Research Status and Prospect of Burkholderia glumae, the Pathogen Causing Bacterial Panicle Blight

Bacterial panicle blight caused by Burkholderia glumae is one of the most severe seed-borne bacterial diseases of rice in the world. Currently, this disease has affected many countries of Asia, Africa, South and North America. It is a typical example of the shifting from minor plant disease to major disease due to the changes of environmental conditions. Some virulent factors of B. glumae have been identified, including toxoflavins and lipases, whose productions are dependent on the Tof I/Tof R quorum-sensing system, and type III effectors. In spite of its economic significance, neither effective control measure for this disease nor resistant rice variety is currently available. In recent years, genomics, transcriptomics and other molecular methods have provided useful information for better understanding the molecular mechanisms underlying B. glumae virulence and the rice defence mechanisms against pathogens. For the prevention of this pathogen, our laboratory has developed a rapid and sensitive multiplex PCR assay for detecting and distinguishing B. glumae from other Burkholderia species. This improved understanding of B. glumae will shed new light on bacterial panicle blight disease management.

Characterization and in Plant Detection of Bacteria That Cause Bacterial Panicle Blight of Rice

Burkholderia glumae presumably induces a grain rot symptom of rice that is threatening to rice production in most rice producing states of the USA. The present study was to identify the causal agent of bacteria panicle blight (BPB), virulence based on hypersensitive reactions and distribution of the pathogen within a plant. 178 rice panicles samples were analyzed with semi-selective media (CCNT), polymerase chain reaction (PCR) with bacterial DNA gyrase (gyrB) specific markers, and hypersensitive reactions on tobacco leaves. A total of 73 samples out of 178 produced a yellow bacterial colony with similar morphology on CCNT medium suggesting they were bacterial panicle diseases. However, with PCR reactions we only determined that 45 of 73 were due to B. glumae, and the causal agent for the remaining samples was undetermined. Within the 45 samples, 31 highly, 6 moderately, and 5 weakly virulent isolates were grouped based on lesion sizes of the hypersensitive reactions. Pathogenicity variability among the 45 B. glumae detected suggests that different degrees of pathogenicity exist. To determine the existence of bacteria in different plant tissues, naturally infected plant parts were examined with CCNT media and PCR analysis. B. glumae was again isolated from seeds followed by stems and sheaths from light yellow pigmented CCNT media. In contrast, roots and leaves show no visible yellow pigment on CCNT. Consistent PCR products were produced from the stem, sheath, and seed, but not from the root and leaves. These findings suggest that B. glumae is distributed in the stem, sheath, and seed, and not in the leaf and root. Together this study demonstrated the usefulness of artificial culture media, tobacco reactions, and DNA test with PCR for characterization of BPB, and distribution of bacteria in plants. These findings will help to understand the mechanism of bacteria translocation in plants.

水稻穗腐病和穗枯病的研究进展

水稻穗腐病和穗枯病是我国新上升或新出现的两个水稻后期穗部病害。近年来,随着气候的变化、耕作栽培制度及肥水管理的改变以及品种(组合)的更替,两病在我国的发生和危害程度越来越严重。穗腐病和穗枯病病原菌有色,可产生毒素,不但直接影响水稻产量,还导致稻米品质降低,危害食用者的健康。穗腐病和穗枯病在发病时期、发生部位和危害程度上具有相似性。综述了两病害的发生、流行规律、危害状况、病原菌生物特性和毒素研究以及防治方法,提出了研究上目前存在的问题和今后的研究方向。

水稻对穗枯病的抗病机理初步研究

【目的】水稻在孕穗期比苗期更容易感染穗枯病(Bacterial panicle blight of rice)并出现病症。本研究旨在探究水稻不同时期对穗枯病的抗性机理,为培育抗病水稻品种奠定基础。【方法】采用喷雾法和注射法分别对苗期和孕穗期的抗、感病水稻品种接种颖壳伯克氏菌(Burkholderia glumae),测定处理组与对照组的3种抗氧化酶(POD、CAT、SOD)活性的差异,并利用实时荧光定量PCR测定5种防卫反应基因(PR1a、PR10b、Rcht、LOX、PAL)的表达量。【结果】B.glumae的侵染能引起水稻活性氧的积累,提高抗氧化酶活性,使部分防卫反应基因大量表达,但是苗期和孕穗期的应答有较大区别。水稻孕穗期的抗氧化酶(SOD、CAT和POD)活性和防卫反应基因(PR10b、Rcht和PAL)的表达量比苗期高,但PR1a和LOX的表达量却低于苗期。【结论】B.glumae能诱导孕穗期的水稻产生更多抗病反应,参与抗病反应的主要是水杨酸信号传导途径。

水稻细菌性穗枯病菌分离条件的优化及产毒黄素观察

水稻穗枯病是水稻生产上重要的细菌性病害,目前针对其病原菌快速高效分离的体系很少有报道。本文以水稻细菌性穗枯病菌Burkholderia glumae标准菌株LMG2196为研究对象,探讨分析了B.glumae的生长温度、培养基上的菌落形态及对抗生素敏感性等。结果表明,选用含50μg/mL氨苄青霉素的KB平板划线,25℃培养36 h,可以快速高效分离B.glumae。B.glumae主要通过分泌毒黄素对寄主产生致病性,本文利用分光光度法测定了LMG2196菌株在不同温度以及营养条件下毒黄素的产生。LMG2196菌株在25～40℃之间均能产生毒黄素,在营养条件不同的LB和PPG液体培养基中,同一温度下,总体上表现为在PPG中产生的毒黄素要比LB中的多;且LB的最适产毒黄素温度是28～30℃,PPG的是37℃,表明毒黄素的产生与温度和营养条件有关。

水稻细菌性穗枯病的病原特性和抗性研究进展

水稻(Oryza sativa)细菌性穗枯病是世界性的重要病害之一,严重威胁全球范围水稻的高产稳产。虽然该病目前仍被列为我国的检疫性病害,但近几年的研究表明,穗枯病随时有在内地蔓延的潜在危险,因此除了加强检疫工作,开展针对性的防控技术研发也十分必要。水稻细菌性穗枯病菌在侵染过程中涉及多种毒力因子,同时,水稻在与病原菌的长期互作过程中演化出了多种防卫机制,抗性基因是主要的防卫机制之一。挖掘水稻基因组中抗细菌性穗枯病遗传位点并培育抗病品种是最安全且经济有效的防治途径。该文综述了水稻细菌性穗枯病的病原菌特性、发病特征、发病机制、病害循环和对水稻细菌性穗枯病的抗性研究现状,以期为挖掘和分离水稻穗枯病抗性位点提供参考。