立枯丝核菌对马铃薯的致病机理研究Ⅱ:病原菌毒素对幼苗活性氧代谢及细胞超微结构的影响

Pathogenesis mechanism of Rhizoctonia solani on potato Ⅱ:Effects of Rhizoctonia solani toxin on active oxygen metabolism and cell ultrastructure of potato plantlets

【目的】探讨马铃薯茎溃疡病的病原菌立枯丝核菌的致病机理.【方法】采用毒素处理组培苗及透射电镜观察相结合的方法,研究了不同浓度的病原菌菌毒素（T2：低浓度,T3：中浓度,T4：高浓度）对马铃薯幼苗体内活性氧代谢及细胞超微结构的影响.【结果】病原菌毒素处理24h后,中、高浓度处理（T3和T4）的马铃薯幼苗体内超氧阴离子（O2-）的产生速率和丙二醛（MDA）的含量显著高于对照CK（T1）,至120h时达到峰值,T3和T4处理的O2-产生速率分别是T1的3.3倍和4.1倍,MDA分别是T1的3倍和5.4倍;毒素处理后马铃薯幼苗体内H2O2含量的变化与O2-和MDA含量相似,处理96h时即可达到峰值;电镜下马铃薯茎基部组织细胞的超微结构显示,毒素处理24-48h后,马铃薯茎基部组织细胞的质体开始变形肿胀,内质网变形;毒素处理72h后,细胞膜消失,细胞线粒体变形,基质外流,细胞壁不再光滑,质膜断裂;毒素处理96-120h后,细胞质溶解,逐渐衰老.【结论】中、高浓度的病原菌毒素处理引起了马铃薯幼苗体内活性氧的积累与膜脂过氧化反应,由此造成的细胞质膜断裂,细胞器受损和细胞质溶解等一系列细胞超微结构的变化是溃疡病最终导致植株死亡的可能机理.

【Objective】To explore the pathogenesis mechanism of stem canker of potato virus-free plantlets treated with R.solani toxin.【Method】Treating the potato tissue culture seedlings with R.solani toxin at different concentrations（T2：low concentration,T3：medium concentration,T4：high concentration）,observing the cell ultrasturcture by transmission electron microscopy（TEM）to research the effects of R.solani toxin on active oxygen metabolism and cell ultrastructure.【Result】O2-generation rate and MDA content in potato seedlings were significantly higher than those of CK after being treated for 24 h with R.solani toxin at high concentration treatment（T3and T4）,reached the maximum at 120 h.O2-generation rate of T3 and T4 was 3.3and 4.1times as that of CK,respectively and MDA content reached 3and5.4times as that of CK,respectively.The changing trend of H2O2 content was similar to that of O2-generation rate and MDA content,reaching the maximum at 96 h.When being treated for 24-48h,the plastid of histocyte at potato stem base began to swell and endoplasmic reticulum deformed.After being treated for 72 h,cell membrane disappeared,plastochondria deformed,cell wall was no longer smooth,matrix outflowed,plasma membrane fractured.After 96-120h,cytoplasm dissolved,more chromatin can be seen in the nucleus and appeared cell aging.【Conclusion】Medium and high concentration toxin caused accumulation of active oxygen species as well as lipid peroxidation,resulting in cell plasma membrane fracture,organelle damage,cytoplasmolysis,which was the possible pathogentic mechanism of canker causing plantlet death.