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Title: The distribution of Longidoroidea (Nematoda) in Europe and variation in the morphology, biology and virus transmission of Xiphinema diversicaudatum (Micoletzky, 1927) Thorne, 1939
Author: Brown, D. J. F.
ISNI:       0000 0001 3488 1705
Awarding Body: Open University
Current Institution: Open University
Date of Award: 1983
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The geographical distributions in European and Mediterranean countries of 58 species in the Longidoroidea are shown on standardised format maps. This information and interspecific variability in the Longidoroidea is used to form groups of nematodes each group generally consisting of an amphimictic species and several thelytokous species. The possibility is discussed that within each group the thelytokous species may have evolved from the ancestral amphimictic species. An examination of intraspecific variability between populations of Xiphinema diversicaudatum from Europe, USA and New Zealand revealed much significant variation in their morphometrics and populations could be grouped according to their morphological similarity. Methods of killing, fixing and processing specimens to glycerol, the microscope-measuring system, operator recording measurements and changes in biotope altered significantly the morphometrics of X. diversicaudatum. Differences occurred in the proportions of males and females in populations of the species and, using a standard test system, populations were found to have different reproductive capacities. However, females from the populations successfully crossbred with males from a Scottish population and produced viable F1 and F2 hybrids which confirmed the populations belonged to the same species. Strains of arabis mosaic and strawberry latent ringspot (SLRV) viruses were transmitted, each with a different degree of efficiency, by populations of X. diversicaudatum and specificity of transmission existed between each virus strain and each nematode population. Different virus source and bait-plants affected the efficiency with which viruses were transmitted and a strain of SLRV from Italy was transmitted consistently only by a population from Italy. Infrequent or non-transmission of viruses by nematodes resulted from an inability of the nematodes to adsorb and retain virus particles at specific sites. A study using parental and F1 and F2 hybrid X. diversicaudatum revealed that the nematodes ability to adsorb and retain virus particles was hereditary and that different maternal and paternal parents could affect the potency of the hybrids as virus vectors. Results from this research programme form a basis with which to compare interspecific variability in the Longidoroidea.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: Human anatomy & human histology