Prevalence and ecological factors affecting the distribution of plant-parasitic nematodes in Prunus groves in Spain

A wide survey was conducted to study plant-parasitic nematodes(PPNs)associated with Prunus groves in Spain.This research aimed to determine the prevalence and distribution of PPNs in Prunus groves,as well as the influence of explanatory variables describing soil,climate and agricultural management in structuring the variation of PPNs community composition.A total of 218 sampling sites were surveyed and 84 PPN species belonging to 32 genera were identified based of an integrative taxonomic approach.PPN species considered as potential limiting factors in Prunus production,such as Meloidogyne arenaria,M.incognita,M.javanica,Pratylenchus penetrans and P.vulnus,were identified in this survey.Seven soil physico-chemical(C,Mg,N,Na,OM,P,pH and clay,loamy sand and sandy loam texture classes),four climate(Bio04,Bio05,Bio13 and Bio14)and four agricultural management variables(grove-use history less than 10 years,irrigation,apricot seedling rootstock,and Montclar rootstock)were identified as the most influential variables driving spatial patterns of PPNs communities.In particular,younger plantations showed higher values for species richness and diversity indices than groves cultivated for more than 20 years with Prunus spp.Our study increases the knowledge of the distribution and prevalence of PPNs associated with Prunus rhizosphere,as well as on the influence of explanatory variables driving the spatial structure PPNs communities,which has important implications for the successful design of sustainable management strategies in the future in this agricultural system.

Evaluation of Soybean Genotypes (Glycine max L. Merr.) Susceptibility to Parasitic Nematodes in Western Part of Burkina Faso

Parasitic nematodes have been reported as one of the major constraints to soybean production worldwide. The majority of nematodes are so-called “free-living” and feed mainly on bacteria, fungi, protozoa and other nematodes. In Burkina Faso, the presence of parasitic nematodes has been reported in crops such as rice and sorghum. The objective of this study was to identify the genera and species of nematodes associated with soybean production in Burkina Faso. Investigations were carried out on 24 genotypes of a medium-maturity group of soybean at the Farako-Ba research station. Soil samples were taken from the trial soil before its installation. At harvest, soil samples with roots were taken from each genotype in the elementary plots. The composite sample is represented by 4 lots of soil samples with roots. Extractions and counts of nematodes were performed on the different lots. In total, 7 genera of plant-parasitic nematodes associated with soybean were identified. Among these genera, Pratylenchus (100% of infected genotypes), Helicotylenchus (97.28%) and Scutellonema (94.44%) were the most prevalent in terms of frequency and abundance. Some soybean genotypes were less susceptible to the genus Pratylenchus is known to be highly pathogenic in soybean. These were mainly the genotypes TGX2025-10E, TGX2023-3E and TGX2025-14E.

Did Species and Functional Diversities of Sandy Intertidal Marine Nematodes Reveal Similar Response to Environmental Changes?

Free living marine nematodes were sampled from two sandy beaches in Dalian City,in December of 2015,and April,July,and October of 2016.The spatial and seasonal variations of marine nematode species diversity(based on species abundance dataset)and functional diversity(based on functional traits dataset:feeding types and life history strategies)were investigated to understand the environmental drivers and how they respond to specific environmental variations.Sediment granularity was revealed to be the main environmental factor causing spatial differences in nematode diversity indices between the two beaches.Species diversity indices,namely species number,Margalef index,Shannon-Wiener diversity index(H’),were higher in fine-grained sediments,while the functional diversity indices,including functional evenness,functional dispersion,and Rao’s quadratic entropy index(RaoQ),were higher in coarse-grained sediments.Nematode species diversity indices also fluctuated with seasonal variations of temperature,dissolved oxygen,pH,salinity,and sediment chlorophyll-a within the study beaches.However,functional diversity indices did not show significant seasonal variations and exhibited weak correlation with the studied environmental variables.Overall,the functional diversity indices were negatively correlated with the species diversity indices,suggesting an inconsistent response to environmental changes.A decrease in nematode species diversity in coarse sands,accompanied by an increase in functional diversity,can be regarded as an early warning signal of environment disturbance.If more biological traits are involved in calculating functional diversity indices,it will be helpful for the future study of the internal connections of species diversity and functional diversity.

Vertical distribution of plant nematodes in an aquic brown soil under different land uses

The vertical distribution of the dominant genera of plant nematodes at the depth of 0–150 cm of an aquic brown soil were studied for four land use patterns, i.e., paddy field, maize field, fallow field and woodland in the Shenyang Experimental Station of Ecology, Chi- nese Academy of Sciences in November of 2003. The results showed that the numbers of some dominant genera under different land uses decreased with the increase of soil depth. Helicotylenchus was most dominant genus under each land use type. Genera of Filenchus, Psilen- chus and Tylenchus in paddy field occurred at the depth of 0–20 cm; while Paratylenchus in fallow field and woodland, as well as Praty- lenchus in maize field presented in the deeper soil layers (0–80 cm). Significant correlations between the numbers of dominant genera of plant nematodes and soil chemical properties were found in this study. The number of Helicotylenchus under different land uses was posi- tively correlated with C/N ratio, total C, total N, total P, alkai-N, and Olsen-P. The numbers of Filenchus and Paratylenchus in paddy field, Pratylenchus in maize field and Paratylenchus in fallow field were negatively correlated with soil pH, and positively correlated with total C, total N and alkai-N. This study results showed that it is essential to sample at a certain depth according to the vertical distribution informa- tion of different genera of plant nematodes in adequately assessing the population size of plant nematodes.

Freeliving marine nematodes as a pollution indicator of the Bohai Sea

A hierarchical diversity index—taxonomic distinctness index Δ +, which was first defined by Warwick and Clark in 1998, was employed to evaluate the pollution status of the Bohai Sea with freeliving marine nematodes. The result showed that the Bohai Bay and other coastal sampling sites might be affected by oil and gas production and other anthropogenic influences. In other words,anthropogenic disturbance was affecting this component of the benthos in these locations. And most offshore sampling sites in the middle of the Bohai Sea were clear and unpolluted.

Four Newly Recorded Free-living Marine Nematodes(Comesomatidae) from the East China Sea

Three species in genus Sabatieria and one in genus Cervonema from the East China Sea were recorded. S. breviseta is characterized by uniformly punctuated coarse dots, large amphids of 5.5 turns (♂) and prominent gubernaculum median piece. The characters of S. breviseta agree quite well with the European original descriptions and only differ in the male amphid turns (5.5 vs. 4.0 turns) and unmodified preanal supplements (5-7 vs. 6). S. pulchra can be recognized by amphid 2.75 turns, irregularly arranged lateral dots, and the first three supplements anterior to the anus, which are more widely spaced than the following ones. The excretory system of S. breviseta and S. pulchra shows sexual dimorphism. S. celtica is defined by amphids 2.00-2.25 turns, weakly developed pharyngeal bulb, curved apophyses and 12-13 conspicuous supplements. C. deltensis is characterized by amphids 4.75 turns, ovate pharyngeal posterior bulb, sperm dimorphism, 7 thin preanal supplements, and long tail cylindrical portion (50%-53% of tail length). All the three Sabatieria species are for the first time recorded in Chinese waters. C. deltensis was originally isolated from the Bohai Sea and Yellow Sea and newly recorded in the East China Sea.

Community structure and biodiversity of free-living marine nematodes in the northern South China Sea

A quantitative study on the community structure and biodiversity of free-living marine nematodes and their relationship with environmental factors in the northern South China Sea were carried out based on the samples collected at five stations in the deep sea （from 313 to 1 600 m） and one station in shallowwaters （87 m） during the cruise in September, 2010. Results showed that the abundance of marine nematodes ranged from 224 to 1 996 ind./（10 cm2）. A total of 69 free-living marine nematode genera, belonging to 26 families and three orders, were identified. The most dominant genera were Sabatieria, Linhystera, Aegialoalaimus and Daptonema according to SIMPER analysis. Results of CLUSTER analysis revealed four types of marine nematode community （or station groups） in the sampling area. In terms of trophic structure, non-selective deposit feeders （1B） and selective deposit feeders （1A） were the dominant trophic types with highest genera numbers and abundances, which implied that organic detritus was the main food source of marine nematodes in the northern South China Sea. The percentage of male nematode was low, ranging from 2.22% to 17.81%, while those of juvenile individuals ranged from 36.99% to 82.09%. For genera level diversity of marine nematodes, Shannon-Wiener diversity indices （H＇） ranged from 3.76 to 4.57 and had highly significant negative correlation with water depth. In general, diversity indices H＇ at the five stations in deep sea （over 200 m） were lower than that at the station in shallow waters （87 m）. BIOENV analysis showed that the most important environmental factor controlling marine nematode communities was water denth.

Two new species of free-living nematodes of genus Tripyloides (Nematoda: Enoplida: Tripyloididae) from mangrove wetlands in the Xiamen Bay, China

Two new species of free living nematodes Tripyloides mangrovensis n. sp. and Tripyloides amoyanus n. sp. of genus Tripyloides de Man, 1886 are described from mangroves of the Tong＇an Bay and Haimen Island in the Xiamen Bay, China. The two species are both characterized by six stout outer labial setae, male without preanal papillae, tail conico-cylindrical without swollen terminally. Tripyloides mangrovensis n. sp. can be additionally by its buccal cavity consisting of two parts, amphid circular, distinct proximal conical and distal slender cylindrical portions, 2/3 of the tail cylindrical. Tripyloides amoyanus n. sp. is distinguished by buccal cavity consisting of three parts with small tooth, amphid small, rounded, like a comma-shaped loop, 1/3 of the tail cylindrical, gubernaculum with four denticles.

Oral administration of Sauce llorón extract to growing lambs to control gastrointestinal nematodes and Moniezia spp.

Objective: To explore anthelmintic effects of oral administration of aqueous extract of Sauce llorón(Salix babylonica; SB) against gastrointestinal nematodes and Moniezia spp. Methods: Sixteen Pelibuey male lambs of 3-4 months of age and(23.7±3.3) kg body weight were used in a completely randomized design to be fed a total mixed ration(Control; SB0), or Control plus SB extract using 20(SB20), 40(SB40) and 60(SB60) mL/lamb/day for 45 days. Lambs had a natural gastrointestinal nematodes and Moniezia spp. infection and had never been treated with chemical anthelmintic drugs. Individual faecal samples were collected for ova counting using Mc Master procedure after 0, 7, 14, 21, 30 and 45 days post extract administration. Results: No extract dose×day interactions for both gastrointestinal nematodes and Monieziaspp. egg count were found. Administration of SB extract had a higher effect(quadratic effect, P=0.0064) at dose of 20 mL SB/lamb/day for gastrointestinal nematode eggs during the first 21 days; however, the dose of SB40 tended(linear effect, P=0.0897) to be more effective than the others for Moniezia spp. egg during the first 7 days. Sampling day had a linear(P=0.0436) effect on Moniezia spp. egg count. Conclusions: The aqueous extract of SB could be more effective against nematodes at 20 and at 40 mL/lamb/day for Moniezia spp. The use of the SB extract could represent a promising alternative to synthetic anthelmintics for the treatment of gastrointestinal nematodes and Moniezia spp. in small ruminants from organic and conventional production systems.

Molecular and morphological characterization of stunt nematodes of wheat, maize, and rice in the savannahs of northern Nigeria

Stunt nematodes(Tylenchorhynchus spp.)are obligate migratory root ecto-parasitic nematodes found in the fields of many cultivated crops.These nematodes,with phyto-sanitary potential,are frequently ignored or misdiagnosed as pests,and this may pose a threat to food security.The accuracy of its identification based on a morphological approach has been challenged recently,due to the overlapping of the morphological and morphometric characters of the species.Consequently,the objective of this study is to identify and characterize stunt nematodes present in 54 fields cultivated with cereal crops(wheat,maize and rice)in the savannahs of northern Nigeria,using integrative taxonomy and molecular approaches.The molecular and morphological studies identified and confirmed the presence of T.annulatus as the occurring specie in the savannahs of northern Nigeria.The phylogenetic analysis was carried out using the internal transcribed spacer(ITS)and 28S genes of ribosomal DNA further confirmed the presence of T.annulatus.The first molecular characterization and sequences of the ITS and 28S rDNA gene for T.annulatus from Nigeria were provided by this research.Also,according to our literature search,this is the first report on T.annulatus in wheat,maize and rice in the savannahs of northern Nigeria.Further study to test the pathogenicity of the parasitic nematode species found in this survey is recommended for the prioritization and development of efficient management strategies.

Profiling soil free-living nematodes in the Namib Desert, Namibia

Functional structure and diversity of soil free-living nematodes in a desert environment depend on plant gender and sampling site.The objective of this study was to compare the composition,abundance and tropic group of soil free-living nematodes in the upper 0–10 cm soil layer under the male and female Acanthosicyos horridus Welw.ex Hook.f.plants and in the inter-shrub open areas(control)in the Namib Desert,Namibia in April 2015.Soil moisture,organic matter(OM)and pH was also analyzed.Free-living nematodes were extracted from 100 g soil using the Baermann funnel procedure,and total number of nematodes was counted under a microscope.Community composition and diversity of soil free-living nematodes were analyzed using 18S rDNA sequences.Results indicated that a total of 67 groups,including 64 species,2 genera and 1 family were identified.Feeding behavior of 58 species were identified as follows:15 bacteria-feeding species,12 fungi-feeding species,10 plant-parasite species,5 omnivorous-predator species,8 animal-parasite species,5 invertebrate-parasite species and 3 non-free-living nematodes,known as marine species.Moreover,soil free-living nematodes were found to be affected by sampling locations and plant gender,and community composition and density of these nematodes were strongly influenced by soil OM content.Result confirmed that spatial location and plant cover were main factors influencing the diversity of soil free-living nematodes.Moreover,molecular tools were found to be very useful in defining the richness of soil non-free-living nematodes.In conclusion,the results elucidated the importance of biotic variables in determining the composition and abundance of soil free-living nematodes in the Namib Desert,Namibia.

Two New Species of Free-Living Marine Nematodes of the Desmodoridae from Mangrove Wetlands of Xiamen Bay, China

Mangroves are unique in their biodiversity,but studies on their meiobenthic biodiversity in China are scarce.Despite the importance of mangroves,little work has been done on the classification of nematodes in mangrove wetlands.Fujian Province is the most northern point of China’s natural mangrove distribution,and it is also one of the provinces with the earliest constructed mangrove forest.In this paper,two new free-living marine nematode species of Desmodoridae from the Xiamen mangrove wetlands in China are described.Metachromadora xiamenensis sp.nov.is characterized by a cylindrical body,and smooth head capsule set off from the rest of the body.The cuticle is finely annulated and thickened at the midbody.Lateral ridges run from the posterior end of the pharynx to the middle of the tail.The amphid foveae is loop shaped and opens at the top with a double contour amphidial,pharynx with bipartite cuticularized internal cavity.There are 18 tubular precloacal supplements and tail with three small protuberances.Molgolaimus euryformis sp.nov.is characterized by a relatively short and plump body with finely annulated cuticle,which is particularly obvious in the tail.The head is small and wide with intensive striates.The inner and outer labial sensilla are indistinct with short spicules and ventral apophysis,a gubernaculum with a block-shaped hook,a swollen conical-cylindrical tail and an absence of precloacal supplements.

Research Advances in Genetic Markers for Resistance to Soybean Cyst Nematodes(SCN)

Soybean cyst nematode(SCN), Heterodera glycine, is one of the important diseases affecting the yield of soybean(Glycine max) worldwide. Host-plant resistance is the most economically effective way to control SCN. Identification of DNA markers linked to SCN resistance genes is one of the important steps in the marker-assisted selection(MAS) for nematode resistance breeding. Quantitative trait loci(QTLs) controlled by mul-tiple resistance genes plays a powerful role in MAS-breeding program. In this paper, we reviewed genetic resistance of SCN, molecular markers of resistance gene and Genome-Wide Associated Study(GWAS) of QTLs linked to SCN resistance, explored the present problems of genetic resistance,and prospected the future of QTL analysis.

Preliminary Species Identification of Parasitic Nematodes from Rhizosphere Soil of Grapes in Mengzi City

The grape cultivation area in Luolongzhuang of Wenlan,Yingfang,Liucun and Shiqicun of Caoba in Mengzi City,Yunnan Province were surveyed from October 2014 to February 2015. Using five-point sampling method,approximately 2 kg of rhizosphere soil were collected from plants with weak growth and brown and wilting root,and 28 soil samples in total were collected. Through morphological identification,the species of parasitic nematodes in rhizosphere soil of grapes were preliminarily identified. There were three genera and four species of parasitic nematodes in grape,including A. avenae（ Aphelenchus avenae Bastian,1865）,R. reniformis（ Rotylenchulus reniformis Linford et Oliverira,1940）,H. dihytera [Helicotylenchus dihytera Sher Cobb,1893,1961] and H. pseudorobustus [Helicotylenchus pseudorobustus Golden（ Steiner,1914）,1956].

Effect of Ensiling on Efficacy of Sericea Lespedeza against Gastrointestinal Nematodes and Coccidia in Goats

Effect of ensiled sericea lespedeza(SL,Lespedeza cuneata)on indicators of gastrointestinal parasitism was investigated in two trials using intact male Spanish goats(n=36/trial).Naturally parasite-infected animals at 24.4±3.7 kg body weight(BW)and nine months of age or 24.6±0.57 kg BW at 4-6 months of age were used for 28 d or 21 d for Trials 1 and 2,respectively.For Trial 1,goats were fed SL silage(SLS),SL hay(SLH),or Bermuda grass(BG,Cynodon dactylon)hay at 70%of the diet.For Trial 2,goats were provided with SLH or SLS and orally drenched with distilled water(Hay or silage plus water,HW and SW,respectively)or polyethylene glycol(PEG;SLS only;SP)daily.Fecal and blood samples were collected weekly to determine gastrointestinal nematode fecal egg counts(FEC)and coccidia fecal oocyst counts(FOC)per gram of feces and blood packed cell volume(PCV).The SL diets significantly reduced(p<0.05)FEC and FOC in both trials,with the SLH diet reducing FEC 7 d faster compared to SLS.In PEG-treated goats,FOC tended to increase(p<0.07)at day 7 before decreasing.There was no treatment effect on PCV scores.Overall,SLH and SLS reduced fecal egg and oocyst counts in goats,but PEG results were inconclusive,so more research is needed.

A comparative analysis of entomoparasitic nematodes <i>Heterorhabditis bacteriophora</i>and <i>Steinernema carpocapsae</i>

Heterorhabditis bacteriophora and Steinernema carpocapsae are microscopic entomoparasitic nematodes (EPNs) that are attractive, organic alternatives for controlling a wide range of crop insect pests. EPNs evolved with parasitic adaptations that enable them to “feast” upon insect hosts. The infective juvenile, a non-feeding, developmentally arrested nematode stage, is destined to seek out insect hosts and initiates parasitism. After an insect host is located, EPNs enter the insect body through natural openings or by cuticle penetration. Upon access to the insect hemolymph, bacterial symbionts (Photorhabdus luminescens for H. bacteriophora and Xenorhabdus nematophila for S. carpocapsae) are regurgitated from the nematode gut and rapidly proliferate. During population growth, bacterial symbionts secrete numerous toxins and degradative enzymes that exterminate and bioconvert the host insect. During development and reproduction, EPNs obtain their nutrition by feeding upon both the bioconverted host and proliferated symbiont. Throughout the EPN life cycle, similar characteristics are seen. In general, EPNs are analogous to each other by the fact that their life cycle consists of five stages of development. Furthermore, reproduction is much more complex and varies between genera and species. In other words, infective juveniles of S. carpocapsae are destined to become males and females, whereas H. bacteriophora develop into hermaphrodites that produce subsequent generations of males and females. Other differences include insect host range, population growth rates, specificity of bacterial phase variants, etc. This review attempts to compare EPNs, their bacterial counterparts and symbiotic relationships for further enhancement of mass producing EPNs in liquid media.

Free-Living Nematodes as Pollution Indicator in Incomati River Estuary, Mozambique

Four sites following the salinity gradient of the Incomati River Estuary E1 (0-3NST), E2 (3-5NST), E3 (6-18NST) and E4 (19-27NST) were selected for the study. The aim of the study was to use free-living marine nematodes as pollution indicators in an area strongly affected by anthropogenic activities. Multivariate statistical analyses were used to determine the relationship between different environmental factors and with free-living marine nematodes. Metals such Cadmium, Colbat, Chromium, Copper, Iron, Manganese, Nickel, Vadium, Zinc and Aluminium influenced the diversity and density of free-living nematodes. Shannon-Wiener Diversity, Maturity Index and colonize-persisters percentage (c% - p%) were found to be good tools for use as pollution indicators in the study. Nematode genera such as Terschellingia, Theristus and Halalaimus were found to be dominant at a site strongly impacted by both metals concentration and organic matters. The three genera are believed to be good indicators of pollution in the Incomati River Estuary. It is recommended that further studies are done along the Mozambican Coast to identify nematodes that can be used as pollution indicators.

Interactions between Entomopathogenic Nematodes and Entomophagous Insects

The objective of this review article is to clarify the different interactions between entomopathogenic nematodes, as bio-control agents, against other bio-control agents (parasitoids and predators) proposed by the researchers. Thus, it gives clear information concerning the potential of combining them as a part of Integrated Pest Management (IPM) programs against insect pests. Some laboratory studies showed that the treatment of predacious insects by entomopathogenic nematodes (EPNs) at different concentrations can infect and kill the treated larva, nymphs and adults of predators. The percentages of mortality were found to be high (up to 100%), moderate (15% - 35%) or low (3% - 7%). Other studies revealed the resistant of treated predators to nematode-infection. Some predators that were offered infected prey avoid feeding on such prey and, in contrast, the soil predators (ants and mites) consumed the offered cadavers as well as the infective juvenile of the nematodes and did not show any detrimental effects. Mostly, parasitoids cannot complete their development inside or on nematode-infected hosts if parasitism occurs before or early after infection. The parasitoid females may avoid laying eggs in the infected hosts or cannot discriminate between healthy and infected hosts. A field study demonstrated that applying EPNs combined with the predator, Labidura riparia significantly reduced the population of the target pest compared to the nematode or the predator alone. Also, two field experiments indicated that the combination of parasitoids and nematodes can be successful for insect pest management.

Susceptibility of Economic Dipteran Fruit Flies to Entomopathogenic Nematodes

The present review article demonstrates laboratory and field evaluations of entomopathogenic nematodes(EPNs)against different developmental stages of fruit flies.The virulence of the EPNs differed clearly even on the same insect species and/or by the same nematode species.Such differences might be attributed to some reasons such as the method of treatment as well as the concentrations of the tested nematodes.Fruit flies are among the most important insect pests infesting vegetables and fruits causing considerable losses in the yields worldwide.In laboratory studies,the tested nematodes proved to be highly virulent to larvae as percentage of mortality may reach 100%.As for treated pupae,at different ages,the results are variable and controversially;some studies revealed their moderate or high susceptibility to nematode infection and others indicated low susceptibility or resistance to infection.Treated adults,or those emerged from treated larvae or pupae,are also susceptible to infection.In semi-field and field trials,EPNs proved to be successful for reducing the populations of some fruit flies with up to 85%at concentrations not less than 100 infective juveniles(IJs)/cm^2 of soil.However,the field applications of commercial EPNs have been recommended to be 2.5-5 x 10^9 IJs/ha(25-50 IJs/cm^2 of soil).

The Use of RNA Interference in Enhancing Plant Resistance against Nematodes

Plant-parasitic nematodes caused severe yield loss in major crops all over the world.The most wild-used strategies to combat the nematodes is the chamical nematicides,but the overuse of synthetic nematicides threaten sustainable agriculture development.Other strategies,like resistance cultivars and crop rotation,have limited efficiency.Thus,the utilization of molecular biotechnology like RNA interference(RNAi)would be one of the alternative ways to enhance plant resistance against nematodes.RNAi has already used as a tool for gene functional analysis in a wide range of species,especially in the non-parasitic nematode,Caenorhabtidis elegans.In plant-parasitic nematodes,RNAi is induced by soaking nematodes with double strand RNA(dsRNA)solution mixed with neurostimulants,which is called in vitro RNAi delivery method.In another way around,in planta RNAi method,which is Host-mediated RNAi approach also showed a great success in conferring the resistance against root-knock nematodes.Two main advantages of RNAi-based transgenics are RNAi technology do not produce any functional foreign proteins and it target organisms in a sequence-specific way.Even though the development of RNAi-based transgenics against plant-parasitic nematodes is still in the initial phase,it offers the prospect into a novel nematode control strategy in the future.