Lance Nematode Research Articles

Prevalence of Plant-Parasitic Nematodes in Horticultural Fields of Assam Agricultural University: Jorhat Campus, India

A random survey of the horticultural crops was conducted to assess the nematode community structure in the Experimental field of Department of Horticulture, AAU, Jorhat during Rabi and Kharif season, 2022-2023. Soil and root samples, representing 200 locations were examined. Analysis of 200 soil and root samples collected from the root rhizosphere of different vegetable, fruit and ornamental crops showed the presence of root-knot nematode(Meloidogyne incognita), reniform nematode (Rotylenchulus reniformis), root-lesion nematode (Pratylenchus spp.), lance nematode (Hoplolaimus spp.), spiral nematode (Helicotylenchus spp.), stunt nematode (Tylenchorhynchus spp.) along with Criconema spp., Xiphinema spp, Longidorus spp., free-living nematodes, mycophagous nematodes and predatory nematodes. Among all the isolated plant-parasitic nematodes, root-knot nematode (Meloidogyne incognita) was found to be more abundant with prominence value of 136.7, 81.3 and 76.3 in vegetable crops, fruit crops and ornamental crops, followed by Helicotylenchus spp. and Rotylenchulus reniformis. The prominence value of reniform nematode (Rotylenchulus reniformis) was found to be 90.5, 54.1 and 54.1 in vegetable crops, fruit crops and ornamental plants respectively.

Depth distribution of plant-parasitic nematodes on bentgrass golf greens in Missouri and Indiana.

Control of plant-parasitic nematodes (PPNs) on golf putting greens with nematicides is dependent on the seasonal occurrence and depth distribution of target PPN populations. This study aimed to determine if plant-parasitic nematode populations on golf course putting greens in Missouri and Indiana peaked at a targetable depth at a specific time in the year, focusing primarily on lance (Hoplolaimus spp.) and root-knot (Meloidogyne spp.) nematodes. To elucidate species diversity in the region, rDNA from a subset of lance and root-knot nematodes was sequenced and analyzed, with additional micromorphology of a lance nematode assessed in scanning electron micrographs (SEM). Soil samples were taken to a depth of 25 cm and stratified into 5 cm increments during April, June, August and October at seven sites across Missouri, three in the Kansas City metro of Kansas in 2021 and in ten sites across Indiana in 2022. Samples were stratified in five-centimeter increments and aggregated for a total of 100 cm3 of soil at each depth for each sampling. Samples were processed using a semi-automatic elutriator followed by the sucrose-flotation method, and populations were counted using a hemocytometer and recorded. For molecular characterization, rDNA was extracted and analyzed from 31 individual lance nematodes from one site in Missouri and eight sites in Indiana, and 13 root-knot nematodes from nine sites across Indiana. A significant interaction occurred between sampling month and depth for lance and ring nematodes Missouri/KS, with both PPN populations peaking at the 0-5 cm depth during October, which is well after most targeted nematicide applications are applied. Ring nematodes in Indiana did not follow this trend and were most abundant in August at a depth of 0-5 cm. No significant interaction between depth and month occurred for lance or root-knot nematodes in Indiana, or root-knot nematodes in Missouri/KS. Hoplolaimus stephanus and H. magnistylus were the lance species identified on golf greens, and Meloidogyne naasi, M. graminicola and M. marylandi were the root-knot species identified. Scanning-electron micrographs confirmed morphological characteristics unique to H. stephanus.

Characterization of Hoplolaimus seinhorsti and Hoplolaimus pararobustus (Tylenchina: Hoplolaimidae) from banana, with phylogeny and species delineation in the genus Hoplolaimus.

The morphological and molecular characterisations of two lance nematode species isolated from the rhizosphere of banana, Hoplolaimus seinhorsti and H. pararobustus, are provided based on an integrative study that includes light and scanning electron microscopy, phylogenetic analysis and two tree-based molecular species delimitation methods (GMYC and bPTP). Nineteen new sequences were obtained, including 5 partial 18S rRNA, 6 D2-D3 of 28S rRNA, 1 ITS rRNA and 7 COI mtDNA (the first COI sequences of H. seinhorsti and H. pararobustus), and an updated morphological character comparison of 37 Hoplolaimus species is presented. The tree-based molecular species-delimitation approaches employed gave markedly differing results, and also showed remarkable discrepancies among the investigated genes, although the bPTP output was found to agree well with established morphological species delimitations. Both species-delimitation approaches did, however, provide the same output for the COI mtDNA sequences, and the COI mtDNA gene sequence was also found to correspond better to established morphological species. It is therefore recommended by this paper as representing the most suitable barcode marker for Hoplolaimus species identification. This integrative study also resulted in the corrective reassignment of 17 gene sequences that were previously unidentified or incorrectly classified, as well as concluding that H. pararobustus consists of two cryptic species.

Occurrence of the Lance Nematode Hoplolaimus stephanus Infecting Bentgrass Agrostis stolonifera in Georgia, U.S.A.

A high population of lance nematodes, Hoplolaimus spp., were found associated with creeping bentgrass (Agrostis stolonifera L.) in May 2019 in Georgia, United States. The nematode was pathogenic to bentgrass as its population increased by over threefold 180 days after inoculation under greenhouse conditions. Morphological measurements of body and stylet lengths of both mature females and males were similar to a grass population of Hoplolaimus stephanus from South Carolina. DNA sequence analyses of the D1-D3 expansion segments of the 28s gene identified the nematode as H. stephanus. The DNA sequence of the nematode was 99.7% identical to a H. stephanus isolate from South Carolina. Also, the PCR method using a species-specific primer set confirmed the identity of H. stephanus. To the best of our knowledge, this is the first report of H. stephanus Sher, 1963 infecting creeping bentgrass in Georgia.

First Genomic Resource of the Columbia Lance Nematode Hoplolaimus columbus.

The Columbia lance nematode Hoplolaimus columbus has been reported frequently from North America due to its negative impact on agricultural production. In this study, for the first time, we sequenced the whole genome of a female specimen by using whole-genome amplification and Illumina MiSeq. Data were de novo assembled to form scaffolds of 205.75 Mbp consisting of 118,374 contigs. The largest scaffold was 636,881 bp. Benchmarking Universal Single-Copy Orthologs completeness was 66.6% (eukaryotic dataset), and >8,000 unique genes were predicted by GeneMark-ES. In total, 61,855 protein sequences were predicted by AUGUSTUS, and 10,085 of them were annotated by PANNZER2 with at least one function. These data will provide valuable resources for studies focusing on pathogenicity and phylogenomics of plant-parasitic nematodes.

Molecular Diagnosis and Evolutionary Relationship Analysis Of Plant Parasitic Tea Garden Nematodes From Different Tea Estates In Sylhet Region of Bangladesh

Nematodes from plant-parasitic sources are ever-present and incidental to plant growth as well as crop production. The damage of tea gardens caused by nematode is often non-specific and easily confused with symptoms. The present study determined the parasitic and non-parasitic nematodes population in different tea gardens of the Sylhet region by their morphological and partial molecular characterization. Out of 13 tea gardens, it was observed that BTRI, Karimpur, Mathiura, and Tarapur tea garden has the highest number of parasitic and non-parasitic nematodes. After PCR amplification, DNA bands with desired amplicon size were detected by gel electrophoresis. Among thirteen soil samples, nematodes from Malnichara, Karimpur, BTRI, Mathiura , and Finlay had partially confirmed the presence of rootknot nematode (Meloidogyne spp.), root-lesion nematode (Pratylenchus brachyurus), burrowing nematode (Radopholus similis), reniform nematode (Rotylenchulus reniformis) and lance nematode (Hoplolaimus columbus) consequently based on approximately base pair of 1.7, 1.1 and 0.52 kb (different Meloidogyne spp.) 0.52, 0.52, 0.25 and 2.3 kb of specific genes. From evolutionary analysis, it might be said that Meloidogyne species are strongly related with each other making clusters except Meloidogyne natalie where this one is closely related with Hoplolaimus columbus in their evolutionary relationship as remaining others (Rotylenchulus reniformis, Radopholus similis, Pratylenchus brachyurus) are in different clusters in the same clade and this result could be confirmed after sequencing. J. Bio-Sci. 29(1): 101-109, 2021 (June)

The complete mitochondrial genome of the Columbia lance nematode, Hoplolaimus columbus, a major agricultural pathogen in North America

BackgroundThe plant-parasitic nematode Hoplolaimus columbus is a pathogen that uses a wide range of hosts and causes substantial yield loss in agricultural fields in North America. This study describes, for the first time, the complete mitochondrial genome of H. columbus from South Carolina, USA.MethodsThe mitogenome of H. columbus was assembled from Illumina 300 bp pair-end reads. It was annotated and compared to other published mitogenomes of plant-parasitic nematodes in the superfamily Tylenchoidea. The phylogenetic relationships between H. columbus and other 6 genera of plant-parasitic nematodes were examined using protein-coding genes (PCGs).ResultsThe mitogenome of H. columbus is a circular AT-rich DNA molecule 25,228 bp in length. The annotation result comprises 12 PCGs, 2 ribosomal RNA genes, and 19 transfer RNA genes. No atp8 gene was found in the mitogenome of H. columbus but long non-coding regions were observed in agreement to that reported for other plant-parasitic nematodes. The mitogenomic phylogeny of plant-parasitic nematodes in the superfamily Tylenchoidea agreed with previous molecular phylogenies. Mitochondrial gene synteny in H. columbus was unique but similar to that reported for other closely related species.ConclusionsThe mitogenome of H. columbus is unique within the superfamily Tylenchoidea but exhibits similarities in both gene content and synteny to other closely related nematodes. Among others, this new resource will facilitate population genomic studies in lance nematodes from North America and beyond.

Management of plant parasitic nematodes in Okra by Bio-fumigation

A pot culture study was carried out to assess the effect of two bio-fumigants viz. Cabbage and Cauliflower leaves on plant parasitic nematode population infecting okra. The experiment resulted in reduction of root knot nematode (40.7%), lance nematode (40.8–80.1%), spiral nematode (49.1–79.7%) and stunt nematode (40.8–81.3%) with improvement of plant growth parameters like shoot length (23.3–54.6%), root length (14.1–46.5%), fresh shoot weight (28.4–81.9%), fresh root weight (22–38.7%), dry shoot weight (11.6–85.7%) and dry root weight (24–39%) of okra plant as compared to untreated control. Both cabbage and cauliflower leaves were found to be at par with respect to reduction of nematode population and enhancement of plant growth parameters. However, Cabbage leaf @ 88 g/kg soil (5.0 kg/m2) exhibited better performance in all above aspects. It reduced the population of root knot nematode, lance nematode, spiral nematode and stunt nematode by 50%, 52.4%, 61.2% and 50.9%, respectively. The enhancement of shoot length, root length, fresh shoot weight, dry shoot weight, fresh root weight and dry root weight to the tune of 49.3%, 46.5%, 79.3%, 78.5%, 38.7% and 39.5%, respectively were observed with this treatment.

Occurrence and distribution of plant parasitic nematodes in Cabbage growing regions of Tamil Nadu

A total of 60 samples were collected from cabbage viz., Quisto, Priyadharshini, Golden Acre and Maha Rani at a depth of 10–15 cm. The soil samples were analyzed by using modified Baermann's funnel technique and the root samples were analyzed by using Acid fuschin lactophenol solution for identification of females. The survey revealed that, the root knot nematode, Meloidogyne incognita, lesion nematode, Pratylenchus penetrans, spiral nematode, Helicotylenchus dihystera, lance nematode, Hoplolaimus indicus, dagger nematode, Xiphinema americanum and Tylenchus filiformis were encountered in the samples. Among the districts, the highest incidence of damage by M. incognita was observed in Krishnagiri followed by The Nilgiris and Coimbatore districts. The maximum population (262.48/250cc soil) and minimum population (72.93/250cc soil) was observed in Krishnagiri and Theni districts, respectively.

Morphological and molecular characterisation of Hoplolaimus smokyensis n. sp. (Nematoda: Hoplolaimidae), a lance nematode from Great Smoky Mountains National Park, USA

Summary Hoplolaimus smokyensis n. sp. is a new species of lance nematode collected in Great Smoky Mountains National Park, USA. Females of H. smokyensis n. sp. have a labial region characterised by six, occasionally five, annules. The basal lip annule is subdivided by about 24 longitudinal striae. The stylet averages 47 μm long with robust, tulip-shaped stylet knobs bearing anterior projections. The hemizonid is ca 4 μm anterior to the excretory pore. The lateral field is incompletely areolated and has four continuous incisures from the metacorpus region to the tail region. There are three pharyngeal gland nuclei. Vulval epiptygma are absent. The scutellate phasmids are located one anterior and one posterior to the vulva. The male is shorter than the female and the head region is higher and more rounded than that of the female. The bursa extends to the tail tip and the gubernaculum is large and protrusible and has titillae and a capitulum. Morphologically, H. smokyensis n. sp. is most similar to H. galeatus and H. stephanus, but can be distinguished by differences such as the number of annules and longitudinal striae on the lip region and morphometric values. Hoplolaimus smokyensis n. sp. is also genetically distinct from other species according to comparisons of ribosomal and mitochondrial DNA sequences. Phylogenetic analyses based on ribosomal and mitochondrial gene sequences suggest that H. smokyensis n. sp. is a lineage distinct from related Hoplolaimus species.

Cropping Practices and Soil Properties Associated with Plant-Parasitic Nematodes in Corn Fields in Ohio.

Ten morphological groups of plant-parasitic nematodes (spiral, lesion, lance, dagger, stunt, pin, ring, stubby-root, cyst, and miscellaneous tylenchids) were detected in corn fields in Ohio, but the presence and population density of these groups varied among fields. Binary and ordinal logistic regression models were fitted to the data to estimate the odds of each group being present, and the lesion, lance, spiral, and pin nematode population densities being at moderate-high risk levels based on soil region, cropping sequence, tillage, and soil pH, silt content, and electrical conductivity. All covariates were associated with at least one nematode group, but soil region had the greatest and most consistent effect. Dagger and ring nematodes were more likely to be present in region 6 than in any of the other regions, whereas lance, stunt, pin, stubby-root, and spiral nematodes were more likely to be present in regions 1 to 5 than 6. Spiral, lance, and pin nematode population densities were more likely to be at moderate-high risk levels in regions 3 and 4 than in region 6. Fields under conservation tillage were two times more likely to have moderate-high risk lance nematode population densities than fields under conventional tillage. Similarly, pin nematode population densities were two times more likely to be at moderate-high risk levels in fields under rotation than in continuous corn. For every unit increase in soil pH, the odds of the spiral nematode population density being at moderate-high risk levels increased by 43%, but the odds of the lesion and pin nematode population densities being at the same risk level decreased by 63 and 29%, respectively. The predicted probability of lesion and lance population densities being at moderate-high risk levels decreased as the silt content of the soil increased. These finding will be useful for developing future nematode sampling protocols and for assessing the risk associated with nematodes in corn fields in Ohio.

Cotton Production Systems for Soil and Energy Conservation in Coastal Plain Soils

Cotton growers in the southern USA are facing new production problems that are reducing farm profits and sustainability: 1) herbicide-resistant weeds are spreading throughout the Southeast, 2) thrips are consistently ranked as an important insect pest group Beltwide, 3) the most effective tool for managing nematodes and thrips (aldicarb) currently is only available in the southeastern USA in limited amounts, and 4) fuel costs have increased significantly over the last ten years. An interseeding system was developed at Clemson University that allows planting of cotton into standing wheat, about 2 - 3 weeks before wheat harvest. This system, which combines benefits of crop residue and minimum tillage operations, has the potential to alleviate many of the production problems cited above, while enhancing farm profits and soil properties. Crop residue associated with the interseeding production system reduced weed populations and required significantly less herbicide inputs compared with the conventional system. Columbia lance nematodes populations were reduced in the interseeding system by 83% without an application of nematicide. Populations of thrips were reduced by 74% in the interseeding production system. No differences were observed between the yields from interseeded and the conventional full-season cotton. However, revenues from the interseeding system were higher due to harvest of the wheat crop. In addition, the interseeding system consumed 35% less fuel than the conventional production systems.

First Report of the Lance Nematode Hoplolaimus stephanus From a Soybean Field in North Dakota

First Report of the Lance Nematode <i>Hoplolaimus stephanus</i> From a Soybean Field in North Dakota

Population dynamics and spatial distribution of Columbia lance nematode in cotton

Hoplolaimus columbus, Columbia lance nematode (CLN), can cause severe stunting and considerable yield losses in cotton. A three-year field study was conducted in South Carolina with the purpose of examining the population dynamics and spatial distribution patterns of CLN as influenced by soil texture, the presence of Rotylenchulus reniformis, reniform nematode (RN), and a cotton–corn–soybean rotation scheme. Four plots with different soil textures inferred by soil electrical conductivity were sampled at plant and at harvest for each crop. Population densities of CLN were aggregated and the host plant did not affect the pattern of spatial distribution. Columbia lance nematode and RN were found in spatially distinct areas in the field influenced by differences in soil texture. Columbia lance nematode was mainly found in areas with high sand content (above 75%) and RN in areas with 60–65% sand content. Therefore, depending on the sand content, whenever there are concomitant infestations of CLN and RN in a field, only one species is likely to be the key pest. Knowledge of the distribution patterns of CLN is essential for selecting sampling strategies and for site-specific management.

High genetic diversity and geographic subdivision of three lance nematode species (Hoplolaimus spp.) in the United States.

Lance nematodes (Hoplolaimus spp.) feed on the roots of a wide range of plants, some of which are agronomic crops. Morphometric values of amphimictic lance nematode species overlap considerably, and useful morphological characters for their discrimination require high magnification and significant diagnostic time. Given their morphological similarity, these Hoplolaimus species provide an interesting model to investigate hidden diversity in crop agroecosystems. In this scenario, H. galeatus may have been over-reported and the related species that are morphologically similar could be more widespread in the United States that has been recognized thus far. The main objectives of this study were to delimit Hoplolaimus galeatus and morphologically similar species using morphology, phylogeny, and a barcoding approach, and to estimate the genetic diversity and population structure of the species found. Molecular analyses were performed using sequences of the cytochrome c oxidase subunit 1 (Cox1) and the internal transcribed spacer (ITS1) on 23 populations. Four morphospecies were identified: H. galeatus, H. magnistylus, H. concaudajuvencus, and H. stephanus, along with a currently undescribed species. Pronounced genetic structure correlated with geographic origin was found for all species, except for H. galeatus. Hoplolaimus galeatus also exhibited low genetic diversity and the shortest genetic distances among populations. In contrast, H. stephanus, the species with the fewest reports from agricultural soils, was the most common and diverse species found. Results of this project may lead to better delimitation of lance nematode species in the United States by contributing to the understanding the diversity within this group.

Population dynamics and interactions between plant parasitic and non-parasitic nematodes: An empirical analysis

Non-linear regression models were used to estimate the effect of own and other taxa previous population levels, nitrogen application, and crop rotation on population dynamics of Mononchidae, Dorylaimidae, microbivorous (Rhabditidae), lance (Hoplolaimus galeatus), spiral (Helicotylencus dihystera), stubby root (Paratrichodorus minor), lesion (Pratylenchus zeae), and cotton root-knot (Meloigogyne incognita) nematodes using data from the Cullars rotation, which is the oldest soil fertility experiment in the Southern United States. Because field experimental data was used, a spatial component was included as populations in one plot were proved to be related to the population level of their neighbors. Own previous levels were found to be very important for all eight groups of nematodes (all groups’ current population relied heavily on its own previous population value) and all the groups had an interaction effect with at least one other group. Lesion and cotton root-knot nematodes were found to be competitive while Mononchidae, Dorylaimidae, microbivorous and lance nematodes were non-competitive. All the populations showed high seasonality patterns having lower populations during winter, to then remain steady until September–October when there is a significant increase in the population of cotton root-knot, Dorylaimidae, microbivorous, and lesion nematodes. Nitrogen had a positive effect on Mononchidae, microbivorous, spiral, and cotton root-knot nematodes. The use of clover after cotton in the rotation crop program proved to be significantly better in reducing plant parasitic nematodes compared to other treatments.

First Report of Lance Nematode (Hoplolaimus magnistylus) on Corn, Soybean, and Cotton in Tennessee.

The lance nematode Hoplolaimus magnistylus Robbins 1982 (3) was found for the first time in Tennessee in a cotton (Gossypium hirsutum L.) field (35°19.550' N, 89°24.535' W) in Fayette County in May 2011. In June of the same year, the species was also found in soil samples collected from a corn (Zea mays L.) field (36°15.736' N, 88°51.121' W) and a soybean (Glycine max L.) field (36°15.616' N, 88°51.118' W) in Weakley County, TN. Nematodes were extracted from the soil with a semi-automatic elutriator and further processed by sugar flotation-centrifugation. Population densities were between 30 and 50 individuals per 100 cm3 of soil in areas with noticeable stunting. Helicotylenchus sp. and Pratylenchus sp. were also present at less than 10 individuals per 100 cm3 of soil. Ten soybean seeds, cv. Hutcheson, were planted and inoculated with 50 H. magnistylus per 100 cm3 in steam-sterilized soil, and were maintained in a greenhouse. Forty-five days later, soybean plants exhibited at least one of the following symptoms: stunting and chlorosis, reduced root growth, and localized root lesions. Individual nematodes were handpicked and identified under a compound light microscope as H. magnistylus based on morphological and morphometric characteristics. The main diagnostic character for this species is the size of the stylet. In the populations collected, females had stylets ranging from 49 to 58 μm (mean 56 μm). Males and females were observed with head distinctly set off and massive cephalic framework, stylet long and robust and stylet knobs pointed anteriorly. The lateral field was areolated and had four incisures most of the body length, the excretory pore was prominent and located 190 μm (175 to 200 μm) from anterior end, hemizonid was large and located one or two annules posterior to the excretory pore, phasmids were large, conspicuous, and variable in position, and vulva was prominent and near midbody. This species is most similar to the more commonly reported H. galeatus, but differs from it in the longer stylet. Total DNA was extracted from single adults from each soil sample and the species-specific primers Hoc-1f (5'-AACCTGCTGCTGGATCATTA-3') and HM-3r (5'-AGACTGGACGGCCAAAGTT-3') designed by Bae et al. (1) were used to confirm the identification by amplification of a distinct 340-bp amplicon that differentiates this species from H. columbus, H. galeatus, H. concaudajuvencus, and H. stephanus. H. magnistylus was first described from soil samples taken from a corn and soybean field in Marianna, AR (3), and has been reported in association with soybean and corn in Louisiana and Mississippi (4). Robbins (4) reported that H. magnistylus was not a serious pest of irrigated cotton in Arkansas, but there are no other pathogenicity studies published for soybean, corn, or non-irrigated cotton. Other lance species, mainly H. galeatus and H. columbus, have been reported to cause serious damage to cotton in the Carolinas and Georgia (3). Previously, H. galeatus was reported in Tennessee by Bernard (2). Lance nematodes feed as migratory endo- and ectoparasites and injure the growing points of roots, causing stunting of plants. Because so little is known about the pathogenicity of this nematode, it becomes relevant to add our records of its known distribution in field crops in the United States. To our knowledge, this is the first report of H. magnistylus in Tennessee.

Quantifying the Effects of Lance Nematode Parasitism in Creeping Bentgrass.

We compared photosynthesis and multispectral radiometry (MSR) measurements with visual quality ratings for assessment of feeding injury to creeping bentgrass caused by the lance nematode (Hoplolaimus galeatus) using artificially infested microplots and a naturally infested putting green. Nematode feeding resulted in negative visual and MSR effects on creeping bentgrass in microplots. Visual quality ratings were correlated more consistently with nematode densities than either individual MSR variables or factor models of MSR variables. Threshold estimates for H. galeatus population densities associated with unacceptable bentgrass quality in microplots varied widely by month and year. Similarly, the relationship between H. galeatus population density and turf health indicators (including MSR measurements, visual ratings, and net photosynthetic rate) varied with cultivar and management practice (irrigation frequency and mowing height) in the naturally infested putting green. Notably, negative effects of nematode feeding were not consistently associated with more stressful management practices, suggesting that stress avoidance is not a reliable deterrent to H. galeatus damage in creeping bentgrass. Damage thresholds for this nematode-host association are dynamic and should be used with caution.

Population Dynamics of the Lance Nematode (Hoplolaimus galeatus) in Creeping Bentgrass.

The effects of management practices and nematode population density on the seasonal fluctuationsin lance nematode (Hoplolaimus galeatus) populations in creeping bentgrass were studiedin a naturally infested experimental putting green and in artificially infested microplots. In general, H. galeatus populations increased from late spring through midsummer, declined in August, and increased again in the fall. Population increase in microplots was strongly density dependent, with final population densities inversely proportional to inoculum levels. Ectoparasitic populationsof H. galeatus in both studies were composed of adults and juveniles, whereas endoparasiticpopulations were almost exclusively juveniles. H. galeatus populations in the naturallyinfested site were aggregated spatially, but the aggregation was not temporally stable. Nematodepopulations were not affected by bentgrass cultivar selection or irrigation frequency.

Studies on Plant Parasitic Nematodes Associated with Banana in Sindh, Pakistan

A survey of banana was conducted to study the occurrence and distribution of plant parasitic nematodes. The samples of soil and banana plants showing retarded growth were collected from three fields of Nasimabad (Khisano Mori), Tando Allah Yar and Mirpurkhas. The nematodes isolated from the roots and soil samples showed the presence of seven genera of plant parasitic nematodes, Hoplolaimus columbus, Belonolaimus longicaudatus, Helicotylenchus dihystera, Meloidogyne incognita, Xiphinema brevicolle, Longidorus africanus and Trichodorus christiei. The maximum population densities (M. P. D %) and maximum frequency occurrence (M. F. O %) and prominence values (P. V %) were calculated for each nematode genus. The M. P. D %, M. F. O % and P. V % of H. columbus (lance nematode), B. longicaudatus (sting nematode), M. incognita (root-knot nematode) and Heli. dihystera (spiral nematode) were higher than those of other nematodes. The occurrence of these nematodes in relatively high population suggests their potential role in reducing banana production.