In: Pratylenchus (Nematoda: Pratylenchidae): Diagnosis, Biology, Pathogenicity and Management
In: Mononchida
In: Systematics of Cyst Nematodes (Nematoda: Heteroderinae), Part A
In: Systematics of Cyst Nematodes (Nematoda: Heteroderinae), Part B
In: Pratylenchus (Nematoda: Pratylenchidae): Diagnosis, Biology, Pathogenicity and Management
In: Systematics of Cyst Nematodes (Nematoda: Heteroderinae), Part A
In: Systematics of Cyst Nematodes (Nematoda: Heteroderinae), Part A

The molecular interactions between hosts and parasites is an active area of research, and the parasitism of root-knot nematodes, obligate parasites of plants, by the hyper-parasitic bacterium Pasteuria penetrans offers a model by which to investigate aspects of innate immunity. Using a pouch system we were able to demonstrate by PCR, infection of Meloidogyne incognita 4 days prior to any microscopic observations of parasitism. The pouch system, although not strictly axenic, offered a relatively clean, flexible approach with a greatly reduced number of contaminating microbial species than in any soil-based system, whereby the early stages of nematode infection could be manipulated and controlled.

In: Nematology

Abstract

Phylogenetic estimations from 18S rDNA sequence data reveal close relationships of dioctophymids with Trichinellida (Trichocephalida), the latter represented by the families Trichinellidae and Trichocephalidae (Trichuridae). This phylogeny is congruent with a scenario of molecular evolution deduced from conservative motifs within the V4 and V9 regions of 18S rRNA. A phylogenetic approach to analyse data containing highly unequal rates of sequence evolution is proposed. The entire gene possesses only a few conservative molecular synapomorphies of a clade consisting of Dorylaimida, Mononchida and Mermithida. Dioctophymida, together with Trichinellida, are inferred as a sister taxon to this clade which jointly constitute the Dorylaimia. Molecular data juxtaposed with morphology were used to reconstruct some of the putative features of the common ancestor of Dorylaimia which is speculated to have possessed a spear and, as found in extant Enoplia and Dioctophymida, pharyngeal gland outlets located in the stoma. Mononchids are postulated to have secondarily lost the spear contrary to all previously published phylogenies. Reduction of caudal glands and transformation of pharyngeal glands into the stichosome are not parsimonious across the tree of Dorylaimia. There are no unequivocal adult morphological synapomorphies for Dorylaimia; the only non-molecular diagnostic feature is the unique specification of the endodermal precursor in early embryogenesis.

In: Nematology

The stubby-root nematode, Trichodorus obtusus, was recently identified on zoysiagrass in South Carolina, USA. In Florida, T. obtusus causes more damage than other stubby-root nematodes encountered in turfgrass. The objective of this study was to use morphological analysis, mitochondrial DNA (COI: cytochrome oxidase 1) and nuclear (18S rRNA) sequence data to study the genetic structure and haplotype diversity of populations recovered from turfgrasses in South Carolina. Numerous morphological differences were observed among populations. Three 18S haplotypes were shared among South Carolina and Florida populations, and six mitochondrial haplotypes were identified in South Carolina samples. Of the six COI haplotypes, four haplotypes were restricted to one population from St Augustinegrass. The lowest haplotype diversity was found in samples from zoysiagrass. Sequences of the COI mtDNA gene of T. obtusus were published in GenBank and represent the first mtDNA sequences for the genus Trichodorus.

In: Nematology