suppressive effect is inadequate in the field compared with the laboratory and greenhouse. BC combined with a microbial inoculant (MI) is a new method for suppressing plant diseases. In this review, we systematically summarized the research progress of BC combined with MI (BC–MI) for controlling plant diseases and analyzed its action mechanisms. BC–MI can efficiently control a variety of plant diseases induced by 6 fungal, 2 oomycetes, 1 nematode and 2 viral plant pathogens. BC coupling with MI strengthens its control effect on plant diseases in most experimental cases (84 %). BC–MI can promote the colonization of MI in roots or the rhizosphere, thereby altering root exudates and upregulating the expression of defense-associated genes. In addition, BC–MI more efficiently improves soil properties. Application strategies of BC–MI for suppressing plant diseases was advised, including BC preparation and MI screening, coupled methods of BC with MI, and targeted plant diseases controlled by BC–MI. This study has reference value for guidance on how to construct a stable and efficient BC-MI system for suppressing plant diseases.