籽用美洲南瓜叶片对白粉病菌的抗逆生理响应

以籽用美洲南瓜(Cucurbita pepo L.)白粉病抗病品系F2和感病品系M3为试材，在人工气候箱内接种白粉病生理小种2US孢子悬浮液，考察在接种白粉病菌后南瓜幼苗植株与白粉病菌的互作、叶片活性氧代谢及保护酶活性的变化，探讨南瓜抵御白粉病的生理机制。结果表明：(1)与感病品系M3相比，接种白粉病菌后，抗病品系F2叶片上病原菌发育缓慢，较难侵染叶片。(2)抗病品系F2在感病初期叶片H₂O₂、O₂^-·含量迅速升高后逐渐下降，而感病品系在感病初期H₂O₂、O₂^-·含量上升缓慢，在达最大值后始终保持较高水平，且感病品系叶片MDA含量始终高于抗病品系；组织化学染色分析发现，抗病品系叶片着色比感病品系快，之后着色面积有所减少并趋于较低水平。(3)抗病品系F2和感病品系M3叶片抗氧化酶CAT、SOD、POD活性及PAL、PPO活性在接种白粉病菌后均显著增加，但抗病品系的活性及其增幅均高于感病品系。研究发现，籽用美洲南瓜抗病品系叶片上白粉病菌发育缓慢，较难受到侵染，生成菌丝体后叶片上粉状斑点较小；抗病品系在被白粉病菌侵染初期依靠活性氧的增加抵御病原菌的入侵，随着活性氧含量增加抗病品系通过迅速增加自身抗氧化酶活性来防止氧化胁迫；与感病品系相比，抗病品系在受病原菌侵染后能迅速增加PAL、PPO活性以抵御病原菌侵染。

Physiological Response of Cucurbita pepo L. Leaves to Powdery Mildew

Using American squash (Cucurbita pepo L.) powdery mildew resistant strain F2 and susceptible strain M3 as test materials, we inoculated the powdery mildew physiological race 2US spore suspension in an artificial climate box. The interaction between pumpkin seedling plants and powdery mildew fungus. The reactive oxygen species(ROS) metabolism of leaves and changes in protective enzyme activities after inoculation with powdery mildew were investigated, and the physiological mechanism of pumpkins against powdery mildew was explored. The results showed that: (1) compared with the susceptible strain M3, after inoculation with powdery mildew fungus, the pathogenic fungus on the leaves of the disease resistant strain F2 developed slowly and were more difficult to infect the leaves. (2) The H₂O₂ and O₂^-· contents of the disease resistant line F2 increased rapidly at the early stage of infection and then gradually decreased, while the H₂O₂ and O₂^-· contents of the susceptible line increased slowly at the initial stage of the disease, and maintained a high level after reaching the maximum, and the MDA content in leaves of susceptible strains was always higher than that of resistant strains. At the same time, through histochemical staining, we found that the leaf coloration of disease resistant strains was faster than that of susceptible strains, after which the staining area decreased and tended to a lower level. (3) The activities of antioxidant enzymes CAT, SOD, POD and PAL and PPO in the leaves of disease resistant strains F2 and susceptible strains M3 were significantly increased after inoculation with powdery mildew, but the activities and increase of disease resistant strains were higher than those of susceptible strains. Studies have found that the development of powdery mildew fungus on the leaves of disease resistant American squash for seeds is slow, and it is more difficult to be infected. After the mycelium is formed, the powdery spots on the leaves are smaller; Disease resistant strains rely on the increase of active oxygen to resist the invasion of pathogenic fungus at the initial stage of being infected by powdery mildew. As the content of active oxygen increases, disease resistant strains rapidly increase their own antioxidant enzyme activities to prevent oxidative stress; compared with susceptible strains, disease resistant strains can rapidly increase the activities of PAL and PPO after being infected by pathogenic fungus to resist infection by pathogenic fungus.