Search

Published data on the presence or absence of phasmids in males of Heteroderidae species are compiled and critically reviewed. Based mainly on results of previous SEM studies and complemented by light microscopy using DIC optics, the conclusion is drawn that male phasmids appear to be absent in all species of the genera assigned to the subfamilies Heteroderinae and Ataloderinae, but present and often distinct in theMeloidoderinae genera Cryphodera and Meloidodera. The presence of male phasmids is considered as ancestral, and loss of phasmids as a derived character. [ABSTRACT FROM AUTHOR]

Cell-cell communication mediated by diffusible signal factor ( DSF) plays an important role in virulence of several X anthomonas group of plant pathogens. In the bacterial pathogen of rice, X anthomonas oryzae pv. oryzicola, DSF is required for virulence and in planta growth. In order to understand the role of DSF in promoting in planta growth and virulence, we have characterized the DSF deficient mutant of X. oryzae pv. oryzicola. Mutant analysis by expression analysis, radiolabelled iron uptake studies and growth under low-iron conditions indicated that DSF positively regulates ferric iron uptake. Further, the DSF deficient mutant of X. oryzae pv. oryzicola exhibited a reduced capacity to use ferric form of iron for growth under low-iron conditions. Exogenous iron supplementation in the rice leaves rescued the in planta growth deficiency of the DSF deficient mutant. These data suggest that DSF promotes in planta growth of X . oryzae pv. oryzicola by positively regulating functions involved in ferric iron uptake which is important for its virulence. Our results also indicate that requirement of iron uptake strategies to utilize either Fe3+ or Fe2+ form of iron for colonization may vary substantially among closely related members of the X anthomonas group of plant pathogens. [ABSTRACT FROM AUTHOR]

Bitter gourd (Momordica balsaminaL.) – indigenous to tropical areas of Africa – has nutritional, ethnomedicinal, neutraceutical and pesticidal attributes which are potentially attractive to various industries with bias towards rural development. However, the southern root-knot nematode (Meloidogyne incognita, Kofoid & White, Chitwood) and its biological races constitute serious limitation to successful introduction of alternative crops with economic attributes, particularly when the target plants have limited degree of nematode resistance. A pot trial was therefore conducted to determine the degree of nematode resistance inM. balsaminaseedlings toM. incognitarace 2. Seedlings were inoculated at seven levels ofM. incognitarace 2, which were laid out in a randomised complete block design, with 12 replications. After three nematode generations, the mean reproductive factor (RF = Pf/Pi) values at all levels of inoculation were less than unity, while nematode infection had no effect on growth ofM. balsaminaseedlings, which suggested that this plant was resistant to the test nematode. In conclusion, due to its resistance toM. incognitarace 2,M. balsaminacould serve as an alternative crop for use as vegetable, ethnomedicinal and/or neutraceutical plant in rural communities with high populations ofM. incognitarace 2. [ABSTRACT FROM AUTHOR]

With the understanding of nematode-plant interactions at the molecular level, new avenues for engineering resistance have opened up, with RNA interference being one of them. Induction of RNAi by delivering double-stranded RNA (dsRNA) has been very successful in the model non-parasitic nematode, Caenorhabditis elegans, while in plant nematodes, dsRNA delivery has been accomplished by soaking nematodes with dsRNA solution mixed with synthetic neurostimulants. The success of in vitro RNAi of target genes has inspired the use of in planta delivery of dsRNA to feeding nematodes. The most convincing success of host-delivered RNAi has been achieved against root-knot nematodes. Plant-mediated RNAi has been shown to lead to the specific down-regulation of target genes in invading nematodes, which had a profound effect on nematode development. RNAi-based transgenics are advantageous as they do not produce any functional foreign proteins and target organisms in a sequence-specific manner. Although the development of RNAi-based transgenics against plant nematodes is still in the preliminary stage, they offer novel management strategy for the future. [ABSTRACT FROM AUTHOR]

An experiment was conducted to assess the effect of Rhizobium sp., waste tea leaves, eggshell powder, and composted cow dung manure on the root-knot nematode, Meloidogyne incognita, on lentil in Botany department AMU, Aligarh, India. When used alone, composted cow dung was better in reducing galling and nematode multiplication and improving lentil growth followed by eggshell powder, Rhizobium sp., and waste tea leaves. Significant result in the integrated management of M. incognita was obtained when Rhizobium sp. was used in combination with cow dung and eggshell powder (with or without waste tea leaves). Combined application of root nodule bacterium and organic wastes like waste tea leaves, eggshell, and cow dung may be suggested to the farmers/growers or related persons who are having great enthusiasm to establish a lentil production business. Application of these organic materials along with the root nodule bacteria may be helpful to foster soil ecosystem which has been a hot topic in the present scenario. [ABSTRACT FROM AUTHOR]

Cryphodera sinensis n. sp. is described from ramie (Boehmeria nivea) based on the morphology and molecular analyses of rRNA small subunit (SSU), D2D3 expansion domains of large subunit (LSU D2D3) and internal transcribed spacer (ITS). This new species is characterized by oval females with a distinct subcrystalline layer and pronounced and protruding vulval lip, distinctly concave vulva–anus profile and a vulva–anus distance of 29.5–35.8 μm. Males possess two annuli in the lip region, a stylet 27–32.5 μm in length with round knobs sloping slightly posteriorly, lateral fields with three lines, spicules 20–28 μm long and the presence of a short cloacal tube. Second-stage juveniles possess three lip annuli, a stylet 28–31 μm in length with well-developed knobs projected anteriorly and three lines along the lateral field. The pointed tail, 52–65 μm long, possesses a mucro-like tip and a hyaline region, 24.5–35 μm long. Large phasmids with a lens-like structure are located 2–6 annuli posterior to the anus. Phylogenetic analysis shows that the species has unique SSU, LSU D2D3 and ITS rRNA sequences. Phylogenetic relationships of the three rDNA sequences of C. sinensis n. sp. and other cystoid/cyst nematodes are analysed together with a comparison of other species within the genus Cryphodera. [ABSTRACT FROM AUTHOR]

Potato cyst nematodes (PCN) are the most economically important nematode pests of potato. Early harvesting is part of a preventive management approach for very early potato varieties. In Belgium, tubers are harvested before 20 June because it is assumed that no cyst formation occurs by that date. However, this assumption might not be valid any more because of climate change, the availability of new cultivars (with new traits), and the increasing prevalence of Globodera pallida. Therefore, pot, microplot and field trials were conducted to study the life cycle of PCN in early potato-growing conditions. The development of populations of G. pallida on three potato cultivars, Eersteling (susceptible to PCN), Premiere (resistant to G. rostochiensis) and Ambassador (partially resistant to G. pallida) and that of G. rostochiensis on cv. Eersteling was monitored in the growth chamber with simulation of field temperatures of the season. On cvs Eersteling and Premiere, second-stage juveniles (J2), males, females and cysts of G. pallida populations were found 28, 56, 63 and 77 days after infestation with cysts (DAI), respectively. The number of degree days (DD) for G. pallida to complete its life cycle using a base temperature of 4°C was calculated 450 DD4. On cv. Ambassador, females of G. pallida were never observed. J2, males, females and cysts of G. rostochiensis were detected 42, 70, 70 and 84 DAI, respectively. This species needed 398 DD6 at a base temperature of 6°C to complete its life cycle. Observations in two fields and in microplots under prevailing weather conditions in 2013 revealed that cysts of G. pallida and G. rostochiensis were formed on June 12, when the accumulated degree days were 463 DD4 and 401 DDg, respectively. Our observations show that both species of Globodera develop earlier than was assumed based on previous data. Therefore, harvesting based on the accumulated heat above the basal development temperature required by PCN species can replace the set harvest date. [ABSTRACT FROM AUTHOR]

The nematicidal activity of Citrullus colocynthis seed, pulp, fruit and creeper extracts were evaluated against rootknot nematodes (Meloidogyne spp.) at 28 ± 2 °C in laboratory. Gas chromatograph interfaced to a Mass spectrometer (GC-MS) results indicated that C. colocynthis contains various bioactive compounds. The mentholic extracts of seed had the highest mortality (100%) at highest exposure time (72 hrs) while, the pulp and fruit extracts showed 60 and 80% mortality, respectively. Among various extracts of creeper hexane extract (HH-CC) showed 100% mortality after 72 hrs at all concentrations as compared with standard carbofuran. Whereas, HE-CC and HWCC showed 100% mortality only at highest concentrations after 72 hrs. Ethyl acetate fraction was most active at highest concentrations causing 60% nematode mortality after 72 hrs. However, aqueous fraction (1 and 0.5) showed 40% mortality after 72 hrs exposure. [ABSTRACT FROM AUTHOR]

The root-knot nematode Meloidogyne hapla can reproduce on a wide range of crop species but there is variability in host range and pathogenicity both within and between isolates. The inbred strain VW9 causes galling but does not reproduce on Solanum bulbocastanum clone SB22 whereas strain VW8 causes little galling and reproduces poorly on this host. Comparison of reproduction on SB22 of nematode F2 lines generated from hybrids between strains VW8 and VW9 revealed that, whereas over half the lines produced no progeny, some lines reproduced to higher levels than did either parental strain. Using a genetic map previously generated using the same set of F2 lines, three quantitative trait loci (QTLs) were identified and positioned on linkage groups. A combination of two QTL alleles from one parent and one from the other was highly represented in F2 lines that exhibited higher reproduction than either parental strain but was absent from lines that failed to reproduce on SB22. This result suggests that sexual hybridization and assortment of opposing alleles leads to segregation of individuals with improved reproductive ability on a particular host. The genome sequence and integrated genetic and physical linkage map of M. hapla provide resources for identification of genes responsible for the identified QTL. [ABSTRACT FROM AUTHOR]

The Japanese cyst nematode Heterodera elachista was detected parasitizing corn cv Rixxer in Bosco Mesola (Ferrara Province) in Northern Italy. The only previous report of this nematode was in Asia (Japan, China and Iran) attacking upland rice; being this work the first report of this cyst nematode in Europe, and confirmed corn as a new host plant for this species. Integrative morphological and molecular data for this species were obtained using D2-D3 expansion regions of 28S rDNA, ITS1-rDNA, the partial 18S rDNA, the protein-coding mitochondrial gene, cytochrome oxidase c subunit I ( COI), and the heat-shock protein 90 ( hsp90). Heterodera elachista identified in Northern Italy was morphologically and molecularly clearly separated from other cyst nematodes attacking corn (viz. H. avenae, H. filipjevi, H. delvii, H. oryzae, H. sacchari, H. sorghi, H. zeae, Punctodera chalcoensis, and Vittadera zeaphila) and rice ( H. oryzae, H. sacchari). The phylogenetic relationships of H. elachista from Northern Italy with other cyst-nematodes using rDNA and mtDNA showed a separation of the genus Heterodera in various morphospecies groups based on vulval cone structures. The development and parasitic habit of H. elachista on naturally infected corn cv Rixxer confirmed a typical susceptible reaction, including multinucleate syncytial cells in parenchymatic cells. Under greenhouse conditions, H. elachista successfully reproduced on two crops widely used in Northern Italy, such as corn (cv PR 33) and rice (cv Baldo). Considering the limited host-range of this nematode, that include two of the three world's most important crops, special attention is needed for avoiding the dispersal of this nematode into new areas, by movement of soil on equipment, water, and contaminated containers infested soil, or agricultural practices. [ABSTRACT FROM AUTHOR]

The non-cyst forming heteroderid nematode Cryphodera brinkmani was detected in Italy parasitizing roots of Japanese white pine bonsai ( Pinus parviflora) trees imported from Japan. Morphology and morphometrical traits of the intercepted population on this new host for C. brinkmani were in agreement with the original description, except for some minor differences on male morphology. Integrative molecular data for this species were obtained using D2-D3 expansion regions of 28S rDNA, ITS1-rDNA, the partial 18S rDNA, and the protein-coding mitochondrial gene, cytochrome oxidase c subunit I ( COI). The phylogenetic relationships of this species with other representatives of non-cyst and cyst-forming Heteroderidae using ITS1 are presented and indicated that C. brinkmani clustered together with other Cryphodera spp. and with Meloidodera alni suggesting a monophyletic origin of non-cyst forming nematodes (Heteroderinae sensu Luc et al. ), which have been considered close to the ancestor of most species of Heteroderidae. Histological observations of P. parviflora feeder roots infected by C. brinkmani indicated that nematode females induce similar anatomical alterations to those reported for C. kalesari, consisting of formation of a single uninucleate giant cell (nurse cell) with hypertrophied nucleus, prominenet nucleolus, thickened cell wall and expanding into the stele and in contact of xylem, vacuum cambium and phloem. These findings are in agreement with the results of the phylogenetic analysis and indicate a close relationship in the plant responses induced by Cryphodera nematode females with those caused by the genetically related Meloidodera spp., which also induce formation of a uninucletate giant cell. [ABSTRACT FROM AUTHOR]

An experimental investigation into the suppressive potential of the shrubChromolaena odorata(L.) (Asteraceae) (also known as “Siam Weed” or “Jack-in-the-Bush”) fallow to the management of plant parasitic nematodes was undertaken between April 2008 and April 2010. The experiment involved comparing nematode population densities in: (i) pure planted fallow ofC. odorata, (ii) a mixture ofC. odoratawith other weeds, and (iii) natural re-growth of weeds from the seed bank in the soil in the field withC. odorataexcluded. The population densities of several nematode species were determined at the outset, and then at 6-month intervals for 24 months. The nematode taxa identified as being present prior to fallowing wereMeloidogynespp. (Heteroderidae),Pratylenchusspp. (Pratylenchidae),Helicotylenchusspp.,Rotylenchulusspp. (Hoplolaimidae); Rhabditids (Rhabditidae) andDorylaimusspp. (Dorylaimoidea).Chromolaena odoratafallow significantly reduced the population densities ofMeloidogynespp.,Pratylenchusspp., andHelicotylenchusspp. after 2 years of fallow, by 77.2%, 75.3% and 81.3% respectively. Under natural re-growth, reduction in populations ofMeloidogynespp.,Pratylenchusspp., andHelicotylenchusspp. ranged between 0.12% and 17%. Densities of non-parasitic species (Rhabditids andDorylaimusspp.) significantly increased under bothC. odorata+ natural re-growth fallow. However, a 16% increase in the population density ofRotylenchulusspp. was observed underC. odoratafallow in contrast to a significant (54.1%) reduction observed under the natural re-growth fallow. Bush fallow withC. odoratamay become part of an integrated management practice in the management of nematode pests in crop production by indigenous farmers in south-western Nigeria. [ABSTRACT FROM PUBLISHER]

Medicinal plants such as plantain, Plantago major, due to having various medicinal compounds are of high importance in pharmaceutical industry. In the present research, while assessing the pathogenicity of root-knot nematode, Meloidogyne javanica on plantain medicinal plant, the effects of various nematode initial inoculums on plant growth parameters as well as nematode reproduction were investigated. Then seed mucilage content, thousand-seed weight, the amount of Quercitin and Ursolic acid compounds as well as Sodium, Potassium, Magnesium and Calcium elements of infected Plantago major 90 days after inoculation recorded. Plantain found to be sensitive to the nematode and in the infected plants, seed mucilage content, thousand-seed weight and the amount of Ursolic acid compound decreased but amount of root Sodium and Calcium elements and shoot Quercitin increased. While increasing the nematode initial inoculums, shoot fresh weight and root length and fresh weight decreased but root fresh weight increased. The highest reproduction factor was observed in plantg inoculated with the lowest level of nematode population tested (1000Jz/2kg soil). [ABSTRACT FROM AUTHOR]

During nematode surveys in the different regions of the country, high infestation of root-knot nematodes were found. On morphological characterization these RKN species were identified as Meloidogyne incognita and M. javanica. Molecular characterization of 16 strains of these root-knot nematodes were also done and incorporated herein including three new species. The 18S rDNA of 16 strains of Meloidogyne spp., were amplified and directly sequenced. Phylogenetic trees based on alignments of these sequences were constructed using distance, parsimony and likelihood optimality criteria. The molecular characterization of 16 strains of RKN was done for the first time from Pakistan. Moreover, during the studies M. incognita and M. javanica were found associated with five new hosts viz., Feverfew (Parthenium hysterophorus L.), olive (Olea europaea L.), malabar spinach (Basella rubra L.), canna (Canna indica L.) and dehla (Jasminium multiflorum Burm. f.) not reported earlier. The molecular analysis of these RKN species associated with new host records are in progress. [ABSTRACT FROM AUTHOR]

Vittatidera zeaphila was described from stunted Zea mays (corn) roots collected in northwestern Tennessee (Obion County) in 2006. Similar cyst specimens had previously been collected in 1978 from Lauderdale County, TN, on Eleusine indica (goosegrass). Comparison of the 1978 specimens deposited in the USDA Nematology Collection at Beltsville, MD, and the 2006 specimens verified that they were identical. The purpose of this research was to determine the distribution of this nematode, determine the host range and determine if there was resistance which could be incorporated into commercial corn hybrids in the event the nematode was a threat to Midwest corn production. This nematode is known only from the 1978 site in Lauderdale County, TN and the two findings in Obion County, Tennessee and a field in Hickman County, Kentucky from this study. Zea mays and E. indica were the only plants supporting increase of this nematode and were good hosts, with Rf values of 6 or more. Nonhosts included common dicotyledous plants that are known hosts of cyst nematodes, a range of native grasses, and teosinte. Preliminary data on potential sources of resistance to V. zeaphila suggest that resistance is not a dominant trait and that there is a potential role of the cytoplasm in conferring resistance. [ABSTRACT FROM AUTHOR]

The P asteuria group of Gram-positive, endospore-forming bacteria are parasites of invertebrates and exhibit differences in host specificity. We describe a cross-infection study between an isolate of P asteuria from pigeon pea cyst nematode, H eterodera cajani, which also infects the potato cyst nematode, G lobodera pallida, from the United Kingdom. A proportion of the attached endospores, 13% on H . cajani and 22% on G . pallida adhere to the cuticle in an inverted orientation. Inverted and conventionally attached endospores germinated and produced bacillus-like rods that completed their life cycle in < 15 weeks within females of G . pallida. This is the first example in which the life cycle of a P asteuria population was systematically followed in two different nematode genera. A 1430-base pair fragment of the 16 S r RNA gene sequence of the P asteuria isolate from H . cajani revealed 98.6% similarity to the orthologous gene in P asteuria nishizawae. Additionally, their respective endospore sizes were not significantly different, in contrast their host ranges are. Potential reasons for this remain unclear and are discussed. [ABSTRACT FROM AUTHOR]

We sequenced the entire coding region of the mitochondrial genome of Heterodera glycines. The sequence obtained comprised 14.9 kb, with PCR evidence indicating that the entire genome comprised a single, circular molecule of approximately 21-22 kb. The genome is the most T-rich nematode mitochondrial genome reported to date, with T representing over half of all nucleotides on the coding strand. The genome also contains the highest number of poly(T) tracts so far reported (to our knowledge), with 60 poly(T) tracts ≥ 12 Ts. All genes are transcribed from the same mitochondrial strand. The organization of the mitochondrial genome of H. glycines shows a number of similarities compared with Radopholus similis, but fewer similarities when compared with Meloidogyne javanica. Very few gene boundaries are shared with Globodera pallida or Globodera rostochiensis. Partial mitochondrial genome sequences were also obtained for Heterodera cardiolata (5.3 kb) and Punctodera chalcoensis (6.8 kb), and these had identical organizations compared with H. glycines. We found PCR evidence of a minicircular mitochondrial genome in P. chalcoensis, but at low levels and lacking a noncoding region. Such circularised genome fragments may be present at low levels in a range of nematodes, with multipartite mitochondrial genomes representing a shift to a condition in which these subgenomic circles predominate. [ABSTRACT FROM AUTHOR]

The rice root-knot nematode Meloidogyne graminicola normally infects rice, wheat and several other graminaceous plants. Meloidogyne incognita is a serious pest of dicotyledonous crops, although it can infect and reproduce on some cereals. This paper demonstrates and compares host recognition, development and reproduction of these two species of root-knot nematodes on rice and tomato plants. Attraction bioassays in pluronic gel clearly showed that M. incognita preferred tomato roots to rice or mustard roots, whilst M. graminicola was more attracted towards rice compared with tomato or mustard roots. Based on the attraction data from this study, it can be hypothesised that either: i) the blend of attractants and repellents are different in good and poor hosts; or ii) relatively long-range attractants, together with shorter-range repellents, might affect nematode movement patterns. Some host specific attractants might also be involved. Meloidogyne incognita was able to invade and develop to adult female but did not produce eggs in rice roots. By contrast, M. graminicola developed and reproduced faster on both rice and tomato plants compared with M. incognita. Nevertheless, second-stage juveniles of both these root-knot nematodes showed a similar pattern of distribution inside the roots, preferring to accumulate at the root tips of rice or in the vascular cylinder and cortical region of tomato. [ABSTRACT FROM AUTHOR]

Three new potato genotypes, designated AR 04-4107, AR 04-4096 and AR 04-4098, with resistance towards Meloidogyne chitwoodi, and the susceptible cv. Désirée were grown at a range of population densities of M. chitwoodi in a climate-controlled glasshouse in order to establish the presence and degree of partial resistance. Tuber parts of about 12 g were planted at densities (Pi) of 0, 0.5, 1, 2, 4, 8, 16, 32, 64, 128 and 256 second-stage juveniles (J2) (g dry soil)-1. The plants were allowed to grow for a period of 105 days. Tomato cv. Moneymaker was included and inoculated at Pi = 2 J2 (g soil)-1 to verify the quality of the inoculum by measuring the multiplication rate. Plant height was measured weekly over 11 weeks. At harvest, fresh shoot, root and tuber weights, and number of tubers were measured to express yield. Final population densities (Pf) were calculated as the total number of nematodes found in soil and roots. Tubers were scored for visible symptoms and a root-knot index was calculated. The relation between pre-plant population densities (Pi) and nematode densities at harvest (Pf) was fitted using R. The multiplication rate a of M. chitwoodi on AR 04-4107, AR 04-4096, AR 04-4098 and cv. Désirée was 0.55, 0.27, 0.91 and 32, respectively. Partial resistance rsa of AR 04-4107, AR 04-4096 and AR 04-4098 was 1.7%, 0.8% and 2.8%, respectively. Partial resistance expressed as rsM was 0.2%, 0.2% and 0.1%, respectively. It can be concluded that AR 04-4107, AR 04-4096 and AR 04-4098 are strongly partially resistant to M. chitwoodi. Also, the population dynamics curves run almost parallel between both the tested genotypes and the reference cultivar, indicating that a simple and cheap partial resistance test is feasible. When tuber yields were fitted to the Seinhorst model for yield reduction, cv. Désirée showed a minimum yield (m) of 0.86, while all three resistant genotypes suffered no yields losses at all (m = 1), which indicates that the observed resistance was associated with tolerance. As a result of the remarkably high partial resistance, quality damage was low compared with cv. Désirée. The root-knot index, which takes into account internal quality damage of the potato tuber, was below 10 for all genotypes with partial resistance, the lower damage threshold used for industrial processing of consumption potatoes. Visible symptoms on the tuber skin were absent up to densities of 32 J2 (g soil)-1 for genotypes AR 04-4098 and AR 04-4096 and 2 J2 (g soil)-1 for AR 04-4107, and significantly reduced at higher densities when compared with the susceptible cv. Désirée. However, when tuber peels were investigated, egg masses were detected in tubers at almost all initial population densities. [ABSTRACT FROM AUTHOR]

We assessed the rate of in vitro polymerase errors at polythymidine [poly(T)] tracts in the mitochondrial DNA (mtDNA) of a heteroderid nematode ( Heterodera cajani). The mtDNA of these nematodes contain unusually high numbers of poly(T) tracts, and have previously been suggested to contain biological poly(T) length variation. However, using a cloned molecule, we observed that poly(T) variation was generated in vitro at regions containing more than six consecutive Ts. This artefactual error rate was estimated at 7.3 × 10 indels/poly(T) tract >6 Ts/cycle. This rate was then compared to the rate of poly(T) variation detected after the amplification of a biological sample, in order to estimate the 'biological + artefactual' rate of poly(T) variation. There was no significant difference between the artefactual and the artefactual + biological rates, suggesting that the majority of poly(T) variation in the biological sample was artefactual. We then examined the generation of poly(T) variation in a range of templates with tracts up to 16 Ts long, utilizing a range of Heteroderidae species. We observed that T deletions occurred five times more frequently than insertions, and a trend towards increasing error rates with increasing poly(T) tract length. These findings have significant implications for studies involving genomes with many homopolymer tracts. [ABSTRACT FROM AUTHOR]

Five varieties viz., CalmartVFN, Roma, UAE-1, Samrutt and Moneymaker were subjected for the invasion and development of Meloidogyne incognita race 1. All the varieties showed variability in their response to M. incognita infestation. Maximum invasion and development of nematodes was recorded in Moneymaker followed by Samrutti, UAE1 and Roma. Minimum invasion and development was recorded in Calmart VFN. Root weight has direct relationship with the number of developing M. incognita. [ABSTRACT FROM AUTHOR]

Root-knot nematodes are obligate parasites of a wide range of plant species and can feed only on the cytoplasm of living plant cells. In the absence of a suitable plant host, infective juveniles of strain VW9 of the Northern root-knot nematode, Meloidogyne hapla, when dispersed in Pluronic F-127 gel, aggregate into tight, spherical clumps containing thousands of worms. Aggregation or clumping behavior has been observed in diverse genera in the phylum Nematoda spanning freeliving species such as Caenorhabditis elegans as well as both plant and animal parasites. Clumping behavior differs between strains of M. hapla and occurs with other species within this genus where strain-specific differences in clumping ability are also apparent. Exposure of M. hapla juveniles to a gradient formed using low levels of cyanide promotes formation of clumps at a preferred cyanide level. Analysis of F2 lines from a cross of M. hapla strains that differ in clump-forming behavior reveals that the behavior segregates as a single, major locus that can be positioned on the genetic map of this nematode. Clumping behavior may be a survival strategy whose importance and function depend on the niche of the nematode strain or species. [ABSTRACT FROM AUTHOR]

Triticum monococcum, the diploid A genome species, harbours enormous variability for resistance to biotic stresses. A spring type T. monococcum acc. 14087 was found to be resistant to Heterodera avenae (cereal cyst nematode, CCN). A recombinant inbred line population (RIL) developed by crossing this accession with a CCN susceptible T. boeoticum acc. 5088 was used for studying the inheritance and map location of the CCN resistance. Based on composite interval mapping two QTL, one each on chromosome 1AS and 2AS, were detected. The QTL on 1A, designated as Qcre.pau- 1A, appeared to be a major gene with 26% contribution to the overall phenotypic variance whereas the QTL on 2A designated as Qcre.pau- 2A contributed 13% to total phenotypic variation. Qcre.pau- 1A is novel, being the only CCN resistance gene mapped in any 'A' genome species and none of the other known genes have been mapped on chromosome 1A. The QTL Qcre.pau- 2A might be allelic to Cre5, a CCN resistance gene transferred from Ae. ventricosa and mapped on 2AS. The Qcre.pau- 1A was transferred to cultivated wheat using T. durum cv. PBW114 as the bridging species. Selected CCN resistant F lines showed introgression for the molecular markers identified to be linked with CCN resistance locus Qcre.pau-1A. Thus, this gene alone could impart complete resistance against CCN. These introgression lines can be used for marker-assisted transfer of Qcre.pau- 1A to elite wheat cultivars. [ABSTRACT FROM AUTHOR]

Developing multi-purpose alternatives to synthetic nematicides for managing the northern root-knot nematode, Meloidogyne hapla, a problem in a variety of temperate vegetable and nursery crop production soils, continues to be challenging. Arugula (Eruca sativa), a high-end green vegetable crop with biofumigant and cover crop attributes, is an effective trap crop (dead-end host) for populations of M. hapla in sandy loam soil. Exploiting arugula's multi-purpose attributes, however, depends on understanding its interaction with M. hapla under a range of conditions. The objectives of this study were to determine if soil types affect: i) the ability of M. hapla to infect arugula; and ii) if M. hapla infection has any effect on arugula's vegetative quality in the respective soils. When 2-week-old arugula cv. Roquette seedlings were inoculated with either 0 (control), 4000 or 8000 M. hapla eggs per 300 cm3 of either sandy, sandy loam or muck soil, and maintained for 23 and 24 days (28±2°C), more nematodes were recovered from sandy loam soil. However, the numbers of nematodes recovered between the inocula were similar in the three soil types and nematode infection had no effect on plant growth or nutritional quality. However, the growth and leaf nutritional quantity of arugula were significantly affected by soil type. The results support the hypothesis that M. hapla will infect arugula in different soil types without affecting its vegetative quantity and quality, providing the basis for testing arugula's trap, vegetable and, possibly, biofumigant attributes from one seeding in fields where M. hapla exists. [ABSTRACT FROM AUTHOR]

We isolated 137 fungal strains from females and eggs of Meloidogyne spp. collected from plant roots and infested soil in Jiangsu, China, and examined their in vitro protease production and chitinase activities. We then selected 20 strains, each with a protease production higher than 2 (protease production was measured as the ratio of diameters of the zone of clearing to that of the colony) and a chitinase activity higher than 0.2 U/min mL. For these strains, we examined their egg parasitic rates, mortality rates of stage 2 juvenile (J2), egg hatching rates and evaluated their biocontrol efficacies under greenhouse conditions. The biocontrol efficacies of these 20 potential biocontrol fungal strains ranged from 29 to 58%. The actual biocontrol efficacy against Meloidogyne root-knot was highly correlated with the in vitro protease production (r=0.82), chitinase activity (r=0.80), and mortality of J2 (r=0.76), but poorly correlated with the egg parasitic rate (r=0.51) and the egg hatch rate (r=0.52). Based on these results, we suggest that in vitro protease production or chitinase activities of the fungal strains could be an applicable indicator for assessing biocontrol efficacy against nematodes. This notion was also supported by our field experiments on tomatoes with Paecilomyces lilacinus strains XT18, XCS46 and Pochonia chlamydosporia strain XT124, which reached the biocontrol efficacies of 60.7, 51.5 and 48.1% in 2007; and 67.8, 57.3 and 53.2% in 2008, respectively. [ABSTRACT FROM AUTHOR]

Assays of antioxidant enzymes, including catalase, peroxidase and superoxide dismutase (SOD), have been carried out on extracts of females and second-stage juveniles (J2) of a pair of Meloidogyne incognita isolates, one virulent and one avirulent, selected on tomato, and an avirulent field population of M. incognita. Catalase and SOD activity were found to be higher in extracts of the virulent isolate SM1 when compared with the avirulent counterparts. Peroxidase activity, assayed with o-dianisidine as the substrate, was enhanced in SM1 J2 compared with the avirulent avr1 J2. Catalase isozymes were separated by isoelectrofocusing into a very acidic and a basic isoform; this latter isoform was found to be responsible for the enhancement of catalase activity in virulent populations. SOD isozyme electrophoresis patterns (IEP) of root-knot nematodes, obtained by native PAGE, showed the presence of slow- and fast-migrating bands. SOD IEP of virulent females contained a slow-migrating band with a relative mobility (Rm) on the gels slightly higher (0.52) than the corresponding band from avirulent populations (0.50). This change was confirmed with native PAGE gels loaded with extracts from J2. To check how widespread this change is in field populations of RKN, a survey of SOD IEP from 12 RKN field (a)virulent populations was carried out. The specificity of the 0.52 Rm band for virulent populations was confirmed. Separation by native PAGE of peroxidases, stained either by o-dianisidine or diamino-benzidine, showed two isoforms with no apparent differences between the populations tested. [ABSTRACT FROM AUTHOR]

The objective of this research was to evaluate the Bacillus subtilis (PRBS-1) effect as growth promoter and suppressor agent of root-knot nematode (Meloidogyne spp.) in tomato cultivation. The treatments consisted in the application of B. subtilis formulation and of the nematicide carbofuran. The plants were maintained in greenhouse during 85 days, when the plants were colleted. Roots were separated from aerial part of the plants to evaluate the treatments effect. The fresh matter production by the aerial part increased either by the chemical or by the biological treatments. The fresh matter of the roots was reduced with application B. subtilis. The effect of the biological treatment on the nematode reproduction was more evident by the reduction of egg masses in the root. The present study indicates that the strain PRBS-1 of B. subtilis promotes tomato plant growth and reduces knoot-root nematode reproduction in tomato roots under greenhouse conditions. [ABSTRACT FROM AUTHOR]

Plant parasitic nematodes infect roots and trigger the formation of specialized feeding sites by substantial reprogramming of the developmental process of root cells. In this article, we describe the dynamic changes in the tomato root transcriptome during early interactions with the potato cyst nematode Globodera rostochiensis. Using amplified fragment length polymorphism-based mRNA fingerprinting (cDNA-AFLP), we monitored 17 600 transcript-derived fragments (TDFs) in infected and uninfected tomato roots, 1–14 days after inoculation with nematode larvae. Six hundred and twenty-four TDFs (3.5%) showed significant differential expression on nematode infection. We employed GenEST, a computer program which links gene expression profiles generated by cDNA-AFLP and databases of cDNA sequences, to identify 135 tomato sequences. These sequences were grouped into eight functional categories based on the presence of genes involved in hormone regulation, plant pathogen defence response, cell cycle and cytoskeleton regulation, cell wall modification, cellular signalling, transcriptional regulation, primary metabolism and allocation. The presence of unclassified genes was also taken into consideration. This article describes the responsiveness of numerous tomato genes hitherto uncharacterized during infection with endoparasitic cyst nematodes. The analysis of transcriptome profiles allowed the sequential order of expression to be dissected for many groups of genes and the genes to be connected with the biological processes involved in compatible interactions between the plant and nematode. [ABSTRACT FROM AUTHOR]

Greenhouse experiments were conducted in 2004-2006 to examine the reciprocal effects of aboveground herbivory by European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae), and belowground herbivory by root-knot nematode, Meloidogyne incognita Chitwood (Tylenchida: Heteroderidae), on one another at three corn, Zea mays L., growth stages. Two experiments were conducted to study the effect of aboveground herbivory by O. nubilalis on the number of M. incognita juvenile penetration / root system and eggs/root system. In the first experiment, the O. nubilalis infestation level by plant growth stage main effect interaction was not significant for either M. incognita juvenile penetration or eggs. The overall effect of stalk tunneling by O. nubilalis resulted in 48.9% fewer juvenile penetration and 40.0% fewer eggs than in the respective controls. In the second experiment, the main effects interaction was significant for juvenile penetration (P = 0.0422) and eggs (P = 0.0134). At the eight- and 10-leaf growth stages, the combined effect of one and three O. nubilalis larvae per plant resulted in 41.2 and 44.7% significantly fewer juvenile penetration than in the respective controls. Similarly, the combined effect of stalk tunneling (with the exception of one larvae per plant at the 10-leaf growth stage) at the six-, eight-, and 10-leaf growth stages resulted in 46.3, 53.3, and 55.2% fewer eggs than in the respective controls. In all instances, M. incognita juvenile penetration and eggs were significantly negatively correlated with O. nubilalis tunnel length. In a reciprocal experiment conducted two times, no significant (F> 0.05) effect of M. incognita inoculation level on stalk tunneling was found in either experiment. [ABSTRACT FROM AUTHOR]

The root knot nematode, Meloidogyne incognita, is an obligate parasite that causes significant damage to a broad range of host plants. Infection is associated with secretion of proteins surrounded by proliferating cells. Many parasites are known to secrete effectors that interfere with plant innate immunity, enabling infection to occur; they can also release pathogenassociated molecular patterns (PAMPs, e.g., flagellin) that trigger basal immunity through the nematode stylet into the plant cell. This leads to suppression of innate immunity and reprogramming of plant cells to form a feeding structure containing multinucleate giant cells. Effectors have generally been discovered using genetics or bioinformatics, but M. incognita is nonsexual and its genome sequence has not yet been reported. To partially overcome these limitations, we have used mass spectrometry to directly identify 486 proteins secreted by M. incognita. These proteins contain at least segmental sequence identity to those found in our 3 reference databases (published nematode proteins; unpublished M. incognita ESTs; published plant proteins). Several secreted proteins are homologous to plant proteins, which they may mimic, and they contain domains that suggest known effector functions (e.g., regulating the plant cell cycle or growth). Others have regulatory domains that could reprogram cells. Using in situ hybridization we observed that most secreted proteins were produced by the subventral glands, but we found that phasmids also secreted proteins. We annotated the functions of the secreted proteins and classified them according to roles they may play in the development of root knot disease. Our results show that parasite secretomes can be partially characterized without cognate genomic DNA sequence. We observed that the M. incognita secretome overlaps the reported secretome of mammalian parasitic nematodes (e.g., Brugia malayi), suggesting a common parasitic behavior and a possible conservation of function between metazoan parasites of plants and animals. [ABSTRACT FROM AUTHOR]

Four field populations of the nematode Globodera pallida were subjected to selection pressure for increased reproductive ability by rearing sub-populations continuously on four partially resistant potato genotypes for 12 generations. The resistance was derived from either Solanum vernei or from S. tuberosum spp. andigena CPC2802. After the 12th generation the original and sub-populations of nematodes were assessed for their reproductive ability on a susceptible genotype and on each of the partially resistant genotypes. Selection pressure was shown to have increased reproductive ability but the increases were specific to the source of resistance used. The average increase on the ex S. vernei clones was from 11% reproduction by the unselected populations to 35·5% reproduction after selection. On the clones derived from CPC2802, which had higher levels of resistance, the increases were larger with an average of 6·6% reproduction for the unselected but 47·4% reproduction after selection. The response to selection differed amongst the initial field populations with some rates of reproduction increased to as much as 79%. A RAPD based analysis of the original and sub-populations after selection indicated small but consistent changes in the genetic structure, which could have been a result of the selection pressure per se and/or the bottlenecks that the populations had gone though. [ABSTRACT FROM AUTHOR]

We sequenced a mitochondrial subgenome from the nematode Globodera rostochiensis, in two overlapping pieces. The subgenome was 9210 bp and contained four protein-coding genes ( ND4, COIII, ND3, Cytb) and two tRNA genes ( tRNA Thr , tRNA Gln ). Genome organization was similar to that of Globodera pallida, which is multipartite. Together with the small number of genes on this subgenome, this suggests that the mitochondrial genome of G. rostochiensis is also multipartite. In the initial clones sequenced, COIII and ND3 were full-length, while ND4 and Cytb were interrupted by premature stop codons and contained point indels that disrupted the reading frame. However, sequencing of multiple clones, from DNA extracted both from multiple individuals and from single cysts, revealed a predominant source of variation—in the length of polythymidine tracts. Comparison of our genomic sequences with ESTs similarly revealed variation in the length of polythymidine tracts. We subsequently sequenced both genomic DNA and mRNA from populations of G. pallida. In each case, variation in the length of polythymidine tracts was observed. The levels of expression of mitochondrial genes in G. pallida were representative of the subgenomes present: little evidence of differential expression was observed. These observations are consistent with the operation of posttranscriptional editing in Globodera mitochondria, although this is difficult to show conclusively in the presence of intraindividual gene sequence variation. Further, alternative explanations cannot be discounted; these include the operation of slippage during translation or that genomic copies of most genes are pseudogenes with a small proportion of full-length sequences able to maintain mitochondrial function. [ABSTRACT FROM AUTHOR]

Cyst nematodes induce specific syncytial feeding structures within the root which develop from an initial cell by successive incorporation of neighbouring cells through local cell wall dissolutions followed by hypertrophy of included cells. Expansins are known to induce cell wall relaxation and extension in acidic pH, and they are involved in many processes requiring wall modification from cell expansion to cell wall disassembly. We studied the expression pattern of tomato ( Lycopersicon esculentum L., cv. Money Maker) expansins during development of syncytia induced by the potato cyst nematode ( Globodera rostochiensis Woll.). Based on semi-quantitative reverse transcription–polymerase chain reaction, two expansin genes, LeEXPA4 and LeEXPA5, were selected for detailed examinations because their expression was either elevated in infected roots ( LeEXPA4) or specifically induced in the root upon nematode infection ( LeEXPA5). Both genes have distinct spatial and temporal expression patterns that may reflect their different roles in syncytium development. LeEXPA4 transcripts were localized predominantly in parenchymatous vascular cylinder cells surrounding syncytia. This finding suggests that LeEXPA4 might be involved in cell wall disassembly or relaxation, mediating syncytium expansion and/or development of conductive tissues. By contrast, LeEXPA5 transcripts were localized in enlarging syncytial elements. Similarly, in immunogold localization experiments, polyclonal antibodies localized the LeEXPA5 protein in cell walls of syncytial elements. This expression pattern suggests that LeEXPA5 gene is specifically involved in enlargement of cells incorporated into syncytium. [ABSTRACT FROM AUTHOR]

The primers PCN280f and NEPCN398r were designed for the quantitative detection of the potato-cyst nematode Globodera rostochiensis using real-time polymerase chain reaction (PCR). One, five, 50, 125 and 250 individuals of the second-stage juveniles (J2) of G. rostochiensis were mixed with various stages of vermiform Caenorhabditis elegans to make a total of 500 individuals and DNA was extracted from the nematode mixture. There was a significant correlation ( r2 = 0.9355, P < 0.001) between the threshold cycle values and the number of G. rostochiensis added. When nematodes were extracted from soils artificially infested with G. rostochiensis to various degrees and real-time PCR was conducted using DNA templates from the nematodes extracted, there was a highly significant correlation in the numbers of G. rostochiensis J2 from the real-time PCR method and morphological identification. Real-time PCR sensitively detected a single G. rostochiensis J2 out of 1,000 individuals of free-living nematodes. Similarly, real-time PCR primers RKNf and RKNr were designed for the detection of the root-knot nematode Meloidogyne incognita. This study demonstrated that the real-time PCR assay for the potato-cyst nematode and the root-knot nematode provides a sensitive and reliable means for the rapid quantification of these vermiform pests. [ABSTRACT FROM AUTHOR]

AbstractBiogenic amines regulate important behaviours in nematodes and are associated with pharyngeal activity in plant-parasitic nematodes. A robust behavioural assay based upon nematode body movements was developed to expand the study of these and other neuroregulators in plant-parasitic nematodes. Dopamine, octopamine and serotonin each had significant but differing effects on the behaviour of soybean cyst nematode Heterodera glycinesand root-knot nematode Meloidogyne incognitajuveniles. Body movement frequency was increased twofold in H.glycinesby 5?mM dopamine (P?=?0.0001), but decreased by 50?mM dopamine in H. glycines(88%) and M. incognita(53%) (P

A new genus, Paradolichodera gen. n., is proposed for a heteroderid species parasitising the rush Eleocharis gracilis on the banks of a lagoon near Christchurch, New Zealand. The slender body of the second-stage juveniles (a = 61-79) makes the type species, P. tenuissima sp. n., unique among known Heteroderidae species. The females weakly tan after death and retain eggs. The cysts are elongate-ovoid with rounded posterior end, a circumfenestral vulva area in terminal position, an indistinct anus and a cuticle with faint striation anteriorly and punctations posteriorly. The male body is not twisted, a cloacal tube is present and phasmids are lacking. Morphologically, the new genus is closest to Dolichodera in the subfamily Punctoderinae. A phylogenetic analysis of the ITS1-rRNA sequence of P. tenuissima sp. n. shows a close relationship to Punctodera and Globodera. [ABSTRACT FROM AUTHOR]

The Hs1pro-1 gene reportedly confers resistance to the beet cyst nematode in wild beet and sugar beet. Here, we tested the hypothesis that Hs1pro-1 confers resistance in soybean against the soybean cyst nematode (SCN). The full-length Hs1pro-1 coding sequence, which encodes a predicted polypeptide of 490 amino acids, was first acquired then expressed in ‘Westag’ soybean using a constitutive octopine synthase – mannopine synthase promoter. Thirty T0 lines that successfully expressed the Hs1pro-1 gene, as indicated by both polymerase chain reaction and reverse transcriptase – polymerase chain reaction analyses, were generated. Bioassay of the T1 progeny from these lines revealed that only five T0 lines grew normally and exhibited a high degree of SCN resistance. On average, these T1 transgenic progeny were about 70% more resistant to SCN than susceptible control cultivars. These preliminary data suggest that Hs1pro-1 is a promising candidate for genetically engineering SCN resistance in elite, locally adapted soybean cultivars. [ABSTRACT FROM AUTHOR]