Towards a more reasoned assessment of the threat to wheat crops from <Emphasis Type="Italic">Tilletia indica</Emphasis>, the cause of Karnal bunt disease

The interpretation of information used to defend an assessment that T. indica, the cause of Karnal bunt of wheat, has a high risk of establishing in Europe and of causing significant yield/quality losses is questioned. Karnal bunt has only established in locations that are arid or semi-arid with hot summers and cool/mild winters. There is very strong circumstantial evidence that substantial amounts of seed contaminated with teliospores of T. indica were sown in Europe in the past without the appearance of Karnal bunt. It is unlikely that sufficient numbers of teliospores would survive long enough on the soil surface under European conditions and then synchronise germination during the period at heading when wheat is vulnerable to infection to guarantee disease expression. Karnal bunt is regarded as a minor disease everywhere it occurs. Almost two thirds of European wheat cultivars inoculated by a severe boot injection method have been categorised as either resistant or highly resistant to T. indica. Yield/quality losses would be expected to be low even if the pathogen were capable of establishing in Europe. The status of T. indica as an important quarantine pest is based on the indirect economic consequences of the appearance of the pathogen and not on the direct damage it causes to wheat crops. Arguments in this and previous reviews advocating a more reasoned and comprehensive assessment of the threat to Europe, North America and other locations from T. indica need to be taken into consideration in any new pest risk analyses. David Jones is a retired employee of the Central Science Laboratory (CSL). Statements and opinions expressed in this paper are those of the author and are not the views of CSL.     

Arguments for a low risk of establishment of Karnal bunt disease of wheat in Europe

Tilletia indica, which causes Karnal bunt of wheat, has been perceived as a pathogen that has a high risk of establishment in the UK and other countries in Europe. This viewpoint is challenged with arguments for the risk of establishment being much lower. The present distribution of the pathogen and its likely widespread dissemination with consignments of germplasm and wheat seed from Mexico over a 20 year period without establishment outside the hot arid and semi-arid zones strongly suggests that T. indica is unsuited to environments other than those similar to where it is now found. A critical density of teliospores needs to remain viable and ungerminated between periods of wheat anthesis and then germinate during a narrow window of opportunity to ensure infection and establishment. Despite the results of outdoor teliospore longevity experiments, it is by no means certain that this can occur under European conditions. Generally cooler conditions and more frequent periods of rain in Europe are likely to trigger teliospore germination at times unsuitable for infection making establishment much more unlikely. A model based on year-round soil conditions, especially moisture content, is seen as appropriate to predict teliospore survival and germination potential. It is only after areas where teliospores can survive and germinate in sufficient numbers to guarantee regular infection cycles have been defined can another model, based on temperature, rainfall and/or humidity prior to anthesis, be applied to determine if environmental conditions are suitable for infection. David Jones is a retired employee of the Central Science Laboratory (CSL). Statements and opinions expressed in this paper are those of the author and are not the views of the Central Science Laboratory.     

Test validation for the detection of Tilletia indica Mitra by multiplex real‐time PCR

Tilletia indica Mitra is a fungal pathogen causing Karnal bunt of wheat. Tilletia indica is a quarantine pest in many countries worldwide. In the European Union, imported wheat grain from countries where the fungus is present must be checked for the presence of T. indica teliospores. The inspection services at the borders need rapid, sensitive and reliable detection tests to identify T. indica spores on wheat grain. In this work, validation was carried out according to EPPO Standard PM 7/98 to evaluate the multiplex real‐time PCR test described in ISPM 27 Diagnostic Protocol for regulated pests (Annex 4 Tilletia indica Mitra) by means of a test performance study with nine participating laboratories, and the performance characteristics of the test were established. The original protocol was modified with regard to the extraction of DNA from the pellet obtained from the ‘washing test’ and the enrichment PCR step in order to increase the amount of template DNA for the real‐time PCR. The optimized test still has five teliospores as the limit of detection for the contaminated pellet but has an increased analytical sensitivity and had positive results with three teliospores in 93% of cases instead of 43% for the original test. The two closest Tilletia species, Tilletia horrida and Tilletia walkeri, were used to evaluate analytical specificity (exclusivity) and no cross‐reactions were obtained. Diagnostic sensitivity, diagnostic specificity, accordance and concordance were also evaluated.     

The insecticidal and acaricidal actions of compounds fromAzadirachta indica (A. Juss.) and their use in tropical pest management

The pest control potential demonstrated by various extracts and compounds isolated from the kernels and leaves of the neem plant (Azadirachta indica) A. Juss. (Meliaceae) seem to be of tremendous importance for agriculture in developing countries. Laboratory and field trial data have revealed that neem extracts are toxic to over 400 species of insect pests some of which have developed resistance to conventional pesticides, e.g. sweet potato whitefly (Bemisia tabaci Genn. Diptera: Aleyrodidae), the diamond back moth (Plutella xylostella L. Lepidoptera: Plutellidae) and cattle ticks (Amblyomma cajennense F. Acarina: Ixodidae andBoophilus microplus Canestrini. Acarina: Ixodidae). The compounds isolated from the neem plant manifest their effects on the test organisms in many ways, e.g. as antifeedants, growth regulators, repellents, toxicants and chemosterilants. This review strives to assess critically the pest control potential of neem extracts and compounds for their use in the tropics. This assessment is based on the information available on the wide range of pests against which neem extracts and compounds have proven to be toxic, toxicity to non-target organisms, e.g. parasitoids, pollinators, mammals and fish, formulations, stability and phytotoxicity.     

<Emphasis Type="Italic">Teratosphaeria (Mycosphaerella) nubilosa,</Emphasis> the causal agent of Mycosphaerella leaf disease (MLD), recently introduced into Uruguay

Mycosphaerella leaf disease on Eucalyptus is well known in Uruguay but none of the more serious Mycosphaerella spp. and Teratosphaeria spp. causing this disease have yet been found. In the autumn of 2007, more severe defoliation than has been known in the past and associated with symptoms resembling Mycosphaerella infections was observed on Eucalyptus globulus. Isolations and identifications based on morphology and DNA sequence comparisons showed that the causal agent of the defoliation is the well known and serious pathogen Teratosphaeria nubilosa (=Mycosphaerella nubilosa). This is the first record of the pathogen in South America. Using ten microsatellite loci previously developed for T. nubilosa, only one multilocus haplotype was found from 46 T. nubilosa collected isolates. Interestingly, this haplotype was the same as one previously found in Portugal and Spain. The results suggest that T. nubilosa has recently been introduced into Uruguay and that it most likely originated from the Iberian Peninsula where E. globulus is widely planted.     

Opogona sacchari,a Pest Risk from Imports of Ornamental Plants of Tropical Origin1

The banana moth, Opogona sacchari, can be considered as a serious pest for a wide range of ornamental plants of tropical and subtropical origin grown in glasshouses in Europe. The insect is difficult to intercept at import inspection. Additional post-entry inspection is recommended. The best way to control the insect is a 3-month programme for the eradication of the adult stages. O. sacchari is a potential candidate for the list of quarantine pests mentioned in phytosanitary import requirements.     

A nested PCR assay targeting the DNA topoisomerase I gene to detect the pine wood nematode, <Emphasis Type="Italic">Bursaphelenchus xylophilus</Emphasis>

The pine wood nematode (PWN), Bursaphelenchus xylophilus, is a disastrous pathogen of the pine forests in East Asia and Europe. Plant quarantine is one of the most important ways to prevent its infection in current situation. A nested polymerase chain reaction (PCR) assay targeting the topoisomerse I gene has been developed to detect PWN in this study. To assess the specificity of the assay, 44 morphologically characterized nematode isolates including B. xylophilus, B. mucronatus, B. hofmanni, Seinura wuae, S. lii and Aphelenchoides macronucleatus were tested. Positive reactions characterized by amplification product of 509 bp were shown from all isolates of PWN. The nested PCR assay can detect 50 femtogram (fg) of template DNA or one individual nematode, as small as an egg. The validity was evaluated by analyzing the nematode samples extracted from the nematode-infested wood in the field. These results show that the assay is a specific, sensitive method for detection of PWN with the potential in relation to the pest risk assessment and quarantine regulations.     

Pathogenic and genetic variability in <Emphasis Type="Italic">Tilletia indica</Emphasis> monosporidial culture lines using universal rice primer-PCR

Tilletia indica Mitra is the causal agent of Karnal bunt of wheat, an important disease prevalent in several countries. The disease is internationally quarantined and the pathogen due to its heterothallic nature shows high variability. In the present study, we compared the pathogenic behaviour of various isolates of T. indica collected from different geographical locations of India and genetically characterized monosporidial (Ms) culture lines raised from these isolates of the pathogen. Pathogenic variability revealed existence of three pathotypes based on aggressiveness on a set of differential host genotypes. Monosporidial culture lines viz., 5 each from KB1, KB2, KB4 and KB5 and three lines of KB3 were established and analyzed genetically using 12 Universal Rice Primers (URPs). Amplification showed 98.44% polymorphism and primer URP 13R produced 100% polymorphic bands. Maximum similarity (83%) was between KB1MsB and KB1MsD as calculated by Jaccard’s similarity coefficient, whereas, minimum similarity was between KB1MsC and KB4MsB; KB1MsE and KB3MsA (46%). Three groups were formed among all Ms culture lines. One major group consisted of 13 lines with approximately 70% similarity, the second group consisted of 7 culture lines showing 55% similarity and the third group consisted of 3 Ms lines. URPs were able to differentiate the Ms culture lines raised from different T. indica isolates and the results indicated heterogeneity in the pathogen population.     

Thousand cankers disease in Europe: an overview

Walnut (Juglans regia L.) is traditionally present in most European countries as an ornamental tree, and in Southern Europe in particular it is grown for both fruit and wood. Since the 1980s, to supply the increasing demand for walnut timber, large areas of southern and central Europe, from France to Hungary, have been planted with black walnut (Juglans nigra L.) to provide wood for furniture production. The fungus Geosmithia morbida and its vector Pityophthorus juglandis, causing the thousand cankers disease of walnut in the USA in the last 2 decades, were recently reported in Europe (in Italy) on both walnut species. Thousand cankers disease can have a high negative impact on the landscape and economy of many agricultural and forest areas. Following a detailed pest risk analysis performed by EPPO in 2015, both organisms were included in the EPPO A2 List of pests recommended for regulation as quarantine pests. The main biological, epidemiological and monitoring aspects of thousand cankers disease and its status in Europe are reported.     

Emmer wheat, a potential new host of Tilletia indica

Two representative Italian emmer wheat (Triticum dicoccum) landraces, two selected lines and three improved emmer wheat cultivars, derived from crosses with durum wheat (Molisano landrace × ‘Simeto’), were tested for their susceptibility to Tilletia indica, the cause of Karnal bunt of wheat. Plants of emmer wheat were inoculated by injecting allantoid sporidial suspensions into the boot cavity of plants, just prior to ear emergence. A highly susceptible Indian spring wheat cultivar (Triticum aestivum) was used as a comparative control. At maturity of the plants, the seeds were harvested and assessed for incidence and severity of disease. All emmer wheat genotypes tested were infected but showed differing levels of susceptibility. The percentage of infected seeds for individual genotypes ranged from 5.4 to 75.0% compared with 99.1% for WL-711. The severity of infection was less in the old landraces, but it was higher in all the improved emmer wheat cultivars. In conclusion, Italian cultivars of emmer wheat were found to be highly susceptible to T. indica, and are potentially able to support the establishment of the pathogen.Authors L. Riccioni and M. Valvassori contributed equally to this work and should both be considered as first author.     

Characterization of <Emphasis Type="Italic">Dickeya</Emphasis> strains isolated from potato and river water samples in Finland

Plant pathogenic enterobacteria in the genera Pectobacterium and Dickeya (formerly classified as Erwinia) were isolated from diseased potato stems and tubers. The isolated bacteria were identified as P. atrosepticum, P. carotovorum and pathogens in the genus Dickeya with PCR tests. Furthermore, Dickeya strains were isolated from river water samples throughout the country. Phylogenetic analysis with 16S-23S rDNA intergenic spacer sequences suggested that the Dickeya strains could be divided into three groups, two of which were isolated from potato samples. Phylogenetic analysis with 16S rDNA sequences and growth at 39°C suggested that one of the groups corresponds to D. dianthicola, a quarantine pathogen in greenhouse cultivation of ornamentals, while two of the groups did not clearly resemble any of the previously characterised Dickeya species. Field trials with the strains indicated that D. dianthicola-like strains isolated from river samples caused the highest incidence of rotting and necrosis of potato stems, but some of the Dickeya strains isolated from potato samples also caused symptoms. The results showed that although P. atrosepticum is still the major cause of blackleg in Finland, virulent Dickeya strains were commonly present in potato stocks and rivers. This is the first report suggesting that Dickeya, originally known as a pathogen in tropical and warm climates, may cause diseases in potato in northern Europe.     

Interlaboratory tests for resistance to Synchytrium endobioticum in potato by the Glynne‐Lemmerzahl method

Synchytrium endobioticum is a major quarantine pathogen of potato causing potato wart disease. In Europe, the pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) are the most widespread and occur locally in almost all countries. Resistance to this disease in potato cultivars is tested for in the majority of the EU countries by the Glynne‐Lemmerzahl method. This paper describes the results of testing two different protocols of this method in five laboratories of three different countries (Germany, Poland, and the Netherlands). The four pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) were tested mainly on the cultivars described in the EPPO Standard PM 7/28 Synchytrium endobioticum. For pathotype 1(D1) and in most cases also for pathotype 18(T1), the results of the cultivars tested were identical to the rating in the EPPO Standard for both protocols. For pathotypes 2(G1) and 6(O1), the cultivars Désirée, Delcora and Miriam showed different results between laboratories as well as between the two protocols. In conclusion, further research is needed to develop one harmonised methodology for resistance testing of potato cultivars to the pathotypes 2(G1), 6(O1) and 18(T1) and to develop a new differential set of potato cultivars for the identification of pathotypes of S. endobioticum.     

Banning of methyl bromide for seed treatment: could Ditylenchus dipsaci again become a major threat to alfalfa production in Europe?

In Europe, the stem and bulb nematode Ditylenchus dipsaci has been listed as a quarantine pest by EPPO: without any control, it may cause complete failure of alfalfa crops. Movement of nematodes associated with seeds is considered to be the highest‐risk pathway for the spread of this pest. Since the 2010 official withdrawal of methyl bromide in Europe, and in the absence of any alternative chemical, fumigation of contaminated seed batches is no longer possible, which makes the production of nematode‐free alfalfa seeds difficult to achieve and leads to unmarketable seed batches. Thermotherapy is being considered as a realistic alternative strategy, but its efficiency still remains to be validated. The combination of the currently available methods (i.e. use of resistant cultivars, seed production according to a certification scheme, mechanical sieving, seed batch inspection) could significantly reduce the likelihood of seed contamination. However, it does not guarantee a total eradication of the nematode. Although it is already widely distributed all over Europe, reclassification of D. dipsaci as a regulated non‐quarantine pest to reduce the possibility of further introductions and the rate of spread of this pest appears to be a risky strategy because of the lack of up‐to‐date documented data to evaluate damage thresholds and determine acceptable tolerance levels. [[ArtCopyrightmsg]]     

Feeding and oviposition of <Emphasis Type="Italic">Anoplophora chinensis</Emphasis> on ornamental and forest trees

Studies were conducted on maturation feeding and oviposition of Anoplophora chinensis (Forster) (Coleoptera: Cerambycidae), a recently introduced quarantine pest in Europe on different plant species of great importance for urban and forest environments in Italy. The tested plant species were Aesculus hippocastanum, Acer negundo, A. campestris, Castanea sativa, Corylus avellana, Platanus x acerifolia, Quercus petrea, Q. pubescens, Q. rubra, Tilia platyphyllos, Ulmus minor and U. pumila. Tested adults of A. chinensis originated from a population of a recently infested site in Italy (Rome) and all experiments were conducted in a walk-in insect cage under quarantine conditions. Adults of A. chinensis showed a maturation feeding preference for twigs of Acer species (A. negundo and A. campestris) and for C. avellana. In the oviposition experiments conducted on bolts of tested plant species, A. chinensis females did not show clear preferences and some data did not reflect the preferences shown during the feeding experiments. Nevertheless, A. negundo and A. campestris were well accepted plant species for oviposition besides A. hippocastanum and T. platyphyllos.     

Resistance to infection by stealth: <Emphasis Type="Italic">Brassica napus</Emphasis> (winter oilseed rape) and <Emphasis Type="Italic">Pyrenopeziza brassicae</Emphasis> (light leaf spot)

Light leaf spot (Pyrenopeziza brassicae) is an important disease on winter oilseed rape crops (Brassica napus) in northern Europe. In regions where economically damaging epidemics occur, resistance to P. brassicae in commercial cultivars is generally insufficient to control the disease without the use of fungicides. Two major genes for resistance have been identified in seedling experiments, which may operate by decreasing colonisation of B. napus leaf tissues and P. brassicae sporulation. Much of the resistance present in current commercial cultivars is thought to be minor gene-mediated and, in crops, disease escape and tolerance also operate. The subtle strategy of the pathogen means that early colonisation of host tissues is asymptomatic, so a range of techniques and molecular tools is required to investigate mechanisms of resistance. Whilst resistance of new cultivars needs to be assessed in field experiments where they are exposed to populations of P. brassicae under natural conditions, such experiments provide little insight into components of resistance. Genetic components are best assessed in controlled environment experiments with single spore (genetically fixed) P. brassicae isolates. Data for cultivars used in the UK Recommended List trials over several seasons demonstrate how the efficacy of cultivar resistance can be reduced when they are deployed on a widespread scale. There is a need to improve understanding of the components of resistance to P. brassicae to guide the development of breeding and deployment strategies for sustainable management of resistance to P. brassicae in Europe.     

Spread risk of Eutypella canker of maple in Europe1

Eutypella canker of maple, caused by the pathogen Eutypella parasitica, has recently been reported for the first time in Europe. A rule‐based model of Eutypella parasitica spread risk in Europe is presented. This model incorporates the effects of spatial and temporal variability of multiple variables on pathogen spread and establishment. Model predictions are based on current knowledge of host susceptibility, pathogen reproduction and pathogen transmission, with particular regard to the host species’ distribution and climate suitability. Maps of host species’ distributions and monthly weather conditions were spatially analyzed in a Geographic Information System using the magnitude and direction of each variable's effect on disease spread. Spread risk predictions were computed for each month and averaged to generate a cumulative risk map. The model was calibrated using data on the natural distribution of Eutypella canker in North America. Extensive areas covering the natural distribution of maples in Europe are at considerable risk from the Eutypella parasitica infection. The most endangered regions are broad areas of the Balkans, the Apennines, France, Central and Eastern Europe and the Caucasus.     

番茄溃疡病菌PCR快速检测技术

番茄溃疡病是一种严重危害番茄生产的细菌性病害，许多国家将其列为检疫性病害。利用ITS通用引物扩增了番茄溃疡病菌（Clavibacter michiganensis subsp．michiganensis）的ITS序列，并进行克隆测序。根据序列比较结果设计了引物BT1和BT2，该引物特异性好，能专一扩增出268bp电泳条带，而马铃薯环腐病菌等不同亚种、不同属的细菌及健康的番茄材料均无扩增条带。从接种但未显症番茄苗叶片及人工模拟染菌种子上提取总DNA，以此为模板均能稳定地扩增出特异性目的条带。该方法直接对种子或植株进行检测，不需进行病原菌分离培养，快速简便，适用于出入境检验检疫及种苗健康检测领域。     

考虑灌溉及气候变化条件下葡萄花翅小卷蛾在中国的潜在地理分布

葡萄花翅小卷蛾Lobesia botrana(DenisSchiffermüller,1775)是我国重要的检疫性害虫,目前尚未传入我国,为了解该害虫在中国的潜在地理分布,根据该物种在全球已知的最新分布情况,利用CLIMEX 4.0.2在考虑灌溉条件的情景下,预测其在不同气候条件下的潜在地理分布。结果显示,葡萄花翅小卷蛾在我国的潜在地理分布范围较广,我国的主要葡萄产区均为葡萄花翅小卷蛾的适生区,且随着气候变化,至2030年,葡萄花翅小卷蛾在我国黑龙江、青海、四川省的部分适生区有所增加,适生程度也有所提高。因此应加强对葡萄花翅小卷蛾的检疫力度,防止其传入我国,保护我国葡萄种植业的生产安全。     

SSR marker analysis of Monilinia fructicola from Swiss apricots suggests introduction of the pathogen from neighbouring countries and the United States

Monilinia fructicola is a quarantine fungal pathogen in Europe, but many major stone fruit growing countries in Europe have reported its presence recently. In Switzerland, the fungus was first found in a single apricot orchard in 2008. This study confirms the presence of M. fructicola in nine out of 22 commercial orchards in Canton Valais, Switzerland. Five simple sequence repeat markers (SSRs) were developed for M. fructicola and samples from Switzerland, Spain, Italy, France and the United States were analysed and compared in order to assess the genetic diversity of the pathogen, identify the origin of the disease, and verify if the fungus reproduces sexually in Europe. In the 119 European samples analysed, 12 different haplotypes were found, indicating a relatively high genetic diversity of the pathogen considering that the first report in Europe was 10 years ago. Three haplotypes found in Europe were identical to those found in the American samples (two from the east coast and one from the west coast). Population structure analysis suggests that the European population is derived from at least two ‘invasion’ events probably originating from the US (one from the east coast, the other from the west coast). Preliminary evidence of sexual reproduction of M. fructicola in Europe is reported.     

Confirmation of the presence of the pistachio psyllid Agonoscena pistaciae Burckhardt & Lauterer, 1989 in Spain

Agonoscena pistaciae is a serious pest of pistachio in the Middle East and the Eastern Mediterranean. In this paper the presence of the species in Spain and Western Europe is confirmed. It is widespread in the regions of Castilla–La Mancha and Extremadura in Central Spain, where it develops mostly on Pistacia terebinthus, in contrast to the Middle East, where its preferred host is Pistacia vera. In the literature and internet sources, A. pistaciae is often confused with other, morphologically similar species, namely A. succincta and A. targionii. Morphological characters are listed and illustrated for the identification of the species found in the West Mediterranean.