Physiological, Biochemical Responses and Transcriptional Regulation of Common Bean (Phaseolus vulgaris) under Anthracnose Pathogen Stress

Anthracnose has become one of the major diseases limiting common bean production, severely affecting its yield and commercial quality. Screening for resistant varieties, exploring their resistance mechanisms, and breeding new resistant cultivars have emerged as urgent issues to address. Therefore, this experiment utilized common bean germplasm resources with varying resistance levels to anthracnose as materials. By inoculating with Colletotrichum lindemuthianum, the activities of key en-zymes—including superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), glutathione S-transferase (GST), and chi-tinase (CHI)—as well as malondialdehyde (MDA) content were measured. Transcrip-tional regulation was analyzed to investigate the physiological and biochemical re-sistance mechanisms among different resistant germplasms. Additionally, differen-tially expressed genes (DEGs) and pathways associated with anthracnose resistance were screened. The results showed that, based on the analysis of physiological and biochemical changes in common bean leaves post-inoculation, the MDA content decreased in all varieties except Wuchang Dayoudou. Regarding antioxidant enzyme activities, the SOD, POD, and PPO activities in the leaves of different common bean varieties in-creased, indicating that pathogen infection could induce the upregulation of antioxi-dant enzyme activities. In contrast, GST activity decreased under pathogen stress. CHI activity increased after pathogen infection. Following pathogen challenge, PAL activi-ty increased in resistant varieties but decreased in susceptible ones. Transcriptome analysis of common bean leaves and pods revealed that the primary metabolic pathways associated with resistance were significantly enriched in phe-nylpropanoid biosynthesis, MAPK signaling pathway, and plant hormone signal transduction. Among these pathways, 13 genes were screened in phenylpropanoid bi-osynthesis, 6 genes in the MAPK signaling pathway, and 3 genes in plant hormone signal transduction. Additionally, other resistance-related pathways and transcription factors were analyzed, identifying 2 genes in the peroxisome pathway, 2 genes in the plant-pathogen interaction pathway, and 12 transcription factors (including AP2, WRKY, and ERF families). These differentially expressed genes are hypothesized to re-spond to Colletotrichum lindemuthianum stress.