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1.
A nematode survey conducted in 2013 in Algeria, revealed that potato cyst nematodes (PCN) and cereal cyst nematodes (CCN) are widely distributed in several potato and cereal growing regions of the country. Sixteen PCN populations from five localities and five CCN populations from four of these localities were collected and characterized at the morphological and molecular levels. The PCN populations were identified as Globodera rostochiensis and G. pallida occurring separately or in mixed populations. Two species of CCN were detected. Heterodera avenae was found in four localities, whereas H. hordecalis only in one locality in association with H. avenae. The morphological and morphometric identification of PCN and CCN was confirmed by diagnostic ITS-RFLP profiles and sequencing. Phylogenetic analysis of the ITS, D2-D3 expansion domains of the 28S rRNA gene and 18S rRNA gene was made for PCN and CCN populations. Globodera pallida and G. rostochiensis from Algeria show great similarity with European and South American populations. Because of the high divergence among Algerian populations of G. pallida and G. rostochiensis it can be assumed that they were multi-introduced in Algeria. The most divergent population of G. pallida, that formed a well-separated group with some populations from Chile and Peru, suggests a later or independent introduction of this population into Algeria. Heterodera avenae and H. hordecalis formed a well-supported cluster with the corresponding populations.  相似文献   

2.
Root-knot nematodes (RKNs) are one of the most important biotic factors limiting crop productivity in many crop plants. The major RKN control strategies include development of resistant cultivars, application of nematicides and crop rotation, but each has its own limitations. In recent years, RNA interference (RNAi) has become a powerful approach for developing nematode resistance. The two housekeeping genes, splicing factor and integrase, of Meloidogyne incognita were targeted for engineering nematode resistance using a host-delivered RNAi (HD-RNAi) approach. Splicing factor and integrase genes are essential for nematode development as they are involved in RNA metabolism. Stable homozygous transgenic Arabidopsis lines expressing dsRNA for both genes were generated. In RNAi lines of splicing factor gene, the number of galls, females and egg masses was reduced by 71.4, 74.5 and 86.6%, respectively, as compared with the empty vector controls. Similarly, in RNAi lines of the integrase gene, the number of galls, females and egg masses was reduced up to 59.5, 66.8 and 63.4%, respectively, compared with the empty vector controls. Expression analysis revealed a reduction in mRNA abundance of both targeted genes in female nematodes feeding on transgenic plants expressing dsRNA constructs. The silencing of housekeeping genes in the nematodes through HD-RNAi significantly reduced root-knot nematode infectivity and suggests that they will be useful in developing RKN resistance in crop plants.  相似文献   

3.
Blackleg disease, caused by the hemibiotrophic fungal pathogen Leptosphaeria maculans, is one of the most devastating disease of Brassica species worldwide. To date, a total of 20 race-specific blackleg resistance (R) genes have been reported and all of those loci are located in either the A or B genomes of various Brassica species. The B. oleracea genome (CC) shares a high ancestral synteny with the A genome of B. rapa, suggesting the presence of qualitative (race specific) resistance to blackleg disease is also possible in B. oleracea germplasm. In the present study the C genome of Korean B. oleracea germplasm was screened for the presence of blackleg R genes. Thirty-two inbred cabbage lines with unknown resistance profiles, along with five control B. napus lines with well-characterised race-specific R genes, were assessed for cotyledon resistance against two L. maculans isolates with known and highly-contrasting avirulence gene (Avr) profiles. Two cabbage accessions were identified which produced a strong resistance when challenged with either isolate, demonstrating the presence of effective blackleg R genes in the cabbage C genome. Additionally, 16 microsatellite markers linked to seven different R genes of the B. napus A genome were converted into markers for their homologous regions on the B. oleracea C genome. These markers were used to screen all B. oleracea lines to assess if the novel C genome R genes were syntenous to known R gene-homologous regions of the A genome. The resistant cabbage lines offer C genome R genes for the protection of B. oleracea varieties against incursion of blackleg disease, as well as novel additional resistance sources for introgression into B. napus and B. carinata breeding material.  相似文献   

4.
Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat in Canada. This study presents the results from resistance evaluation of Yr genes and western Canadian wheat cultivars from different milling classes, to natural infection in southern Alberta and British Columbia which are considered hot spots of stripe rust occurrence in Canada, due to proximity to Pacific Northwest of the United States where stripe rust epidemics are frequent. Genes Yr1, Yr5, Yr15, and YrSP were effective in all environments; Yr17 and Yr28, which were earlier reported ineffective to existing stripe rust races at the seedling stage in Canada, were effective at adult plant stages in most of the environments because of warmer climates in southerly locations, a favourable condition for expression of the genes. Yr17 is common in winter wheat cultivars and only reported spring wheat cultivar carrying it is CDC Stanley, which can serve as donor parent in breeding programs. Gene Yr24/26 was not very effective in western prairies although reported as effective in eastern prairies. Residual resistance from combination of defeated genes (Yr3, Yr7, Yr9, Yr27) in some supplementary differentials was observed. Most cultivars carry slow-rusting, pleiotropic adult-plant resistance gene Yr18 and some Yr29, which were effective in some locations. These genes failed to provide complete protection under high disease pressure. Seedling and adult plant resistance genes Yr5, Yr15, Yr17 and Yr18, Yr36, respectively could be good targets for resistance breeding. Stacking adult plant resistance genes with seedling resistance genes can provide durable resistance to stripe rust.  相似文献   

5.
Composed mostly of fungivorous species, the genus Aphelenchoides also comprises 14 plant-parasitic species. The most common and devastating, A. besseyi, A. fragariae, A. ritzemabosi and A. subtenuis have been reported on more than 900 plant species. The combination of low inter-specific and high intra-specific morphological variability makes morphology-based identification extremely difficult within this genus, and has led to molecular tools being employed to ensure accurate diagnoses. rDNA markers are widely used for the identification of nematodes while the Cytochrome Oxidase I gene (COI) remains relatively unexplored despite its role as the standard barcode for almost all animal groups. To explore its suitability as a diagnostic tool, we studied a fragment of the mtCOI region of the four main plant-parasitic Aphelenchoides within a phylogenetic framework. We generated 69 mtCOI and 123 rDNA sequences of diverse Aphelenchoides taxa; 67 belong to the main plant-parasitic species including the first mtCOI sequence of A. fragariae and the first mtCOI and 28S sequences of A. subtenuis. mtCOI had a similar success rate for PCR amplification. Phylogenetic trees based on the three studied markers are largely in agreement with one another, validating their use for Aphelenchoides diagnosis; additionally, we were able to locate several misidentified sequences of plant-parasitic Aphelenchoides in existing databases. The concatenated analysis from the three markers resulted in a more robust insight into the phylogeny and evolution of Aphelenchoides, revealing that plant-parasitism has evolved independently at least three times within this genus, presumably from fungal-feeding ancestors.  相似文献   

6.
Parasitoids are characterized by a defined range of hosts, either more specialist or generalist. Under natural conditions, females may encounter different host species on the same plant or in the same location. In this case, their preference for one host could influence their choice. However, the presence of less suitable hosts may also affect their choice and, in some cases, may reduce their interest in a patch where both preferred and less preferred hosts are available. The aim of the present study was to test the consequences of the simultaneous presence of three cereal aphids (Sitobion avenae Fabricius, Metopolophium dirhodum Walker, and Rhopalosiphum padi Linnaeus) on the parasitism by two of their parasitoids, Aphidius ervi Haliday and Praon volucre Haliday. Firstly, in the no-choice experiment, A. ervi parasitized on S. avenae at a significantly higher rate as compared to M. dirhodum, whereas no parasitism on R. padi was observed. P. volucre parasitized the three species of cereal aphids with a significant preference for S. avenae. Interestingly, when two or three host species were offered simultaneously in the same quantity to pairs of parasitoids, the level of parasitism was less than that observed for one host species alone. This observation exhibits a distractive effect on non-host species, from the defense mechanism of a non-suitable host or from the perception of bad quality patches. These results raise the question of the practical application of inundative release of parasitoids for biocontrol when several hosts are available simultaneously.  相似文献   

7.
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8.
The cereal cyst nematode Heterodera avenae is a pathogen of cereal crops and causes high yield losses worldwide. In this study, a collection of 37,348 expressed sequence tags (ESTs) of H. avenae was mined for EST-based simple sequence repeat (SSR) markers, which resulted in the identification of 5604 SSRs. A total of 210 pairs of SSR primers were further developed and used for validation of the amplification rate and assessment of the polymorphism. Eight SSR markers were finally identified and analyzed using 96 individual cysts of H. avenae sampled from three provinces in China. These loci were found to be moderately polymorphic with 3–8 alleles per locus. The observed and expected heterozygosity across the three populations ranged from 0.000 to 0.594 and from 0.000 to 0.731, respectively. The polymorphism information content (PIC) was medium and ranged from 0.080 to 0.562, with a mean of 0.409. The F ST ranged from 0.1034 to 0.1550, indicating moderate genetic differentiation among the three H. avenae populations. These EST-SSR markers can be used to study population genetic diversity and the dispersal route of H. avenae in China.  相似文献   

9.
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10.
Cyst nematodes obtained from commercial carrot fields in Ontario (Canada) and northern and southern Italy were subjected to morphological and molecular examination. Morphology of cyst cone tops, males and second-stage juveniles (J2) indicated the nematode species was the Carrot Cyst Nematode (CaCN), Heterodera carotae. The sequence of the Internal Transcribed Spacer (ITS), D2-D3 region of the 28S gene of ribosomal RNA, cytochrome oxidase I of mitochondrial DNA (coxI), and a heat shock protein gene (hsp90), from single cysts were also examined. Sequences of ITS and D2-D3 placed all the nematodes with Heterodera carotae and other Heterodera spp. belonging to the Goettingiana group in the same clade. The novel nine coxI sequences obtained also clustered in a well-supported phylogenetic clade for H. carotae. Similarly, the six new hsp90 sequences of H. carotae generated in this study were placed in a well-supported clade (PP = 1.00) together with other two sequences of H. carotae from Greece. Restriction Fragment Length Polymorphism (RFLP) of ITS-PCR products gave a restriction pattern for RsaI different than H. carotae but the other 6 restriction patterns were similar as described in former research. A diagnostic conventional PCR method was developed based on a primer set to be specific for H. carotae using coxI sequence. These primers were also used in real time PCR to generate a melt curve specific to H. carotae. Limit of detection for CaCN in conventional PCR reaction was a single J2.  相似文献   

11.
A survey was conducted in 16 fields cultivated with broad bean (Vicia faba L.) and garden pea (Pisum sativum L.) in nine localities of Apulia, southern Italy, to determine whether annual weeds were susceptible to the pea cyst nematode (PEACN), Heterodera goettingiana, and could therefore serve as alternate host for the nematode. The results of this study showed that black medick (Medicago lupulina L.) is a good host for the nematode increasing its population levels in the soil in the absence of the primary hosts. The identity of the PEACN was confirmed by integrative taxonomic approaches (classical, and molecular), resulting identical in all cases (broad bean and garden pea, as well as the spontaneous black medick infections). The phylogenetic analyses using ITS and coxI gene regions strongly support the identification of the populations of H. goettingiana from Italy. Also, ITS and coxI gene sequences were obtained from the same cyst, confirming the species identity in comparison to other nematodes and populations in the Goettingiana group, demonstrating that ITS and coxI gene regions of the PEACN are suitable molecular markers for accurate and unequivocal identification of the PEACN. Reproduction and histopathological analyses demonstrated a good host-suitability of black medick to the PEACN. This record enlarges the relatively narrow host-range of the pea cyst nematode and indicates the need to control M. lupulina to avoid the increase of the nematode population in the absence of the main host crop.  相似文献   

12.
Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo), remains a major production constraint in rice cultivation especially in irrigated and rainfed lowland ecosystems in India. The pathogen is highly dynamic in nature and knowledge on pathotype composition among the Xoo population is imperative for designing a scientific resistance breeding program. In this study, four hundred isolates of Xoo collected from diverse rice growing regions of India were analyzed for their virulence and genetic composition. Virulence profiling was carried out on a set of differentials consisting of 22 near isogenic lines (NILs) of IR24 possessing different BB resistance genes and their combinations along with the checks. It was observed that different NILs possessing single BB resistance gene were susceptible to about 59–94% of the Xoo isolates except IRBB 13 (containing BB resistance gene xa13), which showed susceptibility to about 35% of the isolates. Based on the reaction of the Xoo isolates on the differentials, they were categorized into 22 pathotypes. Among the 22 pathotypes, IXoPt-1 and IXoPt-2 were least virulent and IXoPt # 18–22 were highly virulent. Pathotype IXoPt-19 which was virulent on all single BB resistance genes except xa13 constituted the major pathotype (22.5% isolates) and was widely distributed throughout India (16 states). This was followed by pathotype IXoPt-22 (17.25%) which was virulent on all the NILs possessing single BB resistance genes. Molecular analysis was carried out using two outwardly directed primers complementary to sequence of IS1112, a repetitive element of Xoo. A high level of genetic polymorphism was detected among these isolates and the isolates were grouped into 12 major clusters. The data indicated complex nature of evolution of the Xoo pathotypes and there was no strong correlation between pathotypes and genetic clusters as each genetic cluster was composed of Xoo isolates belonging to different pathotypes. The study indicated that none of the single BB resistance genes can provide broad spectrum resistance in India. However, two-gene combinations like xa5 + xa13 and different 3 or 4 genes combination like Xa4 + xa5 + xa13, Xa4 + xa13 + Xa21, xa5 + xa13 + Xa21 and Xa4 + xa5 + xa13 + Xa21 are broadly effective throughout India.  相似文献   

13.
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14.
Wheat leaf rust caused by Puccinia triticina (Pt) is one of the most severe fungal diseases threatening the global wheat production. The use of leaf rust resistance (Lr) genes in wheat breeding programs is the major solution to solve this issue. Wheat isogenic line carrying the Lr39/41 gene has shown a moderate to high resistance to most of the Pt pathotypes detected in China. In the present study, a typical hypersensitive response (HR) was observed using microscopy in leaves of the Lr39/41 isogenic line inoculated with the avirulent Pt pathotype THTT from 48 h-post inoculation. Two Lr39/41 resistance-associated suppression subtractive hybridization (SSH) libraries with a total of 6000 clones were established. Microarray hybridizations were performed on all obtained SSH clones using RNAs extracted from leaves of the Pt-inoculated and non-inoculated Lr39/41 isogenic lines, and leaves of the Pt-inoculated and non-inoculated Thatcher susceptible lines. Differentially expressed clones were analyzed by significance analysis of microarrays (SAM), followed by further sequencing. A total of 36 Lr39/41-resistance-related differentially expressed genes (DEGs) were identified, many of which had been previously reported to be involved in the plant defense response. The expression levels of eight selected DEGs during different stages of the Lr39/41-mediated resistance were further quantified by a qRT-PCR assay. Several pathogenesis-related (PR) and HR-related genes seem to be crucial for the Lr39/41-mediated resistance. In general, a brief profile of DEGs associated with the Lr39/41-mediated wheat resistance to Pt was drafted.  相似文献   

15.
Xanthomonas perforans is the causal agent of bacterial spot, one of the most devastating diseases of tomato that results in considerable yield losses worldwide. Rutin, as a polyphenolic substance, was used to induce resistance in tomato against X. perforans. Rutin at concentration of 2 mM had ability to reduce the disease severity of bacterial spot. On the other hand, 2 mM rutin had no antibacterial activity in vitro. Expression profiling of pathogenesis-related gene 5 (PR-5), Phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) was probed during the enhanced resistance by rutin. Pretreatment with rutin (rutin/ X. perforans) led to induction of PR-5, PAL and LOX compared to controls (water/ X. perforans). Our results suggest that rutin-induced resistance against X. perforans in tomato might be mediated through stimulation of some defense genes such as PR-5, PAL and LOX.  相似文献   

16.
Several species of Xanthomonas cause bacterial leaf spot, a disease that affects solanaceous crops worldwide. The diversity of 64 Australian isolates of Xanthomonas spp. associated with bacterial leaf spot in tomato, capsicum and chilli crops in eastern Australia was determined using multi-locus sequence analysis of atpD, dnaK, efp and gyrB genes, species-specific PCR assays and biochemical analyses. At least five species of Xanthomonas associated with bacterial leaf spot were identified in Australian tomato, capsicum and chilli crops and their pathogenicity assessed. Phylogenetic and biochemical analyses identified X. euvesicatoria, X. perforans and X. vesicatoria as the most frequently recovered pathogenic species. Non-pathogenic and weakly pathogenic species were also identified. The suitability of the identification methods used and the implications of the detection of these species will be discussed.  相似文献   

17.
The nematicidal effect of a formulated product containing extract from Quillaja saponaria was evaluated against the root-knot nematodes. The product QL Agri® 35 (QL) was tested to record the effect on second stage juveniles motility, egg hatch and also against field populations in greenhouse experiments contacted in three different locations of Greece. Convulsive movement of second stage juveniles of Meloidogyne incognita was recorded after exposure for 8 days at a series of doses, while the most paralyzed juveniles were counted at the dose of 8 mg l?1. There was also a gradual decrease in the number of juveniles emerging from egg masses of the same nematode species when the dose of Q. saponaria was increased from 0 to 8 mg l?1. In greenhouse experiments, the use of Q. saponaria could control root-knot nematodes and prevent nematodes increase in soil. The present study demonstrates that the use of Q. saponaria extract has the ability to control root-knot nematodes. Control given by Q. saponaria in field populations infecting cucumber was similar to that of cadusafos (Rugby®) and oxamyl (Vydate®) under the tested dosages and the specific conditions of the experiments.  相似文献   

18.
Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) has seriously threatened global banana production. Recently, identification of Foc TR4 in the Caribbean and Mozambique has aroused widespread concern because it may be directly related to food security for millions of people in Africa and Latin America. To identify a resistant or highly resistant germplasm, 129 accessions were evaluated for Foc TR4 resistance in greenhouses and 100 of them were also assessed in the field. In total, 10 accessions were highly resistant (HR) to Foc TR4; these include four from the AA group, two from the BB group, one of the East African highland bananas (EAHBs), two plantains, and one from wild relatives of banana. Of these, Pahang (AA), Calcutta 4 (AA), and Musa itinerans exhibited the highest degree of resistance with an index of disease (ID2) less than 10, and Foc TR4 could not infect any of them in the field. Furthermore, 31 accessions from AA, AB, AAB, AAAB, and ABB groups and wild relatives were identified as a resistant (R) germplasms. All tested EAHBs and plantains exhibited resistance or high resistance to Foc TR4 infection. Our results provide valuable genetic resources for banana breeding and for studying the mechanisms underlying Fusarium wilt resistance. Furthermore, evaluation of EAHBs and plantains provided a rational for local banana producers and researchers to grow EAHBS and plantains.  相似文献   

19.
The reniform nematodes of the genus Rotylenchulus are semi-endoparasites of numerous herbaceous and woody plant roots and distributed in regions with Mediterranean, subtropical and tropical climates. In this study, we provide morphological and molecular characterisation of three out of 11 valid species of the genus Rotylenchulus: R. macrodoratus, R. macrosoma, and R. reniformis from Greece (Crete), Italy and Spain. The overall prevalence of reniform nematodes in wild and cultivated olives in Greece, Italy, and Spain was 11.5%, 19.0% and 0.6%, respectively. In Greece, R. macrodoratus and R. macrosoma were detected in cultivated olive with a prevalence of 8.2% and 6.2%, respectively, but none of them were found in wild olive. This is the first report of R. macrosoma in Greece. Only one reniform nematode species was detected in olive from Italy and Spain, viz. R. macrodoratus and R. macrosoma, respectively. The parasitism of R. macrosoma on hazelnut in northern Spain was also confirmed for the first time. This study demonstrates that R. macrodoratus and R. macrosoma have two distinct rRNA gene types in their genomes, specifically the two types of D2-D3 for R. macrosoma and R. macrodoratus, the two types of ITS for R. macrodoratus and the testing of the ITS variability in other R. macrosoma populations in different countries. Rotylenchulus macrosoma from Greece and Spain showed differences in nucleotide sequences in the ITS region and D2-D3 of 28S rRNA gene.  相似文献   

20.
The common bean (Phaseolus vulgaris L.) is widely cultivated in Brazil and is known as a very important crop for families in this country. Fusarium wilt severely harms common beans and has become a big issue for this crop. In order to assist the breeding programs that target resistance to this disease, the evaluation of genetic diversity of the pathogen and its molecular characterization are crucial. Thus, the present goal was to identify Fusarium isolates obtained from several places in Brazil using molecular tools; select molecular markers for these isolates; and analyze their diversity. All of isolates were molecularly identified as Fusarium oxysporum f. sp. phaseoli (Fop). By using seven selected SSR markers, the results of diversity obtained by the dendrogram and the Bayesian analysis formed four groups where a large diversity of this fungus was found within each state. However, the groups were more homogenous according to the collection source and the pathogenicity test. More specifically, group 2 was composed of the most virulent strains and originated from Minas Gerais State – UFV, and group 3 was mostly composed by isolates from Goias state. Group I was also more diverse in terms of location and virulence. The overall results indicated a positive correlation between Fusarium diversity and its virulence to common bean. Furthermore, the use of these markers was effective in molecular identification and in detecting polymorphism within F. oxysporum f. sp. phaseoli.  相似文献   

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