Infection of potato and wheat by isolates of Rhizoctonia solani and R. cerealis

Isolates of Rhizoctonia were obtained from potato crops with stem canker or black scurf and from cereal crops with sharp eyespot. Those with many nuclei per cell, wide cells, darkening colonies and fast growth were assigned to R. solani ; those with two nuclei per cell, narrow cells, pale colonies and slow growth were assigned to R. cerealis . Only R. solani was obtained from potatoes and only R. cerealis from cereals. On young plants in the glasshouse, the isolates of R. solani infected potato substantially but not wheat; R. cerealis infected wheat substantially and potato slightly. This host preference was shown at temperatures between 10 and 25°C in growth rooms. R. solani on potato caused more disease with increasing temperature; no trend with temperature was observed for R. cerealis on wheat.     

利用荧光定量PCR检测禾谷丝核菌的相对生物量

小麦纹枯病是以禾谷丝核菌(Rhizoctonia cerealis)侵染为主的小麦土传病害。为建立检测禾谷丝核菌在寄主小麦(Triticum aestivum)中的相对生物量的可靠方法,促进小麦抗纹枯病机制的研究,本研究克隆了禾谷丝核菌肌动蛋白基因RcActin的部分(3′端)cDNA,并设计了RcActin的特异引物。该引物不仅能区分禾谷丝核菌与寄主小麦,还能区分全蚀病菌(Gaeumannomyces graminis)、根腐病菌(Bipolaris sorokiniana)和立枯丝核菌(Rhizoctonia solani)等常见小麦土传病害的病原菌,表明该引物能用于小麦纹枯病的分子检测,也能用于相对表达量的测定。利用相对定量法,以RcActin相对于寄主管家基因的相对表达量作为禾谷丝核菌相对生物量的指标,结果表明,此方法能准确反映禾谷丝核菌在寄主中的相对生物量和对小麦纹枯病抗性程度进行快速鉴定。     

Visual disease and PCR assessment of stem base diseases in winter wheat

Stem base disease (eyespot, sharp eyespot and brown foot rot) was assessed visually and by the polymerase chain reaction (PCR) technique on single plants sampled at four-week intervals in two crops of winter wheat grown in the UK in 1992–3. PCR assays were conducted for Fusarium avenaceum , F. culmorum , both varieties of Microdochium nivale , both eyespot-causing species of Tapesia and Rhizoctonia cerealis . PCR diagnoses were compared with visual diagnoses at each time point. Eyespot was caused principally by T. acuformis (R-type) and developed rapidly late in the season. Visual diagnoses of eyespot were largely confirmed by PCR but T. acuformis was detected in many plants lacking eyespot symptoms. R. cerealis was detected at relatively low incidences on both sites, and sharp eyespot visual diagnoses did not correlate with the incidence of any of the pathogens assayed by PCR. Brown foot rot, caused principally by Microdochium nivale var . majus , accumulated earlier in the season than eyespot. Overall, visual diagnoses of stem base disease coincided poorly with PCR data until after growth stage (GS) 30.     

中国小麦纹枯病化学防治研究进展

随着秸秆还田等耕作栽培措施的推广,中国小麦纹枯病发生日趋严重,对小麦的高产、稳产造成了很大威胁。由于缺乏免疫及高抗病性小麦品种,生产中对纹枯病一直采用播期拌种及春季喷雾相结合的化学防治方法。文章总结了当前中国小麦纹枯病的发生现状及主要病原;评述了三唑类药剂对纹枯病菌的毒力及对纹枯病的防治效果,介绍了生产中小麦纹枯病菌对三唑类药剂的抗药性现状及机理,分析了三唑类药剂对小麦的安全性;同时阐述了井冈霉素、甲基立枯磷及其他种类药剂在小麦纹枯病综合防治中的应用;指出小麦纹枯病化学防治的发展方向应是将生防菌剂同化学药剂相结合,实现生物防治与化学防治的协同应用。     

小麦纹枯病菌的分子检测

小麦茎基部可寄居多种真菌,并可导致发褐、坏死等症状,与小麦纹枯病相混淆.为准确诊断小麦纹枯病,根据江苏省小麦茎基部常见寄居菌禾谷丝核菌Rhizoctonia cerealis、立枯丝核菌Rhizoctonia solani、长蠕孢菌Helminthosporium spp.、交链孢菌Alternaria spp.、小麦全蚀病菌Gaeumannomyces graminis var.tritici和禾谷镰刀菌Fsarium graminearum rDNA的ITS区段序列差别,设计合成了2对特异性扩增引物(DNF77 DNR554,DNF81 DNR564)用于小麦纹枯病菌检测.2对引物均能从小麦纹枯病菌株扩增到特异性的分子片段,说明设计的特异性引物可以用来检测小麦纹枯病菌.采集田间具有小麦纹枯病症状、茎基部变褐及健康麦苗,进行病原菌分离,同时提取这些麦苗茎基部DNA,利用上述2对引物进行扩增.结果表明,仅从能分离到禾谷丝核菌的麦组织中扩增到约480bp的特异性条带.说明设计的特异性引物可以对田间小麦纹枯病进行早期、快速分子诊断.     

The escalating threat of Rhizoctonia cerealis, the causal agent of sharp eyespot in wheat

Rhizoctonia cerealis, the causal agent of sharp eyespot on wheat, was not considered to be an important pathogen for many years. Recently, the disease has become endemic in many countries except for South America. The disease has created a new threat to world wheat production because the damage of wheat sharp eyespot has become increasingly severe. In this paper, previous studies on this pathogen, including the disease geographical distribution, pathogen identification, life cycle, symptoms, favourable environmental conditions, effects on wheat yield and control strategy, are reviewed. Such information will be helpful in management of sharp eyespot.     

小麦纹枯病菌中的dsRNA及其与菌株生物学特性的相关性

对采集自我国山东、河南、江苏、安徽4省的21株小麦纹枯病菌菌丝中的dsRNA进行了检测,研究了dsRNA条带与菌株菌落形态、生长速度、对小麦的致病力等生物学特性之间的相关性。结果表明,从16个菌株中检测到dsRNA条带,dsRNA的大小和数量存在丰富的多样性。致病力测定结果表明这21个小麦纹枯病菌菌株的致病力差异显著。目前暂未发现小麦纹枯病菌中dsRNA的类型和数量与菌株的菌落形态、生长速度及致病力等性状存在明显的相关性,但是致病力较弱的菌株中dsRNA条带的多样性更丰富。本研究为今后发掘小麦纹枯病菌中的低毒真菌病毒作了初步的探索。     

小麦苗期抗纹枯病鉴定方法的改良及抗病品种筛选

Wheat sharp eyespot, caused by Rhizoctonia cerealis and R. solani, is a soil-borne fungal disease, which poses a great threat to wheat yield. In order to increase the identification efficiency of wheat sharp eyespot resistance, an improved method of rapidly identifying wheat sharp eyespot resistance was established by inoculating wheat seedlings with diseased wheat grains in greenhouse. To verify its reliability, four standard materials and 96 wheat varieties from Huanghuai wheat region were used for resistance assessment to sharp eyespot. Meanwhile, the resistance to Rhizoctonia solani of aforementioned materials in the field was identified by traditional methods. The results showed that the correlation coefficient between the four repetitions of the improved method ranged from 0.735 to 0.825, and the correlation coefficient between the average number of repetitions and the traditional method was 0.630. The results of wheat sharp eyespot resistance identification in Huanghuai wheat area showed that 66 wheat varieties were susceptible, accounting for 68.8% of tested materials. This indicated that the resistance of wheat varieties in Huanghuai wheat area to sharp eyespot was poor on the whole and needed to be improved urgently. At the same time, eleven wheat varieties which showed resistance to sharp eyespot at seedling and adult stages were screened, which include Zhengzhou 8998, Beijing 841, Handan 94-5316, Jimai 32, Jinmai 50, Jinmai 54, Longmai 157, Lumai 23, Shanhe 6, Shi 02-1 and Xinmai 18. Therefore, this study provides a method for identification of wheat sharp eyespot resistance at seedling stage, by which the resistance of wheat varieties to sharp eyespot can be quickly and efficiently identified. Furthermore, selected resistant materials provide important material resources for wheat sharp eyespot resistance breeding in Huanghuai wheat region and even in China.     

小麦纹枯病流行预测的研究

作者根据小麦纹枯病在冬麦区发生具有明显阶段性的特点,利用1984～1993年连续10年在纹枯病常发区山东省文登市的多品种、多地点的病情系统调查数据,采取统计学和流行学相结合的方法,组建了具有预测秋苗冬前发病率和返青后生长期病情指数的回归模型。并通过对小麦纹枯病普遍率和病情指数相关性的研究,将二阶段的模型耦联,完成对小麦整个生长期的病害流行动态全过程的预测。     

小麦苗期抗纹枯病鉴定方法的改良及抗病品种筛选

<正>小麦纹枯病又称尖眼斑(点)病,是由禾谷丝核菌(Rhizoctonia cerealis)和立枯丝核菌(Rhizoctonia solani)引起的一种以土壤传播为主的小麦真菌病害~([1])。引起小麦纹枯病的病原菌主要是禾谷丝核菌的第一菌丝融合群(CAG-1)~([2～4])。在自然条件下,病原菌首先侵染寄主植株基部叶鞘,随着     

Pathogenicity, symptom development, and mycotoxin formation in wheat by Fusarium species frequently isolated from sugar beet

Crop rotations with putative non-host crops such as sugar beet are often recommended to reduce Fusarium head blight (FHB) in cereals. However, recent observations have shown pathogenic, endophytic, and saprotrophic colonization of sugar beet with various Fusarium spp. Therefore, strains of seven species frequently isolated from sugar beet were tested for pathogenicity on wheat. Species-specific symptoms on heads and kernels were evaluated and the grains were analyzed for 20 mycotoxins with liquid chromatography-tandem mass spectrometry. Fusarium graminearum, F. culmorum, and F. cerealis from sugar beet caused typical FHB symptoms and mycotoxin contamination with deoxynivalenol and nivalenol, while a high incidence of black point was observed in heads inoculated with F. tricinctum or F. equiseti. Black point kernels revealed 3.4 to 14.5 times higher mycotoxin concentrations than symptomless grains, containing enniatin B1 at 38,000 μg/kg, moniliformin at 4,900 μg/kg, and 2-amino-14,16-dimethyloctadecan-3-ol at 5,500 μg/kg, as well as monoacetoxyscirpenol at 2,600 μg/kg and nivalenol at 3,800 μg/kg. Monitoring of these latter two species in the field is hampered by the lack of typical head symptoms after infection. In further experiments, the impact of sugar beet residues on FHB severity and the correlation between mycotoxin contamination of cereal lots and the amount of black point have to be evaluated.     

Development and use of a PCR assay to detect Rhizoctonia cerealis, the cause of sharp eyespot in wheat

Random amplified polymorphic DNA assays were carried out on a range of isolates of Rhizoctonia cerealis to identify markers common to all isolates. Two fragments were isolated, cloned and used to probe Southern blots of DNA from R. cerealis and isolates from a range of anastomosis groups of Rhizoctonia solani. The two fragments hybridized specifically to DNA of R. cerealis and not to DNA of any of the isolates of R. solani. Both fragments were partially sequenced and two pairs of primers were generated for use in the polymerase chain reaction (PCR). Amplification of a fragment of the anticipated size occurred following PCR of all isolates of R. cerealis and not from any of a range of fungal species associated with disease of the stem base of cereals. The primer pairs for R. cerealis were also used, along with those for Microdochium nivale and W and R-type of Pseudocercosporell herpotrichoides , to deled these pathogens in extracts from field-grown wheat plants exhibiting symptoms of sharp eyespot, eyespot, foot rot or a combination of the diseases. No relationship was found between visual disease assessment of sharp eyespot at growth stage 37 and the results of PCR However, the results of PCR and visual disease assessment at growth stage 75 were similar, indicating that visual disease assessment may not be reliable until later growth stages. This system offers the potential to detect the presence of R. cerealis in cereals and avoid problems commonly associated with conventional diagnosis of this disease and isolation of the pathogen.     

戊唑醇种子处理防治小麦纹枯病

种子处理是控制小麦纹枯病的有效措施,在小麦纹枯病的综合治理技术体系中起着举足轻重的作用。在苏南宜兴和淮北徐州,2％戊唑醇湿拌剂和6％戊唑醇悬剂胺10kg麦种拌药0.3-0.4g有效成分,对小麦的出苗没有显著影响,对根系和冬前分蘖具有促进作用。对小麦纹枯病的控制效果较为理想,表现为冬前效果显著,病析率防效60％－100％,从而有效地抑制了冬前发病高峰。戊唑醇处理区拔节期的病情指仍然极显著地低于对照区,亦显著低于对照药剂纹霉净,侵茎高峰明显推迟,最终的枯白穗防效突出,0.3-0.4g ai/10kg种子拌种的枯白穗防效达到85％以上。由于控病和对小麦生长调控的双重作用,保穗、保产效果明显,最终产量较对照增加10％－15％。     

Detection of Gibellina cerealis infection on winter common wheat in Ukraine

Journal of Plant Diseases and Protection - False eyespot disease caused by Gibellina cerealis (Pass.) Pass. was first detected in Ukraine during field inspections of wheat canopies in...     

Characteristics and pathogenicity of isolates of Rhizoctonia spp. associated with damping-off of sugar beet

Rhizoctonia solani and R. cerealis were isolated from diseased sugar-beet seedlings in Ireland. Isolates of R. solani were assigned to anastomosis groups AG-2, AG-4, AG-5 and an unidentified group that did not anastomose with recognized tester isolates. Cultures of AG-2 were similar to those of AG-5 on oatmeal agar (OA) and potato-dextrose-marmite agar (PDMA). Cultures of AG-4, the unidentified group and R. cerealis were morphologically distinct from one another, AG-2 and AG-5. The optimum temperature for growth of AG-2 was 225 C, with optimum growth of AG-4, AG-5 and the unidentified group at 275-C. R. cerealis grew slower than all groups of R. solani, with optimum growth at 225°C. Hyphae of R. cerealis were significantly narrower than those of the groups of R. solani studied. In glasshouse pathogenicity tests, some AG-2 and all AG-4, AG-5 and isolates from the unidentified group caused damping-off of beet seedlings. In controlled environments of 10-25°C, an AG-2 isolate was the most aggressive at 10 C whilst AG-4, AG-5 and the unidentified group caused most disease at or above 15°C. R. cerealis was also pathogenic to beet seedlings, causing damping-off at 10 and 15 C.     

河南省小麦纹枯病菌对三唑酮的敏感性

正小麦纹枯病是一种世界分布的土传真菌病害。近年来该病在我国冬小麦种植区发生普遍,已成为小麦高产、稳产的重大障碍~([1])。河南省是我国小麦主产区之一,近几年小麦纹枯病的发生面积连续在300万hm~2左右,危害严重~([2])。目前,尚未发现高抗纹枯病的小麦品种,控制该病害主要依靠药剂种子处理结合春季喷雾来进行,所用药剂包括井冈霉素和以三唑酮为代表的三唑类化学药剂。随着     

小麦纹枯病品种抗性鉴定技术及抗病资源的筛选与分析

分别用玉米粉－砂、麦粒和玉米秸秆作为小麦纹枯菌生长基质,培养获得小麦纹枯病菌接种物。土壤接种诱发试验表明,三种接种物在合适的接种强度下,均能有效诱发泪科纹枯病。据此建立的人工病围２对１５份小麦产多年连续鉴定结果表明,病圃具有较稳定的发病率,表现为典型的尖眼点或云纹病斑。对我国主要冬麦区的１３００份小麦品种资源、生产品种以及新育成品系进行了病圃鉴定,共筛选出抗纹枯病材料８５份,包括菜籽黄、紫秆子、白     

不同茬口条件下的作物根渗出物对大豆胞囊线虫(Heterodera glycines)卵孵化影响

 取北方5种作物轮作茬口和休闲土壤种植火豆、玉米、小麦、亚麻和甜菜,出苗后22 d制备作物的根渗出物,观察其对大豆胞囊线虫卯孵化的影响。试验表明,麦豆麦迎茬的甜菜根渗出物在后期大豆胞囊线虫(SCN)的卵孵化率最高,豆麦米轮作茬的大豆根渗出物9 d后SCN的卵孵化率明显高于其它作物,米豆米茬口的玉米根渗出物SCN的卵孵化率较高,豆麦豆迎茬甜菜根渗出物SCN的卵孵化率明显高于所有供试作物,12年大豆连作茬甜菜从一开始卵孵化率就高于对照和其它4种作物,休闲区的5种作物根渗出物也有对SCN卵孵化的刺激作用。     

小麦纹枯病拮抗细菌的筛选

 从小麦纹枯病病田土壤中分离到722株细菌,通过对峙培养法筛选出拮抗细菌397株,拮抗菌率为55.0%。细菌对小麦纹枯病病原菌的拮抗作用分为两种类型:其一以竞争作用为主,表现为菌株生长快,抑菌率高但抑菌带较窄,如菌株BNT-25抑菌效果可达100.0%,抑菌带仅为2 mm;其二为抗生物质的产生,表现为菌株生长慢,菌落小,抑菌率高且抑菌带宽,如JJ-5菌株抑菌效果可达94.3%,抑菌带为12 mm。选用18株抑菌作用良好的拮抗细菌在室内测定其防治小麦苗期纹枯病的效果。结果发现,与空白对照相比,有9株拮抗细菌的防治效果达到了极显著水平,有15株拮抗细菌的防治效果达到了显著水平。在极显著水平中菌株NZT-47、MTT-8和DHT-12的防治效果分别为76.45%、64.03%和58.89%,对小麦纹枯病表现了较高的防治效果;菌株HNT-7-16、BDT-94和BNT-28的防治效果分别为43.47%、40.97%和40.97%,具有一定的防治作用。其中NZT-47的防治效果最好。     

Evaluation of diagnostic and quantitative PCR for the identification and severity assessment of eyespot and sharp eyespot in winter wheat

Diagnostic and quantitative polymerase chain reaction (PCR) provided clarification of the causes of symptoms and the extent of infection by eyespot ( Tapesia spp.) and sharp eyespot ( Rhizoctonia cerealis ) on winter wheat at early growth stages. Disease assessments made before stem extension, when decisions to apply fungicides are usually made, often did not agree with the pathogen diagnoses using PCR, suggesting that such early visual diagnoses may be unreliable. Visual and PCR diagnoses made on stems in summer generally supported each other, but there were often discrepancies in relating disease severity to amounts of pathogen present when determined by regression analyses of incidence or severity of symptoms on amount of pathogen DNA. Mixed symptoms caused by different pathogens may sometimes have been confounded. Relationships between symptoms and DNA of eyespot pathogens were less clear on some cultivars, often those with least disease. Sharp eyespot symptoms had a stronger relationship to DNA of its pathogen. Significant regressions often accounted for a small percentage of the variance, suggesting either that pathogens not assayed were contributing to symptoms or that lesions were in some cases persisting longer into the season than pathogen DNA. The frequency of pathogen detection before stem extension was a poor predictor of the amounts of pathogen DNA measured later in the season.