关键词: 玉米, 种质资源, 瘤黑粉病, 抗病, 糖代谢, 氧化应激

Abstract:

【Objective】 Common smut (Mycosarcoma maydis) is a major fungal disease affecting maize production in China. This study aimed to screen for resistant germplasm resources and analyze their physiological and biochemical responses to pathogen infection, providing scientific support for disease resistance breeding. 【Method】 A total of 425 maize germplasm resources were selected and systematically screened for their resistance to common smut. Sugar metabolism, oxidative stress responses, and photosynthetic parameters were analyzed to identify high-resistant, moderate-resistant, and susceptible inbred lines. WGA-AF488/PI staining was used to analyze the hyphal proliferation to reveal the disease resistance traits of different inbred lines. 【Result】 The study found significant annual differences in the disease index and incidence of common smut in 2021 and 2022, primarily influenced by temperature and precipitation. Principal component analysis showed that the disease index on day 4, 8, and 12 post-inoculation was a key indicator of disease severity, while the disease incidence at the grain filling stage (R2) and wax ripening stage (R4) revealed differences across growth stages. Additionally, 6 high-resistance inbred lines (e.g., Q319), 67 medium-resistance inbred lines (e.g., D599), and 171 susceptible inbred lines (e.g., M407) were identified. Sugar metabolism analysis showed significant differences in sucrose, fructose, and glucose contents across inbred lines with different disease resistance, indicating the critical role of sugar metabolism in the competition between the pathogen and the host. Oxidative stress analysis revealed significant increases in H₂O₂ and O^2- contents post-infection, with the high-resistant inbred line Q319 exhibiting the strongest OH^- scavenging capacity. SOD and POD activities were significantly increased on days 4 and 8 post-inoculation, with the SOD activity of D599 increasing by 114.98% on day 8 and the SOD activity of Q319 increasing by 96.08%. On day 12, the POD activity of D599 and Q319 increased by 164.27% and 160.91%, respectively, indicating strong antioxidant defense capabilities in resistant materials. WGA staining showed that hyphal extension was limited in Q319, primarily concentrated near the vascular bundles, suggesting strong cell wall defense. D599 exhibited intermediate hyphal expansion speed and range, representing moderate defense capacity, while M407 displayed extensive hyphal spread with large intercellular infection, indicating weak cell wall defense. Post-inoculation, the net photosynthetic rate of Q319, D599, and M407 decreased by 52.5%, 52.8%, and 100.2%, respectively, compared to the control group, with significant reductions in photosynthetic pigment content; however, the decline decreased from 4 to 12 d. 【Conclusion】 This study reveals significant differences in sugar metabolism, oxidative stress responses, antioxidant capacity, and photosynthesis among different maize inbred lines under Mycosarcoma maydis infection. The high-resistance inbred line Q319 exhibits strong disease resistance through low sucrose, high fructose and glucose metabolism, along with higher chlorophyll and carotenoid content and efficient antioxidant ability. The high-susceptible inbred line M407 shows increased sucrose accumulation and insufficient antioxidant response, resulting in significantly decreased net photosynthetic rate and transpiration rate, leading to increased disease susceptibility. The medium-resistance inbred line D599 displays intermediate photosynthetic function and pigment accumulation, with disease resistance between Q319 and M407.

Key words: maize, germplasm, common smut, disease resistance, sugar metabolism, oxidative stress