苦瓜叶片结构与白粉病抗性的关系

以不同抗白粉病的苦瓜品系幼苗为材料,对它们的叶片及上下表皮厚度、栅栏组织及海绵组织厚度、叶片结构紧密度及疏松度、蜡质含量、比叶重、气孔及茸毛密度等叶片结构进行观察比较,探讨苦瓜白粉病抗性与其主要叶片结构指标的关系。结果显示:（1）抗病苦瓜品系叶片的蜡质含量显著高于感病品系,与病情指数呈显著负相关关系,蜡质层是其抵抗和延迟病原菌侵入的一个有力结构屏障。（2）感病品系叶片的气孔和叶背面茸毛数量显著多于抗病品系,且叶背面的气孔及茸毛密度与病情指数呈显著正相关关系,即气孔和茸毛越少越抗病。（3）抗病苦瓜品系的叶片栅栏组织以及海绵组织排列整齐、紧密,而高感品系的叶片组织出现大量孔隙,较难观察到完整细胞。（4）抗病品系叶片厚度、下表皮厚度、栅栏组织厚度、叶片结构紧密度明显高于感病品系,而感病品系的海绵组织厚度、叶片结构疏松度明显高于抗病品系;且苦瓜比叶重与其白粉病抗性关系不大。研究认为,苦瓜叶片蜡质含量、叶背面气孔及茸毛密度可以作为苦瓜白粉病抗性鉴定的参考指标。

Relationship between the Leaf Structure of Bitter Melon and Resistance to Powdery Mildew

The leaf structure of different bitter melon cultivars resistant to powdery mildew was compared and studied.They mainly included thickness of upper and lower epidermis;thickness of palisade tissue and spongy tissue;compactness and porosity of leaves structure;waxes content;leaf weight ratio;density of stoma and fuzz,etc.The result indicates that:(1)The waxes content of resistant cultivars is significant higher than that of susceptible one and significant negative correlation with disease index.Wax layer is an important structure barrier to resist and delay the pathogen invading.(2)The stomatal number and hair densities of abaxial leaves of susceptible cultivars are significant more than that of resistant ones.The stomatal number and hair densities of abaxial leaves are significant positive correlation with disease index.It indicates that the less stoma and fuzz,the more resistance.(3)The palisade and spongy tissue of resistant bitter melon cultivars arranged closely and in good order,but the leaf tissue section of high susceptible cultivars present lots of pores and hard to observe whole cells.(4)The thickness of leaves,lower epidermis and palisade tissue and leaves structure compactness of resistant cultivars is significant higher than that of susceptible ones,but the thickness of spongy tissue and porosity of leaf structure is opposite.To the powdery mildew resistance ,the leaf weight ratio count for little.Wax content,the stomatal number and hair density of abaxial leaves can be the reference designators to identify the resistance to powdery mildew for bitter melon.