Blue Light Suppresses Pepper Resistance Against Phytophthora capsici Through CRY2-Mediated ROS and SA Signaling Pathways

Phytophthora capsici is frequently found in pepper (Capsicum annuum L.) cultivation, causing severe yield loss and fruit quality deterioration. Light quality is known to influence pepper growth and stress responses, but its role in pepper resistance against P. capsici remains poorly understood. This study displayed that, among pepper plants treated with red, green, and blue light (BL) and infected with P. capsici, those under BL exposure showed the highest disease index accompanied by lower H2O2 and salicylic acid (SA) contents. Correspondingly, the blue light photoreceptor CaCRY2 was induced by both BL exposure and P. capsici infection (PCI). Silencing of CaCRY2 in pepper led to a decrease in disease index and lesion area with higher ROS and SA accumulation, while overexpression of CaCRY2 in tobacco increased disease index. In addition, we also found that CaCRY2 manipulated the resistance of pepper against P. capsici through ROS and SA signaling pathways. These results provide a new perspective on the involvement of blue light exposure in pepper resistance to P. capsici.