Distribution and characterization of Streptomyces species causing potato common scab in Germany

Field‐grown potatoes showing scab infections were sampled in two successive years and analysed for prevailing Streptomyces strains. In 2008 and 2009, 293 Streptomyces isolates were collected in Germany and analysed for morphology, pathogenicity and strain type. Isolates varied in mycelium colour, sporulation and pigmentation. Based on their morphology, no clear differentiation of species was possible. At the genetic level, sampled isolates, as well as a number of type strains from culture collections, were characterized by PCR using 16S rRNA‐specific primers and PCR‐RFLP of the 16S–23S internal transcribed spacer (ITS) region with Hpy99I. Using this fingerprinting approach, Streptomyces species could be differentiated genotypically. The data from this study show that diversity among scab‐causing species in Germany is much higher than previously thought. Isolates belonged to various Streptomyces spp. previously associated with common scab. This is apparently the first report of pathogenic strains of S. europaeiscabiei, S. stelliscabiei, S. acidiscabiei, S. turgidiscabiei and S. bottropensis within Germany. Streptomyces europaeiscabiei was the predominant species found. Other scab‐causing species were identified, but their local distribution was uneven. For most of the isolates, the presence of the txtAB gene was demonstrated, indicating pathogenicity. This analysis is one of the first reports to examine the distribution of common scab‐causing species in Germany.     

黑龙江省部分地区马铃薯疮痂病菌种类及致病性鉴定

为明确黑龙江省马铃薯疮痂病病原菌的种类及其特征,2012-2013年从黑龙江省克山县、绥化市、哈尔滨市、杜尔伯特蒙古族自治县采集具有疮痂病病斑的马铃薯块茎,从中分离纯化病原菌,根据16SrRNA基因的差异采用分子手段对所分离的菌株进行种类和致病性鉴定,并对txtAB阳性菌株采用萝卜幼苗法或马铃薯致病性试验测定其致病性。共分离出74株菌株,鉴定出致病性菌株26株,其中Streptomyces scabies或S.europaeiscabiei 21株,S.turgidiscabies 3株和S.acidiscabies 2株。所有的致病性菌株中共有4种致病岛基因型,即nec1+/tomA+、nec1-/tomA+、nec1+/tomA-和nec1-/tomA。     

Detection and characterization of Streptomyces causing potato common scab in Western Europe

A PCR-based diagnostic method was developed for direct detection from tuber lesions of pathogenic Streptomyces causing common scab of potato. Primers were designed to amplify a fragment of the txtAB ( txtA and txtB ) genes, which are pathogenicity determinants in the main pathogenic Streptomyces species. The method was evaluated on 84 naturally infected potato samples, comprising 19 potato cultivars, harvested in the years from 2000 to 2004 in the Netherlands, the UK, France, Germany and Spain. Pathogenic Streptomyces in tuber lesions were detected by PCR in 70 samples and were also successfully isolated from these 70 samples. All pathogenic isolates showed the basic general phenotypic traits of the S. scabiei phenetic cluster. RFLP analysis of amplified rRNA sequences, together with carbon source utilization and repetitive BOX profiles, allowed most isolates to be assigned to S. europaeiscabiei , which emerged as the main cause of potato common scab in Western Europe.     

Phytotoxin produced by Streptomyces sp. causing potato russet scab in Japan

A phytotoxin isolated from the Stretomyces sp. causing potato russet scab in Japan (Kamenoko-byo in Japanese) was identified as a 16-membered macrolide, FD-891. It induced necrosis in potato tuber slices above 50 µg/disk, which is about 1/100 the activity of thaxtomin A. The phytotoxin was detected in potatoes infected by the pathogen and was produced by other pathogenic strains with different geographic origins.     

云南省马铃薯疮痂病致病链霉菌种类组成研究

 为明确云南省马铃薯疮痂病病原菌(Streptomyces spp.)的种类及其生物学特征,自2013年从云南省13个马铃薯主产区采集疮痂病病样,共分离到200株链霉菌,通过温室盆栽致病性试验筛选出67株致病菌。通过形态学、生理生化指标、致病性测定及16S rDNA序列分析对获得的菌株进行鉴定。结果显示,引起云南地区马铃薯疮痂病的病原为10种链霉菌,分别为S. caviscabies、S. anulatus、S. scabies、S. turgidiscabies、S. acidiscabies、S. europaeiscabiei、S. luridiscabiei、S. enissocaesilis、S. griseus和S. aureofaciens。其中S. enissocaesilis和 S. anulatus为优势种群,S. caviscabies、S. anulatus和S. luridiscabiei为国内首次报道的病原菌。因此,认为云南省马铃薯疮痂病菌种类复杂多样。     

Isolation and characterization of Streptomyces species from potato common scab lesions in Norway

The present survey was conducted to isolate and characterize Streptomyces species from common scab lesions of potato in Norway. Bacteria were isolated from scab lesions on tubers sampled in two consecutive years at different locations in Norway spanning ～1400 km from south to north. In total, 957 independent isolations from individual tubers were performed, with 223 putative pathogenic isolates obtained from 29 different potato cultivars and 130 different fields. Streptomyces europaeiscabiei was the most abundant species isolated from common scab lesions (69%), while 31% of the isolates obtained were S. turgidiscabies. Streptomyces scabies was not found. Pathogenicity of selected Streptomyces isolates was tested on potato. The ability of the bacterial isolates to infect potato was consistent with the presence of the txtAB operon. The results revealed no pattern in geographical distribution of S. europaeiscabiei and S. turgidiscabies; both could be found in the same field and even the same lesion. Four different pathogenicity island (PAI) genotypes were detected amongst the txtAB positive isolates: nec1+/tomA+, nec1–/tomA+, nec1+/tomA? and nec1?/tomA?. The current findings demonstrate that there is genetic variability within species and that the species are not spread solely by clonal expansion. This is thought to be the most comprehensive survey of Streptomyces species that cause common scab of potato in a European country.     

Differences in host range, pathogenicity to potato cultivars and response to soil temperature among Streptomyces species causing common and netted scab in France

The pathogenicity and ecology of some isolates representative of the four main Streptomyces species ( S. scabies , S. europaeiscabiei , S. stelliscabiei and S. reticuliscabiei ) identified as pathogenic to potato tubers were investigated. Three pathogenicity groups could be distinguished. Group 1 included all isolates of S. scabies , S. europaeiscabiei and S. stelliscabiei from common scab lesions of potato and other susceptible root crops. All these produced similar symptoms and were pathogenic to potato, carrot and radish. Group 2 included all isolates from S. reticuliscabiei netted scab lesions; they were pathogenic to both tubers and roots of only a few potato cultivars, and did not infect carrot or radish. Group 3 included three isolates of S. europaeiscabiei from netted scab lesions on cv. Bintje, which produced either common or netted scab symptoms depending on the potato cultivar or plant species. In an experiment on a few isolates from each of the three groups, held at various soil temperature regimes, the three from group 1 were most pathogenic at higher temperatures (20°C or 20/30°C), the two from group 2 were most pathogenic at a lower temperature (17°C). The group 3 isolate caused netted scab symptoms on susceptible cultivars at low temperatures (≤ 20°C) and deep-pitted lesions at higher temperatures. Since the groups identified differ in ecological requirements, it is important to adapt the control methods to the pathogenic species present in the soil.     

A Streptomyces species identified as the cause of carrot scab

Samenvatting In 1986 werd een ernstige schurft-aantasting bij peen (Daucus carota) gevonden met name in NO-Nederland. Vanuit schurftlesies werd steeds weer eenzelfde type streptomyceet geïsoleerd. In proeven met zeven isolaten van peen en één van aardappel bleek dat deze morfologisch en biochemisch sterk overeen kwamen, terwijl alle isolaten, ook dat van aardappel, pathogeen waren voor peen Amsterdamse bak.De hier onderzochte isolaten komen sterk overeen met een soort die in de literatuur bekend is alsStreptomyces scabies, de veroorzaker van aardappelschurft.S. scabies is echter een ongeldige naam door het ontbreken van een typestam. Zolang er niet een geldig neotype is gepubliceerd kan geen speciesnaam aan deze isolaten worden gegeven. Taxonomisch en nomenclatorisch onderzoek is dus gewenst, evenals onderzoek naar schade, invloed van vruchtwisseling met aardappel en/of andere gewassen en effectieve bestrijding (wellicht door beregening?) van schurft bij peen.     

Occurrence and survival of potato scab pathogens (Streptomyces species) on tuber lesions: quick diagnosis based on a PCR-based assay

A time-saving and cost-effective polymerase chain reaction (PCR)-based method was developed for species-specific detection of the scab pathogens ( Streptomyces scabies and S. turgidiscabies ) prevalent in potato ( Solanum tuberosum ) in northern Scandinavia. Species specificity of primers was verified using a collection of previously characterized Streptomyces strains isolated from potato scab lesions in Finland and Sweden. A total of 1245 scab lesions was tested from potato cvs Matilda and Sabina grown in the field in two geographic regions of Finland in 2000 and 2001. Freshly harvested or stored potato tubers were incubated at room temperature (18–21°C) under humid conditions for a few days. Bacterial growth was collected from scab lesions for DNA isolation and PCR. The two scab pathogens were detected in the same potato fields, tubers and scab lesions. The relative incidence of S. scabies was high in freshly harvested tubers but was much lower than that of S. turgidiscabies following storage. Both pathogens were seed-transmitted in Matilda and Sabina after 24 weeks of storage at 4°C.     

Involvement of Colletotrichum coccodes causing atypical symptoms of potato tubers in Turkey

Journal of Plant Diseases and Protection - In 2015 and 2017, potato storages were surveyed for the prevalence of atypical potato tuber rots in Nevşehir and Isparta Provinces of Turkey. About...     

Using the TxtAB operon to quantify pathogenic Streptomyces in potato tubers and soil

The phytotoxin thaxtomin, produced by plant pathogenic Streptomyces species, is the only known pathogenicity determinant for common scab diseases of potato and other root and tuber crops. Genes encoding thaxtomin synthetase (txtAB) are found on a pathogenicity island characteristic of genetically diverse plant pathogenic Streptomyces species. In this study, an SYBR Green quantitative real-time polymerase chain reaction (PCR) assay using primers designed to anneal to the txtAB operon of Streptomyces was developed to quantify pathogenic bacterial populations in potatoes and soil. The real-time PCR assay was specific for pathogenic Streptomyces strains. The detection limit of the assay was 10 fg of the target DNA, or one genome equivalent. Cycle threshold (Ct) values were linearly correlated with the concentration of the target DNA (correlation coefficient R(2) = 0.99) and were not affected by the presence of plant DNA extracts, indicating the usefulness of the assay for quantitative analyses of the pathogenic bacteria in plant tissues. The amount of pathogenic Streptomyces DNA in total DNA extracts from 1 g asymptomatic and symptomatic tubers was quantified using the assay and ranged from 10(1) to 10(6) pg. A standard curve was established to quantify pathogenic Streptomyces in soil. Using the standard curve, numbers of pathogenic Streptomyces colony forming units were extrapolated to range from 10(3) to 10(6) per gram of soil from potato fields where common scab was found. This real-time PCR assay using primers designed from the txtAB operon allows rapid, accurate, and cost effective quantification of pathogenic Streptomyces strains in potato tubers and in soil.     

生物有机肥GSJ-1对马铃薯土壤疮痂病病原菌分布影响及生防效果研究

为了确定生物有机肥 GSJ －1对连作马铃薯土壤疮痂病病原菌分布影响及对马铃薯疮痂病的防治效果,本试验进行了土壤疮痂病病原菌含量测定、马铃薯疮痂病病情田间调查。结果表明,连作土壤疮痂病病原菌在盛花期之前向根际富集,盛花期之后向匍匐茎和薯块富集。施用生物有机肥 GSJ －1显著降低了土壤疮痂病病原菌含量,比对照下降了19．6％～74．9％,且改变了土壤中疮痂病病原菌原有的分布规律：从连作处理的根际多于非根际改变为生物有机肥 GSJ －1处理的根际少于非根际,且对疮痂病的防效达到47．2％。     

A survey of genetic variation in streptomyces isolates causing potato common scab in the United States

ABSTRACT Common scab is a serious disease of potatoes and other root and tuber crops, affecting crop quality and market value. The disease is caused by gram positive soil bacteria in the genus Streptomyces. Disease incidence and severity vary in different locations and years; this is due in part to variation in the environment (weather) and genetic variation in potato cultivars. Little information is available on the contribution of genetic variation by the pathogen. To examine genetic diversity in different locations within the United States, streptomycetes were isolated from lesions on field-grown potatoes from six states. Isolates were classified into species based on sequence of variable regions in the 16s rRNA gene. The presence of genes associated with the recently described S. turgidiscabies pathogenicity island (PAI) was also determined. About half of the isolates belonged to S. scabies or S. europaeiscabiei based on 16s rDNA sequence, and had characteristic features of the PAI. They were found in all six states, and were pathogenic on potato and radish. The remaining isolates included pathogens and nonpathogens. They were varied in appearance, and represent several species, including one pathogenic species not previously reported. Some pathogenic isolates lacked one or more genes characteristic of the PAI, although all had genes for biosynthesis of the pathogenicity determinant thaxtomin. In this relatively small survey, regional differences in scab-causing streptomycetes were seen. This report furnishes tools and baseline data for population genetic study of scab-causing streptomycetes in the United States.     

广东省甘薯疮痂病病原菌鉴定及国内主要菜用甘薯种质抗性评价

为明确广东省甘薯疮痂病病原菌种类及当前国内主要菜用甘薯种质对疮痂病的抗性,结合形态学特征和rDNA-ITS序列分析对病原菌进行鉴定,并通过病圃诱发结合人工喷雾接种法对来自9个省区30个菜用甘薯种质进行连续2年的抗性鉴定。结果显示,共获得15株形态学特征及培养性状相似的菌株,其中代表菌株CRI-CJ的形态学特征与甘薯痂圆孢菌Elsinoe batatas基本一致,且在基于rDNA-ITS序列的系统发育树中与甘薯痂圆孢菌聚在一支,表明甘薯疮痂病病原菌为甘薯痂圆孢菌。30个菜用甘薯品种(系)中,抗性、中抗、中感和感病品种(系)分别为7、7、5和11个,占总数的23.3%、23.3%、16.7%和36.7%。其中抗性品种(系)有广菜薯11-52、广菜薯15-6、广菜薯16-1、广菜薯16-19、广菜薯17-23、广菜薯17-9和广菜薯18-6,中抗品种(系)有EC01、广薯菜2号、广菜薯3号、广菜薯6号、广菜薯7号、广菜薯17-25和广菜薯18-3。不同地理来源的品种(系)对甘薯疮痂病的抗性水平存在差异,11个非广东省品种(系)中感病、中感和中抗品种(系)分别为8、2和1个,占比分别为72.7...     

Temporal association of potato tuber development with susceptibility to common scab and Streptomyces scabiei‐induced responses in the potato periderm

Using hydroponics and novel non‐destructive pot culture systems which enable inoculation at specific tuber development stages, the dynamics of common scab infection patterns in potato were studied in order to provide more precise identification of tuber physiological factors associated with susceptibility. At the whole‐tuber level, infection percentages were greatest when Streptomyces scabiei inoculation occurred early; at 2 weeks after tuberization (WAT) 68% of tubers became infected, contrasting with late inoculation (8 WAT), when only 4% infection occurred. The first‐formed internodes were most susceptible to infection, whilst later‐forming and slower‐expanding internodes were less susceptible. Detailed tuber physiological examination of internode 2 showed that pathogen‐induced changes, including increased phellem (periderm) thickness, cell layers and phellem suberization (key physiological features believed critical to S. scabiei infection) were promoted through S. scabiei inoculation. Sequential harvesting showed enhanced phellem suberization (28% greater than the control) within 7 days of pathogen exposure, while phellem thickness and layer responses were also initiated early in the infection process (10–14 days after pathogen exposure) and these responses were independent of symptom expression. Differences in cultivar response were observed, with greater phellem suberization observed 10 days after tuberization (DAT) in the common‐scab‐tolerant cv. Russet Burbank than in the susceptible cv. Desiree. Likewise, Russet Burbank had thicker and more numerous cell layers in the phellem (up to eight cell layers) during early tuber growth (20–30 DAT) than Desiree (up to six cell layers).     

Occurrence,identification, and host range of Pectobacterium brasiliense causing soft rot on seed potato tubers in Turkey

Journal of Plant Diseases and Protection - Pectobacterium brasiliense is an important bacterial species that causes soft rot disease in a wide range of host plants including potatoes worldwide. In...