| Sugar beet (Beta vulgaris L.) is important sugar and cash crops in our country even in the world. Under the various attacked of sugar beet diseases not only have causing huge economic losses in the sugar beet production industry but also restricted the development of the sugar industry. Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) and mediated by Polymyxa betae which was one of the most serious soil-born diseases. Recently, numerous researchs had studied the mechanism of rhizomania at domestic and abroad were main under the views of genomics, molecular biology, physiological and biochemical. No research studying the mechanism of rhizomania and its resistance signal transduction pathway from the cytological at present. Therefore, in this study, sugar beet varieties and BNYVV interaction system were the research objects, the morphological and cytological features of the two objects were studied. Also, to make sure the time-varying characteristics and located the spatial distribution in the sub-cellular level of the production of the active oxygen species (H2O2and O2-·) and the protection of enzymes (POD and SOD) in the interaction system, the physiological and biochemical methods and electron microscopic cytochemistry labeling technique were used, And we have detected the locating differences within organization of the lignin and the law of cell wall glycoprotein accumulated in the host cell in the interactions system to observed the roles of the active oxygen metabolism and cell wall components in the sugar beet resistance to rhizomania disease resistance, then lay a theoretical foundation for the further study of the signal conduction mechanism of sugar beet resistance to rhizomania disease. The main results obtained through the study were as follows:1. We have utilized optical microscopy and transmission electron microscopy to reveal the structural features of the morphology and ultrastructure between the interaction of the resistant and susceptible beet varieties and the BNYVV. The results showed that the morphology and ultrastructure of the sugar beet roots of the resistant and susceptible interaction system, infected by BNYVV, showed significant differences, the ultrastructure of the sugar beet vein have been seriously affected too, but the morphological anatomical structure of the sugar beet vein was no difference. The performance of the Morphology happened in the resistant and susceptible sugar beet included the epidermal destruction, the fracture of the cortical parenchyma tissue, the shed in most cell and the damage of the wood parenchyma cells near the xylem, the protection for the roots loss completely. The performance of the susceptible beet is more serious than the resistant beet. In the susceptible beet, the cortical parenchyma cells were almost all off, growing slowly and the root’s development was blocked. However, there are no abnormal changes in the morphological anatomical structure of the beet vein. In addition, the resistant varieties have a well developed vascular bundle structure than susceptible varieties. When observed from the sub-cellular level, we found that BNYVV resulted in a series of damaged on cell ultrastructure of the susceptible beet, such as the deformation, empty and the structure of the nuclear is disorder, the mitochondria and the Golgi apparatus was significantly increased, small and medium-sized vacuoles were increased in the cytoplasmic. We observed some round or oval vesicles containing thin filaments broke into the vacuole at the edge of the vacuolar membrane. In the Vein cells the chloroplast disintegrated completely and a abundance of Osmiophilic globule emerged. Destruction of the cell ultrastructure of resistant varieties was lighter, a series of significant structural defense reaction produced in:the host cells:there was sediments in the cell wall and black granular sediment showed in the vacuolar membrane. These indicated that the description of the morphological changes of the tissue and the pathological changes of the organelle were relative to the resistance to rhizomania.2. We have utilized Physiological and biochemical methods and electron microscopy cytochemistry labeling technique to study the time-varying characteristics and the orientation of spatial distribution of the H2O2and O2-·generated between the process of the beet-BNYVV interaction. A large number of H2O2and O2·detected both in the resistant and susceptible beet, but the production in the resistant beet was higher than the susceptible beet significantly. H2O2whose position of distribution was similar in the resistant and susceptible beet, which was located in the roots, the tonoplast and plasma membrane of the veins cell, and exist in the gap of the veins cell also. The O2-·is detected in the vein and the plasma membran of the veins cell in the resistant, but found that in the tonoplast in the susceptible beet. However, the content of H2O2and O2-·was distinctly different in the different beet systems, the content in the susceptible system was significantly lower than the resistant system. The results suggested that the production and distribution of the H2O2and O2-·were significantly different in the different interactive system, these difference were close with the beet’s resistance to the rhizomania. As a signaling molecule, the H2O2and O2-·located in different positions involved in the defense response of the beet to virus infection. 3. Research was carried on POD and SOD activity and their intracellular distribution characteristics in sugar beet and BNYVV interaction processes by using biochemical detection and enzyme cytochemical methods. The results showed that before the viral infection, the POD was mainly localized in the root cell wall and mitochondria of the vein cells and the gaps between the cells. after the virus infection, in the resistant and susceptible sugar beet varieties, the POD activity in the cell wall, plasma membrane and tonoplast of the tuberous root cortex cells, and in the cell wall, plasma membrane, tonoplast, mitochondria and the gap of the veins cells is significantly increased than that of the control group. Although the distribution of POD was almost same in both beet system, but the deposition in the former was significantly higher in the latter. When the resitant and susceptcible were not infected virus, SOD was defected in plasma membrane and tonoplast of the beet root cortical parenchyma cell, cytoplasmic membrane of vein collenchyma thin-walled, mitochondria of veins and the gaps of the cells. The distribution of SOD in susceptible varieties and resistant sugar beet root is the same after the infection by virus, which was in the cells, and the same position are located in the plasma membrane and tonoplast, But superoxide dismutas is mainly distributed on the plasma membrane for resistant varieties, while it was distributed on the’vacuole membrane for susceptible ones. Resistant varieties SOD activity was not only significantly higher than the control group, but also significantly higher than susceptible varieties, which were infected by virus. The results of POD and SOD intracellular distribution and physiological and biochemical detection in Resistant sugar beet varieties were the same with susceptible varieties, higher activity of POD and SOD in resistant sugar beet plexus root disease was one of the important mechanisms of biochemical markers at the subcellular level.4. By the methods of histochemical staining and electron microscope cytochemical, We have Studied the Influence of BNYVV on lignin and HRGP, which were in sugar beet cell wall, clearly to see the relationships between different resistance beet cell wall lignin as well as different HRGP accumulation and distribution and the nature of anti plexus root disease in sugar beet roots. The results showed that no matter it was the resistant sugar beet varieties or not, no matter the beet varieties were infected by BNYVV before or after, there are lignin and HRGP deposition in their roots and all catheters on vein transverse. In addition, lignin deposition was shown gradually from deep to shallow, which was throughout the parenchyma cell walls from the outside to the inside in roots; lignin and HRGP accumulation in resistant varieties is more significant than susceptible varieties and its control group; it was notable that it also showed black granular sediment on sugar beet cell vacuoie membrane when determinated the cell wall surface glycoprotein, and vacuole membrane deposition was deeper·in disease-resistant varieties than susceptible varieties and the control group. It explains that HRGP was involved in the synthesis of lignin between sugar beet and BNYVV interaction system, the rapid accumulation of Lignin and HRGP in Sugar beet tissue was one of the manifestations of rhizomania. |
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