Uses of molecular techniques in rust systematics

Vogler, D. R. 1995.

Department of ESPM, University of California, Berkeley 94720.

Pages 9-15 in Proc. 4th IUFRO Rusts of Pines Working Party Conf., S. Kaneko, K. Katsuya, M. Kakishima, and Y. Ono, eds., Tsukuba, Japan. (1995)


Summary

Molecular genetic techniques were used to characterize taxa, delineate species relationships, and elucidate evolutionary pathways within the rust genera Cronartium (anamorph Peridermium) and Endocronartium, which cause stem, branch, and cone rust diseases of pines (Pinus spp.) in the northern hemisphere. Soluble proteins were extracted from spores of North American hard pine (subgenus Pinus) stem rusts for isozyme analysis. Isozyme banding patterns were interpreted as phenotypes and analyzed by pairwise distance algorithms. Isozymes were primarily suitable for delineating species and describing species diversity, but the data also contained phylogenetic information. For sequencing, DNA was extracted from spores collected from infected pines or from dried telial host material. The internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene repeat was amplified using the polymerase chain reaction (PCR) and the resulting product used for direct sequencing. Multiple sequences were aligned and analyzed using both distance and parsimony methods. ITS sequence diversity within species was generally slight, and parsimony analysis yielded a small set of equally parsimonious trees that illustrate evolutionary relationships within and among the genera. In addition, published morphological and biological characters (host preference, symptoms, and other behavioral traits) were coded as unordered character states and analyzed by both distance and parsimony methods. Trees derived from isozymes, nucleotide sequencing, and morphology were remarkably congruent, and provide a clear view of species relationships among the pine stem rusts.


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