宿根矮化病菌对甘蔗品质及茎、叶超微结构的影响

Effects of Leifsonia xyli subsp.xyli(Lxx) on quality and ultrastructure of stalks and leaves in sugarcane

甘蔗宿根矮化病(Ratoon Stunting Disease,RSD)是由Leifsonia xyli subsp.xyli(Lxx)引起的,是目前世界所有植蔗地区危害性极大的病害之一。本实验以甘蔗品种新台糖22号(ROC22)健康植株为对照,感染RSD植株为处理,观察和测定RSD侵染甘蔗引起的蔗株农艺性状、蔗糖分以及茎、叶超微结构的变化。结果表明:(1)感染RSD种茎的出苗率比对照减少2.94个百分点;株高比对照下降28.85 cm;茎径比对照减少0.28 cm;节间长度比对照减短3.50 cm;单茎重比对照低0.36kg。(2)感染RSD植株的蔗糖分低于对照0.9个百分点(绝对值)。(3)利用透射电镜技术对感染RSD植株茎、叶细胞超微结构进行观察表明,叶片叶肉细胞、维管束鞘细胞及茎细胞内的细胞器及细胞核都发生了明显的病理变化。与健康叶片相比,叶绿体变形,叶绿体基质片层大部分消解,基粒结构消失,叶绿体外膜和内膜剥离。线粒体形态异常,有的肿大、内嵴模糊,严重者内嵴消失并空泡化,仅剩未被消解的残骸;细胞核形态变为不规则,核膜破裂,染色质分布不均匀,呈降解状态。在感染RSD甘蔗茎维管束导管细胞内积累有大量的电子致密物质,细胞壁有不同程度的溶解和断裂,这可能和RSD病原细菌侵染有关。以上结果表明:RSD侵染甘蔗后,可能导致光合效率下降,对水分和营养物质的运输能力降低,从而导致甘蔗品质和产量的降低。

Ratoon stunting disease （RSD） of sugarcane （ Sacchrum spp.Hybrids）, caused by bacterium Leifsonia xyli subsp, xyli （ Lxx）, is one of the economically damaging diseases worldwide. The effects of RSD on agronomic characters, sucrose content and ultrastructure of stalk and leaf of sugarcane were determined with the infected and healthy cane plants of the sugarcane variety ROC22.The results showed： （ 1 ） The emergence rate of seedcane, plant height, stalk diameter, intemode length and single stalk weight was decreased by 2.94%, 28.85 cm, 0.28 cm, 3.50 cm and 0.36 kg respectively in the RSD infected treatment than in the control. （2） The sucrose content in cane was decreased by 0.9% （absolute value） in the RSD infected treatment than in the control. （3）The ultrastructure of stalks and leaves under transmission electron microscopy showed apparent difference between healthy and infected plants in chloroplast, mitochondria and nucleus of mesophyll cells, bundle sheath cells and stalk cells. The chloroplasts in diseased leaves were deformed, most chloroplast grana were dissolved and the inner and outer membrane of chloroplast delaminated. The abnormal mitochondria expanded with indistinct cristae. In serious abnormal mitochondria, of cristae disappearance and vacuolation of mitochondria with a few remains found. The abnormal nucleuses were found and envelope of nucleus was split. The chromatin distributed asymmetrically and degraded. There was a large amount of electron-dense substances accumulated in the infected stalk cells that might be associated with the bacterial, and xylem cell walls were degraded and broken in different degree. The results indicate that sugarcane quality and yield reduced due to RSD infection might associate to the disorder of water and nutrition transportation and the decline of photosynthetic efficiency in the plants.