合肥地区发生的西瓜花叶病的病原鉴定

 从合肥市郊区的西瓜病叶上分离出一病毒分离物,该分离物的热钝化温度为60~65℃,稀释终点为10^-4~10^-5,寄主体外存活期为20~23 d,电镜观察病毒粒子约750 nm×13 nm。参考已发表的小西葫芦黄化花叶病毒(Zucchini yellow mosaic virus,ZYMV) CP基因序列设计引物,RT-PCR扩增得到CP基因片段。将该CP片段克隆到pGEM-3Zf (+)中,测序结果表明,该CP基因全长840 nt,共编码279个氨基酸,与国内报道的ZYMV CP基因的核苷酸序列同源性为83.0%~97.3%,氨基酸序列的同源性为91.8%~99.8%,证明该分离物为ZYMV。     

小西葫芦黄花叶病毒北京分离物的鉴定及其基因组3′端特性分析

在北京东郊自然感病的南瓜Cucurbita moschata上获得一病毒分离物(BJ-1),经生物学、血清学和分子生物学鉴定,确定为小西葫芦黄花叶病毒(Zucchini yellowmosaic virus,ZYMV)。为分析其基因组3′端特性,以发病叶片中提取的总RNA为模板,对基因组3′端进行RT-PCR扩增,产物克隆到pMD18-T载体上进行序列分析,共测定了该病毒分离物包括全部CP基因在内的1269bp。该分离物CP基因由837个核苷酸组成,编码279个氨基酸。对包括该分离物在内的30个序列的760bp(含NIb基因3′端56bp和CP基因中的704bp)片段、NIb蛋白与CP蛋白的切割位点、蚜传必需基序的变异、寄主来源及地域来源进行了分析。结果表明,ZYMV不同分离物的基因分型与上述五个因素无明显关系。     

小西葫芦黄花叶病毒北京分离物的鉴定及其基因组3''端特性分析

在北京东郊自然感病的南瓜Cucurbita moschata上获得一病毒分离物（BJ-1），经生物学、血清学和分子生物学鉴定，确定为小西葫芦黄花叶病毒（Zucchini yellow mosaic virus，ZYMV）。为分析其基因组3’端特性，以发病叶片中提取的总RNA为模板，对基因组3’端进行RT-PCR扩增，产物克隆到pMD18-T栽体上进行序列分析，共测定了该病毒分离物包括全部CP基因在内的1269bp。该分离物CP基因由837个核苷酸组成，编码279个氨基酸。对包括该分离物在内的30个序列的760bp（含NIb基因3’端56bp和CP基因中的704bp）片段、NIb蛋白与CP蛋白的切割位点、蚜传必需基序的变异、寄主来源及地域来源进行了分析。结果表明，ZYMV不同分离物的基因分型与上述五个因素无明显关系。     

小西葫芦黄花叶病毒外壳蛋白基因的克隆及序列分析

 以小西葫芦黄花叶病毒(Zucchini yellow mosaic virus,ZYMV)的中国分离物(CH-87)接种发病的叶片中提取的总RNA为模板,经RT-PCR扩增获得ZYMV CP基因,将其克隆到pUCm-T质粒上进行序列分析。结果表明该CP基因由837个核苷酸组成,编码279个氨基酸。与已发表序列相比较,该CP基因与国际上已报道的4个基因型不同,应属于新的基因型,暂命名为基因型Ⅴ。     

侵染西葫芦的中国南瓜曲叶病毒的检测及序列分析

2019年山东种植的西葫芦上广泛发生病毒病,症状与之前常发症状有差异,发病植株叶片向下卷曲、黄化,植株矮化。为明确引起此次西葫芦病毒病的病原,我们以田间采集的10份西葫芦病叶为材料,进行PCR扩增并测序。测序结果显示扩增片段核苷酸序列与我国广东的中国南瓜曲叶病毒(SLCCNV)南瓜分离物(MW389917.1)一致性最高。根据同源序列设计引物,经PCR扩增获得SLCCNV全长序列,DNA-A 全长为2 730 bp(OM692270.1)、DNA-B 全长为2 711 bp(OM692269.1),经序列比对发现DNA-A序列与已登录的SLCCNV一致性为89.65%~99.42%,其中与我国广东的SLCCNV-GDHY南瓜分离物(MW389917.1)一致性最高,为99.42%;DNA-B序列与已登录的SLCCNV一致性范围为81.82%~97.29%,其中与我国广东的SLCCNV-GDHY南瓜分离物(MW389918.1)一致性最高,为97.29%。因此推测引发山东西葫芦病毒病的病原物是SLCCNV,由于该病毒是在山东西葫芦上首次发现,将其命名为SLCCNV-SD。前人已报道SLCCNV可侵染南瓜、甜瓜、烟草、番茄等作物,但SLCCNV可侵染西葫芦在国内未见报道。     

多重PCR检测籽用西葫芦种子带毒及热处理脱毒效果分析

为了明确籽用西葫芦种子携带病毒的情况,以籽用西葫芦种子为材料,采用多重PCR技术检测种子带毒率。同时为了筛选出有效脱除病毒的方法,通过相对定量法分析了不同温度湿热和干热处理对种子携带病毒的钝化效果。结果表明,从7个籽用西葫芦品种种子幼苗中均可检测到CMV、ZYMV及WMV,其检出率分别为67.1%、50.0%和72.3%,多个病毒的复合检出率为66%。不同品种种子幼苗的病毒检出率有明显差异,其中‘粒丰9号’种子幼苗的病毒检出率最低,为60%,而‘京丰9号’,‘瑞丰9号’,‘绿丰9号’及‘金葫360’的病毒检出率均为100%。8种处理均能不同程度降低籽用西葫芦种子幼苗的带毒率,其中干热60、70、75℃,湿热75℃处理同时脱除WMV、CMV和ZYMV的效果最好。     

两种葫芦科病毒的分子检测和致病性研究

 小西葫芦黄化花叶病毒(ZYMV)和黄瓜花叶病毒(CMV)是浙江及其周边地区侵染葫芦科植物最主要的病毒种类。本文通过RT-PCR和基因克隆,获得了侵染南瓜的CMV杭州分离物(HZ01S10)的3'端序列,通过CP氨基酸序列同源性分析,确定其属于CMV亚组I;分别以³²P标记的ZYMV和CMV基因组cDNA作为探针,用RNA点杂交方法定点检测了浙江地区自然感病的葫芦科作物中以上2种病毒的发生情况。ZYMV和CMV在葫芦科作物上的发生表现出显著的季节性差异:夏季CMV发生普遍,只有部分南瓜和甜瓜感染ZYMV;ZYMV则主要发生在秋季,同一时期未检测到CMV。此外,幼苗期接种试验显示:以上2种病毒对西葫芦(早青一代)、丝瓜(中长)、黄瓜(津绿4号)的致病性存在明显差异,供试西葫芦对ZYMV比较敏感,供试丝瓜对CMV更敏感,而供试黄瓜品种对以上2种病毒均表现抗病。复合侵染在丝瓜和西葫芦上加重病害发生程度。     

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.     

利用RT-PCR方法检测甜瓜种子中南瓜花叶病毒

通过设计特异性引物SQCPF/SQCPR,扩增南瓜花叶病毒(Squash mosaic virus,SqMV)CP基因的保守序列,进行RT-PCR,对扩增得到的特异性片段进行序列测定,测序结果显示扩增产物序列与GenBank中登录的SqMV外壳蛋白基因存在87%～96%的一致性;建立了适用于检测甜瓜种子中南瓜花叶病毒的RT-PCR结合ELISA方法,通过在酶联板的反应孔中直接进行反转录合成cDNA,能扩增到预期大小的DNA条带,且检测灵敏度高于DAS-ELISA方法10倍以上。用建立的RT-PCR结合ELISA方法检测进境甜瓜种子携带的SqMV,在42份样品中检出4份阳性样品。     

西瓜花叶病毒2号南瓜分离物的鉴定及其外壳蛋白基因序列分析

 利用电镜和酶联免疫吸附测定法(ELISA)在黑龙江省采集的南瓜病样中检测到西瓜花叶病毒2号(WMV-2)。再利用免疫PCR (IC-PCR)和反转录PCR (RT-PCR)方法,扩增获得其外壳蛋白(CP)基因片段,并克隆到pGEM-T载体中。核苷酸序列测定表明,该分离物CP基因全长为852个核苷酸,编码由284个氨基酸组成的31.8 kDa蛋白。与国外已报道的WMV-2 CP基因相比,其核苷酸序列同源性为92.2%~94.0%,由此推导的氨基酸序列同源性为94.5%~98.1%。与国内2个分离物相比,和山西分离物核苷酸和氨基酸的同源性都达到98.5%,和郑州分离物核苷酸和氨基酸的同源性分别为91.5%和95.0%。     

Molecular,biological and serological variability of Zucchini yellow mosaic virus in Tunisia

A study was conducted to better understand the population structure of Zucchini yellow mosaic virus (ZYMV), a severe virus affecting cucurbit crops worldwide, in Tunisia and to estimate whether the use of resistant cultivars may provide durable control. Analysis of the polymerase and coat protein (NIb‐CP) partial sequences of 83 isolates collected in the three main cucurbit‐growing areas in Tunisia showed that ZYMV grouped into two distinct clusters within ZYMV molecular group A. An important variability was observed in the MREK motif of the P3 protein, a motif associated with tolerance breaking in ZYMV‐tolerant zucchini squash cultivars. Interestingly, significant differences were found in the distribution of the MREK variants in the two clusters defined by the partial NIb‐CP sequences, MREK and MKEK sequences being more common in cluster 1 and cluster 2, respectively. When combining NIb‐CP and P3 sequence information, ZYMV molecular variability was shown to be significantly higher in the Cap Bon region than in the Bizerte area. An important biological variability was observed in a subset of 23 isolates regarding symptomatology in susceptible or resistant cucurbits. Some isolates overcame ZYMV tolerance or resistance in zucchini squash and melon, but not in cucumber. Three serotypes were differentiated using a set of 13 monoclonal antibodies (MAbs). Seven parameters characterizing the 23 isolates, including molecular, serological and biological properties, were used for a multiple component analysis (MCA). This analysis revealed that symptom intensity of a given isolate was similar in different susceptible cucurbit hosts, suggesting similar degrees of aggressiveness in different hosts.     

Zucchini yellow mosaic virus

Zucchini yellow mosaic potyvirus (ZYMV), first isolated in Italy in 1973, described in 1981, and then identified in all continents within a decade, is one of the most economically important viruses of cucurbit crops. It is efficiently aphid-transmitted in a nonpersistent manner and it is also seed-borne in zucchini squash, which could have contributed to its rapid spread worldwide. Biological variability has been observed among ZYMV isolates, concerning host range, symptomatology and aphid transmissibility. More recent studies also revealed a serological and molecular variability. The survival of ZYMV in areas where cucurbits are not grown throughout the year remains to be elucidated, because very few natural over-wintering hosts have been identified so far. Partial control of ZYMV can be achieved by limiting transmission of the virus to the crops by aphids, using adapted cultural practices. Cross-protection with a mild strain has been shown to be effective against most ZYMV isolates. Resistance genes found in cucurbit germplasms are currently being introduced into cultivars with good agronomical characteristics. Pathogen-derived resistance strategies using the expression of ZYMV genes in transgenic plants have also been developed and appear promising. Nevertheless, the high biological variability of ZYMV justifies a careful evaluation of the deployment of genetic control strategies in order to increase their durability.     

Increase in Zucchini yellow mosaic virus Symptom Severity in Tolerant Zucchini Cultivars Is Related to a Point Mutation in P3 Protein and Is Associated with a Loss of Relative Fitness on Susceptible Plants

ABSTRACT Zucchini yellow mosaic virus (ZYMV, Potyvirus) is a very damaging cucurbit virus worldwide. Interspecific crosses with resistant Cucurbita moschata have led to the release of "resistant" zucchini squash (C. pepo) F(1) hybrids. However, although the resistance is almost complete in C. moschata, the commercial C. pepo hybrids are only tolerant. ZYMV evolution toward increased aggressiveness on tolerant hybrids was observed in the field and was obtained experimentally. Sequence comparisons and recombination experiments revealed that a point mutation in the P3 protein of ZYMV was enough to induce tolerance breaking. Competition experiments were performed between quasi-isogenic wild-type, and aggressive variants of ZYMV distinguished by monoclonal antibodies. The aggressive mutants were more fit than wild-type strains in mixed infections of tolerant zucchini, but they presented a drastic fitness loss in mixed infections of susceptible zucchini or melon. Thus, the ability to induce severe symptoms in tolerant zucchini is related to a genetic load in susceptible zucchini, but also on other susceptible hosts. This represents the first quantitative study of the fitness cost associated with tolerance breaking for a plant virus. Thus, although easily broken, the tolerance might prove durable in some conditions if the aggressive variants are counterselected in susceptible crops.     

Characterization and occurrence of Zucchini Yellow Mosaic Virus in Sudan

Zucchini yellow mosaic potyvirus (ZYMV) was isolated in 1993 from a squash plant ( Cucurbita pepo cv. Eskandrani) showing severe leaf and fruit distortions, collected in the Gezira region (Sudan). This isolate (ZYMV-Su) was found to be very closely serologically related if not identical to the type strain from Italy. The host range was mostly limited to Cucurbitaceae but systemic infection was found to occur on sesame ( Sesamum indicum ), an important cultivated crop in Sudan. ZYMV-Su induced mosaic symptoms on the resistant melon accession PI 414723, indicating that it belongs to pathotype 2, but did not cause wilting of melon cv. Doublon. ZYMV-Su was efficiently transmitted by Myzus persicae and Aphis gossypii in a non-persistent manner. Surveys conducted from 1993 to 1995 revealed that ZYMV occurred in the major cucurbit growing areas in Sudan, in a diversity of crops and agroecosystems.     

Aphid-borne viruses infecting cultivated watermelon and squash in Spain: Characterization of a variant of cucurbit aphid-borne yellows virus (CABYV)

Aphid-borne viruses are responsible for major cucurbit diseases and hamper the sustainability of crop production. Systematic monitoring can reveal the occurrence and distribution of these viruses, in addition to unadvertised viruses, facilitating the control of diseases. For three consecutive (2018–2020) seasons, the presence of aphid-borne viruses was monitored from a total of 292 samples of watermelon and squash plants that showed yellowing symptoms in three major cucurbit-producing areas (Castilla La-Mancha, Alicante, and Murcia) in Spain. We observed that cucurbit aphid-borne yellows virus (CABYV) was the most common virus found (29%) in the plants from both crops. Likewise, except for squash samples from Castilla La-Mancha and Alicante, watermelon mosaic virus (WMV) was also found (23%) with a relatively high frequency. Furthermore, we observed the exacerbation of bright yellowing symptoms in watermelon plants that was often accompanied by considerable fruit abortion. CABYV was the only causative agent for this new yellowing disease, and two infectious cDNA clones (one from watermelon, CABYV-LP63, and another from melon, CABYV-MEC12.1) were constructed to further compare and characterize this CABYV disease. Based on the full-length genome, both isolates were grouped phylogenetically together within the Mediterranean clade. However, the Koch's postulates tests were only successfully completed for the LP63 isolate, which also showed several amino acid changes and two potential recombination events, as compared to MEC12.1. Remarkably, the LP63 isolate caused more severe symptoms and showed higher RNA accumulation than MEC12.1 in five cucurbit plant species. These results suggest that a novel CABYV variant that causes severe yellowing symptoms may be causing outbreaks in cucurbit crops.     

Characterization of Synergy Between Cucumber mosaic virus and Potyviruses in Cucurbit Hosts

ABSTRACT Mixed infections of cucurbits by Cucumber mosaic virus (CMV) and potyviruses exhibit a synergistic interaction. Zucchini squash and melon plants coinfected by the potyvirus Zucchini yellow mosaic virus (ZYMV) and either Fny-CMV (subgroup IA) or LS-CMV (subgroup II) displayed strong synergistic pathological responses, eventually progressing to vascular wilt and plant death. Accumulation of Fny- or LS-CMV RNAs in a mixed infection with ZYMV in zucchini squash was slightly higher than infection with CMV strains alone. There was an increase in CMV (+) strand RNA levels, but no increase in CMV (-) RNA3 levels during mixed infection with ZYMV. Moreover, only the level of capsid protein from LS-CMV increased in mixed infection. ZYMV accumulated to similar levels in singly and mixed infected zucchini squash and melon plants. Coinfection of squash with the potyvirus Watermelon mosaic virus (WMV) and CMV strains increased both the Fny-CMV RNA levels and the LS-CMV RNA levels. However, CMV (-) strand RNA3 levels were increased little or not at all for CMV on coinfection with WMV. Infection of CMV strains (LS and Fny) containing satellite RNAs (WL47-sat RNA and B5*-sat RNA) reduced the accumulation of the helper virus RNA, except when B5*-sat RNA was mixed with LS- CMV. However, mixed infection containing ZYMV and the CMV strains with satellites reversed the suppression effect of satellite RNAs on helper virus accumulation and increased satellite RNA accumulation. The synergistic interaction between CMV and potyviruses in cucurbits exhibited different features from that documented in tobacco, indicating there are differences in the mechanisms of potyvirus synergistic phenomena.     

Biological characteristics and nucleotide sequences of three Korean isolates of Zucchini yellow mosaic virus

Zucchini yellow mosaic virus (ZYMV) is one of the most economically important viruses of cucurbit crops, causing severe mosaic, necrosis, and malformation. Three ZYMV isolates were obtained from pumpkins at Andong (ZYMV-PA), Euiryung (ZYMV-PE), and Suwon (ZYMV-PS), and their biological variability was determined on different hosts, including cucurbit crops as well as other indicator plants. ZYMV-PA caused the most severe symptoms, including severe mosaic, size reduction, and deformation, in oriental melon (Cucumis melo) and cucumber (Cucumis sativus) leaves. In contrast, ZYMV-PE and ZYMV-PS caused mild mosaic symptoms on oriental melon and cucumber. The nucleotide sequences of the genomic RNAs were determined and compared to the sequences of other potyviruses, including ZYMV isolates Reunion Island and TW-TN3. Each ZYMV Isolate had a genome of 9593 nucleotides, excluding the poly(A) tail, and contained 139 and 214 nucleotides in the 5- and 3-untranslated regions, respectively. Each had one large open reading frame encoding a protein of about 351kDa. The nucleotide sequences of ZYMV-PA, ZYMV-PE, and ZYMV-PS were more than 96.0% and the deduced amino acid sequences were more than 98.1% identical. When compared with other ZYMV isolates in a phylogenetic analysis, these three viruses formed a distinct virus clade and were more distantly related to other potyviruses (43.5%–62.8% identity).The nucleotide sequence data reported are available in the GenBank database under the accession numbers AY278998 to AY279000 for ZYMV-PA, ZYMV-PE and ZYMV-PS