水稻白叶枯病菌的RAPD分型

对植物病原菌的分型是生物技术应用的新领域,水稻白叶枯病菌(Xanthomonas oryzae pv． Oryzae)是亚洲地区水稻的主要病害。前人曾根据不同菌株在5个鉴别品种上的反应型将中国白叶枯病菌分为7个致病型⑴。近来,Leach等⑵已开始利用基因组特异的重复顺序对白叶枯病菌株进行DNA指纹分析,章琦等⑶也利用相同的探针对我国部分菌株进行了RELP分型,其结果与传统病理学的分类结果有相符之处．但又有相当的不同,说明传统分类结果尚有许多值得探索之处。与RFLP相比,RAPD(Random　Amplified Polymorphic DNA)具有简便和快速的优点,而且相当灵敏,在动植物基因组分型(gennome typing)上已得到较为广泛的应用〔4.5〕。我们利用RAPD标记对我国28个菌株进行分型,发现随机引物A－14可用以区分所研究的28个菌株。进而对扩增带型进行了相似百分率分析,并利用另一随机引物A一1 3作了进一步分析。本文是用RAPD方法尝试对部分水稻白叶枯病菌分型的首次报道。     

水稻主基因-多基因混合遗传控制白叶枯病抗性的基因效应分析

利用主基因－多基因混合遗传模型分析了５个抗感交组合对水稻白叶枯病菌抗性的基因效应,结果表明５个组合中的３个主基因抗性遗传符合德尔分离比的前提下存在多基因抗性,而且这３个组合彼此间抗病基因的加性效应,主基因和多基因遗传方差及其遗传率存在变异。说明水稻白叶枯病抗性虽以主基因作用为主,但考虑到抗性的持久性,建议在水稻白叶枯病育种中构建主基因－多基因混合遗传体系,以有效抑制白枯病菌群体中小种的波动。     

水稻对白叶枯病Xanthomonas oryzae pv.Oryzae水平抗性的数量性状位点(QTL)定位

利用“Lemont/特青”重组自交系（RI）群体研究了水稻对白叶枯病致病菌株CR6的水平抗性。双亲和F1均为感病,重组自交系（RILs）的病斑长度（LL）为带有明显双向超亲的连续变异,显示出典型的多基因遗传特征。部分重组自交系（约占总数90％）对CR6表现高水平抗性（LL≤3cm）。利用由178个良好分离的RFLP标记构建的饱和连锁图,鉴定出11个数量形状位点（QTLs）和3对互作位点解释了RI群体的大部分病斑变异。抗性QTLs定位于水稻第2、3、4、8、9、10、11、12等8条染色体。在来自特青的Xa－4位点上检测到一个有很大加性效应的QTL。其余10个QTLs的抗性等位基因有7个来自特青,3个来自Lemont。研究结果表明多个数量性状位点和失效主基因（Xa－4）残效的累加效应构成了对白叶枯病水平抗性的遗传基础,是重要的抗性组成部分。可以预期在DNA标记的辅助下,这些数量性状位点与主效抗性基因的组合将使水稻品种具有持久抗病性。     

Analysis of Pathogenic Diversity of the Rice Bacterial Blight Pathogen (Xanthomonas oryzae pv. oryzae) in the Andaman Islands and Identification of Effective Resistance Genes

Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major disease of rice in the tropics for which genetic resistance in the host plants is the only effective solution. This study aimed at identification of resistance gene combinations effective against Xoo isolates and fingerprinting of the Xoo isolates of Andaman Islands (India). Here, we report the reaction of 21 rice BB differentials possessing Xa1 to Xa21 genes individually and in different combinations to various isolates of pathogen collected from Andaman Islands. Pathological screening results of 14 isolates revealed that among individual genes tested across 2 years, Xa4, Xa7 and Xa21 conferred resistance reaction across all isolates, whereas among combinations, IRBB 50 (Xa4 + xa5), IRBB 52 (Xa4 + Xa21) and IRBB 60 (Xa4 + xa5 + xa13 + Xa21) conveyed effective resistance against tested isolates. The nature of genetic diversity among four isolates selected on the basis of geographical isolation in the islands was studied through DNA finger printing. The RAPD primers S111, S119, S1117, S1109, S1103, S109 and S105 were found to be better indicators of molecular diversity among isolates than JEL primers. The diversity analysis grouped 14 isolates into three major clusters based on disease reaction wherein isolate no. 8 was found the most divergent as well as highly virulent. The remaining isolates were classified into two distinct groups. The importance of the study in the context of transfer of resistance gene(s) in the local cultivars specifically for tropical island conditions is presented and discussed.     

Novel Candidate Virulence Factors in Rice Pathogen Xanthomonas oryzae pv. oryzicola as Revealed by Mutational Analysis

Bacterial leaf streak, caused by Xanthomonas oryzae pv. oryzicola, is an important disease of rice. Transposon-mediated mutational analysis of the pathogen with a quantitative assay revealed candidate virulence factors including genes involved in the pathogenesis of other phytopathogenic bacteria, virulence factors of animal pathogens, and genes not previously associated with virulence.     

镍处理对水稻叶片H_2O_2 积累和抗病的诱导效应

2 .2 0mmol/L的硝酸镍处理水稻幼苗后第 3天用稻白叶枯菌 (Xanthomonasoryzaepv .oryzae)挑战接种 ,硝酸镍处理的稻苗病情比对照明显减轻 ,并且叶片中过氧化物酶 (POD)活性上升 ,过氧化氢酶 (CAT)和抗坏血酸过氧化物酶 (APX)活性明显下降 ,H2 O2 和丙二醛 (MDA)含量显著增加。这些结果表明 ,H2 O2 积累与镍诱导的抗病作用密切有关     

Role of Seed in Survival and Transmission of Xanthomonas campestris pv. oryzae Causing Bacterial Blight of Rice

Survival period and possibility of seed transmission of X. campestris pv. oryzae were studied. The bacterium survived for longer (170–180 days) in kharif than rabi (120–130 days) harvested seed. The percentage of infected seeds was higher in kharif than rabi. The infected seed when sown failed to produce the symptoms on respective seedlings due to the low number of bacterial population. Present studies indicated that infected seed though may not produce symptoms on the seedlings directly but serve as a source of inoculum form season to season.     

体细胞突变体HX-3抗水稻白叶枯病基因的鉴定

以感病杂交稻恢复系明恢63的成熟胚为外植体,利用离体筛选技术获得了抗水稻白叶枯病细胞突变体HX-3。连续8年以我国长江流域白叶枯病代表菌析浙173（IV型）对HX-3的R1到R9代进行抗性鉴定,HX-3的抗病性可以稳定遗传。抗性遗传分析表明HX-3的抗性由1对显性核基因控制。1999～2000年连续两年利用我国、菲律宾和日本的32个水稻白叶枯病菌株,测定HX-3及IRBB1等13个具不同显性抗病基因的近等基因系抗性,HX-3抗谱广,且与已知显性抗病基因的抗谱不同。在此基础上,以抗白叶枯病近等基因系IRBB4、IRBB7、CBB12和IRBB21和HX-3杂交,进行等位性分析,4个杂交组合的F2代均出现抗、感分离,说明HX-3与这4个基因不等位。综合以上研究结果,HX-3具有1个新的抗白叶枯病基因,暂命名为Xa-25(t）。     

Dynamic and Coordinated Expression Changes of Rice Small RNAs in Response to Xanthomonas oryzae pv.oryzae

Endogenous small RNAs are newly identified players in plant immune responses, yet their roles in rice(Oryza sativa) responding to pathogens are still less understood, especially for pathogens that can cause severe yield losses. We examined the small RNA expression profiles of rice leaves at 2, 6, 12, and 24 hours post infection of Xanthomonas oryzae pv. oryzae(Xoo) virulent strain PXO99, the causal agent of rice bacterial blight disease. Dynamic expression changes of some mi RNAs and trans-acting si RNAs were identified, together with a few novel mi RNA targets, including an RLK gene targeted by osa-mi R159 a.1. Coordinated expression changes were observed among some small RNAs in response to Xoo infection, with small RNAs exhibiting the same expression pattern tended to regulate genes in the same or related signaling pathways, including auxin and GA signaling pathways, nutrition and defense-related pathways. These findings reveal the dynamic and complex roles of small RNAs in rice-Xoo interactions, and identify new targets for regulating plant responses to Xoo.     

非寄主抗病基因Rxo1介导的水稻对Xanthomonas oryzae pv.oryzicola的抗病反应

通过表型鉴定、反转录PCR和实时定量PCR方法,利用转基因和非转基因水稻植株,研究由Rxol基因介导的,水稻对细菌性条斑病菌的抗性反应。结果观察到3个涉及过敏性反应的基因由Rxol基因诱导表达,并对其进行了分析。这3个基因参与编码病程相关蛋白,在转基因水稻植株中呈上调表达,表明水杨酸信号转导途径在抗性反应中发挥重要的作用。     

New Multilocus Variable-Number Tandem-Repeat Analysis Tool for Surveillance and Local Epidemiology of Bacterial Leaf Blight and Bacterial Leaf Streak of Rice Caused by Xanthomonas oryzae

Multilocus variable-number tandem-repeat analysis (MLVA) is efficient for routine typing and for investigating the genetic structures of natural microbial populations. Two distinct pathovars of Xanthomonas oryzae can cause significant crop losses in tropical and temperate rice-growing countries. Bacterial leaf streak is caused by X. oryzae pv. oryzicola, and bacterial leaf blight is caused by X. oryzae pv. oryzae. For the latter, two genetic lineages have been described in the literature. We developed a universal MLVA typing tool both for the identification of the three X. oryzae genetic lineages and for epidemiological analyses. Sixteen candidate variable-number tandem-repeat (VNTR) loci were selected according to their presence and polymorphism in 10 draft or complete genome sequences of the three X. oryzae lineages and by VNTR sequencing of a subset of loci of interest in 20 strains per lineage. The MLVA-16 scheme was then applied to 338 strains of X. oryzae representing different pathovars and geographical locations. Linkage disequilibrium between MLVA loci was calculated by index association on different scales, and the 16 loci showed linear Mantel correlation with MLSA data on 56 X. oryzae strains, suggesting that they provide a good phylogenetic signal. Furthermore, analyses of sets of strains for different lineages indicated the possibility of using the scheme for deeper epidemiological investigation on small spatial scales.     

镍处理对水稻叶片H202积累和抗病的诱导效应

2.20mmol/L的硝酸镍处理水稻幼苗后第3天用稻白叶枯(Xanthimonasoryzaepv.oryzae)挑战接种,硝酸镍处理的稻苗病情比对照明显减轻,并且叶片中过氧化物酶(POD)活性上升,过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性明显下降,H     

Changes in the Plasma Membrane Distribution of Rice Phospholipase D during Resistant Interactions with Xanthomonas oryzae pv oryzae

Phospholipase D (PLD; EC 3.1.4.4), which hydrolyzes phospholipids to generate phosphatidic acid, was examined in rice leaves undergoing susceptible or resistant interactions with Xanthomonas oryzae pv oryzae. RNA analysis of leaves undergoing resistant interactions revealed different expression patterns for PLD over 5 days relative to control plants or those undergoing susceptible interactions. By using an activity assay and immunoblot analysis, we identified three forms of PLD (1, 2, and 3). PLD 1 was observed only at 1 day after tissue infiltration. PLDs 2 and 3 were detected up to 3 days in all interactions. Immunoelectron microscopy studies revealed PLD to be associated predominantly with the plasma membrane. In cells undergoing a susceptible response, PLD was uniformly distributed along the plasma membrane at 3, 6, 12, and 24 hr after inoculation. However, within 12 hr after bacterial challenge in resistant interactions, PLD was clustered preferentially in membranes adjacent to bacterial cells.