Cultivar-specific physiological and proteomic patterns underlying mango susceptibility to bacterial black spot disease.

Mango bacterial black spot (MBBS) disease caused by Xanthomonas citri pv. mangiferaeindicae (Xcm) is a global problem that threatens mango productivity and quality worldwide. However, our understanding of mango physiological and proteomic responses to Xcm infection on leaves in different cultivars remains limited. Herein, we explored how two mango cultivars (Guifei and Aomang) respond to Xcm challenge at the physiological, biochemical, and proteomic levels at 6 and 12 ad post-inoculation. Our results revealed that Xcm infection induced progressive disease development in both cultivars as Guifei showed larger lesions and higher disease severity than Aomang. We further observed stronger induction of defense-related enzymes peroxidase, catalase and phenylalanine ammonia-lyase activities in Aomang, suggesting enhanced antioxidant and defense capacity against Xcm colonization. In addition, we observed decreased chlorophyll, soluble sugar, and reducing sugar contents, but increased hydrogen peroxide, superoxide, and malondialdehyde levels, pointing to oxidative stress and impaired photosynthetic activity. Proteomics analysis further showed cultivar-specific alteration in proteins abundance associated with primary metabolism, plant-pathogen interaction, hormone signaling, MAPK signaling, phenylpropanoid biosynthesis, and glutathione metabolism. Notably, Aomang showed early accumulation of defense-associated proteins, including receptor-like kinases, disease-resistance related proteins, hormone signaling components, and phenylpropanoid-associated enzymes, indicating early activation of immune-related pathways before subsequent metabolic suppression during prolonged infection. Overall, Guifei displayed greater disease susceptibility accompanied by early suppression of metabolic pathways, whereas Aomang exhibited reduced disease severity associated with enhanced antioxidant enzyme activation and early induction of defense-related proteins before broad pathway downregulation at late infection stage. Our findings integrating physiological and proteomic data revealed cultivar-specific changes in key metabolic pathways and provide a basis for targeted breeding or biotechnological approaches to manage MBBS disease.