Isolation and characterization of Clavibacter tritici associated with Anguina tritici in wheat from Western Australia

Two infestations of Anguina tritici in Western Australia were investigated for the presence of Clavibacter tritici. Five strains of C tritici were isolated from each site and compared with strains from Egypt, India, Iran and Iraq by allozyme electrophoresis. The Australian strains were genetically homogeneous but distinct from the non-Australian strains. A. tritici galls were found to be colonized by C. tritici , a feature of C. tritici infection not previously reported. C. tritici strains from Australia adhered to A, tritici but not to Anguina funesta. No corynetoxins were detected in C. tritici-infected galls. The potential of non-toxigenic Clavibacter species, such as C. tritici , for biocontrol of Clavibacter toxicus , the species responsible for poisoning livestock, is discussed.     

麦蒲螨对黑沙蒿主要害虫寄主选择行为研究

麦蒲螨[Pyemotes tritici(LaGreze-Fossat et Montagne)]是黑沙蒿主要钻蛀性害虫沙蒿大粒象(Adosomus sp.)和沙蒿尖翅吉丁(Sphenopterasp.)的重要寄生性天敌。为明确麦蒲螨的寄主选择行为,本文分别研究了麦蒲螨对黑沙蒿4种钻蛀性害虫、同一寄主不同发育阶段、受害黑沙蒿根部以及害虫虫粪的选择行为。结果表明:麦蒲螨对4种害虫以及同种害虫不同龄期幼虫有明显的选择现象,其中,对沙蒿尖翅吉丁的趋向性相对最高,沙蒿蛀茎蛾次之,沙蒿大粒象相对较小;相对于寄主的初孵幼虫,麦蒲螨对其老熟幼虫和蛹的趋向性更为强烈;不同种类害虫幼虫对麦蒲螨的寄主定位起到重要作用,而不同种害虫的虫粪对麦蒲螨的寄主选择行为也有一定的作用。相比受害黑沙蒿而言,健康黑沙蒿对麦蒲螨有明显的驱避现象。研究结果为揭示麦蒲螨对黑沙蒿不同钻蛀性害虫的寄主偏好性,利用麦蒲螨进行黑沙蒿主要害虫的生物防治提供了理论依据。     

麦蒲螨寄生麦蛾柔茧蜂初报

本文对麦蒲螨Pyemotes tritici(Lagreze-Fossat et Montagne)侵染印度谷螟Plodia interpunctella (Hubner)和麦蛾柔茧蜂Habrobracon hebetor(Say,1836)的症状进行了扼要的记述,同时介绍了该螨的主要寄主及分布情况。这是该螨寄生麦蛾柔茧蜂的首次报道。     

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。     

Cytological Evidence of an Active Role of Silicon in Wheat Resistance to Powdery Mildew (Blumeria graminis f. sp. tritici)

ABSTRACT Silicon (Si) amendments in the form of exogenously supplied nutrient solution or calcium silicate slag protect wheat plants from powdery mildew disease caused by the fungus Blumeria graminis f. sp. tritici. The most striking difference between Si- and Si+ plants challenged with B. graminis f. sp. tritici was the extent of epidermal cell infection and colonization by B. graminis f. sp. tritici. Histological and ultrastructural analyses revealed that epidermal cells of Si+ plants reacted to B. graminis f. sp. tritici attack with specific defense reactions including papilla formation, production of callose, and release of electron-dense osmiophilic material identified by cytochemical labeling as glycosilated phenolics. Phenolic material not only accumulated along the cell wall but also was associated with altered integrity of haustoria in a manner similar to localized phytoalexins as reported from other pathosystems. These results strongly suggest that Si mediates active localized cell defenses against B. graminis f. sp. tritici attack.     

Resistance stability to Septoria tritici blotch and comparison of screening methods for ranking STB disease

Journal of Plant Diseases and Protection - Septoria tritici blotch (STB), caused by the ascomycete fungus Zymoseptoria tritici (formerly known as Mycosphaerella graminicola), is a devastating...     

3种粒线虫多重PCR检测方法

 剪股颖粒线虫[Anguina agrostis (Steinbuch,1799) Filipjev,1936]、小麦粒线虫[Anguina tritici (Steinbuch,1799) Filipjev,1936]和维氏粒线虫[Anguina wevelli (Van den Berg,1985) Siddiqi,2000]都是重要的植物病原线虫,它们在成熟种子和虫瘿中的虫态通常是幼虫,而这3种线虫的幼虫形态非常相似,难以根据其特征对它们进行快速准确的种类鉴定。本研究根据这3种线虫的rDNA-ITS区域序列,分别设计筛选了特异性引物AgrF₁/AgrR1、TriF₁/TriR1、WevF₁/WevR1,构建了这3种线虫单条幼虫多重PCR检测体系,获得3个大小差异明显的片段,表明这些引物设计合理,适合这3种线虫的快速准确检测。     

Suppression of septoria tritici blotch and leaf rust on wheat seedling leaves by pseudomonads

Application of cells of two isolates of fluorescent pseudomonads from soil to wheat seedlings prior to inoculation with Mycosphaerella graminicola (anamorph, Septoria tritici) or Puccinia recondita f.sp. tritici markedly reduced symptom expression. These Pseudomonas isolates, LEC 1 and LEC 2. also reduced in vitro growth of Geotrichum candidum. Rhizoctonia solani. Sclerotium rolfsii and S. tritici. Growth of the melanin-producing isolate ISR398 of S. tritici was inhibited on silica gel thin-layer chromatograms by compound(s) extracted with diethyl ether from King's Medium B colonized by Pseudomonas isolate LEC 1. The growth of the antagonistic pseudomonads on defined medium was not affected by the following commercial fungicides: benomyl, captafol, chlorothalonil, fenarimol, mancozeb, maneb, metalaxyl, prochloraz, propiconazole, triadimefon, and the herbicides 2,4-D and diclofop-methyl at the recommended concentrations     

Removal of urediniospores of brown (Puccinia recondita f.sp. tritici) and yellow (P. striiformis) rusts of wheat from infected leaves submitted to a mechanical stress

The passive spore removal from colonies due to mechanical stress was compared in the brown (Puccinia recondita f.sp. tritici) and yellow (P. striiformis) rusts of wheat. Mechanical stress was applied using either a miniaturized wind tunnel or a centrifuge. In wind-tunnel experiments, a wind of minimum velocity of 1.3 and 1.8 m s^-1 for P. recondita f.sp. tritici and P. striiformis, respectively, applied for at least 10 seconds, was necessary to remove spores. The interaction between wind velocity and cumulated duration was significant for both rusts. At low wind velocity, a longer duration was required to remove the spores than at high wind velocity, and vice versa. In centrifugation experiments, the maximum spore removal occurred for angular velocities of 10³ and 2 10³ rotations min^-1, for P. recondita f.sp. tritici and P. striiformis, respectively, applied for 5 min. Calculation of the aerodynamic and centrifugal forces showed that the forces necessary to remove spores are greater for P. striiformis than for P. recondita f.sp. tritici. This difference can be related to the size of the dispersal unit, which is larger in P. striiformis than in P. recondita f.sp. tritici due to spore clustering. These observations are consistent with the differences in the mean spore dispersal distance, which is usually smaller in P. striiformis than in P. recondita f.sp. tritici.     

小麦白粉菌HSP70基因的克隆及高温胁迫对其表达的影响

小麦白粉病是由专性寄生菌Blumeria graminisf.sp.tritici引起的一种重要的气传真菌病害,该病曾于1990-1991年两年在我国发生大流行,近年来其发生面积也一直维持在500万公顷以上,给我国小麦生产造成了严重的损失.已有的研究结果表明,温度不但影响小麦白粉病的发生和流行,而且温度胁迫作用还会对白粉病菌群体产生影响,从而使病菌群体对温度的敏感性降低.目前已发现在我国白粉病菌群体中存在抗高温或耐高温的菌株,而且这些菌株在较高的温度下其寄生适合度要高于对温度高敏感性的菌株[1].由于病菌群体对温度敏感性的变化有可能影响病害越夏和越冬的范围,进而影响病害的发生和流行程度,因此,有必要对其耐高温的分子机制进行研究,这对于了解小麦白粉菌对温度的适应性以及气候变暖对此病害发生和流行的长期影响具有重要的意义.     

Specificity of Prehaustorial Resistance to Puccinia hordei and to Two Inappropriate Rust Fungi in Barley

ABSTRACT To elucidate the specificity of prehaustorial resistance to inappropriate rust fungi, we studied two populations of recombinant inbred lines of barley that segregated for partial resistance (PR) to Puccinia hordei and for the resistance to the inappropriate rust species P. recondita f. sp. tritici and P. hordei-murini. PR to P. hordei is prehaustorial and nonhypersensitive, and its level can be assessed accurately by measuring the latent period of the fungus. The resistance to the inappropriate rust species is a combination of prehaustorial (nonhypersensitive) and posthaustorial (hypersensitive) mechanisms. The amount of nonhypersensitive, early abortion of P. recondita f. sp. tritici and P. hordei-murini sporelings reflects the degree of prehaustorial defense to the two inappropriate rust species. All lines showing a long latent period of P. hordei also had a relatively high level of early abortion of the growth of P. recondita f. sp. tritici and P. hordei-murini. This indicates that genes for PR to P. hordei are also effective against these two inappropriate rust species. The reverse was not necessarily true; some lines showing a high level of early abortion of P. recondita f. sp. tritici and P. hordei-murini had a low level of PR to P. hordei. Moreover, lines with a similar level of prehaustorial resistance to P. recondita f. sp. tritici could differ considerably in their prehaustorial resistance to P. hordei-murini. This indicates that genes for prehaustorial resistance may exhibit rust species specificity.     

Evidence of a Multicopper Oxidase in Mn Oxidation by Gaeumannomyces graminis var. tritici

ABSTRACT Manganese (Mn) oxidation by the plant-pathogenic fungus Gaeumannomyces graminis var. tritici has been correlated with virulence in take-all disease. The mechanism of Mn oxidation has not, however, been investigated adequately. Research on bacteria and other fungi indicates that Mn oxidation is most often the result of the activity of multicopper oxidases. To determine if G. graminis var. tritici oxidizes Mn by similar means, the Mn oxidizing factor (MOF) produced by G. graminis var. tritici was characterized by cultural, spectrophotometric, and cellulose acetate electrophoresis methods. Based on our results, the MOF is an extracellular enzyme with an estimated molecular weight of 50 to 100 kDa. Electrophoresis and spectrophotometry indicate that the MOF is a multicopper oxidase with laccase activity.     

Wheat Diseases in Turkey1

Cereal crop production is one of the most important projects in the agricultural improvement programme for Turkey. Overall, wheat represents 61 % of the cereal crop. While wheat production was almost 4 million tons in 1950, this reached a limit of 10 million tons in 1970. A number of diseases continue to afflict the crop from time to time, causing heavy losses. The most important of these are: bunt ( Tilletia foetida and T. caries ), loose smut ( Ustilago nuda ), rusts ( Puccinia strilformis, P. graminis f. sp. tritici, P. recondita f. sp. tritici ), leaf blotch ( Septoria tritici ), root and foot rots ( Fusarium spp., Drechslera sorokiniana, Pseudocercosporella herpotrichoides, Alternarla alternate, Sclerotium spp. and Rhizoctonia spp.). The diseases appear all over the country. Average losses due to rusts in epidemics are estimated at about 30–35 % in the whole country. Annual losses from covered smut are about 15–20 %, and from loose smut from 0.1 % to almost 20 % depending on the weather conditions of the year, on variety and on locality. Root rots have gained importance in some places, especially in Thrace in the last few years. In addition to the above diseases, several others occur occasionally but are of minor importance: powdery mildew ( Erysiphe graminis f. sp. tritici ), dwarf smut ( Tilletia contraversa ), flag smut ( Urocystis tritici ), take-all ( Gaeumannomyces graminis ) and a wheat mosaic virus (recently observed in a province of Central Anatolia).     

Suppression of Septoria tritici and Puccinia recondita of wheat by an antibiotic-producing fluorescent pseudomonad

A fluorescent Pseudomonas sp. (strain LEC 1) isolated from soil suppressed Septoria tritici by 88% and Puccinia recondita by 98% when applied to wheat seedlings 3 h prior to inoculation with the pathogens. Fractionation and analysis of two inhibitory compounds from cultures of strain LEC 1 on thin-layer chromatography plates yielded the phenazine antibiotics 1-hydroxyphenazine (phOH) and chlorora-phin. 1-hydroxyphenazine reduced the growth of Pythium aphanidermatum, Fusarium oxysporum f.sp. vasinfectum, Sclerotinia sclerotiorum and S. rolfsii on a denned medium, with greatest activity against P. aphanidermatum and least against S. rolfsii. Application of 160 mg/l phOH to wheat seedlings reduced S. tritici by 61% and P. recondita by 75%. Lower concentrations of the antibiotic were less effective. Growth of 5. tritici in liquid medium was reduced by phOH at 5–20 mg/l and prevented at 40 mg/l. When phOH was added to the medium 48 h after inoculation (logarithmic growth phase), growth was interrupted but later recovered with phOH concentrations up to 40 mg/l; there was no recovery at 60 mg/l. Chlororaphin inhibited the growth of S. tritici on malt agar medium.     

Host-pathogen relationship of geographically diverse isolates of Septoria tritici and wheat cultivars

Pathogenic variability of 14 Septoria tritici isolates from different locations in the USA (California, Oregon, and Texas) was determined on seedlings of two sets of geographically diverse wheat cultivars under greenhouse conditions. Significant isolate effects, cultivar effects, and isolate × cultivar interactions were found, and a substantial amount of variation was accounted for by the interaction terms compared with the main effects of isolate and cultivar. All isolates were pathogenic on the cultivars tested but the degree of virulence on the individual cultivars varied among isolates. Linear contrasts between all homologous combinations (isolate × cultivar combination of same geographic location) and all heterologous combinations (isolate × cultivar combination of different locations) indicated that homologous combinations produced significantly more disease than heterologous combinations. The results demonstrate location-specific adaptation of S. tritici. Implications of pathogenic variability and local adaptation in S. tritici are discussed.     

The effects of various crops on the survival and carry-over of the wheat take-all fungus Gaeumannomyces graminis var. tritici

The effects of various crops on the saprophytic survival and carry-over of Gaeumannomyces graminis var. tritici were studied in the glasshouse and field.
In the glasshouse, survival of G. g. tritici was greater in unplanted pots than in pots planted with either cereals or non-cereals. In the field, fallow and various non-cereal crops reduced carryover of take-all but the disease was severe after wheat, barley and triticale. Grain yields were higher after fallow and non-cereals than after cereal crops.     

PSR(Puccinia Striiformis Repeat)序列的基因组特异性和指纹遗传稳定性研究

 以PSR331S₃(Puccinia striiformis repeat)为探针,对感染小麦条锈菌P. striiformis f. sp. tritici模式菌系的叶片和常用繁殖寄主健康叶片总DNA进行Southern分析,结果显示PSR331S₃具有良好的指纹分辨力和基因组特异性。对系列单孢系的指纹分析表明,PSR位点在有丝分裂中是稳定遗传的,可以用于条锈菌的遗传分析。     

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。     

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。     

河北省小麦全蚀病菌变种类型鉴定

2007年从河北省的保定、石家庄、邢台小麦主产区采集小麦全蚀病株,共分离得到62个菌株,对其所属的变种类型进行了形态学和分子生物学鉴定。根据形态、培养性状、生理特性以及在小麦、高粱、水稻、玉米、燕麦等禾本科作物上的致病性,初步认定测定的所有菌株均为禾顶囊壳小麦变种(Gaeumannomyces graminisvar.tritici)。进一步采用4个变种的特异性引物进行PCR扩增,在所有菌株中扩增出870bp的条带,该片段为禾顶囊壳小麦变种特异性片段,证实所测菌株均为禾顶囊壳小麦变种。