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.

Influence of biochar on growth performances,yield of root and tuber crops and controlling plant-parasitic nematodes

Root and tuber crops are important sources of food and provide income for millions of people worldwide besides an observed high demand for organically produced harvests.Hence,recent attention has been given to utilizing biochar,a carbon-rich material produced from the pyrolysis of organic materials,which improves soil structure,water-holding capacity,and nutrient availability,as an amendment to produce organic root and tuber crops.These effects are caused by the formation of organic coatings on the surface of biochar,which decreases hydrophobicity and increases the ability to retain nutrients,acting as a slow-release mechanism delivering nutrients dependent on plant physiological requirements.However,comprehensive studies on the impact of biochar application on root and tuber crop growth,productivity,and effectiveness in eliminating soil parasites have not been extensively studied.Thus,the purpose of this review is to explore the use of biochar and biochar-based soil amendments and their potential applications for improving the growth,yield,and efficacy of controlling parasitic nematodes in a wide range of root crops.Most of the studies have investigated the effects of biochar on cassava,sweet potatoes,and minor root crops such as ginger and turmeric.It has been observed that biochar application rates(5-20 t ha^(−1))increase the vine length and the number of leaves,tubers,and tuber weight.The addition of biochar demonstrates the ability to control plant-parasitic nematodes in a rate-dependent manner.While biochar has shown promising results in improving crop growth and yield of limited root and tuber crops based on a few biochar types,ample opportunities are around to evaluate the influence of biochar produced in different temperatures,feedstock,modifications and controlling parasitic nematodes.

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.

Biofumigation: An alternative strategy for the control of plant parasitic nematodes

Plant-parasitic nematodes wreak havoc on the yield and quality of crops worldwide.Damage from these pests is estimated to exceed US$100 bllion annually but is likely higher due to misdiagnosis.Nematode damage may be catastrophic,but historically the solution has been damaging as well.Use of the synthetic nematicide methyl bromide(MBr)poses risks to the environment and to human health.Biofumigation,the use of plant material and naturally produced compounds to control pests,is an increasingly feasible method of pest management.The process acts through the growth or incorporation of plant material into the soil,that,over the course of its degradation,releases glucosinolates that break down into nematotoxic isothiocyanates.These secondary plant metabolites exist naturally in commonly grown plants,most of which belong to the Brassicaceae family.Research endeavors have increasingly explored the potential of biofumigation.The reaction of target pests,the selection of biofumigant,and ideal environments for efficacy continue to be evaluated.This review seeks to provide a cost and benefit assessment of the status of biofumigation for the control of plant-parasitic nematodes as an alternative to conventional methyl bromide usage.

Advance of entomopathogenic nematodes

This paper summarized the history and present condition of studying and utilizing entomopathogenic nematodes at home and abroad, expounded its taxonomy, life cycle and the mechanism with symbiotic bacteria killing host insect. Taxonomy, mycelial form, pathogenic function and anti-bacteria function of symbiotic bacteria were introduced. Production and utilization of entomopathogenic nematodes, the characteristic genetic improvement by use of biological engineering technology, as well as the existing problem and applying foreground were also discussed.

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.

One new species and two new records of free-living marine nematodes from the Huanghai Sea

One new species of free-living marine nematode of the genus Curvolaimus, Curvolaimus filiformis sp. nov. from the Huanghai Sea is described and illustrated. This new species is characterized by the buccal cavity teeth, large amphids and two ventral seta at the conical part of tail. Meanwhile, two new records of genus Halalaimus, Halalaimus longicaudatus and H. isaitshikovi are fast reported in China. Types are deposited in the College of Marine Life Sciences, Ocean University of China.

Studies on the species composition and biodiversity of free-living marine nematodes in the southern Huanghai Sea

Free-living marine nematodes were sampled and studied at a grid of 22 stations （from 32°29.35′ to 37°0.56′N, 122°0.37′ to 125°1.16′ E） in the southern Huanghai Sea in January 2003. Nematode abundance varied from 50.5 to 127.2 ind./cm^2 [（83.1 ±24.7） ind./cm^2] at different stations, 80.1% of the total nematodes were in the surface layer （0-2 cm） of sediments. Two hundred and twenty-three species or taxa of marine nematodes belonging to 145 genera, 32 families and four orders were identified and first recorded in the Huanghai Sea. The common dominant species were Dorylaimopsis rabalaisi, Terschellingia longicaudata, Sphaerolaimus bolticus, Metalinhomoeus longiseta, Quadricoma scanica, Prochromadorella sp., Paramonohystera riemanni, Marylynnia sp. 1, Vasostoma spircaum, Halalaimus spp., Pierrickia sp. 1 and Promonhystera faber. Nematode diversity was correlated with sediment granularity. Pearson correlation analysis showed that Shannon-Wiener index had highly significant positive correlation with a sand content and negative correlation with a silt-clay content （P〈0.01）; species richness index （d） had significant positive correlation with the sand content and negative correlation with the silt-clay content （P〈0.05）. The diversity of the southern Huanghai Sea was lower than that in the center of Bohai Sea, but the dominance was higher.

One new species of free-living marine nematodes (Enoplida,Anticomidae,Cephalanticoma) from the Huanghai Sea

One new species of free-living marine nematodes Cephalanticomafilicaudata sp. nov. from the Huanghai Sea, China is described and illustrated. Cephalanticomafilicaudata sp. nov. is characterized by well developed cephalic capsule, three teeth at the anterior of oesophagus, excretory pore opens posterior to cervical setae, only two cervical setae per file, body length longer than 5 200 μm, tail long and no ventral-lateral seta between the supplement and the cloacal opening. Types are deposited in the College of Marine Life Sciences, Ocean University of China.

Impact of Soil Fumigation Practices on Soil Nematodes and Microbial Biomass

This study was designed to understand the impact of methyl bromide (MB) (CH3Br) and its alternatives on both free-living and root-knot nematodes in the soil. A randomized complete block experiment with six treatments and 4 replicates (each replicate in a separate greenhouse) was established in Qingzhou, Shandong Province, China. In addition to MB and untreated control (CK) treatments there were four alternative soil fumigation practices including MB+virtually impermeable films (VIF), metam sodium (MS), MS +VIF and soil solarization combined with selected biological control agents (SS+BCA). Two tomato (Lycopersicum esculentum Mill.) cultivars, cv. Maofen-802 from the Xian Institute of Vegetable Science, China, and cv. AF179 Brillante from the Israeli Hazera Quality Seeds, were selected as test crops. The results indicated that Rhabditidae was the most dominant population with percentage abundance as high as 85% of the total number of identified free-living nematodes, followed by that of Cephalobidae. Methyl bromide and its alternatives except for the non-chemical SS+BCA treatment controlled the target pest, root-knot nematodes. Also, the impact of the three chemical alternatives on free-living nematode number and functional group abundance was similar to the impact associated with a typical methyl bromide application. Chemical fumigation practices, especially that with MB, significantly reduced the number of nematodes in the soil and simultaneously significantly reduced the number of nematode genera thereby reducing nematode diversity. All the four soil chemical fumigation activities decreased soil microbial biomass and had an obvious initial impact on microorganism biomass. Furthermore, both plant-parasitic and fungivore nematodes were positively correlated with soil microbial biomass.

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 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.

Response of Nematodes in a Hapli-Udic Argosol to Urea Amended with Urease and Nitrification Inhibitors

Effects of urea amended with urease and nitrification inhibitors on soil nematode communities were studied in a Hapli- Udic Argosol （Cambisol, FAO） in Liaoning Province of Northeast China. A completely random design with four treatments, i.e., conventional urea （CU）, slow-release urea amended with a liquid urease inhibitor （SRU1）, SRU1 ＋nitrification inhibitor dicyandiamide （SRU2）, and SRU1 ＋ nitrification inhibitor 3,5-dimethylpyrazole （SRU3） and four replicates were applied. Thirty-nine genera of nematodes were identified, with Cephalobus and Aphelenchus being dominant; and in all treatments, the dominant trophic group was bacterivores. In addition, during the growth period of spring wheat （Triticum aestivum L.）, soil urease activity was lower in SRUs than in CU. The numbers of total nematodes and bacterivores at wheat heading and ripening stages, and omnivores-predators at ripening stage were higher in SUR3 than in CU, SRU1 and SRU2 （P 〈 0.05）.

Occurrence,identification and phylogenetic analyses of cereal cyst nematodes(Heterodera spp.)in Turkey

Plant-parasitic nematodes are very common on cereal crops and cause economic losses via reduction in grain quality and quantity. During 2014, 83 soil samples were collected from wheat and barley fields in 21 districts of 13 provinces across five regions （CentralAnatolia, Marmara, Aegean, SoutheastAnatolia, and Black Sea Region） of Turkey. Cyst-forming nematodes were found in 66 samples （80%）, and the internal transcribed spacer （ITS） sequencing and species-specific PCR identified the species in 64 samples as Heterodera filipjevi, Heterodera latipons, and Heterodera avenae. The predominant patho- genic cereal cyst nematode was H. filipjevi, which was found in all five regions surveyed. H. avenae was only detected in Southeast Anatolia whereas H. latipons was detected in Southeast Anatolia and Central Anatolia. ITS-rDNA phylogenetic analyses showed that H. avenae isolates from China clustered with H. australis, and Turkish isolates were closely related to European and USA isolates of this species. H. filipjevi from Turkey and China were clustered closely with those from the UK, Germany, Russia, and the USA. The density of many of these populations exceeded 6r approached the maximum threshold level for economic loss. To our knowledge, this is the first report of H. filipjevi in Diyarbakir, Edirne, and Kutahya provinces, and the first report of H. avenae in DiyarbakJr Province. These results exhibit the most rigorous analysis to date on the occurrence and distribution of Heterodera spp. in Turkey＇s major wheat-producing areas, thus providing a basis for more specific resistance breeding, as well as other management practices.

Resistance of Grafted Tomato with Guozhen 1 as Stock against Root Knot Nematodes in Field

[Objective] This study aimed to study the resistance of grafted tomato with Guozhen 1 as stock against root knot nematodes. [Method] Tomato seedlings were grafted with Guozhenl （T1） and Solanum torvum （T2） as the rootstock, respectively. Self-rooted tomato seedlings were treated as the control （CK）. The resistance of tomato against root knot nematodes was compared among the three treatments. [Result] Compared with those in the T2 and CK groups, the yield of tomato in the T1 group was increased by 17 436.75 and 31 753.65 kg/hm2 respectively, the plant height was increased by 10.55 and 14.54 cm respectively （P〈0.05）, and the stem diameter was increased by 0.56 and 1.13 cm respectively （P〈0.05）. The disease indexes of root knot nematodiasis in the three treatments were 0.55, 10.42 and 45.31, respectively, and there were significant differences among them （P〈0.05）. [Conclusion] This study will provide a theoretical basis for the control of root knot nematodes in tomato by grafting.

Control of Southern Root-knot Nematodes on Tomato and Regulation of Soil Bacterial Community by Biofumigation with Zanthoxylum bungeanum Seed

Biofumigation is an environmentally friendly strategy used to control nematodes and plant diseases.The volatile oil of Zanthoxylum bungeanum has high insecticidal and antibacterial activity.However,it is not known if the seed of Z.bungeanum is a suitable material for biofumigation to control southern root-knot nematodes(SRKN)on tomato,and how it may regulate the soil bacterial community structure.We used pot experiments in the greenhouse to determine the effects of Z.bungeanum seeds on SRKN,plant growth parameters,soil physicochemical and microbial characteristics.A total of 26 volatile components,including nematicidally active substances,were identified from Z.bungeanum seeds.Z.bungeanum seed biofumigation significantly reduced the SRKN population by 88.89%and 81.55%on the 50th and 100th day after transplanting,respectively.Compared to the control,the total soluble sugar,soluble solids,soluble protein,titratable acid,root activity and the fruit yield per tomato plant increased significantly.The content of soil alkali-hydrolyzed nitrogen,available potassium and the soil enzyme activities were also significantly increased.The soil bacterial diversity and the co-occurrence network complexity were increased by Z.bungeanum seed biofumigation.Relativelymore keystone OTUs in biofumigation soil had potential plant growth-promoting capabilities.The function of Z.bungeanum seed increasing tomato production in SRKN-infected soil depends on directly killing SRKN and improving soil properties.These results indicate that Z.bungeanum seed can be used as both a nematicide and a high quality organic fertilizer in tomato production.

Five New Records of Free-living Marine Nematodes in the Yellow Sea

Five species of free-living marine nematodes are redescribed and illustrated as new records in the Yellow Sea of China. These species include one monhysterid, Campylaimus gerlachi in the family Diplopeltidae and four enoplids species, Oxystomina elongata, Oxystomina elegans, Halalaimus lutarus and Halalaimus wodjanizkii in the family Oxystominidae. Ecological and taxonomic remarks are provided and discussed in comparison with the original description. The key to all known species of the genus Campylaimus is given. Our findings have offerred the taxonomic information of nematodes to the benthic ecology and biodiversity studies of the Yellow Sea.

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.