Genera Of Plant Parasitic Nematodes Research Articles

Plant sex and phenological stage affect interactions with rhizosphere nematode communities

ABSTRACTBackground: In dioecious plants, females and males associate differently with mycorrhizal fungi, but interactions with other rhizosphere organisms are less well studied.Aims: We investigated the effect of plant sex on rhizosphere nematode communities associated with Corema album, a dioecious shrub occurring in coastal habitats.Methods: Rhizosphere samples were collected from males and females in three populations (150 plants), during fruiting and flowering. Nematode communities were characterised and compared between plant sexes through statistical analyses of the abundance of trophic groups, plant parasitic nematode (PPN) genera and ecological indices.Results: Free-living nematodes showed no statistically significant differences owing to plant sex. Conversely, PPN community composition was significantly different between plant sexes during fruiting but not flowering, suggesting that physiological requirements over the annual phenological cycle of the plant influence ecological interactions with the rhizosphere.Of the 13 PPN genera identified, the ectoparasitic Criconema and Hemicriconemellawere more abundant in the rhizosphere of males during fruiting, whereas the endoparasitic Meloidogyne associated more frequently with females, suggesting that plant host suitability is related to PPN feeding strategy.Conclusions: It appears that interactions of individuals of different sexes of C. album with the rhizosphere nematode community vary with phenological stage, especially for PPN.

Occurrence and prevalence of nematodes in yam fields from four community-based farming scheme locations in Ogun State, Nigeria

Nematodes is one of the major biotic constraints affecting profitable yam production throughout Nigeria. They affect yams both in the field and in storage thus threatening food security and economic deprivation to growers and their households. The research work identified the types, frequency and population of nematodes associated with Dioscorea rotundata grown by the Farm Practical Year Programme Trainees of the Federal University of Agriculture, Abeokuta in four Community-based Farming Scheme locations, namely Isaga-Orile, Iwoye-Ketu, Ode-Lemo and Odogbolu in Ogun State. Soil samples were taken and assayed for nematode populations. Results showed that 26 Nematodes genera were found in the four locations ranging from 11 to 3201 individuals/250 g soil. Genera of plant-parasitic nematodes recovered included Scutellonema, Meloidogyne, Pratylenchus, Paratylenchulus, Trichodorus, Helicotylenchus, Hoplolaimus, Tylenchorhynchus, Aphelenchus, Xiphinema, Ditylenchus, Rotylenchulus, Rotylenchus and Aphelenchoides while the free-living nematode genera found included Aulolaimoides, Cephalobus, Cylindrocorpus, Lotonchus, Monhystera, Oncholaimus, Paraplectonema, Prismatolaimus, Dorylaimus, Tylencholaimellus, Tylencholaimus, and Tyleptus. Out of the twenty-six nematodes encountered, Meloidogyne spp. Scutellonema spp. and Pratylenchus spp. were mostly encountered in the soil and the only three recovered from the tubers which mean that these three nematodes are of economic importance to yam production. Farmers are therefore advised to go into yam production with management measure of nematodes putting the three key nematodes in mind, in order to avoid yield loss.Keywords: White guinea yam; Meloidogyne spp.; Scutellonema spp.; Pratylenchus spp.

Plant-parasitic nematodes associated with organic and conventional vegetable farms in Laguna Province, Philippines

A survey was conducted to determine the prevalence of plant-parasitic nematodes associated with vegetable crops grown in organic and conventional farms in Laguna province, Philippines. Seven nematode genera (Aphelenchoides, Aphelenchus, Helicotylenchus, Meloidogyne, Pratylenchus, Rotylenchulus and Tylenchus) from organic farms and five (all those found in organic except Aphelenchoides and Pratylenchus) from conventional farms were isolated using modified Baermann tray method. Among these taxa, Meloidogyne and Rotylenchulus were the most prevalent and abundant in both organic and conventional farms. Pratylenchus was also prevalent in organic farms and Helicotylenchus in conventional farms. Rotylenchulus was found associated with every vegetable in both organic and conventional farms and Meloidogyne was also observed with all vegetables in conventional farms. Organic vegetable farms were more diverse in terms of genera of plant-parasitic nematodes than conventional farms.

Control and Management of Plant-Parasitic Nematodes in Integrated Production of Garden Strawberries (Fragaria×Ananassa Duchesne Ex Rozier)

AbstractArable soils are one of the most valuable natural resources and their long-term sustainable management is a determining factor in the integrated production of strawberries. It is well known that the current large-fruited garden strawberry (Fragaria × ananassa Duchesne ex Rozier) cultivars are more susceptible to many species of plant-parasitic nematodes and other plant pathogens. The aim of this study was to evaluate the effects of some cultural practices as potential methods for control of nematodes in the integrated production of strawberries. The investigation of the nematode populations was carried out in the region of western Balkan Mountains in Bulgaria (43°33'22.3"N 22°47'03.4"E), with cultivar ‘Maya’. In the surveyed area, plant protection products were applied under an approved scheme complying with the requirements for integrated fruit production (IOBC, IFP). Nematode populations were identified and classified to trophic level. The following genera of plant-parasitic nematodes were identified: Pratylenchus crenatus, P. neglectus, P. thornei, Tylenchorhynchus sp., and Paratylenchus spp. The density and species composition of plant parasitic nematodes were significantly reduced at the end of the study period comparing to the beginning of the study. From the results, it is clear that the integrated production can be defined as an economically feasible production of high quality fruits, giving priority to environmentally safe methods of pest control.

Nematodos fitoparásitos asociados al cultivo de piña (Ananas comosus) en Amazonas, Perú

The present study aimed to identify the main genera of plant parasitic nematodes associated with the pineapple crop (Ananas comosus) and their respective percentages of occurrence (frequencies) and average population densities. Soil and root samples were collected from twenty eight pineapple fields in the province of Rodriguez de Mendoza, located between 1796 and 1936 meters above sea level. Sample were processed in duplicate by the method of modified Baerman on tray, using 50 cc. of soil and 5 g of root. In soil samples, eleven genera of plant parasitic nematodes associated with pineapple crop were identified. The genus Helicotylenchus was found in all evaluated fields and presented higher population averages in soil and root samples (24.5 and 3.9 respectively). This work is the first study to identify plant parasitic nematodes in pineapple cultivation in the department of Amazonas and provides us with information that will establish future strategies for controlling these plant parasitic nematodes.

Free-Living Plant-Parasitic Nematodes do not Affect the Efficiency of Seed Tuber Fungicide Treatment against Rhizoctonia solani

Stem canker on germinating potato sprouts is often caused by seed-borne inoculum of the fungus Rhizoctonia solani. However, high amounts of free-living plant-parasitic nematodes have been found in field patches of potato plants with stem canker. Fungicide treatment of the seed tubers can be used to avoid stem canker caused by seed-borne inoculum but it is unknown if nematodes can affect this. To investigate whether free-living plant-parasitic nematodes, the root-lesion nematode Pratylenchus penetrans or a combination of several plant-parasitic nematode genera in a full nematode community, may have a negative effect on the fungicide seed treatment, a pot experiment with seed tubers inoculated with R. solani, half of which were treated with fungicides, was performed. The seed-borne inoculum caused severe damage to the plants, while no fungal damages were observed on the fungicide treated plants. This shows that the nematodes did not affect the fungicide treatment. The probability of black scurf decreased in treatments with a full nematode community, which may be due to the action of fungal-feeding nematodes.

Incidence and population of plant parasitic nematodes in green amaranth (Amaranthus hybridus L.) (Caryophyllales: Amaranthaceae) from three selected areas in Dutsin-Ma Town, Katsina State, Nigeria

An experiment was conducted in the Department of Biological Sciences, Federal University Dutsinma, Katsina State Nigeria, between May to August, 2016. A survey was carried out from three farm areas around Dutsin-Ma Metropolis to investigate and determine the incidence and population of plant parasitic nematodes of green amaranth (Amaranthus hybridus L.). A total of 240 soil root samples from an infested A. hybridus were taken 10 cm deep from the rhizosphere of the green amaranth plant. The samples were extracted using Cobb-Seiving and Decanting Method. From the supernatants residue, a total of nine genera of plant parasitic nematodes were identified, with 6 genera in Farm 1, 8 genera in Farm 2, and 5 genera in Farm 3. The genera Meloidogyne (23.33%), has the highest incidence followed by Xiphinema (14.58%), Pratylenchus (13.33%), Heterodera (10.83%), Paratrichodorus (10.83%), Aphelenchoides (9.16%), Helicotylenchus (8.33%), Tylenchorhychus (7.92%) and Longidorus (7.08%). Data on incidence from root galling was also taken from the examined samples, with Farm 2 having highest value for moderate root gall damage. It has been deduced from the result that most of the plants with high parasitic load of the nematodes exhibit root gall, chlorotic and perforated leaves, darker weak stems, stunted growth and poor flowering. This results shows that there is a widespread distribution of plant parasitic nematodes against the A. hybridus plants in the surveyed areas (Farm 1, 2 and 3). The presence of these parasitic nematodes, even at low populations in the soil is not significant (P > 0.05) in comparison with all the root samples from the three selected farms (F = 0.12, P = 0.8803). The parasitic nematode population built up could eventually result in great reduction of the crop yield. Establishing efficient research control on the damaging potentials of these parasitic nematodes as against this vegetable crop; hence, awareness programs ought to be created for researchers, farmers and lay men.

Isolation of Plant Parasitic Nematodes in Pear Orchard at Chhaimale (Pharping) VDC of Kathmandu

Plant-parasitic nematodes are of considerable importance worldwide and their devastating effects on crops have major economic and social impacts. They depend on plants and feed on all parts of the plant including roots, stems, leaves, flowers and seeds. The majority of species of plant-parasitic nematodes live on or around plant roots. Nematode damage of the plant’s root system also provides an opportunity for other plant pathogens to invade the root and thus further weakens the plant. A study was carried out to isolate and identify different genera of plant parasitic nematodes from the rhizospheres of pear plants in one of the major pear producing area of Nepal, Chhaimale VDC of Kathmandu district.
 Altogether seven species of root nematodes were isolated from soil samples collected: Tylenchorhynchus sp., Longidorus sp., Helicotylenchus sp., Hoplolaimus sp., Aphelenchus sp., Mononchus sp. and Diplogaster sp. Among isolated species of nematodes Tylenchorhynchus sp., Longidorus sp., Helicotylenchus sp., and Hoplolaimus sp. are parasitic, Aphelenchus sp. is mycophagic and Mononchus sp. and Diplogaster sp. are predatory in nature. Number of nematodes were not significantly different in different season and at different locations.

Identifikasi Nematoda Parasit pada Tanaman Wortel di Dataran Tinggi Malino, Sulawesi Selatan Berdasarkan pada Ciri Morfologi dan Morfometrik

Plant-parasitic nematodes are important pests on carrot ( Daucus carota ) in Malino Highland. This research aimed to identify plant-parasitic nematodes on carrot. The identification was carried out based on the morphological and morphometric characters of second-stage juveniles that were extracted from soil samples. Nematodes were extracted using the flotation-centrifugation technique. Morphometric measurement included body length, stylet length, esophagus length from the basal knob to the esophagus end, tail length from the posterior end to the anus, anterior diameter, maximum body diameter, and posterior diameter. Three genera of plant-parasitic nematodes were identified as Meloidogyne , Rotylenchulus , and Pratylenchus .

Incidence and management of plant parasitic nematodes under continuous vegetable production in a rainforest agroecology in Nigeria

SummaryField studies were conducted in 2012 and 2013 in the tropical rainforest zone of Nigeria to investigate the effects of a composted, pelletised organo-mineral fertiliser applied as an organic amendment at 5 metric tonnes (MT) ha-1 or at 10 MT ha-1 in four replications, on soil population densities of five genera of plant-parasitic nematodes and on crop yields of Telfairia occidentalis (fluted pumpkin). The experimental field was naturally infested with Meloidogyne incognita, Tylenchus spp., Helicotylenchus spp., Hirschmaniella spp., and Longidorus spp. The compost was applied as an amendment to soil planted with T. occidentalis 3 weeks after seedling emergence. At the end of both annual experiments, the addition of compost as a soil amendment resulted in 16.25 - 65.75% reductions in the populations of all five genera of plant-parasitic nematodes compared to an increase in each nematode population in the untreated control plots. There was also a higher crop yield of T. occidentalis in all eight treated plots compared to the control plots. Compost applied at 10 MT ha-1 reduced the soil populations of all nematode species significantly, with correspondingly higher yields of the crop compared to 5 MT compost ha-1 in both years of study. Correlation analysis showed that the population density of each nematode species had a negative effect on the cumulative leaf biomass (fresh weight) of the test crop. The results of this study suggest that nematodes constrained the production of T. occidentalis under continuous cropping and that a composted, pelletised organo-mineral fertiliser, applied as a soil amendment at 10 MT ha-1, suppressed soil populations of all five nematodes significantly and increased yields of T. occidentalis by 109 - 366% compared to the untreated control plots.

COI haplotype groups in Mesocriconema (Nematoda: Criconematidae) and their morphospecies associations.

Without applying an a priori bias for species boundaries, specimen identities in the plant-parasitic nematode genus Mesocriconema were evaluated by examining mitochondrial COI nucleotide sequences, morphology, and biogeography. A total of 242 specimens that morphologically conformed to the genus were individually photographed, measured, and amplified by a PCR primer set to preserve the linkage between specimen morphology and a specific DNA barcode sequence. Specimens were extracted from soil samples representing 45 locations across 23 ecoregions in North America. Dendrograms constructed by neighbor-joining, maximum likelihood, and Bayesian Inference using a 721-bp COI barcode were used to group COI haplotypes. Each tree-building approach resulted in 24 major haplotype groups within the dataset. The distinctiveness of these groups was evaluated by node support, genetic distance, absence of intermediates, and several measures of distinctiveness included in software used for the exploration of species boundaries. Five of the 24 COI haplotype groups corresponded to morphologically characterized, Linnaean species. Morphospecies conforming to M. discus, Discocriconemella inarata, M. rusticum, M. onoense, and M. kirjanovae were represented by groups composed of multiple closely related or identical COI haplotypes. In other cases, morphospecies names could be equally applied to multiple haplotype groups that were genetically distant from each other. Identification based on morphology alone resulted in M. curvatum and M. ornatum species designations applied to seven and three groups, respectively. Morphological characters typically used for species level identification were demonstrably variable within haplotype groups, suggesting caution in assigning species names based on published compendia that solely consider morphological characters. Morphospecies classified as M. xenoplax formed a monophyletic group composed of seven genetically distinct COI subgroups. The species Discocriconemella inarata is transferred to Mesocriconema inaratum based on its phylogenetic position on the COI tree as well as previous phylogenetic analyses using 18S, ITS1, and cytochrome b nucleotide sequences. This study indicates that some of the species considered cosmopolitan in their distribution are actually multispecies polyphyletic groupings and an accurate assessment of Mesocriconema species distributions will benefit from molecular determination of haplotype relationships. The groups revealed by COI analysis should provide a useful framework for the evaluation of additional Mesocriconema species and will improve the reliability of designating taxonomic units in studies of nematode biodiversity.

First Report of Plant-Parasitic Nematodes on Seashore Paspalum (Paspalum vaginatum) in Barbados.

Seashore paspalum (Paspalum vaginatum Swartz) is a warm-season perennial turfgrass commonly used for golf courses that are grown in saline environments or using saline water for irrigation. However, seashore paspalum is also grown in non-saline conditions due to its low fertilizer and water requirements (2). In Barbados, on a newly constructed golf course, seashore paspalum 'Sea Isle Supreme' sprigs were imported from Georgia (United States) and were planted over 2006 and 2007 on greens, tees, fairways, and rough. Golf greens were constructed following the United States Golf Association Green Section (Far Hills, NJ) putting green guidelines. Tees and fairways were constructed using native soil. Two years after the grow-in, the putting greens began to exhibit irregular chlorotic patches, followed by gradual thinning and decline of turfgrass stand density in those areas. Additionally, turfgrass roots sampled from those symptomatic patches appeared to be abbreviated compared to non-symptomatic areas of the greens. A survey was conducted in May 2013 to determine if plant-parasitic nematodes were present coinciding with the observed symptoms, which were similar to those described in a previous report (3). Consequently, two samples were collected from each green with a total of four greens sampled. Each sample consisted of 20 soil cores (15 cm depth × 1.2 cm in diameter) from either areas of the greens showing symptoms or from non-symptomatic areas. Nematodes were extracted from 100 cm3 soil samples using a modified centrifugal-sugar flotation technique (4). No plant parasitic nematodes were present in any of the samples from the non-symptomatic areas. Three genera of plant parasitic nematodes were found in all the samples from the symptomatic areas: Helicotylenchus. Mesocriconema, and Pratylenchus. Nematode populations of these genera averaged 30, 60, and 200 nematodes per 100 cm3, respectively. Populations of the genera Helicotylenchus and Mesocriconema were below the action threshold levels for seashore paspalum used by the University of Florida Nematode Assay Laboratory (1). Currently, no threshold exists for Pratylenchus for seashore paspalum. Conversely, the genera Helicotylenchus. Mesocriconema, and Pratylenchus were found associated with the irregular chlorotic patches but not with the non-symptomatic areas. To our knowledge, this is the first report of plant parasitic nematodes associated with seashore paspalum maintained as putting greens in Barbados.

The complete mitochondrial genome of Meloidogyne graminicola (Tylenchina): a unique gene arrangement and its phylogenetic implications.

Meloidogyne graminicola is one of the most economically important plant parasitic-nematodes (PPNs). In the present study, we determined the complete mitochondrial (mt) DNA genome sequence of this plant pathogen. Compared with other PPNs genera, this genome (19,589 bp) is only slightly smaller than that of Pratylenchus vulnus (21,656 bp). The nucleotide composition of the whole mtDNA sequence of M. graminicola is significantly biased toward A and T, with T being the most favored nucleotide and C being the least favored. The A+T content of the entire genome is 83.51%. The mt genome of M. graminicola contains 36 genes (lacking atp8) that are transcribed in the same direction. The gene arrangement of the mt genome of M. graminicola is unique. A total of 21 out of 22 tRNAs possess a DHU loop only, while tRNASer(AGN) lacks a DHU loop. The two large noncoding regions (2,031 bp and 5,063 bp) are disrupted by tRNASer(UCN). Phylogenetic analysis based on concatenated amino acid sequences of 12 protein-coding genes support the monophylies of the three orders Rhabditida, Mermithida and Trichinellida, the suborder Rhabditina and the three infraorders Spiruromorpha, Oxyuridomorpha and Ascaridomorpha, but do not support the monophylies of the two suborders Spirurina and Tylenchina, and the three infraorders Rhabditomorpha, Panagrolaimomorpha and Tylenchomorpha. The four Tylenchomorpha species including M. graminicola, P. vulnus, H. glycines and R. similis from the superfamily Tylenchoidea are placed within a well-supported monophyletic clade, but far from the other two Tylenchomorpha species B. xylophilus and B. mucronatus of Aphelenchoidea. In the clade of Tylenchoidea, M. graminicola is sister to P. vulnus, and H. glycines is sister to R. similis, which suggests root-knot nematodes has a closer relationship to Pratylenchidae nematodes than to cyst nematodes.

Diagnóstico y dinámica poblacional de nematodos fitoparásitos en dos sistemas de cultivos de piña en Costa Rica

<p class="p1">La presente investigación determinó la presencia de géneros, densidad de población y dinámica poblacional de nematodos fitoparásitos en plantaciones de piña (<em>Ananas comosus, </em>var. <em>comosus</em>) en dos sistemas de cultivos en Costa Rica, período 2006-2008.</p> <p class="p1">El estudio comprendió un diagnóstico a nivel de suelo y raíz en plantas de dos a doce meses de edad que permitiera la determinación de la dinámica poblacional de los nematodos en los diferentes lotes cultivados de piña, durante el lapso de tiempo señalado en sistemas de cultivos convencionales y orgánicos en las regiones Huetar Norte y Huetar Atlántica de Costa Rica. Se seleccionaron lotes comerciales, los cuales fueron muestreados una vez al mes durante febrero a diciembre en los años 2006-2008. Se caracterizaron y cuantificaron los géneros de nematodos encontrados.</p> <p class="p1">El diagnóstico permitió la identificación de siete géneros a nivel de suelo: <em>Helicotylenchus </em>spp., <em>Meloidogyne </em>spp., <em>Pratylenchus </em>spp., <em>Tylenchus</em>, <em>Tylenchorhychus</em>, nematodos depredadores y de vida libre, donde el género <em>Helicotylenchus </em>spp. el que se indentificó con más frecuencia. La mayor población de nematodos fitoparásitos fue observada a nivel de suelo y correspondió a los géneros <em>Pratylenchus </em>spp. y <em>Helicotylenchus </em>spp.</p> <p class="p1">Los nematodos más frecuentemente observados en raíces de plantas de piña bajo técnicas orgánicas fueron: <em>Criconemella </em>spp., <em>Helicotylenchus </em>spp., <em>Pratylenchus </em>spp.; en el suelo se presentaron <em>Helicotylenchus </em>spp., y <em>Pratylenchus </em>spp., con frecuencias del 100%. En raíz y suelo de plantas de piña bajo técnicas convencionales el género <em>Helicotylenchus </em>spp. ,fue el más frecuente. El género <em>Pratylenchus </em>spp. presentó la densidad poblacional promedio más alta en la raíz en sistemas orgánicos y convencionales con 1.009,83 y 1.075,22 ind/100 g de raíz, respectivamente.</p> <p class="p1">En las áreas de manejo orgánico se presentó una mayor diversidad de géneros de nematodos en la raíz de la piña, los nueve géneros fitoparásitos que se observaron fueron: <em>Pratylenchus </em>spp., <em>Helicotylenchus </em>spp., <em>Meloidogyne </em>spp., <em>Haplolaimus </em>spp., <em>Tylenchus </em>spp., <em>Criconemella </em>spp. y <em>Xiphinema </em>spp. y nematodos de vida libre, en comparación con muestras de raíz de plantas con manejo convencional donde se presentaron seis géneros fitoparásitos (<em>Pratylenchus </em>spp., <em>Helicotylenchus </em>spp., <em>Nacobus </em>spp., <em>Tylenchus </em>spp., <em>Meloidogyne </em>spp.,<em>Criconemella </em>spp.) y nematodos de Vida Libre.</p> <p class="p1">A nivel de raíces, los géneros de nematodos identificados fueron cinco: <em>Helicotylenchus </em>spp., <em>Meloidogyne </em>spp.<em>, Pratylenchus </em>spp., <em>Rotylenchus </em>spp. y nematodos de vida libre. La mayor población de nematodos fitoparásitos observada a nivel de raíz corresponde a los géneros Helicotylenchus spp. con y <em>Pratylenchus </em>spp.</p> <p class="p1">Con manejo convencional se presentaron siete géneros de nematodos fitoparásitos (<em>Pratylenchus </em>spp., <em>Helicotylenchus </em>spp., <em>Tylenchus </em>spp., <em>Meloidogyne </em>spp., <em>Criconemella </em>spp., <em>Haplolaimus </em>spp. y <em>Tylenchorhynchus </em>spp. y nematodos de vida libre, mientras que en suelo de plantas cultivado con manejo orgánico se presentaron seis géneros fitoparásitos <em>Pratylenchus </em>spp., <em>Helicotylenchus </em>spp., <em>Tylenchus </em>spp., <em>Meloidogyne </em>spp., <em>Criconemella </em>spp. y <em>Rotylenchus </em>spp. y nematodos de Vida libre.</p>

Principales géneros de nematodos fitoparásitos asociados a plátano y piña en las regiones Huetar Norte y Huetar Atlántica de Costa Rica

<p class="p1">Durante esta investigación se muestrearon periódicamente sistemas productivos de piña y plátano en la Región Huetar Norte (RHN) y de piña en la Región Huetar Atlántica (RHA), con el objetivo de identificar los géneros de nematodos fitoparásitos asociados a estos cultivos, su frecuencia y densidad de población. También se exploró la dinámica poblacional de los principales géneros. En el cultivo de piña, los nematodos con mayor densidad de población y más frecuentemente detectados en ambas regiones estudiadas fueron <em>Pratylenchus </em>y <em>Helicotylenchus</em>. Las poblaciones de estos nematodos fueron fluctuantes en la RHN y con un crecimiento que puede explicarse mediante funciones polinómicas en la RHA. En el caso del plátano, los nematodos con mayor densidad de población y más frecuentemente detectados fueron <em>Radopholus similis</em>, <em>Pratylenchus </em>y <em>Meloidogyne. </em>Las poblaciones de estos nematodos también mostraron fluctuaciones en el tiempo.</p>

Plant parasitic nematodes associated with ornamental plant Pseuderanthemum atropurpureum in Aligarh district of western Uttar Pradesh

A survey was conducted to determine the nematodes associated with the soil, substratum and roots of the ornamental plant, Pseuderanthemum atropurpureum, grown in the Aligarh district of western Uttar Pradesh, India. Ten genera of plant parasitic nematodes, viz. Meloidogyne spp., Helicotylenchus sp., Hemicriconemoides sp., Hoplolaimus sp., Xiphinema sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp., were isolated from 345 soil samples collected from 15 different localities. Our study indicates that among the 10 genera of the plant parasitic nematodes, Meloidogyne spp. was widely spread in all the examined localities of Aligarh district, except at Khair. It was observed that the population density and diversity of nematodes in all the soil samples was not uniform. Meloidogyne spp. showed the highest absolute frequency and relative frequency followed by Helicotylenchus sp., Hemicriconemoides sp., Xiphinema sp., Hoplolaimus sp., Pratylenchus sp., Trichodorus sp., Tylenchorhynchus sp., Aphelenchoides sp. and Rotylenchus sp. Since no records are available in the literature related to the association of root-knot nematode in P. atropurpureum, it is worthy to note that this study may be considered as a new hope towards further study of the interaction between the root-knot nematode and ornamental plant P. atropurpureum if any.

Nematodes associated with three indigenous leafy vegetables commonly grown in inland valley ecology in Nigeria

Field study was conducted between January and June 2011 to determine the plant-parasitic and non-parasitic nematodes associated with three indigenous leafy vegetables (Amaranthus viridis, Celosia argentea and Corchorus olitorius) commonly grown in inland valley by farm practical year students’ trainees at the Federal University of Agriculture, Abeokuta. The 1.76-ha land was laid out in randomised complete block design with four replicates. Six soil cores were taken per replicate and bulked. Two sub-samples weighing 250 g per replicate were assayed for nematodes using WhiteHead and Hemming Tray method. Results revealed the presence of five genera of plant-parasitic nematodes, namely Tylenchus, Pratylenchus, Helicotylenchus, Meloidogyne and Rotylenchulus. Populations of Tylenchus differed statistically (p = 0.05) from all others in C. olitorius. The non-parasitic nematodes varied significantly (p = 0.05) among the vegetable types. Galls incited by Meloidogyne spp. were more (p = 0.05) in C. argentea and C. olitorius than A. viridis.

Influence of cover crops and tillage systems on nematode populations in a maize-cover crop intercrop

Cropping systems affect the distribution/diversity of soil microorganisms, including soilborne pathogens. In order to examine the effect of the cropping systems on soil nematodes, maize (Zea mays) was intercropped with different cover crops [Glycine max (GM), Macrotyloma uniflorum (MU), Centrosema pascuorum (CP), Cucurbita maxima (CM) and a control experiment with no cover crop (NC)] under different tillage systems [no till, reduced tillage and conventional tillage] to evaluate the effect of the various treatments on nematode population. The treatments were arranged in a split-plot design with three replications each. Tillage was the main treatment while cover crops were applied to subtreatment. In all, nematodes belonging to twenty-two (22) plant parasitic nematode genera were identified. While most of the genera were identified on all the treatments, the interaction of tillage systems and cover crops had significant effect on the population of Xiphinema and Trichodorus only, showing the nullifying effect of some tillage practices on the other nematodes which were significant under crops as only treatments inter alia. This information could be used in nematode management when integrated management systems are being considered for such intercrop mixtures.

English

A survey was conducted to determine the diversity and distribution of soil nematodes associated with tea in Ngere tea catchment area in Kenya. Soil samples were collected from six electoral zones of Ngere factory in Gatanga division Thika district, Murang’a County, Kenya. Nematodes were extracted and recovered from soil samples using a modified Baermann funnel method and identified under a light microscope based on their morphological characters. They were also classified according to their feeding habits. Ten genera belonging to, bacteriovores, fungivores, and omnivores were identified. Fungal feeding and parasitic nematodes were the most widely distributed trophic groups across the tea catchment area. Plant-parasitic nematodes recovered included Pratylenchus spp., Helicotylenchus spp., Rotylenchus spp., Aphelenchus spp., Rotylenchulus spp., and Xiphinema spp. Tylenchus spp was the most frequently occurring species in the soil (60.47%) where the population was 429 followed by Pratylenchus spp with 55.81% frequency rating and a population of 404 whileAphelenchus spp had frequency rating of 48.84% and a population of 530. Ditylenchus and Rotylenchus spp had the lowest frequency rating of 6.98 and 4.65%, respectively, while Rotylenchus spp had the lowest population of 33. Six genera of plant parasitic nematodes were encountered in the collected soil samples. These plant parasitic nematodes were identified as Pratylenchus spp., Aphelenchus spp., Helicotylenchusspp., Tylenchus spp., Xiphinema spp and Duotylenchus spp. Pratylenchus spp. and Tylenchus spp. were the most frequently occurring species in the soil (50%) with a population of 25 and 21, respectively, which was followed by Helicotylenchus spp., Aphelenchus spp., Xiphinema spp., and Duotylenchus spp. with 16.67% frequency rating and a population of 10, 10, 3 and 20, respectively. Pratylenchus spp had the highest nematode population of 28.09% and the lowest nematode population was Xiphinema spp., having a population of 3.37%. The correlation between nematode population counts and total organic carbon content was not significant at P≥0.05.       Key words: Tea, frequency, nematode population, carbon content, Pratylenchus spp., Helicotylenchus spp.,Rotylenchus spp., Aphelenchus spp., Rotylenchulus spp., and Xiphinema spp.

Influence of different fertilization regimes on plant-parasitic nematodes in the black soil region of Northeast China

Plant-parasitic nematodes can cause serious plant diseases and adversely affect crop production. We investigated the temporal and vertical dynamics of plant-parasitic nematodes in northeast China to determine if long-term fertilizer application suppresses the population of plant-parasitic nematodes and influences their vertical distribution in the black soil region. The long-term fertilizer application lasted for 14 years, and included three treatments: pig manure combined with chemical fertilizer (MCF), chemical fertilizer (urea and ammonium phosphate, CF), and no fertilizer (NF). A 3-year corn-wheat-soybean rotation was grown on the field site, soil samples were obtained in the corn phase and nematodes were extracted, identified and counted. Six plant-parasitic nematode genera with relative abundance over 0.1% were found in this study. Heterodera was the dominant genus in all three fertilizer treatments, and its relative abundance was highest in NF (45.4%) and lowest in MCF (32.8%). Fertilizer application had a significant effect on abundance of total soil nematodes but not on either plant-parasitic nematodes or Heterodera. Significant differences in the abundance of total soil nematodes, plant-parasitic nematodes and Heterodera were observed among soil depths and interaction of fertilizer × soil depth. Total soil nematodes were mainly distributed in the 0–20 cm soil layer, and plant-parasitic nematodes and Heterodera were mostly distributed in the 10–30 cm soil layer. Fertilizer application did not show a significant effect on plant-parasitic nematodes or Heterodera at any of the sampling depths from 0 to 80 cm. The results indicated that fertilizer has no effective control on plant-parasitic nematodes when dominant genera and their respective plant hosts exist in relatively high abundance.