Prophage region and short tandem repeats of “Candidatus Liberibacter asiaticus” reveal significant population structure in China

Whole-genome sequencing of “Candidatus Liberibacter asiaticus” (Las) indicated some polymorphic gene regions enabling the molecular characterization of this bacterium. Although the population diversity of Las in China has been previously studied, no reports have used a combination of a prophage region and short tandem repeat (STR) loci for phylogenetic relationship characterization. In this study, we investigated the genetic diversity and structure of 667 Las strains from nine provinces in southern China using multiple genetic loci including three type-specific prophage loci, two STR loci, and a miniature inverted-repeat transposable element (MITE) region. The results indicated that the genetic diversity varied according to the gene loci used. The prophage regions, including the MITEs, revealed significant genetic differences of Las populations in Yunnan and Guizhou from other provinces, while the STR loci only indicated a difference of Las population in Guizhou from those of other provinces. In particular, the Las population shown to be diverse in Jiangxi at the CLIBASIA_01215_STR locus was not diverse when measured using the other loci. Considering all loci, the Las populations from Yunnan and Guizhou were different, those from Guangdong and Guangxi were complex, while the Las population in Jiangxi was comparatively simple. Las populations from five neighbouring provinces, including Guangdong, Guangxi, Hunan, Fujian, and Jiangxi were grouped in a big cluster. The Las population structure changed with age according to the prophage type. This study evaluated the method used for studying the molecular diversity of Las populations and provided more detailed information on the geographical origin and epidemic trend of Chinese Las populations.     

花生青枯菌潜伏侵染的酶联免疫血清检测技术

采用酶联免疫吸附（ELISA）技术对花生青枯菌（Pseudomonassolanacearum）潜伏侵染进行检测，检测灵敏度为104菌／ml，对潜伏侵染的检测可准确到组织水平，样品制备可用缓冲液浸泡代替研磨，样品保存时间不影响检测效果。     

罗汉果青枯病病原菌株的鉴定

 The pathogen of Siraitia grosvenorii wilt was identified.Six strains were isolated from diseased plants of S.grosvenorii collected from Yongfu County in Guangxi.By using bacteriological identification,pathogenicity tests assay,16S rDNA sequence analysis,the S.grosvenorii wilt was caused by Ralstonia solanacearum.The results of pathogenicity and carbohydrate utilized test demonstrated that the pathogen belonged to race 1 and biovarⅢ of R.solanacearum.     

烟草根围土壤对主要烟草病害的拮抗放线菌株筛选及其鉴定

从采自我国烟草主要产区的38份土壤样品中分离获得放线菌296株.采用平板对峙培养法从中筛选出对烟草青枯病菌(Ralstonia solanacearum)和黑胫病菌(Phytophthora parasitica var.nicotianae)有拮抗活性的菌株227株,其中对青枯病菌拮抗活性较高的YYD3-17、YYD3-19、YYD3-29、YYD3-32和HLL4-9菌株抑菌圈直径达45 mm以上;对黑胫病菌拮抗活性较高的BXⅡ3-1、BXⅡ5-4、BXⅡ5-5、BXI21-1和YYD1-4菌株抑菌圈直径达25 mm以上.依据前人的研究成果,对这10株放线菌进行初步坚定,结果显示它们均属于链霉菌属(Strepto myces spp.).其中YYD3-17、YYD3-19、YYD3-29和YYD3-32属于灰红紫类群;BXⅡ3-1、BXI21-1同属于吸水类群;而BXⅡ5-4、BXⅡ5-5、YYD1-4和HLL4-9分属白色亚群、白孢亚群、金色亚群和绿色亚群.BXⅡ5-4和BXⅡ5-5分别被坚定为白色链霉菌种(S.albus)和阿布拉链霉菌种(S.aburviensis).     

马铃薯块茎青枯病菌潜伏侵染的酶联免疫学检测

试验采用武汉市场上来源不同产地的 7份马铃薯材料 ,用CIP提供的RS NCM ELISA试剂盒进行了块茎青枯病菌携带情况的检测。试验结果显示 ,应用该试剂检测马铃薯块茎青枯病菌携带情况具有较高的灵敏度 ;检测前样品的富集时间对检测结果具有明显的影响 ,其最佳富集时间为4 8h ;不同来源的马铃薯块茎携带青枯病菌的程度具有显著差异     

青枯雷尔氏菌在芝麻植株内的分布及消长动态

芝麻青枯病是我国南方芝麻生产上的重要土传病害。通过测定健康植株、不同发病时期的自然病株及人工接种病株内不同部位青枯雷尔氏菌数量,旨在明确病菌在芝麻植株内的分布及消长动态。结果表明:发病初期,病株内青枯雷尔氏菌总数量随着病情的发展而增加,之后随着病情严重度的加重而下降。病菌的致病力则随着病情发展呈现持续上升的趋势。检测的所有芝麻健株各部位均无青枯雷尔氏菌分布,说明芝麻植株不存在无症状侵染现象。青枯雷尔氏菌在芝麻病株内的分布呈现丰富的多态性,自然病圃和灌根接种的Ⅱ类、Ⅲ类病株各部位菌量分布随着植株高度的升高而递减,但其Ⅰ类病株中下部菌量却高于基部。针刺接种的Ⅰ类、Ⅱ类和Ⅲ类病株,接种点以下的根部和基部均有青枯雷尔氏菌分布,说明青枯雷尔氏菌不仅可随植物蒸腾向上扩散,也可向下蔓延。     

番茄新品种特宝1号苗期对青枯病的抗性测定

对从荷兰引进的番茄新品种特宝1号进行番茄青枯病（Ralstonia solanacearum）抗性测定试验,结果表明,该品种表现出较好的抗性.苗期人工接种后,30d才出现症状,比抗病品种抗青1号的发病时间推迟15d,发病率低且病害发展缓慢,校正发病率差异达到极显著水平.该品种还具有早熟、生长势强、不易早衰、丰产性好和特别耐贮运等特点.     

福州地区植物青枯病菌生理分化的研究

从福建省福州市的3个郊县（区）采集分离茄科作物青枯病菌青枯雷尔氏菌（Ralstonia solanacearum）菌株17个。对其中具代表性的7株用剪叶法接种鉴别寄主的结果表明,来自番茄、茄子、生姜和辣椒的青枯雷尔氏菌均属于生理小种1。对17个菌株根据其对乳糖、麦芽糖、纤维二糖和甘露醇、山梨醇、卫茅醇的利用能力以及对硝酸盐还原作用的测定结果表明：5个菌株属于生化型I,占29.4%;分别有1个菌株属于生化型II、III和IV;另有9个菌株不完全符合Hayward（1964）和何礼远（1983）的5个生化型标准,其中2株菌株能利用3 种双糖和甘露醇及山梨醇而不能利用甜醇,暂定为生化型Ⅲ-1。在供试的12个番茄青枯雷尔氏菌株中,4个为生化型I,2个为生化型III-1,1个为生化型IV,其余5个不符合生化型标准;供试的1个生姜青枯雷尔氏菌株不符合生化型标准;供试的2个茄子青枯雷尔氏菌株分别属于生化型II和III;供试的2个辣椒青枯雷尔氏菌株中,1个为生化型I,1个不符合生化型标准。     

一种引起茄科作物病害的病原:Candidatus Liberibacter solanacearum

Candidatus Liberibacter solanacearum是Liefting等人于2009年鉴定并命名的一种能够引起茄科作物病害的新病原,该病菌可引起茄科作物植株矮化、畸形并造成巨大的经济损失。目前该病菌在我国尚无分布。本文从病原鉴定、寄主范围、地理分布、传播途径、危害情况及防控措施等几方面对该病菌进行了简要介绍,以期引起重视,并为防范其入侵提供参考。