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1.
After natural desiccation in the field, anhydrobiotic populations ofPratylenchus thornei Sher & Allen andMerlinius brevidens (Allen) Sidiqqi were treated in three different ways: some were kept dry to maintain nematodes in the anhydrobiotic stage; some were rehydrated and then allowed to dry again to induce a new desiccation cycle; and some were rehydrated and maintained as such, to reactivate and keep nematodes active.P. thornei populations from the dry treatment had a greater survival rate than the two other treatments. Culturing of the nematodes under wheat revealed that the three treatments did not alter the ability ofP. thornei to penetrate the roots, but nematodes given two cycles of desiccation had a greater rate of reproduction than those exposed to one desiccation cycle and kept in dry soil for a longer period (dry treatment). Survival ofM. brevidens rehydrated and retained in the active state was lower than that of nematodes undergoing the two other treatments.  相似文献   

2.
Root-lesion nematodes of the genus Pratylenchus are migratory endoparasites with worldwide economic impact on several important crops including potato, where certain species like P. penetrans, P. neglectus, and P. scribneri reduce the yield and quality of potato tubers. Morphological identification of Pratylenchus spp. is challenging, and recent advancements in molecular techniques provide robust and rapid diagnostics to differentiate species without the need of specialist skills. However, the fact that molecular diagnostics are not available for all Pratylenchus species means that there are limitations in worldwide application. In general, root-lesion nematodes are difficult to manage once introduced into agricultural land and damage can be related to pathogenicity and population densities. In addition, root-lesion nematodes interact with fungi such as Verticillium dahliae, resulting in disease complexes that enhance the damage inflicted on the potato crop. Management interventions are often focused on limiting nematode reproduction before planting crops and include the application of nematicides, and cultural practices such as crop rotation, cover crops, biofumigation, and biological control. Understanding the limitations of the available crop protection strategies is important and there are many gaps for further study. This review discusses the status of the diagnosis, distribution, pathogenicity, and management of the main species of root-lesion nematodes, reported to infect potatoes worldwide, and highlights areas for potential future research.  相似文献   

3.
Two different molecular tools for the diagnosis of the cereal and legume root-lesion nematode Pratylenchus thornei were developed. A randomly amplified DNA (RAPD) fragment specific to P. thornei was identified. After sequencing the fragment, longer primers were designed that complement the terminal sequences of the RAPD fragment, and this pair of specific primers was used to amplify the sequence-characterized amplified region (SCAR). Using the developed pair of SCAR primers, the SCAR fragment specific to P. thornei was easily amplified with DNA extracts obtained from different life stages of the nematode. The described SCAR-PCR-based assay has the potential to be optimized for routine practical diagnostic tests. In addition, the use of a species-specific satellite DNA sequence to distinguish P. thornei from other Pratylenchus spp. is discussed.  相似文献   

4.
Pratylenchus penetrans is one of the most economically damaging plant-parasitic nematodes and is found on a wide variety of crops. Correct identification and quantification of this nematode are necessary for providing advice to farmers, but are not easily obtained with the traditional way of microscopic observation. We developed a qPCR assay to detect and quantify P. penetrans in a short but accurate manner. A qPCR primer set, including two primers and a TaqMan probe, was designed based on the sequence of the β-1,4-endoglucanase gene. The assay was optimized by using the primers in a qPCR assay with SYBR green I dye and setting the qPCR program to different annealing temperatures ranging from 60 °C to 64 °C. Based on the Ct-values, we retained the program with an annealing temperature of 63 °C. The assay with the probe was very sensitive as it was able to detect a single individual of P. penetrans, even when mixed with up to 80 individuals of P. thornei. The specificity of the reaction was confirmed by the lack of amplification of DNA from 28 populations of 18 other Pratylenchus species and from plant-parasitic nematodes from nine other genera. DNA from 21 different isolates from P. penetrans was amplified. DNA extraction from 80 individuals and quantification by qPCR was repeated four times; Ct-values showed consistent results (Ct?=?24.4?±?0.4). A dilution series from DNA of P. penetrans resulted in a standard curve showing a highly significant linearity between the Ct-values and the dilution rates (R2?=?0.99; slope?=??3.23; E?=?104 %). The tests showed a high correlation between the real numbers of nematodes and the numbers detected by the qPCR. The developed qPCR assay provides a sensitive means for the rapid detection and reliable quantification of individuals of this pest. This method does not require expertise in nematode taxonomy and morphology, and can be used as a rapid diagnostic tool in research, as well as in diagnostic labs and extension services advising farmers for pest management.  相似文献   

5.
Initial applications of 104 spores g−1 of Pasteuria penetrans, and dried neem cake and leaves at 3 and 2% w:w, respectively, were applied to soil in pots. Juveniles of Meloidogyne javanica were added immediately to the pots (500, 5,000 or 10,000) before planting 6-week-old tomato seedlings. The tomatoes were sampled after 64 days; subsequently a second crop was grown for 59 days and a third crop for 67 days without further applications of P. penetrans and neem. There was significantly less root-galling in the P. penetrans combined with neem cake treatment at the end of the third crop and this treatment also had the greatest effect on the growth of the tomato plants. At the end of the third crop, 30% of the females were infected with P. penetrans in those treatments where spores had been applied at the start of the experiment. The effects of neem leaves and neem cake on the nematode population did not persist through the crop sequences but the potential for combining the amendments with a biological control agent such as P. penetrans is worthy of further evaluation.  相似文献   

6.
The gene CreAet for resistance to Heterodera avenae, transferred from Aegilops triuncialis to Triticum aestivum introgression line TR-353, was assessed for responses to Pratylenchus thornei under field conditions. After 2.5 months, P. thornei infestation on TR-353 was similar to those on its progenitors (T. aestivum H10-15, T. turgidum H1-1 and A. triuncialis A-1) and on the cultivar Capa. After 5 months, TR-353 hosted significantly more P. thornei per plant than A. triuncialis, T. aestivum H10-15 or cultivar Rinconada, being very close to the maximum value obtained from T. turgidum. The final infestation of line TR-353 by H. avenae was significantly lower than on the other plants, except for A. triuncialis. In addition, at 2.5 months, the abundance of P. thornei on TR-353 was intermediate between the introgression wheat line H93-8 (Cre2 gene) and the cultivar Loros (Cre1 gene), but the final number of P. thornei per plant on TR-353 was significantly greater than on Loros. Line TR-353 was not able to control P. thornei in the field, but it confirmed its resistance to H. avenae, which was significantly lower than those due to Cre1 and Cre2 genes. No competition was observed between P. thornei and H. avenae populations on line TR-353 or A. triuncialis.  相似文献   

7.
Pratylenchus thornei densities were monitored in field plots of two winter wheat cultivars in a dry farming area of southern Spain. Samples were taken fortnightly during the wheat-growing season and from the following dry fallow. Under bread wheat cv. ‘Yecora’, densities ofP. thornei increased for 5 to 6 months and then were maintained or slightly decreased thereafter, surviving the summer dry fallow in an anhydrobiotic state (78.2% and 85.3% survival in soil and roots, respectively). Under durum wheat cv. ‘Donpedro’, nematode densities decreased over the growing season, although densities within the roots increased during the first 2 months of the wheat-growing period, indicating that nematodes could penetrate the roots of this cultivar but were unable to reproduce. These observations suggest resistance of wheat cv. Donpedro toP. thornei.  相似文献   

8.
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9.
Field and pot experiments with over 35 different Compositae, mainly perennial and annual flower crops, show thatHelenium hybrids,Gaillardia hybrid ‘Burgunder’ andEriophyllum caespitosum, in addition toTagetes patula ‘Harmony’, suppress populations ofPratylenchus penetrans very effectively. In other genera of Compositae species also occur which are poor hosts ofP. penetrans, although their suppressive action is generally significantly less marked than that of the species mentioned. Within the same plant genus considerable differences in host suitability were found. These results may prove to be useful in providing indications as to the most suitable sequence of crops for the control ofP. penetrans in nurseries of perennial crops, parks and gardens. Some data collected on host suitability of Compositae toRotylenchus robustus andTylenchorhynchus dubius show differences, though less marked than those relating toP. penetrans.  相似文献   

10.
Pasteuria penetrans, an endospore-forming obligate parasite of root-knot nematodes, can be an effective biological control agent, particularly when used in pots, small plots or container-grown crops. The absence of adequate mass-production techniques prevents its deployment on a field scale. The spores are not mobile and their concentration and distribution influence parasitism since attachment of spores to free-living juvenile root-knot nematodes depends upon chance contact. Efficacy can also be influenced by the specificity of the population of P. penetrans to the root-knot nematode population. If these problems can be overcome, the use of P. penetrans in integrated management systems developed over several crop cycles would appear to have good prospects for decreasing root-knot nematodes in intensively cultivated soils.  相似文献   

11.
The root lesion nematode Pratylenchus penetrans parasitizes a wide range of economically important crops, including potato (Solanum tuberosum). Damage by P. penetrans impacts not only the potato yield but can also reduce the tuber quality. Detailed information on tuber infection by P. penetrans is scarce for most cultivars and molecular detection of nematodes from infected tubers is needed. The objective of this study was to assess tuber symptomatology due to P. penetrans infection in 10 potato cultivars and to provide an accurate molecular methodology for nematode detection using tuber peels. Sprouts of certified potato seed from cultivars Agata, Agria, Camel, Désirée, Dirosso, Kennebec, Laura, Picasso, Royata, and Stemster were planted in 2 L pots, and soil was inoculated with 4 P. penetrans/g of soil. Sixty days after inoculation, tubers were harvested, inspected for lesions, and the number of nematodes/g of potato peel assessed. Observations of tubers with symptoms showed the presence of P. penetrans in superficial layers of peels around the lenticels and injured necrotic tissue. Different nematode stages were detected in tubers of all inoculated cultivars, varying from 4 to 46 nematodes/g of potato peel. Species-specific primers showed suitable sensitivity and reproducibility for the detection of P. penetrans in tuber potato peel samples. The molecular detection of P. penetrans directly from tuber peels can facilitate routine nematode inspections of potato seed tubers or cull potatoes for nematode detection, and prevent further dissemination of this species.  相似文献   

12.
Root and stem rot with wilt of above ground parts of cultivated chrysanthemums was first found in Ibaraki, Toyama and Kagawa prefectures, Japan in 2002 and 2003. Pythium species were isolated from the diseased tissues and identified as P. dissotocum, P. oedochilum, P. sylvaticum, P. ultimum var. ultimum and asexual strains of P. helicoides based on their morphologies and sequences of rDNA-ITS region. All the Pythium species were strongly pathogenic to chrysanthemums in pot conditions and were reisolated from the inoculated plants. Because Pythium root and stem rot of chrysanthemum has never been reported in Japan, we propose that this is a new disease that can be caused by the five Pythium species.  相似文献   

13.
M. DI VITO  N. GRECO 《EPPO Bulletin》1994,24(2):489-494
Control of food legume nematodes should consider the nematode species, type of crops, whether for grain or fresh pod production, environmental conditions and the economics of the crops. In general, 3–4-year crop rotations could provide sufficient control of Heterodera goettingiana and H. ciceri and to a lesser extent also of Meloidogyne artiellia. Soil solarization has shown promise in controlling Pratylenchus thornei and H. ciceri on chickpea and has also been reported to be effective against Meloidogyne spp. The use of fumigants such as 1,3-dichloropropene or 1,3-dichloropropene + methylisothiocyanate and also of non-volatile nematicides (aldicarb, oxamyl, carbofuran, thionazin and fenamiphos) gives good control of these nematodes resulting in impressive yield increases in heavily infested soil. However, both nematicides and soil solarization are expensive and their use may not be economic in most cases. The use of resistant cultivars is, so far, of little importance due to very limited number of those with good agronomic characteristics. To ensure good yield of faba bean, attention must also be paid to producing seed stocks free from Ditylenchus dipsaci. In addition, quarantine regulations must avoid spread of this nematode among different countries.  相似文献   

14.
Lectins and polyclonal antiserum that bind specifically and reproducibly to the overall surface of Paratrichodorus anemones were identified and bound to monodisperse superparamagnetic particles (Dynabeads) to assess their efficiency as probes for capturing target nematodes from test suspensions. In recovery experiments, while both types of probe isolated nematodes, antibody-coated beads recovered them more efficiently than beads coated with lectins. When immunomagnetic capture was used to isolate P. anemones from mixtures of naturally occurring populations of nematodes extracted in bulk, from soil samples, 80% of the target nematodes were recovered.  相似文献   

15.
A technique based on the use of specific primers for polymerase chain reaction (PCR) was developed for the identification of the stem and bulb nematode belonging to the Ditylenchus dipsaci species complex. The internal transcribed spacer region ITS1 and ITS2, the gene 5.8 S and part of genes 18 S and 26 S of twenty populations of the D. dipsaci species complex belonging to both D. dipsaci sensu stricto and Ditylenchus sp. B (corresponding to populations of giant individuals associated to Vicia faba) and three congeneric species were amplified with two universal ribosomal primers. PCR-amplified DNA samples were digested with five restriction enzymes in order to reveal some polymorphism allowing the identification of D. dipsaci populations associated with Fabaceae seeds. The polymorphism among species was confirmed by the sequencing of the PCR products. A primer (DdpS2) was designed in a region conserved in all populations of both D. dipsaci sensu stricto and D. sp. B studied in the present work. The other Anguinidae species (except a few species from Central Asia associated to Astereaceae and D. sp. G associated to Plantago maritima) differ in two to four nucleotides at the 3′ extremity of this region. This sequence portion coincides with a TspEI restriction site. In combination with a primer located in the ribosomal region, this first primer is a good candidate for identification by PCR of populations of the D. dipsaci species complex found in Fabaceae seeds. A second primer (DdpS1) was designed in a similar way and was specific to D. dipsaci sensu stricto. The utility of these two sets of primers is discussed against the background of quarantine regulation.  相似文献   

16.
N. GRECO  M. DI VITO 《EPPO Bulletin》1994,24(2):393-398
Several endoparasitic nematodes have been reported on leguminous plants in the Mediterranean area. The most widespread are the root-lesion nematodes Pratylenchus mediterraneus, P. penetrans and P. thornei. Symptoms induced by these nematodes usually are not very impressive, but 50% yield loss of chickpea may occur. Among root-knot nematodes, Meloidogyne artiellia is associated with severe yield losses of chickpea in Italy, Spain and especially Syria. Tolerance limits of 0.14 and 0.02 of this nematode per ml soil are reported for winter and spring-sown chickpea, respectively. Meloidogyne incognita and M. javanica can be noxious to French bean and cowpea in sandy soil. The cyst nematode Heterodera goettingiana reduces yields of pea, broad bean and vetch when its population densities exceed 0.5, 1, and 2.1 eggs per g of soil, respectively. Heterodera ciceri occurs in northern Syria and Turkey and is responsible for economic yield losses of chickpea and lentil in fields infested with more than 1 or 2.5 eggs per g of soil, respectively. Pea and grass pea also suffer from infestation of this nematode. The stem and bulb nematode Ditylenchus dipsaci causes severe decline of broad bean, pea and probably lentil during wet seasons. Other nematodes, although present in moderate numbers, appear to have little importance.  相似文献   

17.
甘肃定西地区马铃薯线虫病病原的分离鉴定   总被引：3，自引：1，他引：2  
为明确甘肃省定西市马铃薯线虫病的病原种群分类地位,采用形态学结合分子生物学的方法对该地区马铃薯上的4个线虫群体进行了鉴定,观察和测量其形态特征值,基于r DNA-ITS序列以UPGMA法构建线虫群体的系统发育树,并按照柯赫氏法则进行了致病性测定。结果表明,4个线虫群体在形态学上与马铃薯腐烂茎线虫Ditylenchus destructor一致,但群体DX27与群体DX11、DX16、DX19雌虫的体长、体长/食道长、体长/尾长值存在极显著差异。利用通用引物TW81/AB28扩增r DNA-ITS序列均获得长度为915 bp的片段;序列比对分析表明,群体DX27与其它3个群体相比在ITS1区的第96~255 bp片段内有25个碱基的差异;系统发育树显示,群体DX27与C型群体聚为1支,群体DX11、DX16、DX19与B型群体聚为1支。根据形态学特征及r DNA-ITS序列分析结果确定该病原线虫为马铃薯腐烂茎线虫,其中群体DX27属于C型,群体DX11、DX16、DX19属于B型。  相似文献   

18.
1,2-Dehydropyrrolizidine alkaloids (PAs), known to be nematotoxic in vitro, represent a class of secondary plant metabolites from hundreds of plant species worldwide. Pot experiments with the commercially available PA-containing plants Ageratum houstonianum, Borago officinalis, Senecio bicolor, and Symphytum officinalis demonstrate that Meloidogyne hapla is not per se repelled by these plants as all species were infested with nematodes. However, the development of M. hapla juveniles was completely suppressed on A. houstonianum and S. bicolor. Soil in which A. houstonianum and S. bicolor were cultivated and incorporated contained 200–400 times less nematodes than soil treated with Lycopersicon esculentum. Depending on their qualitative composition of PAs at least some of these plants thus appear to be valuable tools for integrated root-knot nematode management.  相似文献   

19.
Novel primers for rep-PCR were developed with the original software and based on `ancient diverged periodical sequences'. Rep-PCR with these primers was applied to study genetic relationships among 51 Xanthomonas campestris strains. The strains were collected from different countries including Russia, Japan, UK, Germany and Hungary. Reference strains of three X. campestrispathovars and five other Xanthomonas species were included. Based on qualitative differences in amplification profiles, the strains were divided into four major groups. Two subgroups recognised within X. campestrispopulation were similar to RFLP haplotypes. The third subgroup included strains of two other pathovariants and Japanese isolates of X. campestris pv. campestriswhile the fourth group comprised the other species of Xanthomonas. The analysis of the diversity within X. campestris resulted in the conclusion that isolates belong to distinct clonal populations (subgroups). The differences between the subgroups of X. campestris were only slightly smaller than between species of Xanthomonas. A PCR fragment about 600 bp amplified by primer KRPN2 was found in nearly all tested strains of X. campestris.SCAR primers designed for this marker produced a single specific band for strains of X. campestris, but not for other Xanthomonas, Pseudomonas and Erwiniastrains tested. Application of the new primer set for rep-PCR offers a rapid, simple and reproducible method for identification of bacterial strains. The X. campestris-specific SCAR primers may be used in diagnostics of this important plant pathogen.  相似文献   

20.
A PCR‐RFLP assay was developed for the identification of trichodorid nematodes belonging to Nanidorus, Paratrichodorus and Trichodorus genera. Using the variability of the 18S SSU rDNA gene, this method provides a new molecular diagnosis tool which allows identification within mixed samples of trichodorid and non‐trichodorid species, differentiation of juveniles, and represents an alternative to the difficult and time consuming phenotyping of similar species. Based on the alignment of previously obtained 18S rDNA nucleotide sequences of trichodorids from Portugal, a pair of selective primers was designed in conserved regions to allow the amplification of a variable region located at the 3′ end of the gene in all known Portuguese species. The 615 bp PCR product showed nucleotide variability enabling the generation of restriction fragment patterns which were consistent among populations of the same species but allowed discrimination of trichodorids at the species level. The proposed protocol was tested and proved effective with 12 trichodorid species from Portugal (N. minor, P. allius, P. anemones, P. divergens, P. hispanus, P. pachydermus, P. porosus, T. beirensis, T. lusitanicus, T. primitivus and two other Trichodorus species, A and B) and six non‐indigenous trichodorid populations (N. minor, P. allius, P. anemones, P. pachydermus, P. porosus and T. primitivus).  相似文献   

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