甘蔗宿根矮化病菌形态特征及其对甘蔗光合作用的影响

Morphological characteristic of Leifsonia xyli subsp.xyli and its effects on photosynthesis of sugarcane

甘蔗宿根矮化病(ratoon stunting disease,RSD)病原物为革兰氏阳性菌Leifsonia xyli subsp.xyli(Lxx)。采用透射电镜和扫描电镜观察Lxx离体培养物形态和感病蔗茎维管超微结构,并用光合仪测定感病甘蔗+1叶光合作用相关指标。结果表明:改良的MSC培养基适于Lxx生长,培养的菌体形态多样,有隔膜和简体;菌体内细胞质分布不均,有电子透明物、电子稠密物及隔膜;RSD病原菌寄居在木质部导管的纹孔和导管壁上,其内粘附许多颗粒状物质;感染RSD蔗株的光合速率、气孔导度、胞间CO2和蒸腾速率均低于健康蔗株,RSD可降低甘蔗的光合作用。

Ratoon stunting disease（RSD）of sugarcane is caused by Leifsonia xyli subsp.xyli（Lxx）,a kind of gram-positive bacterium.The present study was conducted to observe the pathogenic morphology of RSD and the ultrastructure of RSD-infected stalk,and investigate its effect on photosynthesis of sugarcane under the pathogen stress.Transmission electron microscope（TEM）and scanning electron microscope（SEM）were used to observe the pathogenic morphology and ultrastructure of RSDinfected stalk.Net photosynthetic rate（Pn）,stomatal conductance（Gs）,intercellular CO2（Ci）and transpiration rate（Tr）of RSD-infected sugarcane were determined by portable photosynthesis system.The results showed that the modified MSC medium was efficient for Lxx culture.The cell bodies showed various shapes and some had septum and mesosome.They showed uneven cytoplasm with electron transparency,electron dense and septum in the cell bodies.The pathogen and many small granular substances were observed in pits and on surface of the secondary wall of the xylem vessel in RSD-infected sugarcane stalk.The Pn,Gs,Ci and Tr were lower in RSD-infected sugarcane plants than the healthy ones.