Development of genetic SSR markers in Blumeria graminis f. sp. hordei and application to isolates from Australia

The barley powdery mildew pathogen, Blumeria graminis f. sp. hordei (Bgh), exists in numerous haplotypes and displays significant differences in fungicide sensitivity. It causes considerable yield losses throughout the world. Microsatellite SSRs are useful tools to study the population level and biogeographic aspects of intraspecific diversity, but so far none have been defined for Bgh. Here, eight polymorphic microsatellite loci were identified and characterized. Primer pairs amplifying the loci were then applied to 111 isolates of Bgh from Australia. The number of alleles per locus ranged from 4 to 13, and Nei's genetic diversity ranged from 0·25 to 0·76. The microsatellite primers detected several clones among the isolates and defined 97 unique haplotypes. There was little evidence for regional genotypic subdivision, suggesting that gene flow may not be restricted among geographic regions. All data was consistent with high levels of genetic diversity, potentially resulting from random mating and spread within each region.     

2008年我国主要麦区白粉菌群体对三唑酮和喹氧灵的敏感性监测

采用拌种离体叶段法对我国6个省(市)分离的小麦白粉菌108个和104个单孢堆菌株分别对三唑酮和喹氧灵的敏感性进行了测定,并对两者之间的交互抗性进行分析。结果表明,供试菌株对三唑酮的平均EC50为94.34mg/L,平均抗性水平达45.14倍,有97.25%菌株产生了抗性,其中高抗菌株(抗性水平40)占35.19%,中抗菌株占55.56%。河北菌株的抗性水平明显高于其他五省。小麦白粉病菌群体对喹氧灵的敏感基线为0.0059mg/L,且与三唑酮无交互抗性。此研究信息可为小麦白粉病抗药性持续治理措施的制定以及杀菌剂生产和使用策略提供依据。     

An apparatus for collecting total conidia of Blumeria graminis f.sp. hordei from leaf colonies using electrostatic attraction

Conidia from living conidiophores of barley powdery mildew ( Blumeria graminis f.sp. hordei ) on host leaves were collected consecutively using an electrostatic spore collector. The collector consisted of an electrical conductor plate linked to an electrostatic voltage generator and insulator plates placed abreast on a timed conveyer. The conductor plate was negatively charged by the potential supplied from the voltage generator. The negatively charged conductor plate caused dielectric polarization of the insulator plate, and the surface charge on the insulator plate attracted mature conidia abstricted from conidiophores on colonies growing on leaves placed 2 cm from the insulator plate. The surface charge on the insulator plate was proportional to the voltage applied to the conductor plate. Under optimized conditions, abstricted conidia were attracted to the electrostatically activated insulator plates without any detriment to their survival. During a colony's life span of c . 460 h, conidia were released throughout the day and c . 12 × 10⁴ conidia were collected during the lifetime of the colony. This is the first report on the direct quantification of progeny conidia produced by powdery mildew infecting host leaves.     

Effect of Film-forming Polymers on Infection of Barley with the Powdery Mildew Fungus, Blumeria graminis f. sp. hordei

The effects of three film-forming compounds, Ethokem, Bond and Vapor Gard, on infection of barley by the powdery mildew fungus Blumeria graminis f. sp. hordei were examined in glasshouse and field experiments. The three compounds provided significant control of powdery mildew infection when applied as pre- or post-inoculation treatments in the glasshouse. Such treatment had no effect on plant growth. Bond and Vapor Gard reduced the germination of conidia of B. graminis by 78% and 85% respectively, and reduced the subsequent formation of appressoria (73% and 85% respectively) and haustoria (75% and 79% respectively). The three compounds were less effective in field experiments, although they provided significant control of mildew infection and had no impact on plant growth and grain yield.     

The effect of fungal density on fungicide dose–response curves in barley powdery mildew (Erysiphe graminis f.sp. hordei)

The effect of inoculation density on fungicide dose–response curves and the estimated ED₅₀ value (the fungicide concentration needed to halve the infected leaf area relative to the infected area of leaves that had not been treated with a fungicide) were investigated theoretically, and predictions were tested experimentally using powdery mildew of barley ( Erysiphe graminis [syn. Blumeria graminis ] f.sp. hordei ). A host leaf was assumed to consist of a number of independent compartments, in each of which only a single fungal spore could germinate successfully. The number of fungal spores landing in a compartment was assumed to be Poisson-distributed. The spores were assumed to vary in their sensitivity toward a fungicide, and the sensitivity of the spore population was assumed to be normally distributed around a mean sensitivity. Under these assumptions, the ED₅₀ value was shown to be a positively biased estimate of the mean sensitivity in the fungal population, and the bias increased with inoculum density. Consequently, the estimated ED₅₀ value is expected to vary between experiments and laboratories if the inoculation density varies over a considerable range. The correlation between inoculum density and estimated ED₅₀ value is expected to be strongest when the assayed fungal population consists of several genotypes differing in sensitivity. This expectation was tested by estimating the ED₅₀ values for one barley powdery mildew isolate at different inoculation densities for three different fungicides. These ED₅₀ values were positively correlated strongly with the inoculum density for fenpropimorph and more weakly for triadimenol, whereas no correlation was observed for propiconazole.     

Levels of resistance of Erysiphe graminis f.sp. hordei to the systemic fungicide triadimenol

A random sample of conidiospores ofErysiphe graminis f.sp.hordei was obtained from the atmosphere above Cambridge, England, by incubating them on barley seedlings exposed on three dates in 1985. The asexual progeny of each spore was tested for its response to a range of doses of a systemic triazole fungicide, triademenol. Principal components analysis of the data revealed that the majority of isolates had a distinct level of response to triadimenol, being resistant to triadimenol at the rate apoplied to seed commercially. The remaining isolates appeared either to be sensitive to the lowest dose of triadimenol used, or to have one of two intermediate levels of resistance. There was a significant increase in the frequency of isolates with higher levels of resistance to triadimenol during 1985. This is likely to have been a response to the continuing widespread use of demethylation inhibitor (DMI) fungicides by British farmers.     

Genetics of responses to morpholine-type fungicides and of avirulences inErysiphe graminis f. sp.hordei

The genetics of the responses of the barley powdery mildew pathogen,Erysiphe graminis f.sp.hordei, to three morpholine-type fungicides were studied. Resistances to a phenylpropylamine fungicide, fenpropidin, and to a morpholine, fenpropimorph, co-segregated in crosses of a sensitive isolate, DH14, with each of two resistant ones, CC151 and CC152. In the cross CC151×DH14, the results were consistent with resistance to both fungicides being controlled by a single gene, at a locus namedFenl. In the other cross, CC152×DH14, the genetics of resistance were more complicated; the data were consistent with the segregation of two complementary, unlinked genes which each conferred resistance to both fungicides. Fenpropidin-resistant progeny of CC151×DH14 were significantly more resistant to fenpropimorph than were fenpropidin-resistant progeny of CCI 52×DH14, although the resistant progeny of the two crosses did not differ significantly in their level of fenpropidin resistance. Fenpropidin-resistant progeny of CC151×DH14 were significantly more resistant to another morpholine, tridemorph, than were fenpropidin-sensitive progeny, but this was not the case for CC152×DH14. Resistance to triadimenol, a C14 demethylation-inhibitor (DMI) fungicide, segregated in both crosses. Triadimenol resistance appeared to be controlled by one gene in each cross and was not associated with morpholine resistance. CC151×DH14 also segregated for eight avirulence genes. Two of these matched theMla6 resistance, while one gene matched a previously unknown resistance in a Pallas near-isogenic line, P17, which also carries a known resistance gene,Mlk. Fenl was not significantly linked to the triadimenol resistance gene,Tdl(a), or to any of the eight avirulence genes.Avr _a6 1, Avr _a12 ,Avr _La ,Avr _p17 andTdl(a) were linked, as wereAvr _a 10 andAvr _k .Abbreviations ED₅₀ median effective dose - Fpd fenpropidin - Fpm fenpropimorph - PCA principal components analysis - Tdm tridemorph     

白粉病菌侵染诱导的大麦叶肉细胞变化的超微结构与细胞化学

 从超微结构和细胞化学角度对大麦白粉病菌侵染诱导的寄主叶肉细胞变化进行了研究。结果发现,病原菌接种后12 h,叶肉细胞光合作用的标志性酶RCA和Rubisco含量发生迅速的变化,感病大麦(Ingrid)中RCA和Rubisco含量急剧减少,而抗病大麦(mlo-3)中则趋势相反。随后,不论在感病或抗病大麦中这2种蛋白的含量一直下降,但感病品种中一直维持相对较高水平。超微结构观察表明,病原菌侵染能够诱导侵染点附近叶肉细胞中叶绿体的增殖,新叶绿体的不断产生,从而延缓了叶肉细胞的衰老和死亡,增加了光合产物的形成。以上结果说明,叶肉细胞可能从养分供给上影响到了表皮细胞中病原菌吸器的发育。     

甘肃省小麦白粉菌群体毒性及小麦品种苗期抗白粉病性分析

由Blumeria graminis f.sp.tritici引起的小麦白粉病是危害甘肃省小麦安全生产的重要病害之一,分析病原菌毒性结构和抗病基因有效性对于指导白粉病的有效控制具有重要意义。2013年对甘肃省小麦白粉菌群体进行毒性分析结果表明,91个供试菌系中,对Pm1、Pm2、Pm3a、Pm3b、Pm3c、Pm3d、Pm3e、Pm3f、Pm4a、Pm4b、Pm5a、Pm6、Pm7、Pm8、Pm19、Pm33、Pm5+Pm6、Pm4+Pm8、Pm4b+Pm5b和PmEra的毒力频率达到70%以上,已无利用价值;对Pm13、Pm16、Pm21和Pm24的毒性频率在15%以下,尚可利用。选用甘肃省不同毒性谱的单孢堆菌系,对35个甘肃省及国内生产品种(系)进行苗期致病性测定,发现仅有‘绵麦37’具有优异抗病性。供试白粉菌系对‘定西40号’等22个品种(系)的毒性频率达到60%以上,甘肃省及中国生产品种中,苗期抗病品种(系)匮乏。     

Sterol composition of isolates of Erysiphe graminis f.sp. tritici differing in sensitivity to fenpropimorph

Isolates of Erysiphe graminis f.sp. tritici with wild-type or reduced sensitivity to fenpropimorph were similar in sterol composition, viz. ergosta-5,24(28)-dienol (±90%) and episterol (±10%). Following treatment with fenpropimorph, the relative content of episterol increased in conidia of all isolates tested, while that of ergosta-5,24(28)-dienol decreased. These results suggest that fenpropimorph, under the test conditions used, does not inhibit activity of sterol Δ¹⁴-reductase or Δ⁸→Δ⁷-isomerase but probably interferes with the final part of the demethyl sterol synthesis. However, modifications in this part of the pathway are probably not responsible for the decreased sensitivity of the pathogen to the fungicide. © 1998 SCI.     

Resistance to powdery mildew (Blumeria graminis f.sp. avenae) in oat seedlings and adult plants

In this work, 165 Avena sativa and Avena byzantina accessions were screened for resistance to powdery mildew caused by Blumeria graminis f.sp. avenae and the defence mechanisms of resistant plants were further characterized. Ten resistant and moderately resistant accessions were selected according to macroscopic assessment. A detailed histological study of selected genotypes showed a range of defence mechanisms, acting alone or in combination, that impeded fungal development at different stages. Since the resistance observed in the collection was scarce, a study of adult plant resistance was carried out in 45 genotypes selected from field trials. Nine oat landraces and two commercial varieties showed very high levels of adult plant resistance. A detailed study of the components of the adult plant resistance revealed a high increase of penetration and post‐haustorial resistance in the fifth compared to the first leaves. Identification of the resistance sources and characterization of underlying defence mechanisms will be useful for future breeding programmes and for further cellular and molecular studies to unravel the genetic basis of resistance, in this species in particular and in cereal–powdery mildew interactions in general.     

田间空气中小麦白粉菌分生孢子的动态监测研究

2012和2013两年度采用Burkard定容式孢子捕捉器,对田间空气中小麦白粉病菌分生孢子的监测结果表明,小麦冠层内、外白粉菌分生孢子浓度存在显著的正相关性,冠层内的白粉菌分生孢子浓度明显高于冠层外;田间空气中分生孢子的浓度逐渐升高,到小麦灌浆期达到最大值之后逐渐降低。时间序列分析结果表明,两年度田间空气中白粉菌分生孢子浓度均符合ARIMA(1,1,0)模型且与温度有显著的相关性,建立了基于温度的白粉菌分生孢子浓度预测模型,模型回归效果均达到了显著水平。研究结果发现,田间白粉病病情与空气中病菌分生孢子和关键气象因子具有显著相关性,并在此基础上分别建立了基于空气中分生孢子浓度,以及基于分生孢子浓度和气象因子的田间白粉病病情预测模型,其中基于分生孢子浓度的预测模型普适性要优于基于分生孢子浓度和气象因子的预测模型,可以用来预测田间小麦白粉病的发生流行程度。     

2007年我国部分麦区小麦白粉菌对三唑酮的抗药性监测

采用拌种离体叶段法测定了我国9个省（市）的112个小麦白粉菌株对三唑酮的抗性。结果表明,供试菌株的平均EC50为57.25mg/L,平均抗性水平为27.39倍,其中86.61%供试菌株已经产生抗性,抗药性比敏感菌株高出10~40倍的菌株占47.32%,四川、山东、甘肃和贵州等地菌株的抗性高于其他地区。此结果可为三唑类杀菌剂在我国的推广应用和制定合理的抗药性治理措施提供依据。     

Recent evolution of multiple resistance of Blumeria (Erysiphe) graminis f.sp. tritici to selected DMI and morpholine fungicides in France

Fungicides inhibiting sterol biosynthesis are frequently used for powdery mildew control and can be subdivided into sterol demethylation inhibitors (DMIs) and morpholines with different modes of action. Whereas fungicide resistance to DMIs (Rdmi) and morpholines (Rmor) has been continuously monitored, there are no data available on the combination of Rdmi and Rmor, which led us to ask whether multiple resistance to triadimenol (Rtria), representing DMIs and to fenpropimorph (Rfen), representing the morpholines, evolved in France from 1993 to 1996. The method used allowed testing of both chemicals simultaneously, with the same inoculum. In 1993, the resistance factor of the mean (RFM) of the French wheat mildew population was 9·59 for Rtria and 5·11 for Rfen. Resistance increased, leading to RFMs of close to 14 for Rtria and 8 for Rfen at the end of the study. From the analysis of single colony isolates (SCI) that are genetically uniform, the presence of multiple resistance and its increase were evident and in line with the results of bulk isolates. Covariance of resistance to both chemicals was close to one. In contrast to the increase of Rfen, the use of morpholines decreased. These effects are supposed to result from multiple selection due to the use of mixtures of DMIs and morpholines that have been favoured in recent years. Fungicide sensitivity is, in general, not normally but lognormally distributed in a population. A new way to evaluate and describe lognormal data is presented. It is easy and convenient to use and provides solutions for current problems in the literature with lognormal distributions. Multiple resistance, its evolution and persistance are discussed in relation to fungicide use and to implications for anti-resistance strategies. © 1998 Society of Chemical Industry     

Overexpression of phytoglobin in barley alters both compatible and incompatible interactions with the mildew pathogen Blumeria graminis

This study showed how barley plants can be shifted in their response to isolates of the mildew pathogen Blumeria graminis with different host adaptation by overexpression of the barley phytoglobin gene HvHb1. At early infection stages, plants overexpressing phytoglobin (GPHb1) showed less papilla formation and more hypersensitive response against both virulent and avirulent pathogen isolates compared to the wildtype (WT) plants. The shift was most pronounced in a wheat-adapted isolate (B. graminis f. sp. tritici). At later infection stages, GPHb1 plants infected with a virulent pathogen isolate (A6) showed less leaf chlorosis compared to the WT plants, indicating delayed senescence. The chlorophyll level was significantly higher in A6-infected GPHb1 plants 9 days after inoculation (dai) and the senescence indicators sphingosine-1-phosphate:ceramide ratio and phytol content confirmed delayed senescence. At 14 dai the percentage of fungal DNA was significantly higher on the GPHb1 plants than on WT plants, probably as a result of the delayed senescence. The results show that overexpression of phytoglobin (previously known as plant haemoglobin) can be an important tool to understand disease-related stress effects in plants of agronomic importance and for understanding basic resistance mechanisms. Studying this process in more detail may provide insights into how to alleviate stress-related senescence in plants.     

2011年我国主要麦区小麦白粉病菌群体对三唑酮和苯锈啶的敏感性

 小麦白粉病(Wheat Powdery Mildew)是我国小麦生产上常发性病害之一^[1]。小麦白粉病的防治主要采用抗病品种和化学药剂,辅之以栽培措施的综合防治技术。由于目前生产上抗病品种相对缺乏,药剂防治成为我国小麦白粉病防治的主要措施之一^[2]。自20世纪80年代以来三唑类杀菌剂一直是我国防治小麦白粉病的主要药剂,由于长期、大范围、单一的使用导致小麦白粉病菌对三唑类杀菌剂的抗药性大大提高。监测结果表明,2009年我国小麦白粉病菌群体对三唑酮的平均抗性水平已经达到56.58倍,抗性频率达到99.09%,其中高抗菌株占49.09%^[3]。目前小麦白粉病菌对三唑酮的抗性形势十分严峻,寻找三唑类杀菌剂的替代药剂成为控制该病害的迫切需求。     

2009年我国部分麦区小麦白粉菌群体对三唑酮和嘧菌酯的敏感性测定

自1976年以来,三唑酮一直就是我国防治小麦白粉病的主要药剂.1991年首次在山东省发现抗性菌株,之后其他地区也相继有抗药性菌株的报道.本实验室从1995年就开始监测小麦白粉菌对三唑酮的抗药性,研究结果表明,平均抗性水平和抗性菌株的频率均总体呈上升趋势[1-3].     

小麦种质N9820抗白粉病的特异基因表达谱分析

小麦白粉病是由白粉菌(Blumeria graminis f.sp.tritici)引起的世界性真菌病害之一,白粉病原菌的生理小种多,毒性变异速度快,很容易造成品种抗病性的丧失。培育抗病新品种有两种基本措施,一是发现与利用新的抗病基因;二是诱导防御