Introduction Nematodes are tiny, worm-like, multicellular animals adapted to living in water. The number of nematode species is estimated at half a mil lion, many of which are “free-living” types found in the oceans, in freshwater habitats, and in soils. Plant-parasitic species form a smaller group. Nematodes are common in soils all over the world (Dropkin, 1980; Yepsen, 1984). As a commentator...

Primary and secondary types housed in the Canadian National Collection of Nematodes are given for 396 species of plant-parasitic, marine, freshwater, terrestrial, and entomophagous nematodes. Species are listed in alphabetical order and include author(s), date, publication source, type category, numbers and sex, and collection accession number. Current nomenclatorial changes in status of a bino...

A non-sodic, non-saline sandy loam soil was salinized to anion-cation ratios similar to those naturally occurring in Iraq and California. The interactions of saline soils (conductivities 4, 8, 12 and 16 mmhos/cm) with a moderately salt-tolerant plant (Lycopersicon esculentum 'Marimond') and a plant parasitic nematode (Meloidogyne javanica) were investigated. Plant parasitic nematodes were shown...

Spatial patterns of Meloidogyne incognita, Tylenchorhynchus claytoni, Helicotylenchus dihystera, and Criconemella ornata were analyzed using Hill's two-term local quadrat variance method (TTLQV), spectral analysis, and spatial correlation. Data were collected according to a systematic grid sampling plan from seven tobacco fields in North Carolina. Different estimates of nematode cluster size we...

In a survey of plant-parasitic nematodes associated with agricultural crops in nine Maine counties, 744 soil samples from 26 potential host plants were analyzed between November 1987 and January 1989. The most commonly encountered nematode genus was Pratylenchus, occurring in 85% of the samples from most crops, except blueberries and onions. Pratylenchus penetrans and P. crenatus were found com...

A natural community of plant-parasitic nematodes is usually polyspecific. The host plant is the most important driving force in nematode populations, but abiotic factors are important in maintaining the steady state. Nematode communities often separate by abiotic soil factors. In any continuous habitat, including crop plants, generally there is a consistency of the most abundant species, which ...

Plant parasitic nematodes have developed the capacity to sense and respond to chemical signals of host origin and the ability to orientate towards plant roots enhances the nematode's chance of survival. Root exudates contain a range of compounds which mediate belowground interactions with pathogenic and beneficial soil organisms. Chemical components of root exudates may deter one organism while...

Several groups of soil microorganisms cause diseases to the roots. These “soilborne” plant pathogens are particularly challenging since they often survive in soil for many years and each crop may be susceptible to several species. They belong to various systematic groups. Major groups are oomycetes, fungi, bacteria, protists, and nematodes. Few soilborne viruses affect vegetable crops. The impa...

Root-knot nematodes belonging to the genus Meloidogyne are the most economically important group of plant-parasitic nematodes. Thei r worldwide distribution, extensive host ranges, and interaction with other plant pathogens in diseas e complexes rank them among the top plant pathogens affecting the world's food supply (5). Even though only four Meloidogyne species M. incognita, M. javanica, M. ...

Lateral gene transfer from prokaryotes to animals is poorly understood, and the scarce documented examples generally concern genes of uncharacterized role in the receiver organism. In contrast, in plant-parasitic nematodes, several genes, usually not found in animals and similar to bacterial homologs, play essential roles for successful parasitism. Many of these encode plant cell wall-degrading...