Zhang Xiaoqiu, Chen Minghui, Liang Yongjian, Xing Yongxiu, Yang Litao, Chen Minghui, Comstock Jack C, Li Yangrui, Yang Litao
Agricultural College, State Key Laboratory of Subtropical Bioresources Conservation and Utilization, Guangxi University, Nanning 530005, China.
Ping Ding Shan University, Pingdingshan, Henan 46700, China.
Plant Dis. 2016 Dec;100(12):2499-2506. doi: 10.1094/PDIS-10-15-1134-RE. Epub 2016 Oct 4.
Ratoon stunt, caused by the bacterium Leifsonia xyli subsp. xyli, is one of the major sugarcane diseases worldwide. The objectives of this study were to determine the variation in morphology and DNA sequence of L. xyli subsp. xyli strains isolated in China, to compare the changes that occurred in vascular ultrastructure and levels of endogenous hormone abscisic acid (ABA), auxins (indoleacetic acid [IAA]), and gibberellic acids (GA) in sugarcane stalks. Experiments were also conducted with two sugarcane varieties, 'ROC22' and 'Badila', in the greenhouse to understand the cytological and physiological mechanisms of L. xyli subsp. xyli-induced growth stunting. There were three treatments in the experiments: (i) healthy plants (L. xyli subsp. xyli-free plants), (ii) infected plants (L. xyli subsp. xyli-infected seedcanes treated with hot water, and (iii) infected plants (healthy seedcanes dipped in L. xyli subsp. xyli cell culture). The results showed that sequence coverage of a locally isolated strain, LxxGXBZ01, was 99.99%, and the average nucleotide identity between LxxGXBZ01 and the other well-characterized Brazilian isolate LxxCTCB07 was 93.61%. LxxGXBZ01 occurred in different sizes and shapes in xylem vessels of infected plants. In comparison with healthy stalks, the secondary walls of the vessel element in L. xyli subsp. xyli-infected stalks were degraded with uneven wall thickness, deformities, sticky substances, and electron-dense substances accumulated inside the cells. Compared with the healthy and hot-water treatments, the contents of IAA and GA were significantly lower, while that of ABA was significantly higher in the L. xyli subsp. xyli-infected stalks. The information obtained in this study will expand our understanding of ratoon stunt etiology and cytological and physiological bases of the disease manifestation.
宿根矮化病由木聚糖利夫森氏菌木糖亚种（Leifsonia xyli subsp. xyli）引起，是全球主要的甘蔗病害之一。本研究的目的是确定在中国分离的木聚糖利夫森氏菌木糖亚种菌株的形态和DNA序列变异，比较甘蔗茎中维管束超微结构以及内源激素脱落酸（ABA）、生长素（吲哚乙酸[IAA]）和赤霉素（GA）水平的变化。还在温室中对两个甘蔗品种‘新台糖22号’和‘拔地拉’进行了试验，以了解木聚糖利夫森氏菌木糖亚种引起生长受阻的细胞学和生理机制。试验中有三种处理：（i）健康植株（未感染木聚糖利夫森氏菌木糖亚种的植株），（ii）感染植株（用热水处理过的感染木聚糖利夫森氏菌木糖亚种的种茎），以及（iii）感染植株（将健康种茎浸入木聚糖利夫森氏菌木糖亚种细胞培养液中）。结果表明，本地分离菌株LxxGXBZ01的序列覆盖率为99.99%，LxxGXBZ01与另一个特征明确的巴西分离株LxxCTCB07之间的平均核苷酸同一性为93.61%。LxxGXBZ01在感染植株的木质部导管中呈现出不同的大小和形状。与健康茎相比，感染木聚糖利夫森氏菌木糖亚种的茎中导管分子的次生壁降解，壁厚不均匀，出现畸形，细胞内积累粘性物质和电子致密物质。与健康和热水处理相比，感染木聚糖利夫森氏菌木糖亚种的茎中IAA和GA的含量显著降低，而ABA的含量显著升高。本研究获得的信息将扩展我们对宿根矮化病病因以及该病表现的细胞学和生理基础的理解。
