Study on the Mechanism of Resistance of Pepper Cultivars Against Phytophthora Blight via Transcriptome Analysis

Pepper blight, caused by Phytophthora capsici, significantly impacts plant health and reduces crop yields, resulting in severe economic losses. Developing resistant varieties and identifying resistance targets through transcriptomic sequencing, along with elucidating their underlying resistance mechanisms, represent pivotal strategies for disease control. In this study, 11 resistant pepper varieties were identified from 21 varieties; among these, the highly resistant line 19K23 and the susceptible line QM were selected for further analysis. Transcriptome sequencing of root samples from both varieties was conducted on day 2 and day 5 after inoculation with P. capsici. Analysis of differentially expressed genes between the resistant variety and susceptible variety revealed pathways such as photosynthesis, oxidoreductase activity, plant-pathogen interaction, and secondary metabolism. Six key biological processes were highlighted among the highly differentially expressed genes, with porphyrin and chlorophyll metabolism activated early in 19K23. The Ras family, MAPK signaling, hormone signal transduction, and GPI-anchor biosynthesis were implicated in resistance. Importantly, secondary metabolism and lipid metabolism pathways such as phenylpropanoid biosynthesis, isoquinoline alkaloid biosynthesis, and unsaturated fatty acid biosynthesis appeared to play pivotal roles. Additionally, cell wall synthesis and structure, as well as stress response processes, were important. These findings enhance understanding of pepper resistance mechanisms against P. capsici and offer valuable molecular insights for future research on genetic regulation and resistance breeding.