Tài liệu Advances in Downy Mildew Research docx

[...]... wild potatoes being used in southern Chile for 11,000 years (Vaughan and Geissler, 1997) 3 Evolutionary origins of the Straminipila, including the Peronosporomycetes It is possible that the straminipilous fungi themselves (as a component of the undoubtedly early-originating monophyletic line of straminipilous organisms) have an ancient origin (Pirozynski and Malloch, 1975; Stanghellini, 1974), but... the kingdom must have originated, and evolved initially, in the marine ecosystem, most probably in littoral and lagoon or estuarine environments (the photoendobiont was probably a red alga, strengthening the marine provenance; Potter et al., 1997) and at an early geological Period (Cambrian? Precambrian?) Nevertheless, all existing evidence points to a freshwater or terrestrial origin for the straminipilous... south-east Asia); ploidy differences in Phytophthora infestans in Europe following the exotic introduction of both host and parasite, which originate from the Equador (Boussingault, 1845) - Central American region (Lucas et al., 1991; Daggett, Knighton and Therrien, 1995) and Peronosclerospora in India (originating from Africa, Ball and Pike, 1984; Idris and Ball, 1984) In contrast to these recent developments,... familiar to mycologists (Dick, 1995), but since the nomenclature within the kingdom spans the zoological and botanical codes, these suffixes may change (cf Labyrinthista instead of Labyrinthulomycetes, Labyrinthulales, previously included within mycological works) The class is divided into three sub-classes, one of which, the Peronosporomycetidae, at present contains two orders, the Peronosporales and... comm., F N Martin, EVOLUTION OF THE DOWNY MILDEWS 17 U.S.D.A., Salinas, Ca.) (vi) Evolution is on-going Species concepts (both real and postulated) vary widely, even in a single genus Incipient speciation will occur Isolation of, and modification of, the gene pool may not, initially, be correlated with or represented by morphological attributes Population diversity and formally defined intra-specific... will be necessary to characterize the DMs and other straminipiles in this respect Shorter sequences such as pertain to the ITS region are frequently used, but in Pythium there are length mutations in this region so that analysis becomes highly dependent on sequence editing In spite of this complication, the ITS region is effective in distinguishing between closely related species; other sections of the... 1998) For entirely understandable reasons, the independent, endosymbiont genes most studied in straminipiles are either in the photoendobiont or in the mitochondrial endosymbiont (heterotrophs), so that comparability is lacking across the whole kingdom Other genes have not yet been studied in sufficiently large samples of straminipilous fungi or other straminipiles to enable a robust phylogenetic hypothesis,... a narrow germ tube developed from an infection peg (narrower hyphae) Phylogeny 12 M W DICK inferred from vegetative and asexual morphology is not acceptable, although subtle differences in morphogenesis might be invoked Morphological elaboration in the asexual system is also found in the continuum of sporangial forms in Pythium; the development of sporangiophores in Phytophthora; caducous zoosporangia;... chromosome to another, with or without changes in chromosome length or number Ploidy levels may be different, and here the breeding systems of the straminipilous fungi need to be taken into account, particularly when selfing and automictic sexual reproduction may be involved (Dick, 1972, 1987, 1995; Win-Tin and Dick, 1975) It is also possible that differences in virulence could be attributed to Simple... mono-oosporous (exceptions in Pythiales); oospores with a semi-solid, hyaline or translucent ooplast, lipid phase dispersed as minute droplets; able to use ability to metabolize different inorganic N sources variable Basal chromosome number x = 4 or 5 Two orders, one order including downy mildews Peronosporales Obligate parasites of dicotyledons (very rarely monocotyledons) Thallus mycelial and intercellular with . class="bi x0 y0 w0 h1" alt="" Advances in Downy Mildew Research This page intentionally left blank Advances in Downy Mildew Research Edited by P.T.N. Spencer-Phillips U held in Edinburgh in August 1998. Our intention was to invite reviews on selected aspects of downy mildew biology from international authorities, and link