Molecular systematics of plant parasitic cyst nematodes
Abstract
The cyst nematodes (Heteroderidae) represent a large group of plant parasitic nematodes which include many agriculturally important pests parasitizing potatoes, soybeans, grains, sugar beat and other crops worldwide. The evolutionary relationships in this group historically have been based on morphological data or restricted to a small subset of taxa. The objectives of my Ph.D. research were to infer phylogeny of cyst nematodes based on molecular data, ribosomal DNA (rDNA) and the β-tubulin protein coding gene, and to investigate congruence between the two data sets. The four cyst-forming genera, Heterodera, Globodera, Cactodera and Punctodera, were monophyletic; and non-cyst forming genera had a basal position on the rDNA tree. With the exception of a few species, each cyst-forming genus was a well supported monophyletic group on the tree. The five species groups of the genus Heterodera are well supported clades, and the species' groupings mostly follow those based on morphology. β-tubulin was shown to be a small gene family in cyst nematodes, and initially shown to consist of three paralogous genes that differed regarding the number of introns in the sequenced region. β-tubulin data could not resolve relationships at the genus and species taxonomic levels, but the evolutionary relationships that were revealed were used to infer additional β-tubulin putative paralogs. Based on this new information about β-tubulin family evolution, congruence among the two molecular data sets was revealed by the presence of different groups of β-tubulin paralogs among the monophyletic groups of species on the rDNA tree.
Degree
Ph.D.
Advisors
Ferris, Purdue University.
Subject Area
Zoology
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