Root-lesion Nematode Research Articles

Arbuscular mycorrhizae maintain lemongrass citral levels and mitigate resistance despite root lesion nematode infection

Cymbopogon citratus (lemongrass) is an essential oil-producing plant with commercially important pharmacological properties. The species is susceptible to plant-parasitic nematodes, which should preferably be managed by environmentally friendly methods, such as biological control. This study aimed to investigate the effectiveness of arbuscular mycorrhizal fungi (AMF) in the control of Pratylenchus brachyurus on C. citratus and assess interaction effects of these microorganisms on vegetative development, essential oil composition, and defense-related enzyme activity. Plants were inoculated with one of two AMF species (Rhizophagus clarus or Claroideoglomus etunicatum) alone or together with P. brachyurus. An uninoculated uninfected control was also included. At 90 days after inoculation, plants were harvested and evaluated for vegetative growth, nematode parameters, mycorrhizal spore count, root colonization, essential oil composition, and activation of defense-related proteins. Citral was the major component of C. citratus essential oil. AMF inoculation increased nematode population by 8.6 × compared with non-inoculation and did not improve plant growth compared with the control. Nevertheless, AMF efficiently colonized plant roots, maintained citral content at levels similar to those of nematode-free plants, and increased the activity of defense-related enzymes, such as peroxidase, β-1,3-glucanase, and polyphenol oxidase.

Interaction between culture filtrates of Fusarium culmorum isolates and some root lesion nematodes

This study was conducted with root lesion nematodes Pratylenchus penetrans, P. thornei and P. neglectus and three isolates of Fusarium culmorum culture filtrates (ISP, B4, FC5) in vitro conditions. The culture filtrates were diluted 1/0,1/10, 1/20, 1/30, 1/40, 1/50, 1/60, 1/70, 1/80, 90, 1/100 in 1.5 ml microtubes, 250 µl of root lesion nematodes adult+larvae were placed in each microtubes that containing different concentrations of culture filtrate with 50 μl of purified water together with micropipette and incubated at 25±1°C. Nematode mortality were determined after 24 h, 48 h and 72 h. As a result, The mortality effect of culture filtrate of FC5 isolates was determined to be high on three lesion nematode species. Fusarium culmorum culture filtrates of B4 and ISP isolates caused more deaths on P. penetrans than P.thornei and P. neglectus. It has been found to mortality rate increase over time in vitro. The lowest mortality rates were generally found at concentrations of culture filtrates of 1/100 and 1/90, while the highest mortality rates were found at concentrations of 1/0 and 1/10. No difference on P. thornei mortality was detected between the three isolates of F. culmorum culture filtrate at each diluted concentration. In the study, the antagonistic relationship between culture filtrates from F. culmorum isolates and root lesion nematodes were determined in vitro conditions.

Morphometric and Molecular Diversity among Seven European Isolates of Pratylenchus penetrans.

Pratylenchus penetrans is an economically important root-lesion nematode species that affects agronomic and ornamental plants. Understanding its diversity is of paramount importance to develop effective control and management strategies. This study aimed to characterize the morphological and genetic diversity among seven European isolates. An isolate from the USA was included in the molecular analyses for comparative purposes. Morphometrics of the European P. penetrans isolates generally were within the range of the original descriptions for this species. However, multiple morphometric characteristics, including body length, maximum body width, tail length and length of the post-vulval uterine sac showed discrepancies when compared to other populations. Nucleotide sequence-based analyses revealed a high level of intraspecific diversity among the isolates. We observed no correlation between D2-D3 rDNA- and COXI-based phylogenetic similarities and geographic origin. Our phylogenetic analyses including selected GenBank sequences also suggest that the controversy surrounding the distinction between P. penetrans and P. fallax remains.

Plants Specifically Modulate the Microbiome of Root-Lesion Nematodes in the Rhizosphere, Affecting Their Fitness.

Plant-parasitic nematodes are a major constraint on agricultural production. They significantly impede crop yield. To complete their parasitism, they need to locate, disguise, and interact with plant signals exuded in the rhizosphere of the host plant. A specific subset of the soil microbiome can attach to the surface of nematodes in a specific manner. We hypothesized that host plants recruit species of microbes as helpers against attacking nematode species, and that these helpers differ among plant species. We investigated to what extend the attached microbial species are determined by plant species, their root exudates, and how these microbes affect nematodes. We conditioned the soil microbiome in the rhizosphere of different plant species, then employed culture-independent and culture-dependent methods to study microbial attachment to the cuticle of the phytonematode Pratylenchus penetrans. Community fingerprints of nematode-attached fungi and bacteria showed that the plant species govern the microbiome associated with the nematode cuticle. Bacteria isolated from the cuticle belonged to Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Sphingobacteria, and Firmicutes. The isolates Microbacterium sp. i.14, Lysobacter capsici i.17, and Alcaligenes sp. i.37 showed the highest attachment rates to the cuticle. The isolates Bacillus cereus i.24 and L. capsici i.17 significantly antagonized P. penetrans after attachment. Significantly more bacteria attached to P. penetrans in microbiome suspensions from bulk soil or oat rhizosphere compared to Ethiopian mustard rhizosphere. However, the latter caused a better suppression of the nematode. Conditioning the cuticle of P. penetrans with root exudates significantly decreased the number of Microbacterium sp. i.14 attaching to the cuticle, suggesting induced changes of the cuticle structure. These findings will lead to a more knowledge-driven exploitation of microbial antagonists of plant-parasitic nematodes for plant protection.

Molecular Characterization of Three B-1,4-Endoglucanase Genes in Pratylenchus loosi and Functional Analysis of Pl-eng-2 Gene.

Pratylenchus loosi is an important root-lesion nematode that causes damage to tea plantations in Iran and all over the world. The present study reports on the characterization and evolution of three ß-1,4-endoglucanase genes: Pl-eng-2, Pl-eng-3 and Pl-eng-4. The gene structure of Pl-eng-2 was fully determined with the predicted signal peptide and devoid of the linker domain and carbohydrate-binding domain, while Pl-eng-3 and Pl-eng-4 were only partially sequenced. The transcription of Pl-eng-2 was localized in the secretory esophageal glands of all life stages, but it was upregulated in male and female stages. The exon/intron structures of Pl-eng-2, Pl-eng-3 and Pl-eng-4 confirmed that they resulted from gene duplication followed by sequence and gene structure diversification with loss of the linker domain and carbohydrate-binding domain during evolution. A phylogenetic analysis further confirmed that nematode endoglucanases resulted from the horizontal gene transfer of a bacterial gene, as Pl-eng-3 showed sister relationships with the CelB cellulase of Bacillus subtilis. Silencing Pl-eng-2 by in vitro RNA interference produced a 60% decrease of the transcript level. The reproductive ability of silenced P. loosi showed a 35% reduction of eggs and larval stages compared to untreated nematodes, suggesting that this gene is involved in the early steps of invasion.

Benzoxazinoids selectively affect maize root-associated nematode taxa.

Although the effects of plant secondary metabolites on plant defence have been studied for decades, the exact roles of secondary metabolites in shaping plant-associated microbial and nematode communities remain elusive. We evaluated the effects of benzoxazinoids, a group of secondary metabolites present in several cereals, on root-associated nematodes. We employed 18S rRNA metabarcoding to compare maize root-associated nematode communities in a bx1 knockout maize line impaired in benzoxazinoid synthesis and in its parental wild type. Both genotype and plant age affected the composition of the nematode community in the roots, and the effects of benzoxazinoids on nematode communities were stronger in the roots than in the rhizosphere. Differential abundance analysis and quantitative PCR showed that the root lesion nematode Pratylenchus neglectus was enriched in the bx1 mutant line, while another root lesion nematode, Pratylenchus crenatus, was reduced. Correlation analysis showed that benzoxazinoid concentrations in maize roots mostly correlated negatively with the relative abundance of nematode sequence reads. However, positive correlations between benzoxazinoids and nematode taxa, including several plant-parasitic nematodes, were also identified. Our detailed nematode community analysis suggests differential and selective effects of benzoxazinoids on soil nematodes depending on both the nematode species and the benzoxazinoid compound.

Genome-wide association study in hexaploid wheat identifies novel genomic regions associated with resistance to root lesion nematode (Pratylenchus thornei)

Root lesion nematode (RLN; Pratylenchus thornei) causes extensive yield losses in wheat worldwide and thus pose serious threat to global food security. Reliance on fumigants (such as methyl bromide) and nematicides for crop protection has been discouraged due to environmental concerns. Hence, alternative environment friendly control measures like finding and deployment of resistance genes against Pratylenchus thornei are of significant importance. In the present study, genome-wide association study (GWAS) was performed using single-locus and multi-locus methods. In total, 143 wheat genotypes collected from pan-Indian wheat cultivation states were used for nematode screening. Genotypic data consisted of > 7K SNPs with known genetic positions on the high-density consensus map was used for association analysis. Principal component analysis indicated the existence of sub-populations with no major structuring of populations due to the origin. Altogether, 25 significant marker trait associations were detected with − log10 (p value) > 4.0. Three large linkage disequilibrium blocks and the corresponding haplotypes were found to be associated with significant SNPs. In total, 37 candidate genes with nine genes having a putative role in disease resistance (F-box-like domain superfamily, Leucine-rich repeat, cysteine-containing subtype, Cytochrome P450 superfamily, Zinc finger C2H2-type, RING/FYVE/PHD-type, etc.) were identified. Genomic selection was conducted to investigate how well one could predict the phenotype of the nematode count without performing the screening experiments. Prediction value of r = 0.40 to 0.44 was observed when 56 to 70% of the population was used as a training set. This is the first report where GWAS has been conducted to find resistance against root lesion nematode (P. thornei) in Indian wheat germplasm.

The Ethiopian staple food crop enset (Ensete ventricosum) assessed for the first time for resistance against the root-lesion nematode Pratylenchus goodeyi

Summary Pratylenchus goodeyi appears to be the most prevalent nematode pest of enset in Ethiopia, where it can occur in extremely high densities. However, the damage to yield or how different enset cultivars react to the nematode has yet to be determined. The current study therefore sought to establish a first assessment of these reactions by enset to P. goodeyi infection. Determining pest-resistant cultivars is an important task in developing management strategies. Our study evaluated nine enset cultivars to establish host response and identify potential sources of resistance. In addition, the pathogenicity of P. goodeyi was assessed on three enset cultivars. After 9 months’ growth, significant differences in final population densities (Pf) and reproduction factor (RF) were observed amongst the nine cultivars, with ‘Gefetanuwa’ the most susceptible (Pf = 25 799 and RF = 12.9), and similarly in a repeat experiment for 4.5 months (Pf = 126 534 and RF = 63.3). ‘Maziya’ and ‘Heila’ were the most resistant in the first experiment (Pf < 455 and RF < 0.2) as well as in the repeat, together with ‘Kellisa’ (Pf < 5255 and RF < 2.6). In the pathogenicity experiment four inoculum densities significantly affected the Pf and RF but not among the three cultivars ‘Maziya’, ‘Arkiya’ and ‘Heila’. This is the first known study to assess genotype reaction to P. goodeyi, which shows that there are significant differences in the reactions of different cultivars and that resistance appears to be present in enset.

Impacts of Root-Lesion Nematode (Pratylenchus thornei) on Plant Nutrition, Biomass, Grain Yield and Yield Components of Susceptible/Intolerant Wheat Cultivars Determined by Nematicide Applications

Field experiments testing rates of various nematicides, with and without NPZn fertiliser, were analysed to investigate how root-lesion nematode (Pratylenchus thornei) affects growth and yield components of susceptible/intolerant wheat cultivars in a subtropical environment. Plant response to nematode attack was assessed by regression and principal components analyses of various plant parameters at different crop development stages, in relation to different nematode population densities in the roots and root-zone soil. Reduction in P. thornei population densities by nematicides resulted in increased numbers of tillers, plant biomass, N and P concentrations and uptakes, numbers of spikes and kernels, and grain yield. Grain yield was strongly correlated with number of kernels, biomass and number of spikes, and negatively correlated with number of P. thornei in the root-zone soil at stem elongation. This study showed that P. thornei damage to roots decreased wheat yield through limiting N and P concentrations and uptakes in plant tops causing poor growth that commenced early and continued through the life of the crop. Genetic, environmental and management factors that reduce population densities of P. thornei, and decrease the impact of the nematodes starting in early crop growth, will greatly increase spike and kernel numbers and grain yield.

Winter cover crops as reservoirs of tobacco rattle virus (TRV) and hosts of root-lesion, root knot and stubby-root nematodes

A greenhouse pot study was conducted on four cover crops (annual ryegrass, perennial tetraploid ryegrass, winter wheat cv. ‘Caledonia’ and sorghum-sudangrass) and one rotation crop (sweet corn cv. ‘Sheba’) to compare the efficiency of these crop species as hosts of Paratrichodorus minor (Colbran) Siddiqi, and the ability of the nematodes to acquire tobacco rattle virus (TRV) from roots of infected plants and re-transmit it to healthy plants. P. minor reproduced rapidly on sorghum-sudangrass and sweet corn and re-transmitted the virus to indicator plants. Annual ryegrass, perennial ryegrass, and winter wheat cv. ‘Caledonia’, all of which re-transmitted TRV poorly in the greenhouse, were evaluated in two years of field studies for fall establishment and soil coverage, nutrient sequestration, effect on parasitic nematode populations and on subsequent potato crops. Annual ryegrass performed best overall in terms of establishment, ground cover, overwintering survival and foliar biomass production. None of the cover crops had a consistently significant effect on populations of parasitic nematodes in field plots, including Pratylenchus, Paratrichodorus, and Meloidogyne. Both ryegrass cover crops appeared to provide a favourable environment for survival of root knot nematodes (Meloidogyne spp.), although they are not considered to be hosts of this nematode. There was no difference in soil carbon, nitrogen or potato yield following any cover crop. Symptoms of corky ringspot were not observed in the field and TRV was not detected in potato plants by RT-PCR.

Morphological and Molecular Characterization of Pratylenchus dakotaensis n. sp. (Nematoda: Pratylenchidae), a New Root-Lesion Nematode Species on Soybean in North Dakota, USA.

Root-lesion nematodes (Pratylenchus spp.) of the genus Pratylenchus Filipjev, 1936, are among the most important nematode pests on soybean (Glycine max (L.) Merr.), along with soybean cyst and root-knot nematodes. In May 2015 and 2016, a total of six soil samples were collected from a soybean field in Walcott, Richland County, ND and submitted to the Mycology and Nematology Genetic Diversity and Biology Laboratory (MNGDBL), USDA, ARS, MD for analysis. Later, in 2019, additional nematodes recovered from a greenhouse culture on soybean originally from the same field were submitted for further analysis. Males, females, and juveniles of Pratylenchus sp. were recovered from soil and root samples and were examined morphologically and molecularly. DNA from single nematodes were extracted, and the nucleotides feature of three genomic regions targeting on the D2–D3 region of 28S rDNA and ITS rDNA and mitochondrial cytochrome oxidase subunit I (COX1) gene were characterized. Phylogeny trees were constructed to ascertain the relationships with other Pratylenchus spp., and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to provide a rapid and reliable differentiation from other common Pratylenchus spp. Molecular features indicated that it is a new, unnamed Pratylenchus sp. that is different from morphologically closely related Pratylenchus spp., including P. convallariae, P. pratensis, P. fallax, and P. flakkensis. In conclusion, both morphological and molecular observations indicate that the North Dakota isolate on soybean represents a new root-lesion nematode species which is named and described herein as Pratylenchus dakotaensis n. sp.

The Root Lesion Nematode Effector Ppen10370 Is Essential for Parasitism of Pratylenchus penetrans.

The root lesion nematode Pratylenchus penetrans is a migratory species that attacks a broad range of crops. Like other plant pathogens, P. penetrans deploys a battery of secreted protein effectors to manipulate plant hosts and induce disease. Although several candidate effectors of P. penetrans have been identified, detailed mechanisms of their functions and particularly their host targets remain largely unexplored. In this study, a repertoire of candidate genes encoding pioneer effectors of P. penetrans was amplified from mixed life stages of the nematode, and candidate effectors were cloned and subjected to transient expression in a heterologous host, Nicotiana benthamiana, using potato virus X-based gene vector. Among seven analyzed genes, the candidate effector designated as Ppen10370 triggered pleiotropic phenotypes substantially different from those produced by wild type infection. Transcriptome analysis of plants expressing Ppen10370 demonstrated that observed phenotypic changes were likely related to disruption of core biological processes in the plant due to effector-originated activities. Cross-species comparative analysis of Ppen10370 identified homolog gene sequences in five other Pratylenchus species, and their transcripts were found to be localized specifically in the nematode esophageal glands by in situ hybridization. RNA silencing of the Ppen10370 resulted in a significant reduction of nematode reproduction and development, demonstrating an important role of the esophageal gland effector for parasitism.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Evaluation of root-lesion nematode (Pratylenchus zeae) resistance assays for sugarcane accession lines.

No sugarcane cultivar is resistant to root-lesion (Pratylenchus zeae) nematode in Australia. Sugar Research Australia commenced a research project to evaluate new sets of accession lines derived from introgression breeding between wild relatives of sugarcane and commercial parents. No established method of assessment was available for comparing the resistance of sugarcane in the glasshouse. This study aimed to determine the most suitable assessment method for comparing resistance in accession lines. Two resistance parameters were measured, (i) number of nematodes per plant, and (ii) number of nematodes per g of roots. Nine screening trials were conducted from 2011 to 2020. Resistance parameter number of nematodes/plant had less variations within trials compared to nematodes/g roots, although both parameters were equally repeatable. Number of nematodes/g of root were negatively correlated (r = ‒0.29 to ‒0.86, p ≤ 0.001) with root biomass in all nine trials, and with shoot biomass in three out of seven trials (r = ‒0.23 to ‒0.31, p ≤ 0.05). In contrast, the number of nematodes per plant were positively correlated with shoot biomass (r = 0.25–0.53, p ≤ 0.05) in three out of seven trials and with root biomass (r = 0.17–0.27, p ≤ 00.05) in three out of nine trials. These results clearly indicated that nematodes per g root is related to reduction in root biomass and shoot biomass.

First report of root-lesion nematode, Pratylenchus oleae from pistachio in Iran.

Pistachio, Pistacia vera is one of the most important cash crops in Iran that is scattered in arid and semi-arid regions. During a survey of plant-parasitic nematodes of pistachio in Ardakan city in Yazd Province, a species of root-lesion nematode was isolated and identified by morphological, morphometrical, and molecular methods as Pratylenchus oleae Palomares-Rius et al., 2014. This species was isolated from several pistachio trees rhizosphere regarding to molecular analysis, D2–D3 expansion segments of 28S rRNA was amplified by PCR and sequenced. The sequence was deposited in GenBank (Accession No. MW338666). Along with the related phylogenetic analysis, placed this species in a monophyletic clade with other Pratylenchus oleae isolates, based on Bayesian inference (BI) phylogeny. A PCR reaction with the P. oleae specific primer set produced a 547 bp fragment. This is the first report of P. oleae infecting Pistachio tree in the world.

Pratylenchus smoliki, a new nematode species (Pratylenchidae: Tylenchomorpha) from the Great Plains region of North America.

Pratylenchus smoliki is a new species of root-lesion nematode described from corn-soybean production fields in the Central Great Plains of North America. It is characterized by populations with relatively abundant males, two lip annuli, females with a round functional spermatheca and a conoid to subcylindrical tail with a non-crenate, smooth terminus. In host preference tests, corn and wheat produce the largest nematode populations, whereas sorghum and soybeans produce less than 20% the numbers observed on corn. Scanning electron microscopy reveals that the en face patterns compare to those seen in Pratylenchus pseudocoffeae, P. scribneri, P. hexincisus, and P. alleni. The pattern is described as rectangular to trapezoidal subdorsal and subventral lips adjoining oral disc, but with a clear demarcation between the oral disc and the subdorsal and subventral sectors. A Maximum Likelihood COI tree recognizes P. smoliki as a moderately-well-supported clade with several haplotype subgroups. A Maximum Likelihood partial 28S tree provides strong support for the P. smoliki clade and reinforces the close relationships between species with similar en face patterns. Topotype specimens of P. alleni were demonstrably different from P. smoliki using DNA markers. The geographic range of P. smoliki overlaps with the ranges of P. alleni, P. scribneri, P. neglectus, P. hexicisus, and P. dakotaensis. The observed host range (corn, rye, sunflower, and wheat) suggests that P. smoliki may be native to the tallgrass prairie region of the Great Plains.

Investigation of the development of root lesion nematodes, Pratylenchus spp. (Tylenchida: Pratylenchidae) in three chickpea cultivars

Bu calismada, Bari 2, Bari 3 ( Cicer reticulatum Ladiz ) ve Cermi [ Cicer echinospermum P.H.Davis (Fabales: Fabaceae)] nohut cesitlerinde Kok lezyon nematodlarinin, Pratylenchus neglectus (Rensch, 1924), Pratylenchus penetrans (Cobb, 1917) ve Pratylenchus thornei Sher & Allen, 1953 (Tylenchida: Pratylenchidae), 3, 7, 14, 21, 28, 35, 42, 49 ve 56 gunlerde populasyon degisimleri, penetrasyon ve ureme oranlari kontrollu oda kosullarinda 2018-2019 yillari arasinda incelenmistir. Ilk 3 gunde nohut cesitlerinin koklerinde larvalar gorulmemistir. Pratylenchus thornei en yuksek populasyon yogunluguna Cermi cesidinde 21 gunde, Bari 3 cesidinde 42 gunde ulasmasina ragmen Bari 2 cesidinde ureme en dusuk duzeyde kalmistir. P. neglectus Bari 3 ve Cermi cesidinde 28 gunde en yuksek populasyon yogunluguna ulasmistir. Bari 2’de ise en dusuk populasyon yogunlugu P. neglectus ’da gorulmustur. Buna ek olarak, P. penetrans populasyon yogunlugu, P. thornei ’ye benzer sekilde, 49 gunde Bari 3 cesidinde en yuksek seviyeye ulasirken, Bari 2 ve Cermi cesitlerinde deneme suresince dusuk populasyon yogunlugu gostermistir.

Phytophagous nematodes in cereal fields in Niğde Province, Turkey

This study evaluated the occurrence and incidence of phytophagous nematodes and identified the cereal cyst nematode species by morphological and molecular tools in the main cereal-growing areas in Nigde in 2018-2019. Phytophagous nematodes within twelve genera were detected in 95% of soil samples. The most common phytophagous nematodes in cereal soil were in the genera Heterodera, Ditylenchus , Merlinius , Pratylenchus , Aphelenchus , Aphelenchoides , Tylenchus , Helicotylenchus , Trophurus , Pratylenchoides , Filenchus and Xiphinema (in decreasing order of incidence). In particular, 75% of the soil samples from surveyed fields were infested with the cereal cyst nematodes (Heterodera spp.). Morphological characteristics of cysts and second-stage juveniles were calculated within the expected ranges for Heterodera filipjevi (Madzhidov, 1981) Stelter, 1984, however, two populations from Camardi was determined as Heterodera latipons Franklin, 1969 (Tylenchida: Heteroderidae). Intraspecific variation was not observed within the populations of H. filipjevi which could be in the same genotypic group. In addition to the high incidence of these Heterodera spp., intensive cereal cropping systems with/without non-cereal rotations in wheat production areas of Nigde also resulted in high incidence of root lesion nematode, Pratylenchus species.

Assessment of infectivity against root knot nematode, Meloidyne incognita and lesion nematode, Pratylenchus zeae in sugarcane genotypes

A greenhouse experiment was conducted to screen against root knot nematode, Meloidogyne incognita with chip bud seedling 27 numbers of clones. Among them 19 clones were found to be moderately resistant, two resistance and six clones were susceptible. Another greenhouse experiment was conducted to screen against lesion nematode, Pratylenchus zeae using chip bud seedling same 27 clones. Among them 20 clones were found to be tolerant, one clone was moderately resistant and six clones were found to be susceptible. A separate field experiment was conducted to screen twelve clones against root knot nematode, Meloidogyne incognita and lesion nematode, Pratylenchus zeae. Among them seven clones were found to be moderately resistant and three clones were susceptible to root knot nematode. The check varieties, CoC 24 and CoC25 were found to be resistant. For lesion nematode eight clones were found to be tolerant and three clones were found to be susceptible. The check variety CoC 25 were found to be moderately resistant. A field experiment was conducted to screening of 33 sugarcane varieties/ clones against root knot nematode, Meloidogyne incognita. Among them seventeen clones were found to be moderately resistant, fourteen clones were susceptible. The two varieties (CoC 24 and CoC 25) were found to be resistant. A field experiment was conducted to screening of 33 sugarcane varieties/clones against lesion nematode, Pratylenchus zeae. Among them thirty clones were found to be tolerant and three clones were found to be moderately resistant C 15157, C 15499 and CoC 25.

A new esophageal gland transcriptome reveals signatures of large scale de novo effector birth in the root lesion nematode Pratylenchus penetrans

BackgroundThe root lesion nematode Pratylenchus penetrans is a migratory plant-parasitic nematode responsible for economically important losses in a wide number of crops. Despite the importance of P. penetrans, the molecular mechanisms employed by this nematode to promote virulence remain largely unknown.ResultsHere we generated a new and comprehensive esophageal glands-specific transcriptome library for P. penetrans. In-depth analysis of this transcriptome enabled a robust identification of a catalogue of 30 new candidate effector genes, which were experimentally validated in the esophageal glands by in situ hybridization. We further validated the expression of a multifaceted network of candidate effectors during the interaction with different plants. To advance our understanding of the “effectorome” of P. penetrans, we adopted a phylogenetic approach and compared the expanded effector repertoire of P. penetrans to the genome/transcriptome of other nematode species with similar or contrasting parasitism strategies. Our data allowed us to infer plausible evolutionary histories that shaped the effector repertoire of P. penetrans, as well as other close and distant plant-parasitic nematodes. Two remarkable trends were apparent: 1) large scale effector birth in the Pratylenchidae in general and P. penetrans in particular, and 2) large scale effector death in sedentary (endo) plant-parasitic nematodes.ConclusionsOur study doubles the number of validated Pratylenchus penetrans effectors reported in the literature. The dramatic effector gene gain in P. penetrans could be related to the remarkable ability of this nematode to parasitize a large number of plants. Our data provide valuable insights into nematode parasitism and contribute towards basic understating of the adaptation of P. penetrans and other root lesion nematodes to specific host plants.

Propidium iodide enabled live imaging of Pasteuria sp.-Pratylenchus zeae infection studies under fluorescence microscopy.

Live imaging allows observations of cell structures and processes in real time, to monitor dynamic changes within living organisms compared to fixed organisms. Fluorescence microscopy was used to monitor the dynamic infection process of the nematode parasitic bacterium Pasteuria sp. and the sugarcane root-lesion nematode, Pratylenchus zeae. Under fluorescence microscopy, green-autofluorescent globules were observed in live control and Pasteuria sp.-infected nematodes. Only nematodes killed by Pasteuria sp. or heat treated displayed a diffuse pattern of autofluorescence. Propidium iodide (PI), used as a cell membrane integrity indicator, confirmed that the nematode's cuticle acts as an impermeable barrier. PI stained cells/DNA of heat-treated control and Pasteuria sp.-infected P. zeae. PI as a counterstain facilitated the location of Pasteuria endospores on the cuticle surface of P. zeae. No PI staining was observed in sporangia and in endospores within the nematode body. However, PI specifically stained endospores on the cuticle surface and within the cuticle carcass showing, in mature propagules, a ring-like pattern. Live imaging, combined with fluorescence microscopy and fluorescent dyes such as PI, appears useful in live studies on plant nematode interactions with nematophagous bacteria.