【作者】 王双；

【导师】 侯明生；

【作者基本信息】 华中农业大学 ， 植物病理学， 2015， 硕士

【摘要】 根肿病是一种重要的土传病害,诸多学者对根肿菌的侵染过程已进行了深刻研究,但仍存在许多问题尚未解决。此外,目前生产上仍然缺乏稳定且有效的防控方法。本课题以白菜为材料,人工接种观察根肿菌的侵染过程,同时采用硼、硅两种营养元素梯度处理,调查其对根肿菌侵染及发病的影响,为合理利用硼、硅元素控制根肿病的发生以及相关机理研究提供理论依据。主要研究结果如下:1.采用沙土-营养液法培养寄主植物,观察了根肿菌侵染白菜后在其体内的发育情况。接种24h后根肿菌初级游动孢子或侵入根毛形成原质团或直接侵入皮层,接种第7d根毛中的原质团分裂形成孢子囊,接种第10d孢子囊进一步发育,形成次级游动孢子并释放,留下空孢子囊结构。此外,接种后36h时观察到一种类似孢子囊的结构,对类似孢子囊结构的侵染过程进行显微观察和石蜡切片观察发现,该结构可直接侵入根毛,也可以以整体形式侵入皮层,我们推测这可能是根肿菌侵染寄主植物的另一条途径。2.采用不同浓度硼处理,调查硼对根肿病发生的影响。硼处理对根肿菌休眠孢子萌发无影响,但可以抑制根肿病的发生,降低发病率和病情指数,表明硼的抑制作用是胞内的。沙土培养中,当硼浓度为0.2mmol/L时可显著降低发病率及病情指数,土壤培养中,对发病率的抑制作用发生在0.4mmol/L,而对病情指数的抑制作用发生在1.6mmol/L。但随着硼浓度的逐渐提高,寄主植物会表现出毒性性状且影响成苗。综合调查结果得出结论,硼处理可抑制根肿病的发生,且沙培中控制根肿病发生的最佳硼浓度为0.4mmol/L,土培中的最佳浓度为0.8mmol/L,两种培养方式中存在的差异可以解释为土壤的缓冲作用。此外,硼处理可降低寄主植物POD、SOD活性,提高丙二醛含量,表明硼处理可诱导植物防卫反应机制,引起过敏反应,提高植物对根肿病的抗性。3.采用不同浓度硅处理,调查硅对根肿病发生的影响。硅处理可抑制根肿菌休眠孢子的萌发、降低根毛侵染率、抑制根肿菌在根毛中的发展,当硅浓度为1.2mmol/L时,根肿病的发生最轻。此外硅处理还可以延缓根肿菌休眠孢子的聚集,其中的原因及影响需进一步研究。更多还原

【Abstract】 Clubroot disease is an important soil borne disease. Many scholars have got some important achievements on the life cycle of Plasmodiophora brassicae. However, there are still many problems unsolved. In the fields, stable and effective prevention methods are still lacking. This subject adopts the method of sand-nutrient solution to cultivate the Chinese cabbage and observe the infection process of Plasmodiophora brassicae by artificial inoculation. At the same time, we investigate the effect of silicon and boron on infection and pathogenesis through setting different concentrations. The research can provide theory basis to us to control Plasmodiophora brassicae by using silicon and boron. The main results are as follows:1. We adopted the method of sand-nutrient solution to cultivate the host plant and observed the development process of Plasmodiophora brassicae. The primary zoospores invade the root hair to form plasmodia or invade cortex directly after inoculated 24 hours. The plasmodia is cleavage into zoosporangia after inoculated 7 days. And then, secondary zoospores are formed in zoosporangium and released, we observed empty zoosporangia in root hair. Furthermore, we found a single sporangium-like structure after inoculated 36 hours. We observed the surface morphology by scanning electron microscopy and observed the infection process by optical microscope and paraffin section. The structure can intrude into root hair and cortex as a whole directly. we speculate that it may be another infection way of Plasmodiophora brassicae.2. We investigate the impact of boron on the occur of clubroot disease through setting different concentrations. Boron treatment have no effect on spore germination, however it can inhibite the occur of clubroot disease and reduce the incidence and disease index, indicating that the effect of boron is intracellular. In the sand culture, boron treatment can inhibite the occur of clubroot disease when the concentration is 0.2mmol/L, In the soil culture, it can reduce the incidence when the concentration is 0.4mmol/L and reduce the disease index when the concentration is 1.6mmol/L. However as the concentration of boron increasing, the host plant will show some toxicity symptom and reduce the seeding rate. In conclusion, boron treatment can inhibite the development of clubroot disease, and the best concentration is 0.4mmol/L in sand culture and 0.8mmol/L in soil culture. The difference can be explained by the soil buffer action. In addition, boron treatment can reduce the activity of POD and SOD and enhance the content of malondiadehyde in host plant, it shows that boron treatment can induce defense response mechansim and cause allergic reaction so that improve the resistance to clubroot disease.3. We investigate the impact of silicon on the occur of clubroot disease through setting different concentrations. Silicon treatment can inhibite spore germination and the infection rate of root hair. Silicon treatment can also inhibite the development of the pathogen in root hair. The incidence and disease index is highly reduced when the concentration of silicon is 1.2mmol/L. Furthermore, silicon treatment can delay the gather of dormant spore and the reasons need to be further studied.更多还原