玉米茎腐病菌毒素致病力初报

通过提取玉米茎腐病菌毒素粗提液,证实玉米茎腐病原菌(镰刀菌和腐霉菌为主)在镰刀菌毒素培养液、查氏培养液和普通培养液中,能产生和玉米小斑病菌毒素(简称HM毒素,下同)类似的致病毒素。该物质能抑制种子根的生长。接种在玉米叶片上能产生典型的萎蔫枯死斑;用上述3种培养液培养病原菌,产生的毒素致病力差异不显著;不同类型病原菌产生的毒素致病力和同一类型病原菌不同菌株产生的毒素致病力差异都极显著。玉米品系对茎腐病原菌产生的毒素抗病性差异也极显著。     

小豆白粉病菌的鉴定与小豆品种抗白粉病评价

为明确小豆白粉病病原菌的种类以及小豆种质资源对白粉病的抗性,采用形态学和系统发育学方法对近年来在北京市发生的小豆白粉病病原菌种类进行鉴定,并采用室内苗期人工接种法评价小豆常见栽培品种（系）对白粉病的抗性。结果表明,从北京市采集的感白粉病小豆病样中培养获得病原菌BJ1,该菌能在小豆叶片和茎上产生明显的白色粉斑,分生孢子梗直立,不分枝,分生孢子单细胞,成链状着生于分生孢子梗上,呈椭圆形或卵圆形。通过rDNA-ITS序列系统发育分析,小豆白粉病菌BJ1被鉴定为白粉菌目白粉菌科的苍耳叉丝单囊壳Podosphaera xanthii。室内苗期人工接种条件下,19个供试小豆品种（系）接种小豆白粉病菌BJ1后均可发病,其中9个审定品种均表现为中度感病或高度感病,10个优良品系发病略轻。     

脱氧雪腐镰刀菌烯醇( DON) 在小麦籽粒中的积累分析

 镰刀菌产生的脱氧雪腐镰刀菌烯醇(deoxynivalenol,DON)污染小麦后对人畜具有较大的毒害作用。为明确DON毒素在小麦籽粒中的积累数量及其与镰刀菌菌株、接菌数量、小麦品种和病害严重度的关系,试验采用单花滴注方法在5个抗病性不同的小麦品种上分别接种9 个禾谷镰刀菌菌株,每个菌株接种1 × 106 、1 × 105 和1 × 104 个/ mL 3 个分生孢子浓度,并利用ELISA 法测定收获麦粒中DON 毒素含量。结果表明,麦粒中DON 毒素含量差异主要是由于不同禾谷镰刀菌菌株产生毒素能力不同所致。接种菌株8003、4020 的所有麦粒中DON 毒素含量均显著高于相同条件下接种其他7 个菌株的小麦。当接种产毒素能力强的菌株时,小麦抗病品种表现出在一定程度上降低DON 毒素积累的能力。不同接菌浓度对小麦赤霉病的发病程度和麦粒中DON 毒素含量有显著影响,在相同条件下,接菌浓度越高,病害严重度越高,DON 毒素含量也越高;反之,接菌浓度越低,病害严重度越低,DON 毒素含量也越低。     

茶一新病害——茶萎芽病研究

茶萎芽病害是茶场中严重病害之一。据3年来的研究结果认为,每年7～8月高温季节,引起茶树芽梢枯萎,主要是由茶萎芽病菌所致。此病原菌在适温28～30℃时,人工接种2～4天后茶芽出现症状,4～6天茶芽枯萎,14天左右能产生分生孢子器,分生孢子器洋梨形或球形、炭质黑色、直径159.6～292.6微米。分生孢子椭圆形或卵形,初期无色单胞,后为淡橄榄色,中间具一隔膜无收缩,表面平滑无纹,大小为19.2～25.6×9.6～12.8微米。通过对病原菌的分离、培养、接种并对分生孢子器和分生孢子大小、形态特性、生理及寄主范围等的测定,认为此病原菌是壳色单隔孢属(Diplodia Fr.)中的一个种。经查阅国内外文献资料,目前在茶上此病尚未见报道,因此暂定此病原菌为 Diplodia sp.,由此病原菌引起的茶树病害定名为茶萎芽病。此外,根据本病的特性和诱病因子,在防治上还提出了建议。     

龙船花赤枯病病原菌鉴定及其生物学特性测定

采用离体接种法对龙船花叶部病害的一种真菌进行了鉴定和生物学特性测定。结果表明,致病性测定与田间症状相似。通过对病原菌形态学、rDNA-ITS和β-微管蛋白序列的综合分析,确定该病原菌为龙船花拟盘多毛孢(Pestalotiopsis ixorae)。生物学特性测定表明,菌丝生长和分生孢子萌发最适温度为25℃,最适pH分别为6和7;光照更有利于菌丝生长;碳源以可溶性淀粉和D-甘露糖、氮源以硝酸钠最利于菌丝生长;分生孢子在液态水中萌发率最高,为85.3%;菌丝致死温度为50℃10 min,分生孢子致死温度为50℃20 min或55℃5 min。     

利用GFP荧光标记比较大丽轮枝菌对抗/感马铃薯品种的侵染过程

为了对马铃薯黄萎病菌的系统侵染进行研究，本研究首先建立了用于观察大丽轮枝菌侵染马铃薯过程的培养皿滤纸体系，在此基础上利用带有GFP标记的大丽轮枝菌对不同抗性水平马铃薯根系侵染过程进行了比较研究，结果表明：马铃薯根系在浓度为10⁷个·mL^-1的大丽轮枝菌分生孢子液中浸泡处理2 h后，分生孢子可附着在抗/感马铃薯根系的根毛上，单个视野中感病品种根系上分生孢子附着平均数量为65个，显著高于抗病品种根系上附着的分生孢子数量(23个);接种12 hpi,根系上附着的分生孢子开始萌发，但抗/感品种根系表面孢子的萌发率无显著差异；接种3 dpi后，菌丝体能够突破根系表皮，进入细胞间隙，但感病品种根系中菌丝的扩展速度更快，并在7 d后到达根系的维管束内部；而抗病品种则在接种9 dpi,在维管束内才能够观察到绿色荧光信号；接种10 dpi,感病品种根系中可见新的分生孢子梗和分生孢子形成，而抗病品种中未见有分生孢子的形成。接种30 dpi,感病品种地上部茎杆中定殖的病原菌量是抗病品种的5倍以上；同时，感病品种叶柄中的病原菌数量也显著高于抗病品种。     

芒果叶片对炭疽病的阶段抗性

为了研究芒果叶片对炭疽病的阶段抗性,在室内人工接种和田间自然发病条件下,对3个芒果品种的不同成熟度叶片的抗病性进行了鉴定,并测定了病原菌分生孢子在不同成熟度叶片表面的萌发率和附着胞形成率.结果表明,在室内人工接种条件下,随着芒果叶片逐渐成熟,对炭疽病的抗性逐渐增强,处于幼嫩期的古铜色叶片最为感病,病情指数在97.0以上,淡绿色叶片表现抗病,病情指数在2.0～2.5之间,成熟的老叶表现高抗或近免疫,病情指数为0.田间自然发病调查结果与室内试验结果基本一致,说明幼嫩的古铜色阶段是芒果叶片对炭疽病的易感期.随着芒果叶片成熟度的提高,病原菌分生孢子萌发率和附着胞形成率有下降的趋势,在古铜色叶片、淡绿色叶片和老叶表面分生孢子萌发率分别为98.1%～99.2%、95.0%～97.0%和86.0%～92.0%,附着胞形成率分别为74.4%～81.0%、70.0%～77.8%和63.4%～69.9%.     

国内橡胶树主要种质对棒孢霉落叶病的抗性评价

棒孢霉落叶病是近年来我国橡胶树新发病害, 发生面积和危害程度有逐年加重的趋势, 已经成为相关产业发展的潜在限制性因素。培育和种植抗病种质是防治该病最经济有效的控制措施, 而育种材料的抗性评价是相关工作的前提。在前期工作基础上, 本研究通过4种方法对国内46份橡胶树主要种质进行了抗病性评价。结果发现, 不同接种方法获得的抗病性评价结果基本一致, 且抗感种质间的差异达到了极显著水平。在供试的46份橡胶种质中, 高抗(HR)种质3份, 占6.52%, 中抗(MR)种质13份, 占28.26%, 轻感(S)和中感(MS)种质各11份, 分别占23.92% , 高感(HS)种质8份, 占17.40%。     

水稻纹枯病流行、预测及损失测定

1982年在美国路州大学水稻试验站进行本试验。流行学研究结果表明,品种抗病性、接种体数量是影响纹枯病发展的重要因素。Mars、Melrose 等品种具有中等抗病性,Lebonnet、Belmont 和 Labelle 等品种最感病,Saturn、Le-ah 和 Brazos 则属中等感病。从品种抗病性和接种量的相互作用关系中看出,品种抗病性在决定病害严重度上作用更大。病害系统观察发现,水稻不同生育期的感病率与成熟期病害严重度呈高度正相关。据此建立了不同抗病水平品种的病害严重度预测模式。纹枯病对不同抗病水平品种的为害损失测定结果表明,感病品种损失率为29%,中等感病种为22%,中等抗痫种为9%。试验发现,水稻拔节期及孕穗期的稻秆感病率与产量损失有中度至高度正相关。据此,亦建立了产量损失预测模式。结论认为防治水稻纹枯病的根本途径是选育和推广抗病高产品种;中抗以上的品种能满足生产防治需要,不必施行其他防治措施。     

水稻叶鞘腐败病的研究——Ⅰ.病原菌的致病性及发病的影响因子

 本文阐述了水稻叶鞘腐败病病原菌Sarocladium oryzae,在水稻各生育期和植株不同部位的叶鞘上之致病性以及由此产生的各种症状。该病原菌不仅在水稻各生育期发生危害,还能侵害叶鞘、谷粒、叶片中脉等。水稻剑叶叶鞘受害,常呈现为典型叶鞘腐败病病斑以及"紫鞘"或"紫鞘黄叶"症状。病谷常引起秧苗发病。发病的最适温度为30℃、湿度为70%(RH)。但发病对温湿度要求并不甚严格。适当的氮、磷、钾配比和适量施用能提高植株的抗病性,氮肥过多或缺乏均会加剧病害的发生与危害。品种的抗病性有着明显差异,但与水稻类型无关。以病原菌分生孢子液对21个常见杂草和野生稻接种,其中属于禾本科的15个种可引起发病。经田间调查,该病原菌也在自然条件下侵染若干禾本科杂草。     

海南橡胶树棒孢霉落叶病菌毒素蛋白基因检测与致病性分析

Cassiicolin毒素蛋白是橡胶树棒孢霉落叶病菌的主要致病因子。本研究对分离自海南省5个市县的橡胶树棒孢霉落叶病菌进行了鉴定,形态学鉴定结合分子生物学鉴定结果表明,病原菌为多主棒孢。利用Cassiicolin毒素不同亚型编码基因特异性引物和菌饼活体接种法分别鉴定了分离菌株的毒素蛋白类型和致病性,结果显示,分离的35个菌株都含有Cas5基因,未发现含其他类型的毒素基因,表明海南橡胶树棒孢霉落叶病菌为含Cas5毒素蛋白优势群体;所有菌株对橡胶树品种‘RRIM600’都能够致病,但是在不同抗性品种上致病性存在一定差异。     

多主棒孢和棒孢叶斑病的研究进展

多主棒孢Corynespora cassiicola是一种重要的植物病原真菌,寄主范围广泛,能够侵染530余种植物。由多主棒孢引起的棒孢叶斑病在橡胶、蔬菜等作物上流行性暴发,对农作物产业发展构成严重威胁。该文简述了多主棒孢的分类地位和形态特征,对该病原菌的遗传多样性和毒素蛋白结构等方面的研究进行了较为全面的概括。另外,总结了近年来国内外在棒孢叶斑病诊断和防治研究中取得的成果和存在的问题,并提出了我国多主棒孢病原学及病害防治方面的研究方向。     

茄子棒孢叶斑病病原菌鉴定及致病性研究

 本研究对茄子棒孢叶斑病的症状进行系统的描述,采用致病性试验、形态学观察及分子生物学的方法对茄子棒孢叶斑病的病原菌进行鉴定。致病性试验证实病原菌对茄子的致病力显著高于黄瓜。显微观察发现同一病原菌在茄子上形成的孢子以圆柱形为主,孢子体较窄;而在黄瓜上形成的孢子具有圆柱形和倒棍棒形两种形态,且较宽。对病原菌rDNA ITS区进行PCR扩增和序列测定。综合形态特征、致病力和分子序列分析结果,确定茄子棒孢叶斑病病原菌为Corynespora cassiicola。     

Single-chain variable fragments antibody specific to <Emphasis Type="Italic">Corynespora cassiicola</Emphasis> toxin,cassiicolin, reduces necrotic lesion formation in <Emphasis Type="Italic">Hevea brasiliensis</Emphasis>

Corynespora leaf disease poses a serious threat to rubber cultivation because infected leaves develop necrotic lesions and abscise, leaving the tree unproductive. The destructiveness of Corynespora cassiicola has been largely attributed to cassiicolin, a protein toxin secreted by the fungus. Recombinant antibody technology offers hope to curtail the disease whereby single-chain variable fragments (scFv) specific to cassiicolin could bind and deactivate the toxin in genetically modified rubber trees that harbour the antibody gene. A scFv phage library was constructed from heavy and light variable chains of IgG from cassiicolin immunized Balb/C mice spleen. Biopanning of the phage library yielded a scFv clone with high specificity to cassiicolin. The nucleotide sequence and deduced amino acid sequence information of the scFv were obtained. Hemagglutinin (HA)-tagged scFv expressed in Escherichia coli is discerned as a band at ca. 30 kDa on SDS-PAGE, and the corresponding band was detected by anti-HA IgG on a Western immunoblot. Deactivation of cassiicolin by the affinity-purified scFv was demonstrated in a detached-leaf bio-assay on selected susceptible Hevea clones (PB 260, RRIM 2020, RRIM 901 and RRIM 929). The assay was also performed on clones that are relatively more resistant to the fungus (RRIM 600 and GT-1), and the results were as expected. Thus, we have successfully demonstrated that the cassicolin-specific scFv can effectively reduce cassicolin toxicity.     

病原菌诱导后黄瓜叶片中脂氧合酶活性与茉莉酸积累的关系

通过酶活性测定和高效液相色谱分析,研究经病原菌诱导后黄瓜叶片中脂氧合酶(LOX)活性与茉莉酸(JA)积累量的关系。结果表明,黄瓜经褐斑菌诱导后,叶片中茉莉酸(JA)大量积累,同时脂氧合酶(LOX)活性上升,接种叶片的上位叶中LOX活性和JA含量于诱导接种褐斑菌12h后开始升高,并于诱导接种24h后达到峰值,接种叶片的下位叶中LOX活性和JA含量在诱导接种12h后变化不大,但在24h后显著升高,并于48h达到峰值,此后逐渐平稳下降。相关分析表明,LOX与JA呈显著正相关,相关系数r为0.92。同时通过喷施脂氧合酶抑制剂(NDGA)和添加茉莉酸的试验证实LOX是JA合成的关键酶。     

利用MAXENT预测橡胶树棒孢霉落叶病在中国的适生区

［目的］ 对引起橡胶树棒孢霉落叶病的橡胶树棒孢霉落叶病菌在我国的适生区进行分析,为相关部门制定相应的防控对策,及进一步进行风险评估和监测区域的确定提供依据。［方法］ 利用MAXENT与ArcGIS,结合橡胶树在中国的分布预测该病在中国的适生区。［结果］ 预测结果显示,该病在我国的橡胶园几乎均可适生且适生程度较高,适生区内监测及预警对橡胶产业持续健康发展具有重要意义。预测结果的AUC值为0.978,预测效果较好。［结论］ 研究结果可为该病害防控策略的制定提供科学依据。     

Induction and expression of systemic resistance to the anthracnose disease in bean

Development of anthracnose symptoms in trifoliate leaves of Phaseolus vulgaris inoculated with Colletotrichum lindemuthianum was greatly restricted when the primary leaves had been inoculated with the same pathogen 1 week earlier. Penetration from appressoria was inhibited and hyphal growth in epidermal cells was sometimes decreased in preinoculated plants. The response of preinoculated plants also differed: wall appositions and encroachment of nuclei at attempted penetration sites occurred more frequently, and earlier cell death often followed successful penetration. Resistance in trifoliate leaves was also induced by injection of primary leaves with conidia or culture filtrates of the pathogen or a dialysis retentate of these filtrates. Resistance in epicotyls and primary leaves was induced by inoculation of the hypocotyl 1 week earlier. Inoculated cotyledons abscissed, and failed to alter the susceptibility of primary or trifoliate leaves to subsequent inoculation. The results are discussed in relation to a hypothesis to explain the process of induced systemic resistance.     

Molecular Characterization and Diagnosis of QoI Resistance in Cucumber and Eggplant Fungal Pathogens

ABSTRACT The molecular mechanism of QoI fungicide resistance was studied using isolates of cucumber Corynespora leaf spot fungus (Corynespora cassiicola) and the eggplant leaf mold (Mycovellosiella nattrassii). In both pathogens, a mutation at position 143 from glycine to alanine (G143A) was detected in the cytochrome b gene that encodes for the fungicide-targeted protein. Moreover, the nucleotide sequence at amino acid position 143 was converted from GGT or GGA in sensitive (wild-type) to GCT or GCA in resistant (mutant-type) isolates. The methods of polymerase chain reaction restriction fragment length polymorphism commonly used for QoI resistance monitoring were employed successfully, leading to the amplified gene fragment from resistant isolates being cut with the restriction enzyme ItaI. However, heteroplasmy (the coexistence of wild-type and mutated alleles) was found when the resistant isolates of C. cassiicola, M. nattrassii, and Colletotrichum gloeosporioides (strawberry anthracnose fungus) were subcultured in the presence or absence of QoI fungicides. QoI resistance of cucumber powdery and downy mildew isolates persisted for a few years following the removal of the selection pressure imposed by the fungicide under both laboratory and commercial greenhouse conditions. The proportion of mutated sequences in cytochrome b gene decreased over time in the pathogen population. The protective efficacy of the full dose of azoxystrobin decreased when the populations of powdery and downy mildews contained resistant isolates at 10%. Using FMBIO, a fluorescence bio-imaging analyzer, the mutant allele from the QoI-resistant isolates could be detected at the level of 1%, whereas the detection sensitivity of ethidium-bromide-stained gels was approximately 10 times lower.     

Assessing resistance of rubber tree clones to <Emphasis Type="Italic">Microcyclus ulei</Emphasis> in large-scale clone trials in Ecuador: a less time-consuming field method

Resistance of rubber tree clones to South American Leaf Blight (SALB) caused by the fungus Microcyclus ulei is normally assessed in specific large-scale clone trials, which in general entail a considerable amount of work. Four variables are observed monthly on each tree over many years: disease severity and conidial sporulation intensity on young leaves, and severity and stroma density on mature leaves. In order to simplify this field assessment method, we tested the resistance of eight rubber tree clones to M. ulei in Ecuador in a Fisher block design with four replicates per treatment. Three months after planting, monthly observations were made for a period of 12 months on the foliage focusing on the four variables, in order to quantify disease development. Given the correlations between the four variables, assessment of conidial sporulation intensity on young leaves and stroma density on mature leaves should be sufficient. The most suitable period to start the assessment was 6 months after planting, for a duration of six to nine months. As repeated observations on the same trees were autocorrelated, it was possible to reduce the assessment frequency to once every 2 months. To conclude, assessing the resistance of rubber tree clones to SALB in large-scale clone trials can be optimized to reduce the number of observation times by 50%.     

Histology of infection by Erysiphe graminis f.sp. hordei in spring barley lines with various levels of partial resistance

The histology of resistance to infection by conidia of Erysiphe graminis f.sp. hordei has been studied in barley lines with various levels of partial resistance. Resistance reduced the proportion of conidia which formed haustoria and was expressed more strongly in fifth than in first formed leaves. Where attempted penetration from the first appressorial lobe failed, a second and sometimes a third lobe could be formed. Most penetrations were from first lobes, a few from second lobes and a negligible number from third lobes. Adult plant resistance decreased penetration success from both first and second lobes. An unidentified component of resistance appeared to impede the development of less vigorous conidia before they stimulated a host cell response. However, in all hosts the majority of failed penetration attempts stimulated a localized host response implicating this response in resistance. Some attempts caused hypersensitive death of epidermal cells in both resistant and susceptible hosts; the proportion of dead cells was higher in fifth than first leaves. Stomatal subsidiary cells were more susceptible to penetration than interstomatal cells and in resistant leaves the majority of successful penetrations were into subsidiary cells. The pathogen was also able to avoid resistance to penetration by establishing endophytic infection following entry of germ tubes through stomates.