白粉病菌对结果期南瓜叶片光合特性和叶绿体超微结构的影响

Effect of Powdery Mildew Pathogens on Photosynthetic Characteristics and Chloroplast Ultrastructure of Pumpkin Leaves during Fruiting Stage

以高抗白粉病南瓜自交系112-2、高感白粉病南瓜品种九江轿顶(JJJD)为试材,在结果期进行白粉病菌喷雾接种,研究南瓜叶片光合指标、叶绿素含量以及侵染点细胞坏死、叶绿体超微结构的变化,探讨白粉病菌影响南瓜光合作用的生理机制。结果表明,与CK(不接种白粉病菌)相比,接种白粉病菌后,112-2和JJJD叶片的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和叶绿素含量均下降,抗性材料112-2 Pn的降幅整体小于感病材料JJJD,二者Pn在接菌后2 d分别降低了45.4%和63.8%,叶绿素含量在接菌后12 d分别降低57.0%和49.0%,而胞间CO_(2)浓度(Ci)增加。接种白粉病菌后4 d,2种南瓜材料侵染点周围均出现坏死斑,叶绿体肿胀变形,基质片层与基粒片层排列疏松,嗜锇体和淀粉粒增多;JJJD坏死斑面积和叶绿体变形程度均大于112-2。因此认为,结果期南瓜叶片感染白粉病后的光合速率下降主要由侵染点细胞坏死、叶绿素含量下降和叶绿体结构破坏引起,抗病材料112-2光合速率降幅较小与细胞坏死和叶绿体结构受损程度较轻有关。

In order to explore the physiological effects of powdery mildew on pumpkin photosynthesis,the photosynthetic indexes,chlorophyll content,as well as cell necrosis and chloroplast ultrastructural changes were studied,with the high powdery mildew-resistant pumpkin inbred line 112-2 and the highly susceptible variety Jiujiang Jiaoding(JJJD)as test materials by spraying powdery mildew pathogens during the fruiting period.The results showed that compared with CK(without powdery mildew inoculation),the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and chlorophyll content of pumpkin leaves(112-2 and JJJD)inoculated with powdery mildew pathogens all decreased.The reduction in Pn of the resistant material was smaller than that of the susceptible material,which decreased by 45.4%and 63.8%at 2 days after inoculation respectively,and the total chlorophyll content decreased by 57.0%and 49.0%at 12 days after inoculation respectively,while intercellular CO_(2)concentration(Ci)increased.At 4 days after inoculation,necrotic spots near the infection point of both two pumpkin materials appeared,and chloroplasts were swollen and deformed,stromal lamella and basal lamella loosely arranged,and osmophilic bodies and starch granules increased.The area of necrotic spots and the degree of chloroplast deformation in JJJD were bigger than those of 112-2.It is concluded that the reduction in Pn of powdery mildew pathogens-infected pumpkin leaves at fruiting stage is mainly caused by cell necrosis occurrence,chlorophyll decrease and chloroplast structure destruction.The lesser decrease in Pn of the resistant material 112-2 is related to milder cell necrosis and chloroplast structure damage.