Hudspeth DEB-9806785 Peronosporomycetes (=Oomycota; Oomycetes) are fungus-like heterotrophic organisms that constitute an economically important group in the newly established and extremely diverse kingdom Straminopila. The primary importance of oomycetes is due to the many species that cause disease in plants and animals. The most publicized plant disease caused by an oomycete is late blight of potato, but many others exist such as downy mildews, white rusts, root rots, and leaf blights of a wide variety of cereals, legumes, and fruit trees and forest resources. In the rapidly expanding area of aquaculture, oomycetes inflict damage on fish, crustaceans, and molluscs. Despite their immense impact on our economic resources, the phylogenetic relationships of these organisms are poorly understood. The primary goal of this study is to infer the evolutionary relationships of genera within and between established orders using DNA sequences of two mitochondrial genes (cox2 and ndh9). Taxa from the orders Leptomitales, Pythiales, Saprolegniales, and Peronosporales will be sampled to include opportunistic and obligate plant pathogens and parasites of terrestrial and marine animals. The resulting phylogeny will form the basis for evaluation of morphologically characters for use in phylogenetic studies. The PIs also may be able to develop hypotheses of the origin(s), of obligate parasitism. Are obligate parasites monophyletic? Have obligate parasites given "rise" to any facultative parasites (i.e., is change always unidirectional)? Future studies involving questions of parasite control strategies should also benefit from the availability of this phylogeny. For example, does clade membership predict that a particular control method might be more suitable for other clade members?
