Distribution Of Parasitic Nematodes Research Articles

Large-scale genetic investigation of nematode diversity and their phylogenetic patterns in New Zealand's marine animals.

Nematodes constitute one of the most speciose metazoan groups on earth, and a significant proportion of them have parasitic life styles. Zooparasitic nematodes have zoonotic, commercial and ecological significance within natural systems. Due to their generally small size and hidden nature within their hosts, and the fact that species discrimination using traditional morphological characteristics is often challenging, their biodiversity is not well known, especially within marine ecosystems. For instance, the majority of New Zealand's marine animals have never been the subject of nematode studies, and many currently known nematodes in New Zealand await confirmation of their species identity with modern taxonomic techniques. In this study, we present the results of an extensive biodiversity survey and phylogenetic analyses of parasitic nematodes infecting New Zealand's marine animals. We used genetic data to differentiate nematodes to the lowest taxonomic level possible and present phylogenies of the dominant clades to illustrate their genetic diversity in New Zealand. Our findings reveal a high diversity of parasitic nematodes (23 taxa) infecting New Zealand's marine animals (62 of 94 free-living animal species investigated). The novel data collected here provide a solid baseline for future assessments of change in diversity and distribution of parasitic nematodes.

Detection and identification of Ektaphelenchoides diversislocis sp. n. isolated from Pinus woodlands of China and Japan

Summary Understanding the occurrence and distribution of parasitic nematodes is crucial – some are economic pests, and some are important predators of their insect associates. In our recent nematode inventory survey, two populations of an ektaphelechid nematode were detected in the branches of Pinus trees; later the same nematode population was detected in plant quarantine examinations of wood packaging material imported from Japan. The species was processed and identified as Ektaphelenchoides diversislocis sp. n. The new species can be characterised by having three lateral lines, stylet long and tripartite, excretory pore at the level of nerve ring, comparatively longer post-vulval uterine sac, indistinct rectum and anus. Female posterior body region conical, gradually narrowing, like a mucron or filiform. Male spicule with well-developed condylus, triangular rostrum, and cucullus absent. The species is morphologically and molecularly close to E. compsi. The new species was characterised with near full-length 18S, 28S D2-D3 regions, and internal transcribed spacer (ITS) rRNA genes and mitochondrial cytochrome oxidase I (COI) gene sequences. The species within the Ektaphelenchoides genus are considered to have predatory roles against insect associates; therefore, the discovery of E. diversislocis sp. n. from local and foreign woodlands warrants increased sampling and research attention.

Distribution of parasitic nematodes in Kenyan rice fields and their relation to edaphic factors, rainfall and temperature

Rice is the third most important crop in Kenya after maize and wheat. Plant parasitic nematodes (PPN) are a major rice production constraint. The objective of this study was to determine the distribution and abundance of rice PPN in Kenya and their association with environmental variables. Soil and plant samples were collected from rainfed upland and irrigated lowland rice fields in Kirogo, Thiba, Nyangati, Ombeyi, Kombura, Kakola and Mwambe Sub-locations. Twenty-two PPN genera were identified across all Sub-locations with the highest (20) number of nematode genera recorded in rainfed upland rice fields. The nematode genera Scutellonema, Hoplolaimus, Ditylenchus, Hemicycliophora, Heterodera, Paralongidorus and Tylenchus were not recorded in the irrigated lowland rice fields while Criconemella and Tylenchorhynchus were not observed in rainfed upland fields. Canonical correspondence analysis of the relationship between soil properties and nematode abundance revealed a significant (P < 0.05) relationship between PPN abundance and potassium, sodium, sand and clay. The relationship between rainfall, minimum temperature and nematode genera was significant (P < 0.05) while maximum temperature was not significant (P = 0.928). Our results provide critical information for designing nematode management strategies in Kenyan rice fields.

Distribution of parasitic nematodes in vineyards in central and north-eastern Victoria

A survey of 16 1 vineyards in central and north-eastern Victoria determined the distribution of plant parasitic nematodes, particularly Xiphinema index, a vector of grapevine fanleaf virus. From the North-Central and Geelong Vine Disease Districts respectively, 185 and 3 soil samples were collected between 1978 and 1982. Fifteen genera of stylet-bearing nematodes were found, and those of known or suspected economic importance were Helicotylenchus (found in 24% of samples), Pratylenchus (21%), Xiphinema ( 13%), Criconemella (8%), Longidorus (7%) and Paratrichodorus (2%) . X. index was found in three samples from two vineyards, both within 10 km of Rutherglen in north-eastern Victoria. Neither Meloidogyne javanica nor Tylenchulus semipenetrans were detected, although both are common in other viticultural areas of Victoria.

Pythiaceous fungi and plant-parasitic nematodes in California pear orchards: II. Incidence and distribution of parasitic nematodes in orchard soils

Plant-parasitic nematodes of various types are prevalent in the upper root zone of pear trees in California. Monthly samplings over a 12-month period, from the same 126 orchards mentioned above, showed that the dagger nematode Xiphinema americanum and the pin nematode Paratylenchus hamatus occurred in more than 90 per cent of the orchards and in all pear-growing areas of the state. Other nematodes frequently found were species of Tylenchorhynchus, Pratylenchus, Helicotylenchus, Meloidogyne, and Criconemoides. No direct relationship was indicated between pear decline and nematodes in orchard soils.