Rice “Instant Inoculation” With Endophytic Fungus Causes Excessive Immune Response To Fusarium Proliferatum And Plant cell Death

Abstract Aims: This article explored the effects and possible mechanism of different inoculation patterns of endophytic fungi Phomopsis liquidambaris B3 on the plant immune response and defense results to pathogen Fusarium. proliferatum.Methods: Rice seedlings pre-inoculated, instant-inoculated and non-inoculated with B3 were infected with F. proliferatum and grown in controllable conditions. The disease severity, F. proliferatum infection and plant growth were evaluated, and the activity of defensive enzymes, defense-related substances, reactive oxygen content, and defense hormone SA content were determined. Chemical treatment experiments and plant cell staining to verify plant cell death.Results: Pre-inoculation of endophytic fungus Ph. liquidambaris B3 may triggered the SA-dependent defense pathways of plants, increased defense-related enzyme activities and up-regulated the expression of defense genes, and thus decreased F. proliferatum colonization. However, instant-inoculation Ph. liquidambaris B3 inhibited its own root colonization, caused excessive burst of ROS and leaves cell death. Conclusion: For a specific plant pathogen, the instant-inoculation Ph. liquidambaris B3 when F. proliferatum infected leads to excessive burst of reactive oxygen species (ROS) and plant cell death. We recommend pre-inoculation of biological control agent and other prevention and control measures before pathogen infection to achieve the best control effect rather than instant control method applicated in the agricultural crop management.