寡聚糖诱导黄瓜对白粉病抗病反应的超微结构研究

 中科6号(2%氨基寡糖素)处理黄瓜植株叶片,5 d后接种白粉菌Sphaerotheca fuliginea(Schlecht.) Poll.,可诱导黄瓜Cucumis sativus产生对白粉病的抗病性,寄主细胞对病原菌的侵入产生了防卫反应结构和物质以及过敏性坏死反应。表现为寄主细胞壁加厚,染色加深,寄主细胞壁下产生多层次结构的乳突,在寄主细胞壁与质膜之间有黑色物质沉积;吸器外质膜皱褶,染色加深,吸器外基质中出现染色加深的颗粒状电子沉积物;寄主细胞质紊乱,细胞器解体,整个寄主细胞解体、坏死。     

硅对瓠瓜酚类物质代谢的影响及与抗白粉病的关系

研究了硅酸盐和诱导接种白粉菌对瓠瓜叶片苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)活性的动态变化和木质素含量的影响.结果表明,诱导接种提高了瓠瓜叶片的PAL、PPO、POD活性,加硅后接种处理植株叶片酶活性更明显增加;接种后瓠瓜叶片中木质素含量增加,加硅处理植株叶片木质素含量是不加硅处理的1.43倍.说明酚类物质代谢在植物抗病机制中起着重要作用,硅能提高酚类代谢的酶活性.1.7mmol/L的硅能显著降低瓠瓜白粉病的病情指数,提高其对白粉病的抗病能力.     

Silicon induced resistance against powdery mildew of roses caused by Podosphaera pannosa

Powdery mildew, caused by Podosphaera pannosa, is a very common disease in greenhouse potted roses, resulting in poor marketing value and hence economic losses. Alternatives to chemical control are necessary, and therefore the ability of silicon (Si) applied to roots to control the disease was investigated, as well as the mechanisms behind the observed disease reductions. Four genotypes of miniature potted roses representing different genetic backgrounds and susceptibility to disease were studied. Plants were watered with a nutrient solution containing either 3·6 mm Si (100 ppm) supplied as K₂SiO₃ (Si+) or no Si (Si?) before inoculation with P. pannosa. Si application increased leaf Si content two‐ to four‐fold compared to control plants. Confocal microscopy showed that Si deposition was larger in Si+ than in Si? plants and that deposition mainly occurred in the apoplast, particularly in epidermal cell walls. Si application delayed the onset of disease symptoms by 1–2 days and disease severity was reduced by up to 48·9%. The largest reduction was found in the two most resistant genotypes, which also had the highest increase in Si uptake. The Si‐induced disease protection was accompanied by increased formation of papillae and fluorescent epidermal cells (FEC) as well as deposition of callose and H₂O₂, especially at the sites of penetration and in FEC, which are believed to represent the hypersensitive response. Si treatment reduced powdery mildew development by inducing host defence responses and can therefore be used as an effective eco‐friendly disease control measure.     

Effect of potassium silicate on epidemic components of powdery mildew on melon

The effects of silicon (Si) supplied in the form of potassium silicate (PS) were evaluated on epidemic components of powdery mildew of melon under greenhouse conditions. The PS was applied to the roots or to leaves. In the first experiment, epidemic components were evaluated after inoculation with Podosphaera xanthii. In the second experiment, the disease progress rate was evaluated on plants subjected to natural infection. The area under the disease progress curve was reduced by 65% and 73% in the foliar and root treatments, respectively, compared to control plants, as a consequence of reductions in infection efficiency, colony expansion rate, colony area, conidial production and disease progress rate. However, root application of PS was more effective than foliar application in reducing most of the epidemic components, except for infection efficiency. This can be explained by the high Si concentration in leaf tissues with root application, in contrast to the foliar treatment where Si was only deposited on the external leaf surfaces. The effects of PS reported in this study demonstrated that powdery mildew of melon can be controlled, and that the best results can be achieved when PS is supplied to the roots.     

壳聚糖和核黄素诱导裸仁美洲南瓜对白粉病抗性的研究

采用喷雾接种法测定了不同浓度壳聚糖(chitosan)和核黄素(riboflavin)诱导裸仁美洲南瓜对白粉病菌(Podosphaera xanthii)抗性的研究。结果表明,经400μg/mL壳聚糖和753μg/mL核黄素处理后,其病情指数显著低于对照,仅为7.10和8.14,且诱导抗病效果较为显著,分别为80.70%和77.86%,诱导抗病持久期可延续15d。诱导后相关生理生化指标测定结果表明,随着处理时间的增加,叶片中POD、PAL和PPO活性总体呈现出先升高后降低的趋势,且处理显著高于对照。壳聚糖处理后POD、PAL和PPO活性分别于第3、5和7天达到峰值;核黄素处理后POD和PAL活性于第5天达到峰值,而PPO活性则于第7天达到峰值。     

化学诱抗剂诱导金银花抗白粉病效果研究

用壳聚糖、草酸、水杨酸、葡聚糖、硅酸钠、硫酸亚铁、氟乐灵、磷酸氢二钾等8种药剂在不同株龄金银花上进行了对白粉病的诱导抗性试验。结果表明壳聚糖、草酸对金银花白粉病有良好的诱导抗性,在1年生、2年生和4年生金银花上对白粉病的平均防治效果分别达82.3%、59.9%和72.1%,54.9%、58.4%和74.1%。水杨酸、硅酸钠、硫酸亚铁有一定的诱导效果,但不稳定。葡聚糖和磷酸氢二钾无明显诱导抗病作用,氟乐灵则有促进发病的作用。     

Effect of temperature on infection and development of powdery mildew on cucumber

Podosphaera xanthii and Golovinomyces orontii are the causal agents of cucurbit powdery mildew. The effect of temperature on conidial germination, infection and sporulation was studied under controlled conditions. Conidia were inoculated on cucumber leaf discs, and incubated at six constant temperatures (from 10 to 35 °C in 5 °C steps) for 3 to 72 h to evaluate conidial germination and infection, and for 6–15 days to evaluate sporulation intensity. Germination took place at all tested temperatures, but was close to zero at 35 °C. The longest germ tubes measured in this experiment were 141.74 μm for the secondary germ tube of P. xanthii at 20 °C after 48 h of incubation, and 67.92 μm for G. orontii for the primary germ tube at 20 °C after 48 h of incubation. The optimal temperatures for conidial germination, infection and sporulation were 24.4, 25.7 and 22.3 °C, respectively, for P. xanthii, and 17.9, 17.3 and 14.9 °C, respectively, for G. orontii. Equations were developed to describe conidial germination with a coefficient of determination (R²) of 0.85 and 0.90 for P. xanthii and G. orontii, respectively. Infection equations resulted in R² of 0.94 and 0.93 for P. xanthii and G. orontii, respectively; and for sporulation, R² of 0.75 and 0.76 for P. xanthii and G. orontii respectively, as a function of temperature. These results can be used to develop models for the risk of cucurbit powdery mildew under field conditions.     

Differential expression of resistance to powdery mildew incited by race 1 or 2 ofsphaerotheca fuliginea inCucumis melo genotypes at various stages of plant development

Thirty-nine genotypes ofCucumis melo (plant introduction entries, open-pollinated cultivars and F₁ hybrids) were evaluated for resistance to powdery mildew under either natural field conditions or artificial inoculation in growth chambers at the cotyledonary stage and the 2-true-leaf stage. Results confirmed that susceptibility in cotyledons was not necessarily associated with susceptibility in either true leaves in growth chambers or adult plants in the field. However, resistance at the 2-true-leaf stage in growth chambers was highly correlated with resistance of field-grown plants. Results also showed that 20 muskmelon genotypes resistant to race 1 at the cotyledonary stage were also resistant at the 2-leaf-stage and as adult plants in the field. The same was true for ten genotypes with race 2 inoculations. Because muskmelon genotypes expressing resistance in cotyledons were also resistant in true leaves in growth chambers or the field, the use of plants at the cotyledonary stage is recommended for screening for powdery mildew resistance caused by race 1 or race 2 ofS. fuliginea. When cotyledons are susceptible, screening should be done at the 2-true-leaf stage.     

解淀粉芽孢杆菌LJ1诱导黄瓜抗白粉病的研究

解淀粉芽孢杆菌LJ1是从土壤中分离得到的一株对黄瓜白粉病具有较好防效的生防细菌。田间试验发现,用LJ1发酵上清100倍稀释液喷施黄瓜幼苗,在施药后14 d时其对黄瓜白粉病的防效可达83.45%。为研究LJ1防治病害的作用机制,用LJ1发酵上清100倍稀释液喷施黄瓜幼苗,测定黄瓜叶片中的超氧化物歧化酶(SOD)、多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)等与诱导抗病性相关的酶活性和信号分子水杨酸含量的变化,并检测了苗期根围土壤中真菌的动态。结果显示,经过LJ1发酵液处理后3种酶的活性和水杨酸的含量在不同时间点均有一个骤增的过程,其活性显著高于对照,并且7 d后土壤中的可培养真菌数量急剧减少。说明LJ1发酵液中有诱导黄瓜产生抗病性的物质,并且诱导后分泌的抗性物质对真菌具有广谱性。     

Understanding pathogen population structure and virulence variation for efficient resistance breeding to control cucurbit powdery mildews

Cucurbit powdery mildew (CPM) is caused most frequently by well-differentiated obligate erysiphaceous ectoparasites Golovinomyces orontii and Podosphaera xanthii, which vary in their ecology and virulence. All economically important cucurbit crops host both of these CPM species. Breeding of cucurbits for CPM resistance is highly important worldwide, but adequate knowledge of CPM species determination, as well as virulence structure, population dynamics, and spatiotemporal variation of these pathogens, has not yet been achieved. New tools have been developed to enhance research on CPM virulence variation for more efficient breeding and seed and crop production. A set of differential genotypes of Cucumis melo, with high differentiation capacity, may contribute substantially to understanding of variation in CPM virulence at both individual and population levels. Long-term observations (2001–2012) of CPM pathogens in the Czech Republic were used to analyse virulence variation within and among annual CPM populations and demonstrate the utility of recently developed tools for studying species variability and virulence variation of CPM pathogens worldwide. Detailed analyses of diversity and spatiotemporal fluctuations in the composition of CPM populations provide crucial information for shaping breeding programmes and predicting the most effective sources of race-specific resistance. The primary aim of this work was to create a uniform framework for determination of CPM species structure and diversity, virulence phenotypes, virulence and phenotype frequencies, phenotype complexity, dynamics, and variation within and among CPM populations. In addition, practical advice is presented on how to select the most relevant data and interpret them for use in cucurbit resistance breeding.     

Effects of barley genotype on induced resistance to powdery mildew

Infection of barley by an avirulent isolate of Erysiphe graminis f.sp. hordei reduces the development of powdery mildew disease by a virulent isolate, inoculated subsequently. This phenomenon, known as induced resistance, was studied in three sets of near-isogenic lines of barley, each of which included varieties with four different race-specific resistance genes. The extent of induced resistance, expressed as a reduction in the number of colonies formed, differed in lines carrying different race-specific resistance genes, being most effective in lines with Mla7 , followed by Mth , then Mla6 and Mla13. These differences may be related to the extent of the hypersensitive response to infection by avirulent spores. A further effect of induced resistance in reducing sporulation, taking the number of colonies into account, was least effective in Mth lines, with the other lines ranking as they did when induced resistance was expressed as colony numbers. By contrast, the genetic backgrounds of the three near-isogenic sets had similar effects on the fractional reduction of colony number by induced resistance. The effect of induced resistance on sporulation was strongest in the most resistant background, and weakest in the most susceptible.     

Genetic differentiation in the French population of Erysiphe cichoracearum, a causal agent of powdery mildew of cucurbits

The relative incidence of Erysiphe cichoracearum and Sphaerotheca fuliginea , both agents of powdery mildew of cucurbits, was determined from 275 samples of mildewed leaves of cucurbits collected in 1994 from five regions of France. E. cichoracearum was identified in 9 to 39% of the mildewed leaf samples from four of the regions but was not detected in samples from the Mediterranean island of Corsica. The genetic structure of the French population of E. cichoracearum was examined using RFLPs of the ribosomal internal transcribed spacers amplified by PCR, random amplified polymorphic DNA (RAPD) markers, pathogenicity and mating-type tests. Forty-one isolates, including one from England, were analysed. Cluster analysis from 147 RAPD fragments using 16 primers revealed the existence of three distinct genetic lineages corresponding to three rDNA haplotypes (designated groups A, B and C). Bootstrap, genetic diversity, gametic disequilibrium and private allele analyses supported this differentiation. The genetic differentiation observed in the French population was not related to the geographical origin of the isolates. Group A isolates may be more specialized on melon as, with one exception, they were of race 1 (growth on four of the five melon cultivars tested) in comparison with group B and C isolates, which were of race 0 (growth on IranH only). Thus, the genetic differentiation observed may indicate a host-specialized subdivision within the French population of E. cichoracearum from cucurbits. Gametic disequilibrium analysis among RAPD loci and biological observations suggest that the sexual stage is of minor importance for epidemics of E. cichoracearum on cucurbits.     

Decreased sensitivity to pyrazophos of cucumber and gherkin powdery mildew

In some cucumber and gherkin greenhouses in the Netherlands, where Curamil (a.i. pyrazophos) had been used for control of powdery mildew, unsatisfactory disease control was obtained in recent years. Laboratory tests revealed a decreased sensitivity of the pathogen to the fungicide. The fitness and the competitive ability of pyrazophos resistant strains in absence of the fungicide appeared to be somewhat lower than that of the normal, sensitive strains. The implications with respect to disease control in practice are discussed.Samenvatting In enkele kassen, waar Curamil (a.i. pyrazofos) in 1977 aangewend werd ter bestrijding van meeldauw op komkommers en augurken, werd onvoldoende effekt met dit middel tegen deze ziekte verkregen. Toetsing in het laboratorium bracht een verminderde gevoeligheid van het pathogeen voor het fungicide aan het licht (Tabel 1). Bij afwezigheid van pyrazofos bleek het competitief vermogen (Tabel 2) en de vitaliteit (Tabel 3) van de pyrazofos resistente isolaten wat lager te zijn dan die van het normale, gevoelige pathogeen. De betekenis hiervan met betrekking tot de ziektebestrijding wordt besproken.     

多因子联合诱导系统的构建及对黄瓜白粉病防治试验

由多个不同的抗病诱导因子组成植物抗病诱导系统的1个子系统。每个因子都是这个系统中的1个要素。系统的性质不但取决于系统中的要素,还取决于要素的结构。合理的配伍可以使要素与要素之间、要素与系统之间的关系得以优化,使系统的功能得以强化。把筛选得到的多个不同的抗病诱导因子进行配伍,组合成新的"诱导组合体",其诱导效应比单一因子显著提高;用不同的"诱导组合体"进行"相继诱导"和"循环诱导",则进一步提高诱导效应,对黄瓜白粉病的田间防治效果达到78.16%,高于常规杀菌剂的防治效果。     

Induction of resistance to downy mildew (Peronospora parasitica) in cauliflower by DL-β-amino-n-butanoic acid (BABA)

Of the three isomers of aminobutyric acid, only the β isomer (BABA) was effective in inducing resistance against Peronospora parasitica , the causal agent of downy mildew, in cauliflower ( Brassica oleracea var. botrytis ). A single foliar spray applied to 7-day-old seedlings protected the plants against Peronospora parasitica for at least 15 days. Of the enantiomers (R and S), only the R was effective. Resistance was accompanied by a hypersensitive-like reaction (necrotic spots) which was evident before inoculation. BABA was systemically effective when applied to the roots, but failed to protect cotyledons adjacent to treated ones. Unlike other chemical inducers, BABA was effective when applied several hours postinoculation. It had no effect on P. parasitica spore germination. In cauliflower seedlings, BABA did not induce the accumulation of the pathogenesis-related protein PR-1, PR-2, PR-3, PR-5 and PR-9. Only treated and challenged seedlings accumulated PR-2.     

黄瓜白粉病菌对己唑醇的敏感基线及实验室抗性获得

为了评价黄瓜白粉病菌对己唑醇的抗性风险,采用子叶法测定了山东地区50个黄瓜白粉病菌菌株对己唑醇的敏感性。结果表明,各菌株敏感性存在较大差异,EC50值最低为0.0017μg/mL,最高达0.16μg/mL,平均值为0.028μg/mL,由于所有菌株均采自未使用过脱甲基抑制剂类杀菌剂的黄瓜日光温室,敏感性频率呈近似正态分布,可作为黄瓜白粉病菌对己唑醇的相对敏感基线。以野生菌株为材料,以紫外线诱导和药剂驯化相结合获得了2个黄瓜白粉病菌对己唑醇的抗性菌株,比较了抗性菌株和敏感菌株的适合度和分生孢子的竞争能力。结果表明,无药情况下2个抗性菌株与野生菌株适合度无显著差异。抗性菌株和敏感菌株分生孢子以80∶20混合培养7代后,抗性菌株的频率变化不明显;50∶50混合培养7代,中抗菌株的抗性频率明显降低,而高抗菌株的抗性频率降低不明显;20∶80混合培养7代,抗性菌株的频率变低甚至消失。     

南瓜品种对白粉病的抗病性与叶绿素含量和气孔密度的相关性

不同南瓜品种对白粉病的抗病性测定结果表明,供试的10个南瓜品种中存在明显的抗病性差异,品种三星、红栗、甜栗表现为高抗;品种二星、日本、金钩、京域表现为抗病;品种光板、天然、红福表现为感病。品种抗病性与南瓜叶片叶绿素含量的高低和叶片气孔数量关系的研究结果表明,南瓜叶片中叶绿素的含量与南瓜品种对白粉病的抗性呈正相关,而气孔密度与抗病性呈负相关。     

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。     

中国香瓜与菜瓜地方品种资源白粉病抗性评价

春秋2个季节在温室利用风媒接种方法对搜集的102份香瓜和14份菜瓜种质资源进行了白粉病抗性评价,结果鉴定出7份香瓜和1份菜瓜高抗白粉病,其病情指数为零,1份菜瓜抗病,其病情指数0.9,表明我国香瓜和菜瓜地方品种资源中蕴涵着潜在的改良甜瓜白粉病抗性的基因资源。