Occurrence of Grapevine Pinot gris virus in Friuli Venezia Giulia (Italy): field monitoring and virus quantification by real‐time RT‐PCR

Since 2003 the presence of a new syndrome characterized by symptoms of stunting, chlorotic mottling, leaf deformation, reduced yields and quality has been reported in some white berry varieties of Vitis vinifera in Trentino‐Alto Adige and Friuli Venezia Giulia vineyards. The identification of a new virus, provisionally called Grapevine Pinot gris virus (GPGV), in a cv. Pinot gris vine suggested an association between this new syndrome and the virus presence (Giampetruzzi et al., 2012), however the contemporary presence of GPGV in both symptomatic and asymptomatic plants has still to be explained. In this work, a large‐scale monitoring over a 3‐year period (2012–14) of Friuli Venezia Giulia vineyards and nurseries has shown a widespread presence of GPGV in symptomatic plants and also in asymptomatic vines, even if at a slightly lower percentage. Quantitative analyses of the virus titer revealed a great variability in the viral content of both symptomatic and asymptomatic plants but the mean GPGV quantity in symptomatic vines was significantly higher than in asymptomatic plants.     

Identification of herbaceous hosts of the <Emphasis Type="Italic">Grapevine Pinot gris virus</Emphasis> (GPGV)

Grapevine Pinot gris Virus (GPGV) is a single stranded RNA of the genus Trichovirus infecting grapevine (Vitis vinifera) and associated with stunting, chlorotic mottling and leaf deformation symptoms. During a monitoring of GPGV infection in vineyards of the Trentino region in Italy, we have detected the virus in the herbaceous plants Silene latifolia subsp. Alba (Mill.) (bladder campion) and Chenopodium album L. (white goosefoot), which showed symptoms of viral infection. The full-length GPGV RNA genome, amplified from these infected hosts, was sequenced and a phylogenetic analysis revealed that its closest relative is the strain SK13, recently isolated in Slovakia. Our results indicate that herbaceous plants can be considered as a reservoir for the GPGV virus. This finding is important for studying the epidemiological aspects of GPGV disease and to formulate appropriate control measures.     

我国灰比诺葡萄病毒分离物检测及基因序列分析

 灰比诺葡萄病毒(Grapevine Pinot gris virus, GPGV)是国内新近报道的葡萄病毒,能引起葡萄叶片褪绿斑驳、皱缩及变形等症状,严重影响葡萄长势。为明确我国GPGV的发生及基因序列变异情况,本研究采用RT-PCR方法对采自我国15个省(市)自治区的195个葡萄样品进行检测,其中55个葡萄样品检测出GPGV。对49个GPGV阳性分离物的外壳蛋白(coat protein, cp)和运动蛋白(movement protein, mp)基因进行克隆、测序, 序列分析结果显示:来源于国内外的GPGV分离物cp基因和mp基因的核苷酸和氨基酸序列同源性分别为85.30%~100%和95.00%~100%、85.73%~99.87%和95.58%~100%。基于cp和mp基因序列构建的进化树,将GPGV分离物划分为3个明显的组群。其中,大部分GPGV分离物被划分在组群1内,其它中国GPGV分离物形成2个新的组群2和3。本研究是关于中国GPGV分离物基因序列变异的初次报道,可为进一步开展GPGV分子检测的技术研发及不同变种的致病性研究提供依据。     

Incidence,distribution and limited genetic variability among Turkish isolates of Grapevine Pinot gris virus from different grapevine cultivars

Journal of Plant Diseases and Protection - Grapevine Pinot gris virus (GPGV) was firstly identified in northern Italy by deep sequencing from grapevine cv. Pinot gris, exhibiting mottling and...     

Identification of grapevine marker genes for early,non‐destructive Eutypa lata infection diagnosis

Eutypa lata is the causal agent of eutypa dieback, a highly damaging trunk disease affecting all grape‐growing areas, with currently neither an efficient curative treatment nor an early non‐destructive diagnostic method. The present work was carried out to discover grapevine genes expressed in response to the presence of E. lata that could be useful to develop an early (before visible foliar symptoms) and non‐destructive (using grapevine leaves) diagnostic tool. Microarray analyses were carried out from (i) infected plants showing characteristic E. lata foliar and vascular symptoms and positive pathogen recovery from vascular lesions (S⁺R⁺), (ii) infected plants showing no symptoms (S^?R⁺), and (iii) symptomless plants with negative pathogen recovery (S^?R^?). Vineyard and greenhouse‐grown plants, naturally or artificially infected respectively, and uninoculated controls were characterized and leaf RNA was hybridized with 15k operon grapevine oligonucleotide microarrays. Among the grapevine genes differentially expressed between S^?R⁺ and S^?R^? plants in greenhouse and vineyard conditions, 10 were highlighted as robust candidate genes for diagnosis: seven were specifically involved in response to infection and three were associated with symptom absence. Five were confirmed to be effective diagnostic marker genes usable in a qRT‐PCR‐based test performed on RNA extracted from grapevine leaves cultivated in either greenhouse or vineyard conditions. Furthermore, their expression profiles in response to infection with E. lata or other major grapevine fungi (Erysiphe necator, Plasmopara viticola, Botrytis cinerea) could be distinguished. The usefulness of these genes to develop an early and non‐destructive method for diagnosis of E. lata infection is discussed with regard to the advantages and drawbacks of previous E. lata diagnostic studies.     

Co‐infection by Botryosphaeriaceae and Ilyonectria spp. fungi during propagation causes decline of young grafted grapevines

Decline of newly planted, grafted grapevines is a serious viticultural problem worldwide. In the Riverina (New South Wales, Australia), characteristic symptoms include low fruit yields, very short shoots and severely stunted roots with black, sunken, necrotic lesions. To determine the cause, roots and wood tissue from affected plants in 20 vineyards (Vitis vinifera cv. Chardonnay grafted to V. champini cv. Ramsey rootstock) were assayed for microbial pathogens. Ilyonectria spp. (I. macrodidyma or I. liriodendra, producers of phytotoxin brefeldin A, BFA, and cause of black foot disease of grapevines) and Botryosphaeriaceae spp. (predominantly Diplodia seriata) were isolated from rootstocks of 100 and 95% of the plants, respectively. Togninia minima and Phaeomoniella chlamydospora (cause of grapevine Petri disease) were isolated from 13 and 7% of affected plants, respectively. All Ramsey rootstock stems of grafted plants sampled from a supplier nursery were infected with Ilyonectria spp. and D. seriata. Diplodia seriata, but not Ilyonectria spp., was also isolated from 25% of canes sampled from the rootstock source block. Root inoculation of potted, disease‐free Chardonnay plants with Ilyonectria isolates from diseased vineyards caused typical disease symptoms, while co‐inoculation with Botryosphaeriaceae spp. increased disease severity. This is the first study to show that a major cause of young grapevine decline can be sequential infection by Botryosphaeriaceae from rootstock cuttings and Ilyonectria spp. from nursery soil. Although the Petri disease fungi were less common in young declining grafted grapevines in the Riverina, they are likely to contribute to the decline of surviving plants as they mature.     

‘阳光玫瑰’葡萄病毒小RNA测序鉴定及RT-PCR检测

 ‘阳光玫瑰’是我国从日本引进的葡萄优良品种。为了明确我国‘阳光玫瑰’葡萄病毒病的病原,本研究采用小RNA测序技术对2株显症和无症状的‘阳光玫瑰’葡萄样品进行病毒鉴定结果显示:显症样品中测定到8种病毒,其中包含葡萄蚕豆萎蔫病毒(Grapevine fabavirus, GFabV)和灰比诺葡萄病毒(Grapevine Pinot gris virus, GPGV);无症状样品中测定到3种葡萄病毒。对46个‘阳光玫瑰’样品进行14种葡萄病毒的RT-PCR检测,结果表明:‘阳光玫瑰’葡萄带毒率较高,病毒复合侵染情况普遍;显症样品中,GFabV检出率为88.2%,GPGV和葡萄浆果内坏死病毒(Grapevine berry inner necrosis virus,GINV)检出率为64.7%和29.4%,均明显高于无症状样品(13.8%和10.3%)。本研究旨在探明‘阳光玫瑰’葡萄携带病毒的种类和侵染状况,为其病毒病防控及病毒脱除奠定基础。     

The reliability of leaf bioassays for predicting disease resistance on fruit: a case study on grapevine resistance to downy and powdery mildew

This study was designed to assess the reliability of grapevine leaf bioassays for predicting disease resistance on fruit in the field. The efficacy of various grapevine quantitative trait loci (QTLs) for conferring resistance to downy and powdery mildew was evaluated in bioassays and in a 2‐year field experiment for downy mildew. The resistance genes studied were inherited from Muscadinia rotundifolia (Rpv1 and Run1) and from American Vitis species through cv. Regent (QTLRgP and QTLRgD). In bioassays, genotypes carrying Run1 blocked powdery mildew development at early stages. Genotypes combining Run1 with QTLRgP displayed no greater level of resistance. For downy mildew, genotypes carrying Rpv1 and/or QTLRgD were more resistant than the susceptible cv. Merlot, and showed a high level of leaf resistance in the field (<10% severity). Disease levels on bunches were much higher than those on leaves, with a high variability between Rpv1 genotypes (1–48%). A Bayesian decision theory framework predicted that an OIV‐452 threshold of 5 in leaf bioassays allowed accurate selection of grapevine genotypes (P = 0·83) with satisfactory disease severity on bunches. Therefore, this study validates that the use of early bioassays on leaves, as currently performed by grapevine breeders, ensures a satisfactory level of resistance to downy mildew of bunches in the field.     

‘阳光玫瑰’葡萄病毒小RNA测序鉴定及RT-PCR检测

 ‘阳光玫瑰’是我国从日本引进的葡萄优良品种。为了明确我国‘阳光玫瑰’葡萄病毒病的病原,本研究采用小RNA测序技术对2株显症和无症状的‘阳光玫瑰’葡萄样品进行病毒鉴定结果显示:显症样品中测定到8种病毒,其中包含葡萄蚕豆萎蔫病毒(Grapevine fabavirus, GFabV)和灰比诺葡萄病毒(Grapevine Pinot gris virus, GPGV);无症状样品中测定到3种葡萄病毒。对46个‘阳光玫瑰’样品进行14种葡萄病毒的RT-PCR检测,结果表明:‘阳光玫瑰’葡萄带毒率较高,病毒复合侵染情况普遍;显症样品中,GFabV检出率为88.2%,GPGV和葡萄浆果内坏死病毒(Grapevine berry inner necrosis virus,GINV)检出率为64.7%和29.4%,均明显高于无症状样品(13.8%和10.3%)。本研究旨在探明‘阳光玫瑰’葡萄携带病毒的种类和侵染状况,为其病毒病防控及病毒脱除奠定基础。     

Biological and genetic characterization of carrot red leaf virus and its associated virus/RNA isolated from carrots in Hokkaido,Japan

Carrot motley dwarf (CMD) is caused by mixed infection of carrot red leaf virus (CtRLV) with either carrot mottle virus (CMoV) or carrot mottle mimic virus, and additional infection with CtRLV-associated RNA (CtRLVaRNA). Here, the author investigated the viruses or virus-like RNA isolated from carrots with reddening symptoms in Hokkaido, the northern island of Japan. Three types of infections were mainly detected: single infection with CtRLV, which was most prevalent; double infection with CtRLV and CMoV; and triple infection with CtRLV, CMoV, and CtRLVaRNA. Fields with the three agents were severely affected, with diseased plants showing mottling, whereas in fields where disease incidence was low and sporadic, CtRLV was often found alone in plants with mild symptoms. Inoculation tests using carrot plants showed that CMoV enhanced disease severity, and the RNA accumulation of CtRLV. However, in the presence of CtRLVaRNA (+ CMoV), distinct symptoms such as systemic mottling and stunting developed, while the enhancement of CtRLV accumulation was abolished. These results imply that CtRLVaRNA (+ CMoV) antagonizes CtRLV despite its dependence on CtRLV for aphid transmission, and that mixed infection with CtRLVaRNA is involved in the development of the conspicuous mottling. All agents detected in Hokkaido were very similar to European and American isolates in terms of their genomic sequences and host range. This represents the first report of CMD in Japan, and provides further information on the genetic and biological properties of CMD-associated agents, as well as the aetiology of the disease.     

Monitoring the occurrence of tomato bacterial spot and range of the causal agent Xanthomonas perforans in Iran

A 2‐year comprehensive field survey was conducted across major tomato‐growing areas of Iran. Two hundred and thirty‐four tomato fields and six tomato‐producing greenhouses were surveyed for the potential presence of bacterial spot disease. Five hundred and ninety‐six tomato samples with and without symptoms were analysed. While Xanthomonas spp. were found in association with tomato plants both with and without symptoms from five surveyed counties, the bacterial spot disease was observed only in plants from three of them. Only strains isolated from plants with symptoms induced disease symptoms on tomato, while those isolated from symptomless plants caused symptoms only on cabbage and common bean. None of the isolates caused disease symptoms on pepper and eggplant. Phylogenetic analysis showed that X. perforans is the causal agent of tomato bacterial spot in Iran, although X. campestris and X. axonopodis were also associated with symptomless tomato plants. All X. perforans isolates in this study were sensitive to streptomycin, copper sulphate and copper oxychloride at concentrations of 50 mg L^?1, 200 mg L^?1 and 0.8 g L^?1, respectively. Unlike the type strain of X. perforans, isolates in this study did not produce bacteriocin against other Xanthomonas spp., nor were they detected using the usual species‐specific primer pair Bs‐XpF/Bs‐XpR. This suggests an atypical nature of X. perforans strains in Iran, which leads to the hypothesis that X. perforans strains in Iran may have a separate origin to those causing disease epidemics elsewhere. The aggregated dispersal pattern of the diseased tomato fields signifies the seedborne introduction of the pathogen into the country.     

Biological and molecular variation of Cherry leaf roll virus isolates from Malus domestica,Ribes rubrum,Rubus idaeus,Rumex obtusifolius and Vaccinium darrowii

Cherry leaf roll virus (CLRV) isolates from Malus domestica, Ribes rubrum, Rubus idaeus, Rumex obtusifolius and Vaccinium darrowii were characterized based on nucleotide sequences of a 371 bp fragment of the 3′ untranslated region (UTR) of their genomic RNAs, symptoms in the herbaceous hosts, Chenopodium amaranticolor, Chenopodium quinoa, Nicotiana benthamiana, Nicotiana occidentalis and Nicotiana tabacum, and seed transmission in N. occidentalis. The different isolates induced a range of localized and systemic disease symptoms, of varying severity, in the herbaceous hosts. The isolates from M. domestica, R. rubrum, R. obtusifolius and V. darrowii all showed greater than 80% seed transmission in N. occidentalis, but no seed transmission was observed for the R. idaeus isolate. Based on symptoms and seed transmission, the isolates appear to be biologically distinct strains of CLRV. Phylogenetic analysis of the nucleotide sequences from the 3′ UTR, commonly used to detect CLRV, showed that four isolates from M. domestica, R. rubrum, R. idaeus and V. darrowii were almost identical but an isolate from R. obtusifolius exhibited a pairwise nucleotide difference of up to 5·4% when compared to these isolates. There was no obvious correlation between sequence differences and symptomatology.     

Phenotypic,molecular and pathogenic characterization of Phlyctema vagabunda,causal agent of olive leprosy

Olive leprosy, caused by the fungus Phlyctema vagabunda, is a classic fruit rot disease widespread in the Mediterranean basin. From 2009 to 2013, new disease symptoms consisting of small circular necrotic leaf lesions, coin branch canker and shoot dieback were observed in Spanish and Portuguese olive orchards showing intense defoliation. Phlyctema‐like anamorphs were consistently isolated from leaves and shoots with symptoms. Representative isolates from affected leaves, shoots and fruits were characterized based on morphology of colonies and conidia, optimum growth temperature and comparison of DNA sequence data from four regions: ITS, tub2, MIT and rpb2. In addition, pathogenicity tests were performed on apple and olive fruits, and on branches and leaves of olive trees. Maximum mycelial growth rate ranged between 0.54 and 0.73 mm per day. Conidia produced on inoculated apple fruits showed slight differences in morphology among the representative fungal isolates evaluated. Phylogenetic analysis clustered all of the Phlyctema‐like isolates in the same clade, identifying them as Phlyctema vagabunda. On fruits, influence of wounding, ripening and cultivar resistance was studied, with cv. Blanqueta being the most susceptible cultivar. On branches, a mycelial‐plug inoculation method reproduced olive leprosy symptoms and caused shoot dieback. On leaves, Koch's postulates were fulfilled and the pathogen caused characteristic necrotic spots and plant defoliation. This is the first time that the pathogenicity of P. vagabunda in olive leaves has been demonstrated.     

Grapevine crown gall caused by <Emphasis Type="Italic">Rhizobium radiobacter</Emphasis> (Ti) in Japan

In 2005, characteristic symptoms of crown gall on grapevines (Vitis vinifera L. cv. Muscat of Alexandria, and cv. Seto Giants) were observed in a commercial greenhouse-orchard in Okayama Prefecture, Japan. Isolations from diseased tissues consistently yielded bacterial colonies that were white, glistening, and produced abundant polysaccharide on potato semi-synthetic agar (PSA) medium. Ten representative isolates were chosen for further characterization. A multiplex polymerase chain reaction (PCR) assay showed these strains were not Rhizobium vitis but did possess a Ti plasmid. The bacteriological characteristics of the isolates corresponded well with R. radiobacter. The almost complete 16S ribosomal DNA sequences of isolates AT06-1 and AT06-2, selected from 10 grapevine isolates, were determined and corresponded to sequences of R. radiobacter. The pathogenicity of the isolates was tested on young grapevine and tomato (Lycopersicon esculentum Mill.) plants. Gall symptoms developed on both plant species after inoculation, and bacteria with the same colony morphology as those inoculated were reisolated. Based on these results, the isolates were identified as R. radiobacter (Ti). This report is the first of the occurrence of R. radiobacter (Ti) on grapevine in Japan. Phylogenetic analyses using the partial nucleotide sequences of virC operon located on a Ti plasmid showed that the isolate of R. radiobacter (Ti) isolated from grapevine and some strains of R. vitis (Ti) belonged to the same monophyletic group, which differed from the groups of R. radiobacter (Ti) isolated from plants other than grapevine and of the majority of R. vitis (Ti) strains isolated from grapevine. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under accessions AB306890, AB306891, and AB465432–AB465459.     

Heterogeneity of Pseudomonas savastanoi populations infecting Myrtus communis in Sardinia (Italy)

Genetic, phenotypic and host range diversity among Pseudomonas savastanoi isolates from Myrtus communis were investigated. Thirty‐one isolates from six Sardinian commercial myrtle orchards and three isolates from plants growing spontaneously on the island of Rhodes (Greece) were compared with reference strains of P. savastanoi from olive, oleander, ash and myrtle. Multilocus sequence analysis (MLSA) indicated the presence of a monomorphic population with a very low level of variability. Conversely, Biolog phenotypic fingerprinting and phytohormone production analyses showed a considerable metabolic diversity, as bacteria obtained from single infected tissue differed more than bacteria obtained from different orchards. When pathogenicity tests were carried out on myrtle plants, different types of symptoms were induced: knots, canker lesions with or without tissue proliferations and, occasionally, wilting of the inoculated twig, a symptom never reported before for P. savastanoi. Comparable symptoms were also observed in the natural environment both on spontaneous and cultivated plants. Moreover, the host range of the myrtle population was heterogeneous and not well defined. Some isolates showed a wide host range whilst others were pathogenic only to their natural host. Overall these findings suggest that the diversity of the P. savastanoi population from myrtle does not depend so much on the locality or the natural host and does not allow the Sardinian and Greek isolates, together with previously characterized myrtle strains, to be ascribed to a known pathovar of P. savastanoi, nor to propose their belonging, as a whole, to a new pathovar.     

Distinct strains of the re‐emergent Cassava common mosaic virus (genus: Potexvirus) infecting cassava in Argentina

Cassava common mosaic disease (CCMD) has been reported in all regions where cassava is grown in the Americas and the causal agent, Cassava common mosaic virus (CsCMV), has been identified as a mechanically transmitted potexvirus (Alphaflexiviridae). In Argentina, cassava is grown mainly in the northeast (NEA) region that shares borders with Brazil and Paraguay. Increasing incidences of CCMD were observed during the years 2014 to 2016 associated with severe leaf mosaic symptoms and yield reductions where the occurrence of CsCMV was confirmed by RT‐PCR and sequencing. In this work, the virus has been successfully purified and a double‐antibody sandwich (DAS‐) ELISA test has been developed from an Argentinean isolate of CsCMV to extend the diagnostics of the disease. A collection of 726 samples was screened and CsCMV was detected with 100% prevalence in the NEA region. Additional co‐infecting viruses were detected in some plants (64.4%); in these, CCMD symptoms correlated with CsCMV only, although more severe symptoms could be observed in mixed infected plants. Sequence analysis of the conserved RdRp domain showed a wider diversity of CsCMV isolates. Interestingly, a separate phylogenetic cluster was formed by isolates from the NEA region that only shared 77.1% to 80.3% nucleotide identity with the other clusters. These results indicate the presence of mixed strains occurring in the NEA region and suggest the presence of geographically distinct strains of CsCMV in South America.     

Different symptoms in carrots caused by male and female carrot psyllid feeding and infection by ‘Candidatus Liberibacter solanacearum’

Carrot psyllid Trioza apicalis was recently found to carry the plant pathogenic bacterium ‘Candidatus Liberibacter solanacearum’ (CLs). To confirm the transmission of bacteria by the psyllids and to dissect the symptoms caused in carrot plants by psyllid feeding and CLs infection, a greenhouse experiment with single psyllids feeding on separate plants was performed. A positive correlation was found between the amount of CLs bacteria in the psyllids and in the corresponding plants exposed to feeding, indicating CLs transmission. The female psyllid feeding caused more severe damage than male feeding, and resulted in a substantial decrease in the root weight. Female psyllid feeding also significantly reduced the carrot leaf weight and increased the number of curled leaves. The number of curled leaves was also increased by the nymphs when their number exceeded 10 per plant. A high titre of CLs bacteria significantly reduced root weight, while not affecting the weight or number of the leaves. However, the amount of CLs correlated with the number of leaves showing discolouration symptoms. Microscopy of infected carrot plants revealed that the phloem tubes throughout the whole plant, from leaf veins to the root tip, were colonized by bacteria. The bacterial cells appeared to be long and thin flexible rods with tapering ends and a transversally undulated surface. Microscopy also revealed collapsed phloem cells in the infected carrots. Damage in the phloem vessels is likely to reduce the sucrose transport from source leaves to the root, explaining the observed leaf discolouration and reduction in root weight.     

Characterization of resistance mechanisms activated by Trichoderma harzianum T39 and benzothiadiazole to downy mildew in different grapevine cultivars

Downy mildew, caused by Plasmopara viticola, is one of the most destructive diseases of grapevine and is controlled with intense application of chemical fungicides. Treatment with Trichoderma harzianum T39 (T39) or benzothiadiazole‐7‐carbothioic acid S‐methyl ester (BTH) has been previously shown to activate grapevine resistance to downy mildew and reduce disease symptoms in the Pinot noir cultivar. However, enhancement of plant resistance can be affected by several factors, including plant genotype. In order to further extend the use of resistance inducers against downy mildew, the physiological and molecular properties of T39‐ and BTH‐activated resistance in different cultivars of table and wine grapes were characterized under greenhouse conditions. T39 treatment reduced downy mildew symptoms, but the degree of efficacy differed significantly among grapevine cultivars. However, efficacy of BTH‐activated resistance was consistently high in the different cultivars. Expression profiles of defence‐related genes differed among cultivars in response to resistance inducers and to pathogen inoculation. T39 treatment enhanced the expression of defence‐related genes in the responsive cultivars, before and after P. viticola inoculation. A positive correlation between the efficacy of T39 and the expression level of defence‐related genes was found in Primitivo and Pinot noir plants, while different genes or more complex processes were probably activated in Sugraone and Negroamaro. The data reported here suggest that the use of a responsive cultivar is particularly important to maximize the efficacy of resistance inducers and new natural inducers should be explored for the less responsive cultivars.     

Seed transmission of Sweet potato leaf curl virus in sweet potato (Ipomoea batatas)

Sweet potato leaf curl virus (SPLCV) infects sweet potato and is a member of the family Geminiviridae (genus Begomovirus). SPLCV transmission occurs from plant to plant mostly via vegetative propagation as well as by the insect vector Bemisia tabaci. When sweet potato seeds were planted and cultivated in a whitefly‐free greenhouse, some sweet potato plants started to show SPLCV‐specific symptoms. SPLCV was detected by PCR from all leaves and floral tissues that showed leaf curl disease symptoms. More than 70% of the seeds harvested from SPLCV‐infected sweet potato plants tested positive for SPLCV. SPLCV was also identified from dissected endosperm and embryos. The transmission level of SPLCV from seeds to seedlings was up to 15%. Southern blot hybridization showed SPLCV‐specific single‐ and double‐stranded DNAs in seedlings germinated from SPLCV‐infected seeds. Taken altogether, the results show that SPLCV in plants of the tested sweet potato cultivars can be transmitted via seeds and SPLCV DNA can replicate in developing seedlings. This is the first seed transmission report of SPLCV in sweet potato plants and also, to the authors' knowledge, the first report of seed transmission for any geminivirus.     

Characterization of Cytospora isolates from wood cankers of declining grapevine in North America,with the descriptions of two new Cytospora species

Cytospora species are ubiquitous pathogens of numerous woody plants, causing dieback and wood cankers in agronomic crops, timber trees and wildland trees (e.g. Prunus, Eucalyptus and Salix, respectively). Cytospora chrysosperma, C. cincta and C. leucostoma have been reported from grapevines in Iran showing symptoms of one or more recognized trunk diseases (esca, botryosphaeria‐, eutypa‐ and phomopsis diebacks); however, only C. chrysosperma was shown to be pathogenic to grapevine. To understand the potential role of Cytospora species in the grapevine trunk‐disease complex, 21 Cytospora isolates were examined that were recovered from dieback and wood cankers of Vitis vinifera and Vitis interspecific hybrids in seven northeastern U.S. states and two Canadian provinces. Phylogenetic analyses of ITS and translation elongation factor 1‐α identified two novel species: Cytospora vinacea sp. nov. and Cytospora viticola sp. nov. Differences in culture morphology and conidial dimensions also distinguished the species. When inoculated to the woody stems of potted V. vinifera ‘Thompson Seedless’ in the greenhouse, both species were pathogenic, based on development of wood lesions and fulfilment of Koch's postulates. Cytospora viticola was the most virulent based on lesion length at 12 months post‐inoculation. As cytospora canker shares some of the same general dieback‐type symptoms as botryosphaeria‐, eutypa‐ and phomopsis diebacks, it may be considered part of the grapevine trunk‐disease complex in eastern North America.