基于ISSR的豚草和三裂叶豚草遗传多样性研究

[目的]研究不同地理种群的豚草和三裂叶豚草的遗传多样性水平和遗传结构。[方法]应用筛选的13条ISSR引物对8个豚草居群和7个三裂叶豚草居群共240个样品进行分子标记。[结果]8个豚草居群128个样品,共扩增出304条带,多态性位点比率为98.68%;Shannon''s信息指数为0.6716,Nei''s基因多样性指数为0.4788。7个三裂叶豚草居群112个样品,共扩增出266条带,多态性位点比率为95.86%;Shannon''s信息指数为0.6593,Nei''s基因多样性指数为0.4670。豚草和三裂叶豚草各居群遗传距离较近。[结论]豚草和三裂叶豚草在居群间具有一定的遗传稳定性;居群内具有丰富的遗传多样性。豚草和三裂叶豚草遗传变异主要来源于居群内部。豚草各居群遗传距离和地理距离有显著相关性,三裂叶豚草各居群遗传距离和地理距离无显著相关性。     

三裂叶豚草锈菌侵染寄主叶片的显微和超微观察

【背景】三裂叶豚草是我国重要的外来入侵植物之一,其传播速度快,已给我国造成巨大的经济损失。近年来发现的三裂叶豚草锈菌是一种对其具有生物防治潜力的病原菌。【方法】本文利用显微技术研究了三裂叶豚草锈菌的侵染过程及其对寄主结构的影响。【结果】三裂叶豚草锈菌菌丝可从多处侵入同一个叶肉细胞,胞间菌丝与叶肉细胞相接触可使部分细胞壁增厚。锈菌侵染使三裂叶豚草叶脉末梢导管分枝增多,造成三裂叶豚草水分代谢失调;叶片细胞内膜系统破碎化,细胞器结构受到不同程度的破坏,导致细胞内膜系统紊乱,细胞器结构稳定性降低。【结论与意义】豚草锈菌侵染破坏了三裂叶豚草叶片的细胞结构。本研究为深入研究豚草锈菌的致病机理奠定了基础。     

三裂叶豚草锈病发生和流行规律的研究

通过田间调查与定点系统观察,结合沈阳地区的气象条件,对三裂叶豚草锈病在沈阳地区的发生和流行规律进行了研究。结果表明：三裂叶豚草锈病属于喜高温、高湿型病害;该病于6月初在沈阳地区开始发病,可持续至9月,以7～8月发病最重。人工接种试验结果表明：在30℃和相对湿度96．9％条件下接种锈菌冬孢子,4d后三裂叶豚草即可发病;冷冻保藏（-20℃）可打破冬孢子休眠,在沈阳地区冬孢子是第二年锈病发生的初侵染菌源。苍耳柄锈菌三裂叶豚草专化型对三裂叶豚草表现出了显著的致病性、致死性及专一性,证明是防治三裂叶豚草的理想生防菌。     

基于SDMs-toolbox预测气候变暖趋势下辽宁省三裂叶豚草潜在入侵区域

为明确气候变暖对三裂叶豚草的潜在适生区域的影响并揭示三裂叶豚草潜在扩散路径及规律,文章选取辽宁省作为研究区域,模拟气候变暖条件下三裂叶豚草在2050年潜在分布范围.研究结果表明,拟合温室气体排放量低的情况下(RCP4.5),三裂叶豚草扩散面积相比2019年增加了10919.9 km2,其中中度和高度适生区分别增加了31...     

三裂叶豚草雄花序分化的气候效应分析

【背景】三裂叶豚草是一种外来恶性杂草,它的入侵不仅影响当地的生物多样性和生态系统,而且给农牧业造成巨大的经济损失。此外,其花粉量大,是引起人体一系列过敏反应的致敏源。【方法】通过对2008～2010年三裂叶豚草分化时期和气象因素进行调查,以当年分化开始前一个月至分化结束的日最高气温、日最低气温、日平均气温、相对湿度、日照时间等数据,分析影响三裂叶豚草雄花序分化的气象因子。【结果】雄花序从未分化期至成熟期平均需26d。三裂叶豚草营养生长后期,较短的日照时间和日平均气温、较高的相对湿度和较大的温差等环境条件有利于三裂叶豚草雄花序较早地开始分化。而在分化早期,长时间较高的相对湿度不利于雄花序的分化。【结论与意义】外界环境的变化能够影响三裂叶豚草雄花序的分化,对其分化开始时间起决定性作用。本研究为制定合理的三裂叶豚草防治措施提供了理论依据,同时为进一步研究其生物安全性提供了参考。     

苍耳柄锈菌三裂叶豚草专化型的超微结构观察(英文)

20 0 3年在沈阳的三裂叶豚草 (AmbrosiatrifidaL .)上发现了苍耳柄锈菌三裂叶豚草专化型 (PucciniaxanthiiSchwein .f.sp .ambrosia trifidaeS .W .T .Batra) ,这是在我国三裂叶豚草上发现的一种新病菌。试验采用扫描电镜和透射电镜对该锈菌的冬孢子和吸器的形态结构进行了观察。     

豚草锈菌对三裂叶豚草叶片生理生化特性的影响

【背景】自20世纪50年代三裂叶豚草传入我国以来,迅速蔓延,已给我国农业生产、生态环境、人民健康造成巨大威胁。近年来发现的豚草锈菌对三裂叶豚草有一定的致病性,具备生物防治潜力。【方法】本文利用植物生理学技术研究了豚草锈菌对三裂叶豚草叶片生理生化特性的影响。【结果】锈菌侵染后,三裂叶豚草叶片的相对电导率随病级的增高和侵染时间的延长而上升,说明锈菌破坏了豚草叶片的细胞膜,导致其电解质外渗。同时,发病初期叶片内的丙二醛(MDA)与超氧自由基(O2.-)含量逐渐上升;当发病程度为3级时,O2.-含量达到最高;4级时,MDA含量达到最高。此外,锈菌侵染后,三裂叶豚草叶片抗坏血酸(AsA)含量持续上升,而脯氨酸(Pro)含量在发病后期下降,说明在三裂叶豚草与锈菌互作时,AsA含量虽然增加,但抗性并不明显,而Pro可能具有更为重要的作用。【结论与意义】豚草锈菌的侵入干扰了三裂叶豚草的生理生化反应,这将为深入研究豚草锈菌的致病机理、发挥其生物防治潜力奠定基础。     

豚草锈菌对三裂叶豚草光合生理特性的影响

【背景】外来人侵恶性杂草——三裂叶豚草在我国迅速蔓延,并对我国经济、人民健康、生态等方面造成巨大影响。【方法】本文运用光合仪（CIRAS-1）测定豚草锈菌侵染后的三裂叶豚草叶片的光合效率、蒸腾速率、叶表面蒸汽压差、胞间CO2浓度、气孔导度等指标,以探讨豚草锈菌影响三裂叶豚草光合作用的机制。【结果】豚草锈菌侵染三裂叶豚草叶片后,对叶片水分代谢与光合代谢有明显影响,从而影响叶片有机物质的合成。豚草锈菌侵染显症1—4d后,受侵染叶片蒸腾速率与气孔导度下降,光合作用有所加强,导致胞间CO2浓度下降,进而使叶片细胞水分代谢与光合代谢加强。显症4d后,随着叶片发病程度增加（4～5级）,胞间CO2浓度增加,蒸腾速率与气孔导度大幅降低,光合速率下降。【结论与意义】豚草锈菌能干扰三裂叶豚草叶片的光合生理活动。该结果可为防治三裂叶豚草提供参考。     

三裂叶豚草(Ambrosia trifida)对大豆根系生长及其结瘤的影响

沈阳效区实地考察中观察到,邻近三裂叶豚草生长的大豆的根瘤形成受到了抑制。土箱实验中得到和野外调查一致的结果,但大豆根系发育和分布不受影响。施用三裂叶豚草水浸液的实验表明,是三裂叶豚草水浸液,即：水浸液中的化学物质,抑制了根瘤菌的活动从而影响大豆根瘤的形成。文章给出了调查和实验的结果,并进行了分析。     

三裂叶豚草雄花序分化期ABA、GAs和IAA的含量动态

【背景】三裂叶豚草为我国外来入侵有害植物,是世界公认的危害性杂草,不仅影响农牧业的生产,而且其花粉含有致敏蛋白,能引起人体一系列的过敏反应,危害人类健康。植物内源激素与植物生长发育的基本规律和代谢过程的调节控制密切相关。【方法】本文利用高效液相色谱法,研究了三裂叶豚草雄花序分化过程中3种内源激素的含量动态。【结果】在三裂叶豚草雄花芽分化过程中,赤霉素(GAs)的含量在分化初期比较平稳,从花蕾分化期开始急剧下降,雄蕊分化期又上升;吲哚乙酸(IAA)的含量始终处于缓慢上升的趋势;脱落酸(ABA)在花瓣分化期出现且迅速上升,在雄蕊分化末期达到峰值。3种激素中,ABA含量与三裂叶豚草花芽分化的相关性较明显。【结论与意义】ABA的出现及其含量是决定三裂叶豚草雄花序分化能否完成的一个关键因素。本研究为利用化学方法防治三裂叶豚草提供了依据。     

Isolation of Oospores of Sunflower Downy Mildew, Plasmopara halstedii, and Microscopical Studies on Oospore Germination

A method was elaborated to isolate oospores of Plasmopara halstedii from tissue of its host, Helianthus annuus . Isolated oospores were studied microscopically and germination was documented with respect to the time course and the mode of germination. Formation of primary sporangia was similarly observed in oospores, harvested from 4- to 6-week-old systemically infected sunflower plants, grown under constant conditions at 16°C, as well as from field plants, harvested late in the season. Pretreatment of oospores with cold temperatures, previously assumed to stimulate the rate and to accelerate the speed of oospore germination, did not result in such effects. Germination usually occurred within 10–30 days of incubation at a highly variable rate of about 1 to 17% (average 6.7%) in deionized water.     

Revision and reclassification of three Plasmopara species based on morphological and molecular phylogenetic data

Based on the results of morphological and DNA sequence (partial D1–D3/D7–D8 nuLSU and partial nuSSU-ITS1-5.8S rDNA) data, three species of Plasmopara are revised and reclassified. A species of Plasmopara parasitic on Scorzonera, invalidly published several times, is assigned to a new genus and species under Novotelnova scorzonerae. Plasmopara euphrasiae sp. nov. is segregated from P. densa, and P. centaureae-mollis is revised and relegated to synonymy of Bremia centaureae. All taxa are described and illustrated.     

Cytological and Physiological Reasons for the Latent Type of Infection in Sunflower Caused by Plasmopara halstedii

Lightmicroscopy was used to investigate cytological and physiological reasons for the latent type of infection of sunflowers with Plasmopara halstedii. Sections of the hypocotyl of inoculated, but healthy looking plants of compatible and incompatible host-pathotype combinations revealed vital hyphae and oospores, thus indicating an uninterrupted life cycle of the pathogen. Plants with latent infections showed enhanced cell division activities which restricted the pathogen to the cortical parenchyma. Additionally, hypersensitive reactions inhibited further growth in the pith parenchyma. In contrast, for systemic infection a successful invasion by the pathogen of the pith parenchyma of the hypocotyl and a growth of the hyphae faster than the hypersensitive reactions of the host tissue are needed.     

马铃薯晚疫病菌卵孢子萌发的初步研究

描述了马铃薯晚疫病菌卵孢子萌发的方式并研究了菌株组合、卵孢子形成时间、在琼脂培养基上培养时间及光照对卵孢子萌发的影响,结果表明不同菌株组合卵孢子萌发率为0—7.2%,对峙培养20天后形成的卵孢子的萌发率最高达8.7%,在琼脂培养基上培养25-30d 萌发率最高达11.4%,卵孢子形成时黑暗及在琼脂培养基上萌发时光照萌发率最高达11.8%。     

Viability and maturation of Aphanomyces cochlioides oospores

Plasmolysis, tetrazolium bromide staining and microscopic appearance were tested for their usefulness in determining viability of oospores of Aphanomyces cochlioides. For comparison, three lethal treatments were employed to contrast the reaction of dead oospores and untreated, presumably viable oospores. Few oospores stained with tetrazolium bromide, even though plasmolysis and microscopic appearance indicated that 85% were viable. Cytoplasm of viable oospores was densely organized and uniformly granular (DOUG), whereas cytoplasm of oospores exposed to lethal treatments was loosely organized and non-uniformly granular (LONG). Dose-response bioassay experiments were conducted with untreated oospores of varying inoculum densities or with mixtures of untreated DOUG and heat-treated LONG oospores in varying proportions. The number of DOUG oospores was correlated (R(2) = 0.62, P < 0.001) with severity of damping-off of sugar beet seedlings caused by A. cochlioides. Thus, the granular appearance of cytoplasm offered a fast, easy and reliable indicator of viability of A. cochlioides oospores. Tests with newly formed oospores/oogonia showed that >80% harvested at 3-4 d after inoculation of hypocotyls stained with tetrazolium, but by 8-9 d <10% stained, apparently because of declining permeability of the spore wall to tetrazolium as oospores matured.     

Testing of life history traits of a soilborne pathogen in vitro: Do characteristics of oospores change according the strains of Aphanomyces euteiches and the host plant infected by the pathogen?

Aphanomyces euteiches is a polyphagous, homothallic soilborne pathogen producing asexual (zoospores) and sexual (oospores) spores. Even if oospores are essential for disease development and survival, to date, no study has focused on the production rates of oospores or the quality of the offspring produced by oospores. In this study, a nonabrasive oospore extraction method from infected roots of leguminous species (pea, faba bean and vetch) was developed. This methodology includes steps of grinding and filtration. The quality of oospores (viable, dormant and dead) was assessed with tetrazolium bromide staining, and germination of oospores was tested using exudates of peas, faba bean and vetch. The average yield of the extraction method was approximately 21%. Staining revealed some differences between strains and between leguminous species. The germination percentage of oospores extracted from pea, faba bean and vetch was 25%, 62% and 70%, respectively, and a significant difference was observed according to the origin of A. euteiches‐inoculated strains. Application of exudates seems to stimulate the germination of oospores (2% for the control, 18% for pea exudates and 1% for vetch exudates). Differences observed between A. euteiches strains and leguminous species indicate that more knowledge concerning the biology of oospores is needed. This will help to better estimate evolution process of the pathogen and manage resistance and crop successions.     

Survival, Germinability and Infectivity of Oospores of Peronospora viciae f.sp. fabae

A series of experiments was conducted to germinate oospores of Peronospora viciae f.sp. fabae. With rare exceptions, dry-stored oospores did not germinate in water nor did they infect faba bean seedlings in soil. Long-term storage, pre-treatment with KMnO₄ or addition of nutrients to the medium did not induce germination. Survival and infectivity of dry-stored oospores were compared to those of oospores incorporated in a silt loam and a loamy sand soil in the field during 21–22 months. Under dry conditions, the percentage of living oospores did not change as determined by the vital stain tetrazolium bromide. In soil, less than 2% of the oospores had survived after 21 months. Infectivity of oospores was determined by a bioassay 17 and 21 months after oospores had been incorporated in soil. Diseased seedlings were obtained after inoculation of faba bean seeds with oospores extracted from the soil but not with the drystored ones. Soil samples from two field plots naturally infested with oospores 2 and 3 years before the bioassay were infective. Oospores collected with diseased plant material on one of these plots and subsequently stored dry for 3 years were not infective. The results suggested that oospores need a period of natural weathering to become germinable and infective.     

Production of Phytophthora infestans oospores in planta and inoculum potential of in vitro produced oospores under temperate highlands and subtropical plains of India

High moisture content of the host tissue ( 88%) and low ambient r.h. (50-54%) favoured oospore formation under controlled environments. It took 14–16 days for oospores to develop; thereafter the number of oospores increased with time and decreased with moisture content of host tissue. High ambient r.h. (> 80%) did not favour oospore formation under field or controlled conditions. Oospore formation was detected in inoculated plants grown in the field when the ambient r.h. declined to 74% and moisture content of host tissue decreased to 83.7–85.6%. It took 8 days (cv. Kufri Chandramukhi) to 13 days (cv. Kufri Jyoti and Kufri Badshah) for oospores to develop. Cultivars also differed in their response to oospore production, cv. Kufri Chandramukhi being more responsive (4800 oospores g⁻¹ f wt) than cv. Kufri Jyoti and Kufri Badshah (1320 and 390 oospores g⁻¹ f wt respectively). Oospores produced in vitro remained viable when buried in soil in the temperate highlands of Himachal Pradesh and sub-tropical plains of Uttar Pradesh, India for more than 150 days, i.e. beginning of the next crop season. The oospores germinated and initiated late blight infection at the base of the stems after 21–30 days of incubation of the potato plants raised in oospore-infested soil. It took 2 days for newly formed oospores to germinate and this delay time increased to 75–77 days after 180-days burial. It took 15 days for their germination (47%) in soil extract as compared to 50 days in sterilised distilled water.     

Factors Affecting Germination of Oospores of Phytophthora infestans

When oospores from the pairing between A¹ and A² mating types of Phytophthora infestans were treated with 0.25 % KMnO₄ solution for 15 min and incubated at 19 °C under light on a modified S+L medium, germination commenced within 4 days and reached about 70 % after 20 days. Under these conditions, more than 25 % of oospores obtained from a 4-day-old culture germinated. To obtain a high germination rate of P. infestans oospores, light was essential during germination but not during growth and oospore formation. The optimum time for activation of oospores with 0.25 % KMnO₄ was 15 to 30 min and a suitable concentration of KMnO₄ for 15 min activation was 0.25 to 0.45 %.     

Agarose Medium for Germination of Oospores of Phytophthora cactorum

When oospores of Phytophthora caetorum from 30-day-old culture were treated with 0.25% KMnO₄ for 20 min and incubated at 24°C under light for 10 days, 65–75% germinated on water agar and water agarose but only 1–21% germinated on V-8 agar and S+L agar. Water agarose was selected because germinated oospores formed restrieted colonies on this medium that could be isolated easily. KMnO₄ treatment killed sporangia, chlamydospores and mycelial fragments present in oospore suspensions. Under the above conditions, approximately 44% of oospores from 10-day-old culture germinated and the optimum germination rate of about 75% was obtained when oospores reached about 20 days old.