Nanoscale Calcium Fertilizer Modulates Pathogenicity of Bacterial Soft Rot Pathogen (Pectobacterium aroidearum) in Konjac (Amorphophallus konjac) Through Suppressing of Virulence Factors and Enhancing Plant Defense

Amorphophallus spp., valued as both crops and medicinal plants, are highly susceptible to soft rot disease, causing substantial yield and economic losses during cultivation and storage. Calcium nanoparticle (CaNP) fertilizer not only has the potential to enhance crop yields but also plays a crucial role in the control of crop pests and diseases. However, its application in the control of soft rot disease in konjac has not yet been investigated. In this study, the antibacterial efficacy of CaNP fertilizer against the typical soft rot pathogen P. aroidearum MY11 in Amorphophallus konjac (A. konjac) was investigated. It was found that CaNP fertilizer significantly inhibited the growth, motility ability and the activity of cell wall-degrading exoenzymes of P. aroidearum MY11. Transmission electron microscopy revealed that the morphology of bacterial cells treated with CaNPs did not change significantly, but significant particle deposition was observed within the cells. Furthermore, CaNPs pretreatment could reduce the reactive oxygen species (ROS) content, activate the antioxidant enzyme system, and enhance the photosynthetic capacity of A. konjac plants. qRT-PCR analysis revealed that CaNPs pretreatment might enhance the resistance of A. konjac plants to the soft rot pathogen MY11 by activating the jasmonic acid (JA), salicylic acid (SA) signaling pathway and the cell wall stress response pathway. This research provides a new candidate for nanopesticides that can be used to control the bacterial soft rot disease of konjac.