黄瓜霜霉病菌对嘧菌酯的敏感基线研究

从山东、河北、武汉等未使用过甲氧基丙烯酸酯类杀菌剂(strobilurins)的地区采集19个黄瓜霜霉病菌 Pseudoperonospora cubensis 样本,采用叶盘漂浮法室内测定新药剂嘧菌酯(azoxystrobin)对该病菌的毒力,其EC50值范围为11.72×10-5~9.340×10-3 μg/mL。在19个菌系中选择最为敏感的河北定兴菌系进行重复测定,将其EC50平均值2.317×10-4 μg/mL 确定为黄瓜霜霉病菌对嘧菌酯的敏感基线。     

6种染色方法对黄瓜霜霉病菌不同发育阶段的染色效果比较

 比较了Calcofluor、苯胺蓝、荧光素钠3种荧光染色方法和曲利苯兰酒精-乳酚酸、考马斯亮兰和苯胺蓝组织透明染色法对黄瓜霜霉病菌不同生长发育阶段的染色效果。结果表明,在一定的染液浓度和pH值条件下,3种荧光染色方法均可进行孢子囊、休止孢、芽管、附着胞、孢囊梗等寄主组织外部菌体的原位染色,其中Calcofluor染色方法更稳定、简捷和易于观察。曲利苯兰组织透明染色法能观察黄瓜霜霉病菌的整个生长发育阶段,但该法更适宜胞间菌丝及吸器的染色。     

20%菌毒·霜霉水剂防治保护地黄瓜霜霉病药效试验

保护地田间试验结果表明,20%菌毒·霜霉水剂在130、160mL/667m2剂量下,药后7d防效分别为74.04%、79.64%,药后14d防效为82.28%～87.16%,在相同的用量下效果与霜霉威单用相当,且持效期较长,对黄瓜安全,是防治黄瓜霜霉病的较好药剂。     

东北霜霉菌Peronospora manschurica （Naum．） Syd．对黄瓜霜霉病的诱导免疫作用

本研究以多年筛选出的东北霜霉菌Ｐｅｒｏｎｏｓｐｏｒａｍａｎｓｃｈｕｒｉｃａ（Ｎａｕｍ．）Ｓｙｄ．为诱导菌，在黄瓜植株的３～４叶期，采用茎部注射、喷雾和灌根等三种诱导接种方法，诱导植株产生诱导抗性，测定东北霜霉菌对黄瓜霜霉病的免疫作用。研究结果表明：东北霜霉菌免疫作用的强弱与诱导接种方法有关。在３种诱导接种方法中，以注茎诱导接种法的免疫作用最强，使黄瓜植株产生的系统保护作用最明显，表现为黄瓜霜霉病的发病始期较对照株向后推迟１２～１３天，平均病情指数降低１７．６；喷雾诱导接种的免疫作用较弱；而灌根诱导接种法，未能反应出东北霜霉菌的免疫作用     

烟草疫霉菌的培养及大量产生游动孢子囊和游动孢子方法的研究

烟草疫霉菌(Phytophthora nicothianae)在燕麦培养基上生长良好 ,菌丝在滴加了土壤浸出液的皮氏培养液中 ,可在 3d内产生大量的游动孢子囊 ,游动孢子囊经低温处理后再培养 2 4h可产生大量游动孢子     

东北霜霉菌Peronospora manschurica(Naum.)Syd.对黄瓜霜霉病的诱导免疫作用

 本研究以多年筛选出的东北霜霉菌Peronospora manschurica(Naum.) Syd.为诱导菌,在黄瓜植株的3~4叶期,采用茎部注射、喷雾和灌根等三种诱导接种方法,诱导植株产生诱导抗性,测定东北霜霉菌对黄瓜霜霉病的免疫作用。研究结果表明:东北霜霉菌免疫作用的强弱与诱导接种方法有关。在3种诱导接种方法中,以注茎诱导接种法的免疫作用最强,使黄瓜植株产生的系统保护作用最明显,表现为黄瓜霜霉病的发病始期较对照株向后推迟12~13天,平均病情指数降低17.6;喷雾诱导接种的免疫作用较弱;而灌根诱导接种法,未能反应出东北霜霉菌的免疫作用。     

大白菜霜霉病菌寄生霜霉对氟吡菌胺的敏感性

为探明大白菜霜霉病病原菌寄生霜霉Peronospora parasitica对氟吡菌胺的敏感性,采用凹玻片保湿法和离体子叶浸泡法测定了氟吡菌胺对寄生霜霉不同生长发育阶段的抑制作用。结果表明:氟吡菌胺对寄生霜霉孢子囊萌发、芽管伸长、病斑扩展、孢囊梗形成及孢子囊产生均有不同程度的抑制作用,其中对孢子囊萌发和芽管伸长的抑制效果最显著,EC50值分别为0.113 3和0.291 8μg/m L;当氟吡菌胺质量浓度为8.00μg/m L时,对病斑扩展和产孢量的抑制率分别达到86.08%和72.48%,且对孢囊梗的产生也有显著的抑制作用。选用离体子叶浸泡法,测定了氟吡菌胺对从山东省不同地区采集分离的60株寄生霜霉菌株的毒力,发现菌株之间对药剂的敏感性差异较小,敏感性频率呈近似正态分布,其EC50值范围为0.163 2~0.802 2μg/m L,因此可以将其EC50平均值0.405 3μg/m L作为寄生霜霉对氟吡菌胺的敏感基线。     

河北省和山东省黄瓜霜霉病菌对氟吡菌胺的抗性及常规药剂对黄瓜霜霉病的田间防效

为明确黄瓜霜霉病菌Pseudoperonospora cubensis对氟吡菌胺的抗性时空动态,2011—2016年从河北省和山东省黄瓜主产区采集1 821株霜霉病菌,采用叶盘漂浮法检测供试菌株对氟吡菌胺的敏感性,并以茎叶喷雾法评估5种常规药剂对黄瓜霜霉病的田间防效。结果表明,河北省和山东省黄瓜主产区的黄瓜霜霉病菌对氟吡菌胺已普遍产生了低度抗性,平均抗性倍数为5.86;所有供试菌株的抗性频率为51.89%,其中低抗菌株及中抗菌株分别占36.18%和15.71%;平均抗性指数为0.34,每年检测的抗性频率、抗性倍数及抗性指数呈增长趋势,且随着监测区域的变化而变化。在河北省定兴县和山东省寿光市进行的田间防效试验结果显示,按推荐剂量喷施,687.5 g/L氟吡菌胺·霜霉威盐酸盐SC对黄瓜霜霉病防效显著高于常规对照药剂68%精甲霜灵·代森锰锌WG、58%甲霜灵·代森锰锌WP、80%代森锰锌WP及250 g/L嘧菌酯SC的防效,但防效明显下降,由2011年的92.58%～93.31%降至2016年的80.07%～80.82%。表明需要制定和实施抗药性治理对策,如限制山东和河北2省黄瓜的每个生长季节中687.5 g/L氟菌·霜霉威SC的使用不超过2次,而且要与不同作用机理的卵菌杀菌剂交替使用防治黄瓜霜霉病。     

太原市郊区黄瓜霜霉病菌对甲霜灵的抗药性检测

对太原市郊区黄瓜主要种植区黄瓜霜霉病菌对甲霜灵的抗药性进行了检测,结果表明:来自于8个不同地区的黄瓜霜霉病菌对甲霜灵的抗性频率均为100%。在检测的27个菌株中有2个中抗菌株,12个高抗菌株,13个特高抗菌株,无敏感菌株。     

黄瓜霜霉病菌抗氟吗啉菌株的适合度研究

 采用离体叶盘法和活体植株法,测定了从田间分离获得的对氟吗啉具有抗药性的黄瓜霜霉病菌菌株和通过室内紫外线诱变获得的对氟吗啉及对照药剂烯酰吗啉和嘧菌酯产生抗药性的突变菌株的生存适合度。试验结果表明,室内诱导获得的氟吗啉和烯酰吗啉抗药性突变菌株的适合度明显低于敏感菌株和嘧菌酯抗药性突变体及田产氟吗啉抗药性菌株,主要表现在菌株的侵染率、产孢能力和致病力的减弱。室内获得的氟吗啉和烯酰吗啉抗药性突变体和敏感菌株混合接种、继代培养后,其抗药菌株的检出率在混合群体中逐渐降低,其中抗性突变体FR4和敏感菌株以2:8的比例混合接种、培养7代后,其无性后代中检测不到抗药性菌株的存在,表明室内氟吗啉抗药性突变体竞争力弱于敏感菌株;而田间氟吗啉抗药性菌株和室内嘧菌酯抗药性突变体则表现出和敏感菌株相似或更强的竞争力,预示田间自然情况下抗药性菌株存在着可能形成优势菌群而导致药剂防治失败的潜在风险。     

PopW蛋白对黄瓜霜霉病的防病促生作用

 前期研究发现来源于青枯菌（Ralstonia solanacearum, ZJ3721）的Harpin蛋白PopW对多种作物有较好的诱导抗病作用。本文研究PopW蛋白在温室和田间条件下对黄瓜霜霉病的生防和促生效果。温室试验结果表明：人工接种霜霉病病原菌后15 d, 250 mg/L PopW蛋白水溶液对黄瓜霜霉病的防效最好（42.85%）,PopW蛋白（250 mg/L）处理的黄瓜苗与对照相比生物量增加26.92%,叶绿素含量显著提高。2010年,PopW蛋白（250 mg/L）间隔15 d喷雾1次,共使用3次。初次喷雾后8、25、35和48 d,对黄瓜霜霉病的生防效果分别为41.87%、48.36%、53.21%和50.85%; 2011年,等量的PopW蛋白间隔10 d使用1次,共使用3次。初次喷雾后的第8、15、22和27 d,生防效果分别为47.07%、48.17%、50.59%和54.48%。试验结果表明,250 mg/L PopW蛋白水溶液可作为黄瓜霜霉病的潜在生防因子,且其抗病作用有一定的持效期,可保持10~15 d,甚至更长时间。分析PopW蛋白处理对黄瓜的促生作用及其对黄瓜品质的影响,结果显示：PopW蛋白处理组黄瓜单株增产达33.01%。PopW蛋白处理的黄瓜果实可溶性蛋白、可溶性糖、游离氨基酸和维生素C含量分别为18.07 mg/g、6.80 mg/g、60.20 mg/100 g、68.27 μg/g,均显著高于对照（10.21 mg/g、5.30 mg/g、59.06 mg/100 g、49.55 μg/g）,结果表明PopW蛋白处理可显著提高黄瓜产量、改善黄瓜品质。     

芽孢杆菌对黄瓜霜霉病的防治效果研究

经黄瓜霜霉病孢子囊萌发抑制试验明确,芽孢杆菌菌株Z-X-3、Z-X-10对黄瓜霜霉病菌有较强拮抗作用。离体叶片法和温室防病试验表明,两菌株对黄瓜霜霉病有较好的防治效果,相对保护效果分别达46.42％、41.55％;治疗效果分别达46.30％、44.44％,高于农药克霜氰的31.81％、37.03％。     

硅对黄瓜霜霉病抑制效果和抗性相关酶活性的影响

在营养液中加入不同浓度硅且接种黄瓜霜霉病菌后,通过调查其病情指数和检测黄瓜叶片内硅元素含量及过氧化物酶(guaiacol-peroxidase,POD)、多酚氧化酶(polyphenol oxidase,PPO)、苯丙氨酸解氨酶(phenylalanine ammonia-lysae,PAL)、β-1,3葡聚糖酶(β-1,3-glucanase)、超氧化物歧化酶(superoxidedismutase,SOD)5种抗霜霉病相关酶活性,探讨硅抑制黄瓜霜霉病的生理生化机制。结果表明,营养液中硅浓度为100mg/L的处理,黄瓜霜霉病病情指数为21.3,防治效果达到62.8%;营养液中硅浓度与黄瓜叶片内硅元素含量呈正相关,200mg/L处理叶片内硅元素含量最高,且7天后达到2.98mg/g;加硅处理接种黄瓜霜霉病菌后,黄瓜叶片抗病相关酶活性变化明显且差异达显著水平,其中硅浓度为100～200mg/L时上述5种酶活性最高。     

黄瓜霜霉病生态防治技术研究

对大棚黄瓜设计了地膜覆盖双垄,膜下垄间浇水防治黄瓜霜霉病的生态防治措施.试验结果表明,这种防治措施可使大棚内的相对湿度在晴天时控制在85%以下,比膜外浇水显著降低了棚内的湿度,使感病和抗病品种的病情指数均控制在6.0以内,相对防效可达90%以上.与通常的明沟浇水相比,可提早上市1周,推迟拉秧30天,折合每亩增产3107.8kg,增收9323.4元.     

Relationship between disease severity and escape of Pseudoperonospora cubensis sporangia from a cucumber canopy during downy mildew epidemics

Fundamental to the development of models to predict the spread of cucurbit downy mildew is the ability to determine the escape of Pseudoperonospora cubensis sporangia from infected fields. Aerial concentrations of sporangia, C (sporangia m^?3), were monitored using Rotorod samplers deployed at 0·5 to 3·0 m above a naturally infected cucumber canopy in two sites in central and eastern North Carolina in 2011, where disease severity ranged from 1 to 40%. Standing crop of sporangia was assessed each morning at 07·00 h EDT and ranged from 320 to 16 170 sporangia m^?2. Disease severity and height above the canopy significantly (P < 0·0001) affected C with mean concentration (C_m) being high at moderate disease. Values of C_m decreased rapidly with canopy height and at a height of 2·0 m, C_m was only 7% of values measured at 0·5 m when disease was moderate. Daily total flux (F_D) was dependent on disease severity and ranged from 5·9 to 2242·3 sporangia m^?2. The fraction of available sporangia that escaped the canopy increased from 0·028 to 0·171 as average wind speed above the canopy for periods of high C increased from 1·7 to 3·6 m s^?1. Variations of C_m and F_D with increasing disease were well described (P < 0·0001) by a log‐normal model with 15% as the threshold above which C_m and F_D decreased as disease severity increased. These results indicate that disease severity should be used to adjust sporangia escape in spore transport simulation models that are used to predict the risk of spread of cucurbit downy mildew.     

Spatial analysis and incidence–density relationships for downy mildew on hop

The spatial pattern of downy mildew (Pseudoperonospora humuli) on hop (Humulus lupulus) was characterized over 4 years to aid in deriving an appropriate incidence–density relationship. From 472 disease assessments (datasets), discrete distributions were fitted to the datasets to determine aggregation of disease density. Where distributions were able to be fitted, the Poisson distribution fitted 4% of the datasets and the negative binomial distribution fitted 87% of the datasets. Larger‐scale patterns of disease were assessed by autocorrelation and runs analysis; both indicated aggregation of diseased plants was less common than aggregation of disease within plants. Taylor’s power law indicated disease density was aggregated and related to mean disease density in all years. Disease incidence and density were linked by saturation‐type relationships based on the zero term of the negative binomial distribution or an empirical regression. Certain individual datasets were not described well by any incidence–density model, particularly when disease density was greater than about 0·8 diseased shoots per plant with the cultivar Cascade. When applied to 56 validation datasets, 88% of the variation in observed disease incidence was explained by the incidence–density models. Under conditions where sampling would be implemented for disease management, the requisite conditions appear to be in place for a binomial sampling plan for downy mildew.     

Occurrence and molecular characterization of azoxystrobin resistance in cucumber downy mildew in Shandong province of China

Cucumber downy mildew caused byPseudoperonospora cubensis (Berk. and Curt.) Rostov. limits crop production in Shandong Province of China. Since management of downy mildew is strongly dependent on fungicides, a rational design of control programs requires a good understanding of the fungicide resistance phenomenon in field populations of the pathogen. A total of 106 and 97 isolates ofP. cubensis were obtained in 2006 and 2007, respectively. The EC₅₀ values for the growth of all the 106 isolates collected in 2006 were 0.0063–0.0688μg ml⁻¹ (average: 0.0196±0.0048μg ml⁻¹) azoxystrobin and these were therefore considered sensitive isolates. However, 57 field isolates ofP. cubensis of the 97 collected in 2007 with EC₅₀ values that ranged from 0.609 to >51.2μg ml⁻¹ were considered resistant to azoxystrobin. Fragments of the fungicide-targeted mitochondrial cytochromeb gene from total pathogen DNA were amplified using polymerase chain reaction and their sequences analyzed to elucidate the molecular mechanism of resistance. A single point mutation (GGT to GCT) in the cytochromeb gene, resulting in substitution of glycine by alanine at position 143, was found in the three selected azoxystrobin-resistant isolates of downy mildew. This substitution in cytochromeb exhibited different resistance levels, with the resistance factor from 21.15 to greater than 2618.9. In addition, the different resistance levels seemed to appear within 1 year (between 2006 and 2007). Therefore, growers of Shandong Province in China now are faced with a challenge in managing the azoxystrobin resistance in cucumber downy mildew. http://www.phytoparasitica.org posting March 10, 2008.     

Importance of secondary inoculum of Plasmopara viticola to epidemics of grapevine downy mildew

To quantify the magnitude and the spatial spread of grapevine downy mildew secondary sporangia, 4685 Plasmopara viticola single lesion samples were collected from 18 plots spread across central Europe. Disease symptoms were collected on two to 22 sampling dates per plot between 2000 and 2002. Four multiallelic microsatellite markers were used for genotypic identification of pathogen samples. Genetic analysis showed more than 2300 site-specific P. viticola genotypes, indicating that populations are genetically rich demographic units. Approximately 70% of the genotypes were sampled once and 14% were sampled twice throughout the various epidemics. In the 18 populations only seven genotypes (0.3%) were identified more than 50 times. Three genotypes particularly successful in causing disease through secondary cycles showed mainly a clustered distribution. The distance of sporangial migration per secondary cycle was less than 20 m and their plot colonization rate was calculated at around 1–2 m² day⁻¹. Downy mildew epidemics of grapevine are therefore the result of the interaction of a multitude of genotypes, each causing limited (or a few) lesions, and of a dominant genotype able to spread stepwise at plot-scale. These findings contrast with current theories about grapevine downy mildew epidemiology, which postulate that there is massive vineyard colonization by one genotype and long-distance migration of sporangia.     

一体化智能孢子捕捉系统在黄瓜霜霉病和黄瓜白粉病预测上的应用

为探索国内研制的新型一体化智能孢子捕捉系统在黄瓜霜霉病和黄瓜白粉病预测预报上的应用,在田间自然发病情况下,通过对捕捉孢子的形态进行识别,优化一体化智能孢子捕捉系统主要工作参数如有/无空气切割头、空气采集口高度和空气采集时间;通过病害及孢子的动态监测分析大棚黄瓜霜霉病和黄瓜白粉病病情指数与孢子捕捉量的关系。结果表明,当不加装空气切割头、空气采集口高度为70 cm、孢子捕捉时间在10:00—10:30时段有利于孢子的捕捉。黄瓜霜霉病和黄瓜白粉病病情指数与连续7 d孢子捕捉总量具有强正相关性。连续多日监测到黄瓜霜霉病菌孢子囊且数量快速增加是黄瓜霜霉病发生或快速上升的一个预测指标。黄瓜白粉病发病之前没有监测到黄瓜白粉病菌分生孢子,且在病害盛发期分生孢子捕捉量仍较少。研究表明,一体化智能孢子捕捉系统适用于黄瓜霜霉病的预测,但在黄瓜白粉病的预测上尚存在一定问题。     

水杨酸诱发黄瓜幼苗对霜霉病抗性的研究

 由霜霉病菌(Pseudoperonospora cubensis)引发的霜霉病是威胁黄瓜生产尤其是保护地黄瓜生产的主要因素之一。目前,生产上多采用嫁接育苗和农药防治来缓解该病的危害,但由于农药用量大及次数频繁,往往导致黄瓜中农药残留量增加,严重影响了黄瓜的品质,因此,黄瓜的抗病性育种及寻求提高黄瓜对霜霉病抗性的方法是科研工作者的重要课题。