稻镰状瓶霉促进水稻生长的机制

稻镰状瓶霉Falciphora oryzae是本实验室从野生稻根系分离获得的一株DSE,具有促生、防病等作用。本研究旨在对其促生机制进行初探。在室内平板共培养条件下,对水稻种子接种稻镰状瓶霉菌饼（4个/皿）,测定植株生长指标、营养元素含量及营养吸收相关基因表达量;温室盆栽条件下,将稻镰状瓶霉以菌肥形式（60g/桶）与水稻进行盆栽共培养,测定植株农艺性状指标。结果表明,接种稻镰状瓶霉后,平板上的水稻幼苗的株高、叶宽和茎秆直径显著增加,根长并未受影响。稻镰状瓶霉能够促进水稻根系对营养元素的吸收,提高地上部分和根系组织中N、P、K、S、Fe和Mg元素的含量,诱导根部与营养元素吸收相关的调控基因OsPTR9、OsAMT3;2、OsPT4、OsSULTR3;1、OsMRS2-8、OsHAK16、OsYSL15和OsIRO2的显著上调表达。盆栽试验表明,稻镰状瓶霉显著提高了水稻各农艺性状指标,包括叶宽、茎秆直径、植株鲜重、植株干重、叶绿素含量和光合强度。结果表明,稻镰状瓶霉的根部定殖能够诱导营养元素吸收相关基因的上调表达,从而促进根系对营养元素的吸收,进而促进水稻植株的生长。     

水稻白叶枯病抗性基因的研究与分子育种

由革兰氏阴性菌黄单孢水稻变种（Ｘａｎｔｈｏｍｏｎａｓ ｏｒｙｚａｅ ｐｖ．ｏｒｙｚａｅ,Ｘｏｏ）引起的白叶枯病是世界水稻生产中最严重的细菌性病害。白叶枯病是一种维管束病害,自然条件下,病菌通常由水孔或伤口侵入,沿叶脉产生灰白色病斑。田间常在分蘖期观察到病症,并随植株的生长而发展,至抽穗期达到高峰。水稻遭受白叶枯病后,一般减产２０％－３０％,严重时甚至绝收。白叶枯病最早于１８８４年在日本福岗地区发现     

水稻抗白叶枯病基因Xa21的研究进展

Xa21是最早克隆的水稻抗病基因,作为类受体激酶类广谱抗病基因它受到广泛的关注。转基因Xa21材料,很可能成为世界上第一个被批准进行大田释放的水稻转基因材料。本文在简要回顾Xa21的发现、定位和克隆过程之后,总结了目前Xa21基因的抗病作用机理和育种应用研究现状,包括XA21蛋白质激酶的生化特性、AvrXa21的鉴别、Xa21介导的抗病途径、抗病机理等,并对今后的研究进行了展望。     

水稻抗白叶枯病基因及其应用研究进展

由黄单胞菌水稻变种Xanthomonas oryzae pv.Oryzae（Xoo）引起的白叶枯病是水稻重要病害之一。目前,已有37个水稻白叶枯抗性基因被鉴定并报道,其中28个被定位到染色体上,7个被克隆。本文简要综述了水稻白叶枯抗性基因的鉴定、定位和克隆的进展,并讨论了合理利用抗性基因防治白叶枯病的前景。     

用PCR技术诊断水稻的白叶枯病抗性

植物育种中应用分子标记辅助选择要求分子标记与目的基因紧密连锁,而且分析手段经济简便、重复性好。Ｘａ２１是最近发现的一个具有广谱抗性的水稻白叶枯病抗性基因,利用一个含Ｘａ２１基因的品系ＩＲＢＢ２１分别与２个感病品种杂交获得２个Ｆ_２群体。用４对引物分别对３个亲本进行ＰＣＲ分析,其中一对引物（ＰＢ７８）的ＰＣＲ产物在抗、感病品种间可揭示多态性。对２个Ｆ_２群体进一步的遗传分析表明,ＰＣＲ标记和Ｘａ２１的白叶枯病抗性紧密连锁,其重组率仅为２．４８％。根据该标记选择基因型纯合的抗性植株,其准确率可达１００％。本文还就植物育种中分子标记的检测途径进行了评价。     

云南“大粒水稻”对稻白叶枯病的抗性遗传

云南地方品种——云南大粒抗水稻白叶枯病菌“江陵691”,其抗性由2对具重叠作用的隐性抗性基因控制,与IR28、南粳15的显性抗病基因不等位;也与已命名的xa-5、xa-8、xa-9和xa-13 4个抗性基因也不等位。     

水稻细菌性条斑病和白叶枯病抗性遗传研究

分析了Ｈａｓｈｉｋａｌｍｉ,Ｄｕｌａｒ和９０ＩＲＢＢＮ４４三个抗源品种对水稻细菌性条斑病Ｓ－１０３菌株和白叶枯病Ｐ１菌系的抗性遗传。结果表明,Ｈａｓｈｉｋａｌｍｉ和Ｄｕｌａｒ对Ｓ－１０３的抗性均由２对隐性基因所控制,９０ＩＲＢＢＮ４４则带有１对隐性抗性基因。经等位性测定表明,Ｈａｓｈｉｋａｌｍｉ和Ｄｕｌａｒ的２对基因中至少有１对是等位的,但它们与９０ＩＲＢＢＮ４４的１对基因均不等位。３个抗源品种对Ｐ１的抗性都受１对隐性基因控制,该基因与ｘａ－５等位。连锁遗传分析表明,Ｈａｓｈｉｋａｌｍｉ和Ｄｕｌａｒ对Ｓ－１０３的２对抗细条病基因中的１对与ｘａ－５相连锁,而９０ＩＲＢＢＮ４４的１对抗性基因与ｘａ－５呈独立遗传。本文还就开展水稻抗细菌性条斑病育种进行了讨论。     

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）。     

水稻抗白叶枯病基因的鉴定、定位和克隆进展

由水稻黄单胞菌水稻变种Xoo引起的水稻白叶枯病是全球性的重要病害之一。已有31个水稻白叶枯抗性基因被鉴定并报道,其中18个被定位到染色体上,5个被克隆。简要综述了水稻白叶枯抗性基因的鉴定、定位和克隆的进展,并讨论了合理利用抗性基因防治白叶枯病的前景。     

内生真菌与禾本科植物之间的关系及其生态学意义

1　前　言内生真菌是一类生长在植物体内的真菌 ,至今已在许多高等植物中发现了内生真菌的存在 ,但以禾本科植物中尤为常见。这些真菌包括子囊菌纲、麦角菌科 (Ｃｌａｖｉｃｉｐｉｔａｃｅａｅ)、瘤座菌族 (Ｂａｌａｎ ｓｉｅａｅ)的许多种类 ,也包括与瘤座菌族关系密切的一些半知菌类 ,如Ａｃｒｅｍｏｎｉｕｍ[1 5] 。与菌根真菌的一个显著不同是 ,它们仅存在于植物地上部分的组织内而不是根的组织中。至少有 80个属、几百种禾本科植物被确认含内生真菌[1 6] ,但到目前为止 ,大量的研究都集中在两个有重要经济意义的植物种 ,即高羊茅 (Ｆｅ…     

云南30个水稻品种对水稻白叶枯病的抗性评价

【目的】水稻白叶枯病是一种严重危害水稻的细菌性病害,培育抗性品种是治理该病害的重要途径。因此,明确云南水稻材料对检疫性病害水稻白叶枯病的抗性,可以为该病害的防治与监测、水稻栽培的合理布局和良好抗性资源的获取提供依据。【方法】采用剪叶接种法测定云南稻区30个品种对7个不同致病型白叶枯病菌的抗性。【结果】在供试的30个云南水稻品种中,2个品种(玉粳16和JS42糯稻)对7个不同致病型菌株均表现为抗性;15个品种对7个致病型菌株均表现感病;对HEN11、SCYC-6、YN7、YN11、FUJ、YN241和PX099等7个致病型菌株表现抗性的水稻品种分别占26.67%、16.67%、23.33%、13.33%、6.67%、10.00%和20.00%。此外,区试材料的抗性比例高于主栽品种,地方稻未发现抗性品种。【结论】现在生产上的大部分水稻品种对优势致病型病原菌入侵的抵抗能力降低甚至丧失。针对云南地区的优势致病小种FUJ筛选得到2个抗性品种:玉粳16和JS42糯稻。     

The genome sequence of Xanthomonas oryzae pathovar oryzae KACC10331, the bacterial blight pathogen of rice

The nucleotide sequence was determined for the genome of Xanthomonas oryzae pathovar oryzae (Xoo) KACC10331, a bacterium that causes bacterial blight in rice (Oryza sativa L.). The genome is comprised of a single, 4 941 439 bp, circular chromosome that is G + C rich (63.7%). The genome includes 4637 open reading frames (ORFs) of which 3340 (72.0%) could be assigned putative function. Orthologs for 80% of the predicted Xoo genes were found in the previously reported X.axonopodis pv. citri (Xac) and X.campestris pv. campestris (Xcc) genomes, but 245 genes apparently specific to Xoo were identified. Xoo genes likely to be associated with pathogenesis include eight with similarity to Xanthomonas avirulence (avr) genes, a set of hypersensitive reaction and pathogenicity (hrp) genes, genes for exopolysaccharide production, and genes encoding extracellular plant cell wall-degrading enzymes. The presence of these genes provides insights into the interactions of this pathogen with its gramineous host.     

Breeding bacterial blight-resistant hybrid rice with the cloned bacterial blight resistance gene Xa21

The cloned bacterial blight (BB) resistance gene Xa21 was transferred into Minghui63, a widely used restorer line of indica hybrid rice in China, through an Agrobacterium-mediated system. Molecular and resistance analyses revealed that the Xa21 gene was integrated in the genomes of transgenic plants and their progeny inherited resistance stably. For the purpose of hybrid breeding, Xa21 transgenic homozygous restorer lines were selected through `within-lane' dosage comparison of hybridization signal in combination with PCR and resistance analyses. The selected transgenic restorer lines were then crossed with a commonly used sterile line, Zhenshan97A, to produce Xa21 transgenic hybrid rice, Shanyou63-Xa21. The hybrid rice plants with Xa21 displayed high broad-spectrum resistance to Xanthomonas oryzae pv. oryzae (Xoo) races and maintained elite agronomic characters of Shanyou63. The propagation of this BB-resistant hybrid variety with Xa21 will benefit rice production.     

Cocculus hirsutus extract inhibits the Xanthomonas oryzae pv. oryzae,the bacterial leaf blight pathogen in rice

Plant-derived natural bactericides and their possible applications in agriculture to control plant bacterial diseases has intensified as this approach has enormous potential to inspire and influence modern agro-chemical research. Naturally occurring and biologically active plant products such as essential oils and organic extracts could be a source of alternative classes of natural biopesticides to serve as templates for new and more effective compounds in controlling plant pathogenic micro-organisms. In the present study, the efficacy of six plants extracts from different solvent system were tested for their antibacterial activity aganist Xanthomonas oryzae pv. oryzae both in vitro and in vivo. Among these extracts, Cocculus hirsutus leaf chloroform extract exhibits significant antibacterial activity against X. oryzae pv. oryzae. Data obtained from the experiments such as minimum inhibitory concentration, effect of C. hirsutus leaf chloroform extract on the incidence of X. oryzae pv. oryzae, phytotoxicity test and effect of C. hirsutus leaf chloroform extract on seed germination and seedling vigour, along with the in vivo experiments under greenhouse conditions showed significant improvement over controls. Thus, the present study demonstrated that the C. hirsutus leaf chloroform extract posses antibacterial activity against bacterial leaf blight pathogen of rice.     

Marker assisted selection of bacterial blight resistance genes in rice

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae is one of the most important diseases affecting rice production in Asia. We were interested in surveying rice genotypes that are popularly used in the Indian breeding program for conferring resistance to bacterial blight, using 11 STMS and 6 STS markers. The basis of selection of these DNA markers was their close linkage to xa5, xa13, and Xa21 genes and their positions on the rice genetic map relative to bacterial blight resistance genes. Eight lines were found to contain the xa5 gene while two lines contained Xa21 gene and none of the lines contained the xa13 gene with the exception of its near-isogenic line. Using the polymorphic markers obtained in the initial survey, marker-assisted selection was performed in the F3 population of a cross between IR-64 and IET-14444 to detect lines containing multiple resistance genes. Of the 59 progeny lines analyzed, eight lines contained both the resistance genes, xa5 and Xa4.     

Induction of bacterial blight (Xanthomonas oryzae pv. oryzae) resistance in rice by treatment with acibenzolar-S-methyl

The role of the plant defence activator, acibenzolar‐S‐methyl (ASM), in inducing resistance in rice against bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) was studied. Application of ASM induced resistance in rice to infection by Xoo. When the pathogen was clip‐inoculated to the rice plants, it caused bacterial leaf blight symptoms in the untreated control. However, in the rice plants pretreated with ASM, infection was significantly reduced. Induced systemic resistance was found to persist for up to 3 days in the pretreated rice plants. Increased phenolic content and accumulation of pathogenesis‐related (PR) proteins, viz. chitinase, β‐1,3‐glucanase and thaumatin‐like protein (TLP; PR 5) were observed in rice plants pretreated with ASM followed by inoculation with Xoo. Immunoblot analysis using rice TLP and tobacco chitinase antiserum revealed rapid induction and over‐expression of 25 and 35 kDa TLP and chitinase, respectively, in rice in response to pretreatment with ASM followed by Xoo inoculation. Based on these experiments, it is evident that induction of disease resistance in rice was accelerated following treatment with ASM.     

Stable resistance to bacterial blight disease in rice

Ten rice cultivars were evaluated for stable resistance to 18 isolates of Xanthomonas campestris pv. oryzae. Stable performance of the host cultivar was evaluated by regressing the cultivar means on the mean level of pathogenicity of the isolates averaged over all cultivars. A cultivar with low disease incidence, a regression coefficient near or equal to zero (b= 0) and the deviation from regression as small as possible (S²_d= 0) was considered highly stable while that with low disease incidence, b= 1 -0 and S²_d= 0 was considered to possess average stability. Accordingly, cvs TKM-6, CB II, DV 85 and Ramakrishna were considered to possess average stability while IR 20 and Indira were the most stable. Cvs Cemposelak, IR 1545, BJ 1 and IR 8 showed high response to disease incidence with relatively small changes in level of pathogenicity of the isolates and hence were considered most unstable. The regression technique was considered as a valuable tool for identification of stable resistance to bacterial blight disease of rice.