Genome-wide association analysis of resistance to wheat spindle streak mosaic virus in bread wheat

Wheat spindle streak mosaic virus (WSSMV) is a major concern for cereal crops in Europe and North America. A strong increase in the occurrence of WSSMV has been observed in each French region where susceptible cultivars are cultivated. Most European bread wheat cultivars are resistant, but assessing the status of newly registered cultivars or breeding lines regarding WSSMV resistance is of importance. This paper describes a genome-wide association study carried out on a panel of 163 cultivars and tested for their resistance to WSSMV. Two regions on chromosomes 5B and 7D showed minor effects on WSSMV resistance. More importantly, a large genomic region on chromosome 2D explained most of the resistance to WSSMV. More than 99% of the cultivars carrying the AA genotype at the most associated marker (Excalibur_c15426_661) were resistant to WSSMV, while 100% of the cultivars showing the GG genotype were susceptible. This large genomic region of 45.8 Mb was found distal to the centromere and showed very high linkage disequilibrium. It is hypothesized that this region may be an alien introgression originating from a wild related species. This region contains a total of 2605 predicted genes based on the Chinese Spring IWGSC RefSeq v. 1.0 including genes potentially involved in plant disease resistance. A kompetitive allele-specific PCR (KASP) single-nucleotide polymorphism (SNP) marker was designed in order to identify breeding lines or registered cultivars resistant to WSSMV.     

The 3' terminal sequence of RNA1 of wheat spindle streak mosaic virus canadian isolate (WSSMV-C)

The sequence of the 3 terminal 1722 nucleotides (nts) of RNA1 of the type (Canadian) isolate of wheat spindle streak mosaic bymovirus (WSSMV-C) was determined. The sequence started within a single open reading frame (ORF), which was expected to encode the carboxyl terminus of the nuclear inclusion b protein (NIb) and the capsid protein (CP) of 294 amino acids, followed by a 3 untranslated region (UTR) of 237 nucleotides. The NIb and CP of WSSMV-C share 99 and 100% amino acid sequence identity with the corresponding proteins of WSSMV-French isolate (WSSMV-F), but only 89 and 77% with wheat yellow mosaic virus (WYMV-J), respectively. The 3UTR of RNA1 of WSSMV-C shares 94% nucleotide sequence identity with that of WSSMV-F but only 73% with WYMV-J and WYMV-Chinese isolate (WYMV-Chi). The results support the classification of WSSMV-C and WSSMV-F as strains of the same virus species which is distinct from WYMV.     

Occurrence of barley yellow mosaic and barley mild mosaic bymoviruses in Greece

In March 1991, large chlorotic patches appeared in an autumn-sown barley crop growing near Thessaloniki, Greece. Leaves had characteristic mosaic symptoms and immunosorbent electron microscopy and enzyme-linked immunosorbent assay confirmed the presence of both soil-borne mosaic viruses of barley, barley mild mosaic and barley yellow mosaic bymoviruses. In the following year, similar symptoms appeared in a crop at Souroti, 30 km east of Thessaloniki but the disease has not been found in other areas of Macedonia. This report is the first record of these viruses from Greece and is the most southerly European record.     

An isolate of Wheat streak mosaic virus from foxtail overcomes Wsm2 resistance in wheat

Wheat streak mosaic virus (WSMV) is an economically important pathogen of wheat (Triticum aestivum) causing major yield losses in regions where severe infection occurs. To detect the presence of any new virus or new WSMV isolates, green foxtail (Setaria viridis) plants exhibiting virus-like symptoms were sampled in a summer-fallowed wheat field at the Agricultural Research Center-Hays, Kansas State University, Hays, Kansas. These plants were tested serologically for four wheat viruses: WSMV, Triticum mosaic virus (TriMV), High Plains wheat mosaic virus (HPWMoV) and Foxtail mosaic virus (FoMV). Among 38 plant samples exhibiting virus-like symptoms, 29 contained WSMV as indicated by ELISA. Four isolates from samples with relatively strong reactions were transferred to healthy wheat seedlings by mechanical inoculation in a growth chamber for pathogenicity testing. Three isolates were avirulent to a wheat variety RonL, which contains Wsm2, a gene providing temperature-sensitive resistance to currently prevalent isolates of WSMV. However, one isolate, KSH294, was able to infect RonL and showed more virulence on two other varieties/lines containing Wsm2. Further sequence and phylogenetic analysis of KSH294 confirmed that this isolate displays a sequence homology with WSMV, but has sequence differences making it distinct from previously identified WSMV isolates included in the phylogenetic analysis.     

A novel putative member of the family Benyviridae is associated with soilborne wheat mosaic disease in Brazil

Soilborne wheat mosaic disease (SBWMD), originally attributed to infections by Soilborne wheat mosaic virus (SBWMV) and Wheat spindle streak mosaic virus (WSSMV), is one of the most frequent virus diseases and causes economic losses in wheat in southern Brazil. This study aimed to characterize molecularly the viral species associated with wheat plants showing mosaic symptoms in Brazil. Wheat leaves and stems displaying mosaic symptoms were collected from different wheat cultivars in Passo Fundo municipality, Rio Grande do Sul State, southern Brazil. Double-stranded RNA was extracted and submitted to cDNA library synthesis and next-generation sequencing. No sequences of SBWMV and WSSMV were detected but the complete genome sequence of a putative new member of the family Benyviridae was determined, for which the name wheat stripe mosaic virus (WhSMV) is proposed. WhSMV has a bipartite genome with RNA 1 and RNA 2 organization similar to that of viruses belonging to Benyviridae. WhSMV RNA 1 has a single open reading frame (ORF) encoding a polyprotein with putative viral replicase function. WhSMV RNA 2 has six ORFs encoding the coat protein, the major protein (read-through), triple gene block movement proteins (TGB 1, 2 and 3) and ORF 6 (hypothetical protein). In addition to the genomic organization and nucleotide and amino acid sequence identities, phylogenetic analyses also corroborated that WhSMV is a virus species of the Benyviridae. However, isolates of WhSMV formed a clade distinct from members of the genus Benyvirus. It was also demonstrated that the plasmodiophorid Polymyxa graminis is associated with wheat roots showing SBWMD symptoms and infected by WhSMV.     

Differences in cultivar response and complete sequence analysis of two isolates of wheat yellow mosaic bymovirus in China

Seeds of selected European and Japanese winter wheat cultivars were grown at two experimental sites in China, namely Yaan, Sichuan province (YA), and Yangzhou, Jiangsu province (YZ), where wheat yellow mosaic bymovirus (WYMV) was severe. There were some differential responses of the cultivars to the virus isolates present at the two sites. The complete nucleotide sequence of both RNAs of both virus isolates was determined. Their genome organization was identical to that reported for a Japanese isolate and the sizes were very similar. Nucleotide comparisons demonstrated that parts of the CI and NIa coding regions on RNA1 and the N-terminal part of the P2 coding region on RNA2 were particularly variable, while substantially conserved regions occurred in the 3' UTR of RNA2, the 7K, one part of the CI and parts of the NIb and coat protein. It seems unlikely that differences in the 7K and NIa-VPg proteins are responsible for virulence differences and the CI and NIb regions were considered the most promising for further study.     

A controlled environment test for resistance to Soil-borne cereal mosaic virus (SBCMV) and its use to determine the mode of inheritance of resistance in wheat cv. Cadenza and for screening Triticum monococcum genotypes for sources of SBCMV resistance

Several wheat genotypes, including eight with known field responses, were evaluated for their reaction to Soil-borne cereal mosaic virus (SBCMV, genus Furovirus) by growing in naturally infested soil under controlled environment conditions. Virus antigen titres in the foliage 8–9 weeks after sowing mostly reflected the field responses, showing that growth chamber-based tests can be used to improve the speed and reliability of germplasm screening. Such tests were used to determine the mode of inheritance of the SBCMV resistance in cv. Cadenza, commonly used in UK wheat-breeding programmes. One hundred and eleven doubled haploid (DH) lines derived from an F ₁ of a cross between cvs Cadenza (resistant) and Avalon (susceptible) were evaluated. This DH population segregated for the reaction to SBCMV in a ratio of 1 : 1 (resistant : susceptible). This suggests that the SBCMV resistance is controlled by a single gene locus. As a first step towards identification of new sources of improved SBCMV resistance (e.g. immunity) as well as sources of the resistance to the virus vector, Polymyxa graminis , a set of 26 Triticum monococcum lines of diverse geographical origin was also screened. Most lines were susceptible to SBCMV, but one line of Bulgarian origin was resistant to the virus and possibly partially resistant to the virus vector.     

甘蔗线条花叶病毒HC-Pro基因的分子变异分析

为了解析甘蔗线条花叶病毒Sugarcane streak mosaic virus(SCSMV)不同分离物HC-Pro基因的分子变异规律,本研究利用RT-PCR法扩增获得SCSMV HC-Pro基因的序列,通过生物信息学分析,分别从重组、系统发生、选择压力等方面研究SCSMV HC-Pro基因的分子变异特征。共测定了44条SCSMV HC-Pro基因序列,相似性最低值为70%;HC-Pro基因重组频率较低,仅发现3个重组位点,其中一个系首次报道;与先前报道相比,部分新测定云南蔗区的SCSMV分离物在HC-Pro基因上形成一个新组-第Ⅲ组;HC-Pro基因处于很强的负选择压力作用,未发现正向选择作用位点。本研究结果进一步证明SCSMV HC-Pro基因具有高度的遗传多样性。     

中国小麦黄花叶病毒(WYMV)分布的RT-PCR鉴定

 镰刀菌产生的单端孢霉烯毒素,包括DON、DAS和T-2毒素,是一类重要的植物病原真菌毒素。这类毒素不仅加强病菌的为害程度,而且人畜食用罹病谷物及其制成品易造成中毒。近年来,单端孢霉烯毒素的生物合成途径、关键酶及其基因克隆,毒素在致病过程中的作用,以及利用毒素作为选择压鉴定小麦抗病性和筛选抗病突变体均取得了明显进展。本文对此作一综述。     

Influence of wheat streak mosaic virus infection on phenylpropanoid metabolism and the accumulation of phenolics and lignin in wheat

Wheat plants infected with wheat streak mosaic virus were studied for their physiological response to infection. Previous histological data suggest that wheat streak mosaic virus-induced deposits of phenolic nature are present along the bundle sheath and mesophyll cell walls. In this study, we examined this phenomenon further by analysis of phenolic compounds and enzymes involved in their synthesis. In infected plants, the amounts of free and wall-bound phenolic compounds increased slightly, and chromatography showed that the type of free phenolic compounds present had changed. The amount of lignin did not change due to infection. Enzyme assays showed that while phenylalanine ammonia lyase and tyrosine ammonia lyase activities decreased as they do in healthy plants, cinnamyl alcohol dehydrogenase activity stayed high throughout infection. In addition, peroxidase activities in infected plants decreased around the time that the leaves ceased to expand. These results suggest that the general phenylpropanoid pathway is stimulated upon infection, but that lignification is not.     

Resistance to Wheat streak mosaic virus– a survey of resources and development of molecular markers

Wheat streak mosaic virus (WSMV) has been newly documented in Australia. The vulnerability of contemporary Australian elite wheat germplasm prompted a survey for effective resistance against an Australian isolate, WSMV‐ACT. This study confirms the effectiveness of previously reported sources of resistance and shows that new sources of resistance also confer protection. The resistance derived from Thinopyrum intermedium (Wsm1) as a 4D translocation and a new 4A translocation, and two bread wheat resistances, Wsm2 and the new source c2652, were effective against WSMV‐ACT in glasshouse experiments. Wsm1 was effective at lower temperatures but ineffective above 20°C, a temperature sensitivity shared with many of the derivatives of Wsm2 except for one new selection which was effective at 26°C. True wheats c2652 and Wsm2 selection CA745, and amphiploids Zhong1, Zhong2, Zhong4, Zhong5, TAF46, Summer1, Ot38 and OK7211542 were uniformly resistant at 20, 25 and 28°C. New sources of resistance were identified in a Th. scirpeum‐wheat amphiploid, B84‐994, and in chromosome addition lines Z2, Z6 and TAi27, derived from wheat‐Th. intermedium partial amphiploids. Several new, tightly linked SSR, RAPD and EST‐ILP PCR markers were developed for tracking the various Th. intermedium translocations associated with Wsm1, including the smaller translocations on wheat chromosome 4AS and 4DS. Three markers for the 4A‐Wsm1 translocation were validated on a segregating breeding population.     

安徽省来安县小麦梭条花叶病的病原鉴定和防治

近年来安徽省来安具发生一种呈典型梭条花叶病症状的小麦病害,用病叶进行一系列抽提,制得病原初提纯制剂。经紫外扫描测定为标准的核蛋白吸收曲线,最大吸收值在260nm处,A260/A280为1.27,Amax/Amin为1.16。电镜观察病原为线状病毒颗粒,宽12—13nm,长度分布在100nm—600nm之间,1000nm以上颗粒所占比例较少。提纯病毒制剂经SDS—聚丙烯酰胺凝胶电泳,可见到36.8kd的模糊蛋白带,但最易出现的是29kd和27kd二条明显的带。病原与小麦梭条花叶病毒抗血清起阳性反应。仪发现侵染小麦,并通过土壤传播,最后鉴定该病病原为小麦梭条花叶病毒,并对该毒源病毒外壳蛋白组分易于降解成较小的产物和不同分离物致病力关系提出讨论。同时在来安引种3165等抗病良种并结合其它措施进行防治,取得了明显的防治效果。     

加拿大进口大麦中小麦线条花叶病毒检疫鉴定

小麦线条花叶病毒(WSMV)是我国进境植物检疫性有害生物。2018年5月秦皇岛海关利用反转录PCR(RT-PCR)和双抗体夹心酶联免疫吸附法(DAS-ELISA), 从加拿大进口的大麦中检出WSMV。同时利用实时荧光定量PCR (Real time RT-qPCR)和序列比对分析方法进行了验证。这是我国首次在进境加拿大大麦中截获WSMV。     

黄淮地区小麦品种对小麦黄花叶病毒抗性评价

小麦黄花叶病是由禾谷多黏菌传播的小麦黄花叶病毒引起的病害,近年在黄淮麦区呈蔓延加重趋势。为了给病害的防治和抗病育种工作提供依据,本研究利用分级评价方法对黄淮地区推广的小麦品种进行了田间抗病性鉴定。两年鉴定结果表明,在145个供试小麦品种中,‘濮优938’、‘新麦208’、‘豫麦416’、‘新原958’、‘豫麦70-36’、‘泛麦5号’等70个品种表现为免疫,占总数的48.28%;‘豫麦47’和‘邯6172’表现为抗病,占总数的1.38%;‘洪育2号’、‘花培2号’、‘偃展4110’、‘豫麦41’、‘郑麦9023’等48个品种表现为中抗,占总数的33.10%;‘兰天06129’、‘兰天0591’、‘徐麦9158’、‘徐麦0054’、‘徐麦1108’等25个品种表现为感病,占总数的17.24%。研究结果为指导小麦黄花叶病区合理选择小麦品种提供了科学依据。     

甘蔗线条花叶病毒P1蛋白基因原核表达及抗血清制备

甘蔗线条花叶病毒Sugarcane streak mosaic virus(SCSMV)是引起甘蔗花叶病的主要病原之一,在世界各大蔗区普遍发生,严重威胁甘蔗产业的发展.建立快速有效的检测方法对于SCSMV的防控有着重要意义.本研究依据SCSMV P1基因序列合成一对引物,扩增获得1 074 bp的目的基因,将目的基因与...     

我国新育成甘蔗品种(系)对甘蔗线条花叶病毒和高粱花叶病毒的抗性评价

甘蔗花叶病是中国蔗区危害最严重的病毒病,利用抗病品种是控制该病害最经济有效的方法。本研究以中国蔗区甘蔗花叶病的2种主要病原甘蔗线条花叶病毒分离物(SCSMV-JP1,Gen Bank登录号JF488064)和高粱花叶病毒分离物(Sr MV-HH,Gen Bank登录号DQ530434)为接种毒源,采用人工切茎接种和RT-PCR检测相结合方法,于2015年、2016年2次对中国近年选育的71个优良甘蔗新品种(系)进行了双抗SCSMV和Sr MV鉴定与评价。结果表明:71个优良甘蔗新品种(系)中,对SCSMV表现高抗到中抗的有24个,占33.8%,感病到高感的有47个,占66.2%;对Sr MV表现高抗到中抗的有27个,占38.03%,感病到高感的有44个,占61.97%。综合分析结果显示,福农30号、福农36号、闽糖01-77、桂糖02-467、柳城05-129、粤甘34号、粤甘40号、粤糖55号、粤糖96-86、粤糖00-318、赣蔗02-70、云蔗03-258、云蔗04-241、云蔗05-51、云蔗06-80等15个优良新品种(系)双抗SCSM V和Sr M V 2种病毒,占21.13%,其中粤甘34号、粤糖55号、云蔗03-258、云蔗05-51、云蔗06-80等5个优良新品种(系)对2种病毒均表现为高抗,占7.04%,。研究结果明确了71个甘蔗优良新品种(系)对甘蔗花叶病2种主要致病病原的抗性,筛选出双抗SCSMV和Sr MV的甘蔗优良新品种(系)15个,为生产用种选择和有效防控甘蔗花叶病提供了科学依据。     

一步法RT-PCR检测小西葫芦黄花叶病毒

本文在两步RT-PCR检测ZYMV的基础上进行了一步法RT-PCR检测小西葫芦黄花叶病毒(ZYMV)的实验,并对商品化一步法RT-PCR试剂盒和本文实验的一步法RT-PCR的效果和成本进行了比较,最终建立了一种比较实用的检测ZYMV的方法.