Support for a stepwise mutation model for pathogen evolution in Australasian Puccinia striiformis f.sp. tritici by use of molecular markers

Since its initial detection in Australia in 1979, wheat yellow (stripe) rust ( Puccinia striiformis f.sp. tritici ) has evolved in Australia and New Zealand into more than 20 pathotypes with assorted virulence characteristics. This evolution is believed to have occurred in a stepwise fashion from an original single pathotype, with no subsequent new introductions. A combination of random amplified polymorphic DNA (RAPDs) and amplified fragment length polymorphisms (AFLPs) was used to examine the level of molecular variation in Australian and New Zealand isolates, and to compare this with variation amongst other isolates of P. striiformis . Using 60 RAPD primers on seven Australian isolates representing seven different pathotypes collected between 1979 and 1991, more than 300 potentially polymorphic loci were analysed and no polymorphisms were detected. Using the same primers on two UK isolates, 3% of loci showed a polymorphism. A similar level of polymorphism was found between UK isolates using AFLP primers, and between 5 and 15% of fragments were polymorphic between an isolate from the UK, an isolate from Denmark, and one from Colombia. However, no AFLP polymorphisms were found amongst 14 Australian and New Zealand isolates tested, at over 100 potentially polymorphic loci. The lack of molecular variation in the Australian and New Zealand collection is consistent with the stepwise mutation theory of pathotype evolution from a single introduction.     

小麦条锈菌鉴别寄主和小种命名现状

 中国是世界上小麦条锈病最大的流行区之一,也是限制中国小麦生产的最严重病害之一,特别是当条件适于其发生时会造成巨大的产量损失.小麦条锈菌小种生理专化性研究及小种监测是掌握小麦条锈菌及其毒性变化动态、抗病基因有效性及病害流行预测预报的重要依据,是治理由此病原菌引起的小麦条锈病的基本环节之一.由于地域、条锈菌群体结构、研究水平和历史等的差异,目前国际上不同国家和地区采用相应的小麦条锈菌鉴别寄主和小种命名方法.中国、美国和印度均使用了各自不同的小麦条锈菌鉴别寄主,并采用了相应的小种命名体系,例如从1957至2002年,中国利用10多个鉴别寄主已鉴定和命名了32个小种和30多个致病类型,美国利用10多个鉴别寄主已鉴定和命名了80个小种;另一类是采用1972年Johnson提出的二进制国际小种命名法,这种体系包括了国际鉴别寄主和欧洲鉴别寄主,象一套鉴别寄主被整体使用,欧洲、中东、亚洲、非洲和南美国家及澳大利亚和新西兰均采用此体系监测小麦条锈菌变化,是一套被最为广泛接受和使用的小麦条锈菌小种鉴别方法和命名系统,但随着研究深入和各国实际情况差异等原因,不同研究人员加入了不同的辅助鉴别寄主,以更能准确和实际地反映本国和地区的现实情况,为生产服务,本文对此现状进行了分析和比较.由于此病菌具有长距离气传和扩散的特点(地区间、国家间和洲际间),因而也讨论了未来小麦条锈菌鉴别寄主组成、小种命名方法和研究结果的交流和比较等实际问题.     

Emergence of a novel population of Puccinia striiformis f. sp. tritici in Eastern United States

The geographic range of stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici, has increased dramatically since 2000 in the United States. Yield losses to the disease have been most severe in the eastern United States, where measurable yield loss had been rare prior to 2000. The objective of this study was to examine the phenotypic and genotypic variation among isolates of P. striiformis f. sp. tritici collected from populations in the eastern United States before and since 2000. Virulence phenotype and amplified fragment length polymorphism (AFLP) markers were used to examine 42 isolates collected between 1960 and 2004. In addition, the genetic structure of 59 isolates collected in 2005 using a hierarchical sampling strategy was examined. The data indicated that the contemporary isolates (collected since 2000) were very distinct from older isolates (collected before 2000) based on virulence and AFLP markers, and that the old population prevalent before 2000 may have been replaced by the contemporary population. The old and new populations appear to be genetically distinct and may represent an exotic introduction rather than a mutation in isolates of the old population.     

BTH和INA诱导小麦抗条锈病性的研究

用不同浓度的苯(1,2,3)噻二嗪-7-硫代羧酸-S-甲酯(BTH)或2,6-二氯异烟酸(INA)喷雾处理小麦幼苗,进行小麦诱导抗病性研究。结果表明,以1.0mmol(毫摩尔)INA处理后接种小麦条锈病的诱导抗性效果最好。以1.0mmolINA和0.3mmolBTH处理小麦叶片5d后接种,叶片中苯丙氨酸解氨酶(PAL)和多酚氧化酶(PPO)的活性均有明显上升,且PAL、PPO和INA、BTH的诱导抗性表达都呈正相关关系。BTH和INA水溶液对小麦条锈菌夏孢子的萌发均无明显抑制作用。据此认为,处理后病情指数的下降是由于试剂处理提高了小麦幼苗的抗病性,即麦苗产生了诱导抗性而引起的。     

种衣剂17号包衣对小麦条锈菌影响的组织病理学研究

种衣剂１７号内含三唑醇等杀菌剂和其它化学成分，小麦种子用种衣剂包衣，出苗后一叶期接咱小麦条锈菌毒性小种，采用荧光染色技术和整叶透明技术，研究了种衣剂１７号对条锈菌在寄主内发育的影响。观察结果表明，该种衣剂对对叶表的夏孢子萌发和芽管入侵无明显影响，但可使菌丝扩展和菌丝分枝严重受抑，吸器母细胞和吸器形成的数目减少，每一侵染点的吸器一般不超过２个，并且对吸器具有致畸作用。在多数侵染点内可观察到寄主细胞坏     

小麦条锈病菌和白粉病菌多重TaqMan Real-time PCR方法的建立

<正>小麦条锈病(Puccinia striiformis f.sp.tritici,Pst)和小麦白粉病(Blumeria graminis f.sp.tritici,Bgt)是我国小麦生产上的重要病害。条锈病主要发生在西北、华北、长江中下游和西南各省、自治区;白粉病则在西南各省和河南、山东、湖北、江苏、安徽等省发生较重,且西北、东北麦区也日趋严重[1]。条锈病菌依靠夏孢子造成小麦初侵染和再侵染并随气流远距离传播导致大区流行,白粉病菌则依赖于分生孢子或子囊孢子进行初侵染和再侵染。二者作为典型的气传病害,空中的接种体在     

特谱唑防治小麦锈病毒理与应用技术的初步研究

据室内测定结果,特谱唑具有很强的内吸传导性能,用灌土法施药的效果可与叶面喷雾法相比拟,但基本上是向上传导。此药具有很强的治疗和铲除作用,在病菌潜育期施药,可控制到不发病,最多只显退绿斑;在退绿期施药,可使病菌夏孢子堆变成褐色小点,孢子粉极少,但对夏孢子的萌发影响则弱。此药剂比三唑酮毒力强,其毒力指数(三唑酮为100)都在900以上,即达到 EC_(50)和 EC_(95)所需的剂量,前者只需后者的11%以下,特别是保护作用突出。据田间试验结果,此药剂的用药量比三唑酮少,如控制条锈病为害所需的剂量只要三唑酮的三分之一。防治条锈病的用药量一般以45—47g/ha(有效成分)为合适;用药期以病叶率5%—10%、小麦处于旗叶伸长期为宜;施药次数以上述的合适剂量和适期喷施1次即可控制整个成株期条锈病为害,收到最佳的经济效益。     

Studies on the origin,spread, and evolution of an important group ofPuccinia recondita f. sp.tritici pathotypes in Australasia

Wheat brown rust pathotype (pt) 104-2,3,(6),(7), 11 was first detected in Australasia in Victoria during 1984. Although it appeared similar to a pre-existing pathotype, 104-2,3,6,(7), detailed greenhouse test revealed nine pathogenic differences between the two rusts. Six differences involved contrasting virulence/avirulence for the resistance genes/specificitiesLr12, Lr27+Lr31 andLr16, and three uncharacterised genes, present in the wheat cultivars Gaza and Harrier, and in triticale cultivar Lasko. Differences in partial virulence between the pathotypes were found for the genesLr2a, Lr13 andLr26. A comparison of the phenotypes for 13 isozyme systems in the two pathotypes revealed two differences, including aPgm2 allele in pt 104-2,3,(6),(7),11 not found in other contemporary AustralasianPuccinia recondita f. sp.tritici pathotypes. On the basis of these differences, it was concluded that pt 104-2,3,(6),(7),11 was introduced into the Australasian region before or during 1984.Seven variants of pt 104-2,3,(6),(7),11, that differed by single virulences, were detected during 1984–1992. Pt 104-2,3,(6),(7),11 and a derivative pathotype with virulence forLr20 underwent rapid increases in frequency, largely displacing pathotypes which predominated before 1984. Although first detected in eastern Australia, both pathotypes spread to New Zealand, and the derivative pathotype appeared in Western Australia. The rapid spread and increase of these pathotypes could not be explained by host selection. Pt 104-2,3,(6),(7),11 and derivatives may therefore be more aggressive than other contemporary Australasian pathotypes.Abbreviations NSW New South Wales - Prt Puccinia recondita f. sp.tritici - Qld Queensland - SA South Australia - WA Western Australia     

GUS基因插入导致的小麦条锈菌突变体遗传稳定性和毒性变异研究

 对3个通过基因枪转化GUS基因获得的小麦条锈菌毒性突变体,进行GUS基因的表达活性检测、插入片段DNA的PCR电泳检测和Southern杂交验证;同时用17个国内鉴别寄主和37个黄淮麦区小麦主栽品种对这3个突变菌株进行了毒性谱的测定。结果表明突变菌株的外源GUS基因可稳定遗传;插入的外源基因片段引起了菌株毒性谱的改变。外源基因的插入位点与条锈菌的毒性基因相关。研究还表明插入突变体具有相对的遗传稳定性。研究结果可为克隆小麦条锈菌毒性基因和探明毒性基因的作用机理奠定理论基础。     

我国小麦条锈菌体细胞遗传重组的分子证据

 小麦条锈病是影响我国小麦生产的重要病害之一,条锈菌毒性变异是引致小麦品种抗病性丧失的主要原因。本文应用SSR分子标记技术,研究了陇南越夏区小麦条锈菌群体遗传结构,以期寻找条锈菌群体遗传重组的分子证据。研究结果表明,陇南地区小麦条锈菌群体遗传多样性比较丰富而遗传分化较小,遗传变异主要存在于群体内部,而在群体之间,遗传多样性有显著的差异。在11对SSR引物中,有4对能够检测到陇南地区小麦条锈菌群体存在遗传重组,而且重组体出现的频率不同,CPS15揭示的条锈菌重组体出现的频率为20.0%,CPS34揭示的条锈菌重组体出现的频率为18.5%,RJ20揭示的条锈菌重组体出现的频率为12.8%,RJ18揭示的条锈菌重组体出现的频率为15.0%,陇南地区小麦条锈菌群体重组体出现频率平均为16.6%。本文揭示的遗传重组现象表明陇南地区条锈菌体细胞结合十分普遍,由此推测我国小麦条锈菌在自然条件下通过遗传重组而导致毒性变异的可能性。     

秸秆覆盖全程节水对小麦病害发生的影响

通过秸秆覆盖全程节水对小麦病害发生影响调查,发现其主要病害有:小麦条锈病(Puccinia striiformis West)、小麦白粉病[Blumeria graminis(DC.) Speer]和小麦散黑穗病[Ustalago tritici(Pers)Jens.],免耕和秸秆覆盖处理对这3种病害的发生几乎没有影响;随冬季灌水量的增加,小麦条锈病发病减轻,小麦散黑穗病发病加重,对小麦白粉病影响不大。     

Effect of yellow rust on yield components of winter wheat in China

Experiments were done in 1983,1984 and 1985 in Beijing and Zhengzhou, People's Republic of China, to determine the relationship of yield components of wheat to the severity of yellow rust ( Puccinia striiformis f.sp. tritici ). Epidemics were manipulated by timing inoculation and fungicide applications. Disease, plant yield, number of ears per plant, number of grains per ear and 1000-grain weight were measured. Analysis indicated that there were interactions among the yield components. However, path coefficient analysis did not detect any statistically significant compensation and showed that there was a positive correlation among yield components. The correlation coefficients between AUDPC (area under disease progress curve, accumulated to each growth stage) and each yield component increased gradually with growth stage, thus providing no evidence of a critical stage at which a yield component was most affected by disease.     

Attempted somatic hybridization of Puccinia striiformis f. sp. tritici and P. striiformis f. sp. hordei

Attempts were made to produce somatic hybrids between isolates of Puccinia striiformis f. sp. tritici and f. sp. hordei. A mixed infection was produced on a common susceptible barley host, Fong Tien, using white-spored isolates of P. striiformis f. sp. tritici and yellow-spored isolates off. sp. hordei. Selection was made for non-parental spore colour on selective wheat and barley hosts, and variants thus isolated were analysed for virulence markers, and for isozyme and double-stranded RNA (dsRNA) markers, all of which clearly differentiated the parental isolates. Two white-spored (non-parental) isolates were found on the selective barley host which otherwise resembled the parental f. sp. hordei isolate in virulence, isozyme and dsRNA markers. The most likely explanation of the origin of these isolates is mutation to white spore colour in the f. sp. hordei isolate.     

小麦条锈菌冬孢子生物学特性研究进展

由小麦条锈菌引起的小麦条锈病是我国广大麦区的严重病害,研究其冬孢子产生原因与作用对于解析该病菌的生活史及遗传变异机制至关重要.通过对国内外相关研究成果的整理,综述了小麦条锈菌冬孢子的形态特征、生物学特性、寄主范围及其作用与功能等方面的研究进展.     

The intriguing and convoluted life of a heteroecious rust fungus in New Zealand

Molecular phylogenetic analyses of New Zealand rust fungi suggested that four taxa, Aecidium otagense on Clematis spp., Puccinia tiritea on Muehlenbeckia spp., Puccinia rhei‐undulati sensu auct. NZ, non (Dietel) Hirats. f. on Rheum ×rhabarbarum, and an unidentified Puccinia species on Rumex sagittatus, are a single species. Morphological studies and multilocus molecular data, together with inoculation studies, confirmed this finding. This species is only the third heteroecious rust fungus known to be native to New Zealand.     

欧洲小麦品种Mega抗条锈病基因的遗传分析及分子标记

 本研究表明欧洲小麦品种Mega对我国小麦条锈病重要流行小种CYR30、CYR31、CYR32、Su-4和Su-14在苗期都具有良好的抗病性。采用小麦条锈菌小种CYR30对Mega与感病小麦品种铭贤169杂交的F₁、F₂和BC₁代及双亲进行苗期抗病性遗传分析,结果表明,Mega对CYR30的抗性由1对显性基因独立控制。采用SSR标记技术对其携带的抗性基因进行分子标记,在237对SSR引物中,发现位于5BL上的2个SSR引物位点Barc232、Wmc640在双亲和抗、感池间能扩增出稳定的特异性片段,与抗病基因连锁的遗传距离分别是3.7cM和8.6cM,暂命名为YrMe。本研究结果为科学利用Mega抗条锈基因培育抗病品种提供了依据。     

冬小麦品种陇鉴9821抗条锈遗传分析

 冬小麦品种陇鉴9821是以甘肃陇南感病生产品种洮157为受体,以高粱总体DNA为供体系统选育而成,具有较好的丰产性和抗条锈性。本文对陇鉴9821抗条锈性及其遗传特点进行了研究,结果表明：苗期抗条锈基因推导分析得出,陇鉴9821对供试菌系的抗性谱与已知基因不同,含有未知抗条锈病基因;遗传分析显示对CYR29和CYR33的抗病性均由1对显性基因控制;通过抗病性鉴定和抗谱比较分析,认为陇鉴9821对CYR29和CYR33表现显性抗病性的基因是2对不同的抗条锈病基因,其中1对来自洮157。陇鉴9821可作为生产品种及抗源材料在生产上利用。     

Genetic analysis and molecular mapping of wheat genes conferring resistance to the wheat stripe rust and barley stripe rust pathogens

ABSTRACT Stripe rust is one of the most important diseases of wheat and barley worldwide. On wheat it is caused by Puccinia striiformis f. sp. tritici and on barley by P. striiformis f. sp. hordei Most wheat genotypes are resistant to P. striiformis f. sp. hordei and most barley genotypes are resistant to P. striiformis f. sp. tritici. To determine the genetics of resistance in wheat to P. striiformis f. sp. hordei, crosses were made between wheat genotypes Lemhi (resistant to P. striiformis f. sp. hordei) and PI 478214 (susceptible to P. striiformis f. sp. hordei). The greenhouse seedling test of 150 F(2) progeny from the Lemhi x PI 478214 cross, inoculated with race PSH-14 of P. striiformis f. sp. hordei, indicated that Lemhi has a dominant resistance gene. The single dominant gene was confirmed by testing seedlings of the F(1), BC(1) to the two parents, and 150 F(3) lines from the F(2) plants with the same race. The tests of the F(1), BC(1), and F(3) progeny with race PSH-48 of P. striiformis f. sp. hordei and PST-21 of P. striiformis f. sp. tritici also showed a dominant gene for resistance to these races. Cosegregation analyses of the F(3) data from the tests with the two races of P. striiformis f. sp. hordei and one race of P. striiformis f. sp. tritici suggested that the same gene conferred the resistance to both races of P. striiformis f. sp. hordei, and this gene was different but closely linked to Yr21, a previously reported gene in Lemhi conferring resistance to race PST-21 of P. striiformis f. sp. tritici. A linkage group consisting of 11 resistance gene analog polymorphism (RGAP) markers was established for the genes. The gene was confirmed to be on chromosome 1B by amplification of a set of nullitetrasomic Chinese Spring lines with an RGAP marker linked in repulsion with the resistance allele. The genetic information obtained from this study is useful in understanding interactions between inappropriate hosts and pathogens. The gene identified in Lemhi for resistance to P. striiformis f. sp. hordei should provide resistance to barley stripe rust when introgressed into barley cultivars.     

Predicting epidemics of yellow rust (Puccinia striiformis) on the upper canopy of wheat from disease observations on lower leaves

Data from field experiments were used to test whether disease observations on lower leaves of wheat were good predictors of future epidemic development in the upper canopy. Fungicide treatments to replicated plots in 1994 and 1995 caused variation in levels of initial inoculum of urediniospores of yellow rust ( Puccinia striiformis ). Observations of symptom severity were made on individual leaf layers throughout the season. Sporulating lesions on lower leaves were considered to be a measure of inoculum source strength for transfer to upper culm leaves. Low source strengths were associated with delays in epidemic development on the upper leaves, as quantified by a location parameter, t _m, the time at which severity reached half of the asymptote value in logistic fits to disease progress data on the upper leaves. However, there was much unexplained variation, probably due to extraneous variation in upward transfer efficiency of inoculum and rates of epidemic development. Vanderplank's sanitation ratio theory was used to account for variation in inoculum transfer and epidemic rate. The analysis revealed that if the aim is to predict disease on a newly emerged culm leaf, during the period when it can be treated effectively with fungicide, then observations of disease two leaves further down the culm were of the greatest predictive value ( R ² = 86%). These observations, however, need to be integrated with information about factors affecting upward inoculum transfer and rates of epidemic development if acceptable predictive precision is to be achieved.     

Clonality and long-distance migration of Puccinia striiformis f.sp. tritici in north-west Europe

The biotrophic fungus Puccinia striiformis f.sp. tritici , a basidiomycete that causes yellow rust on wheat, is spread by wind-dispersed spores. Analysis of amplified fragment length polymorphism (AFLP) variation showed that the fungus frequently migrates between the UK, Germany, France and Denmark. There is no biological evidence for sexual or parasexual reproduction under natural conditions, and this was supported by the lack of recombination, as revealed by AFLP, over the time and area represented by the samples in this study. A phylogeographic analysis revealed that there was effectively a single, clonal population in the four countries, up to 1700 km apart, consistent with a 'continent-island' model in which Denmark is the recipient of migrants from other countries. In five cases, specific pathogen clones were dispersed between the UK and Denmark, and on at least two recent occasions clones were also spread from the UK to Germany and France, causing outbreaks of yellow rust on wheat cultivars that were previously resistant to the disease in these countries. The agronomic consequences of migration were enhanced because of the limited genetic diversity for yellow rust resistance in wheat cultivars in the area. These results demonstrate that long-distance migration of pathogen clones, coupled with low diversity in the host species, may cause previously useful resistance genes to become ineffective for disease control on a continental scale.