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Abstract Background Pythium ultimum is a ubiquitous oomycete plant pathogen responsible for a variety of diseases on a broad range of crop and ornamental species. Results The P. ultimum genome (42.8 Mb) encodes 15,290 genes and has extensive sequence similarity and synteny with related Phytophthora species, including the potato blight pathogen Phytophthora infestans. Whole transcriptome sequencing revealed expression of 86% of genes, with detectable differential expression of suites of genes under abiotic stress and in the presence of a host. The predicted proteome includes a large repertoire of proteins involved in plant pathogen interactions, although, surprisingly, the P. ultimum genome does not encode any classical RXLR effectors and relatively few Crinkler genes in comparison to related phytopathogenic oomycetes. A lower number of enzymes involved in carbohydrate metabolism were present compared to Phytophthora species, with the notable absence of cutinases, suggesting a significant difference in virulence mechanisms between P. ultimum and more host-specific oomycete species. Although we observed a high degree of orthology with Phytophthora genomes, there were novel features of the P. ultimum proteome, including an expansion of genes involved in proteolysis and genes unique to Pythium. We identified a small gene family of cadherins, proteins involved in cell adhesion, the first report of these in a genome outside the metazoans. Conclusions Access to the P. ultimum genome has revealed not only core pathogenic mechanisms within the oomycetes but also lineage-specific genes associated with the alternative virulence and lifestyles found within the pythiaceous lineages compared to the Peronosporaceae.

Nonfungicide alternatives for control of brown patch (caused by Rhizoctonia solani Kuhn) and dollar spot (caused by Sclerotinia homoeocarpa F.T. Bennett) diseases are needed. Calcium silicate (CaSi[O.sub.3]) was applied as a topdressing (2440 or 4880 kg [ha.sup.-1]) to evaluate brown patch suppression in 'Bonsai 2000' and 'Tar Heel' tall rescue (Festuca arundinacea Schreb.) and 'L-93' creeping bentgrass (Agrostis palustris Huds.) in the field, or amended into soil at 7325 or 14650 kg [ha.sup.-1] to evaluate dollar spot on 'Peancross' creeping bentgrass in a growth chamber. The Chase silty day loam (fine, montmorillonitic, mesic Aquic Argiudoll) under tall rescue had a pH of 6.4, a high initial Si content (173 mg [kg.sup.-1]), and Si accumulation in leaves was minimal (one of five observations). Calcium silicate applied at 2440 kg [ha.sup.-1] increased the area under disease progress curves (AUDPC) for brown patch by 26% in 2002 and 30% (both rates) in 2003. Tall fescue leaf P and K concentrations were reduced by CaSi[O.sub.3] and were negatively correlated (r = -0.41 for P; -0.44 for K; P < 0.02) with brown patch. Calcium silicate topdressing increased Si in creeping bentgrass leaf tissue as well as the sand root zone, which initially contained

Irrigation management is generally assumed to have a significant effect on turfgrass pest management, yet little research has been done in this area. This field study was conducted on perennial ryegrass (Lolium perenne L.) maintained under golf course fairway conditions in 1995 and 19%. Objectives were to evaluate water savings afforded by monitoring turf ET and adjusting irrigation accordingly; to compare preventive and curative pesticide control measures for control efficacy and amounts required; and to evaluate effects of two irrigation regimes on turf quality, weed infestation, disease incidence, and pesticide requirements. Turf received either daily irrigation of 7.6 mm of water regardless of prevailing weather conditions or irrigation to replace approximately 80% of atmometer-estimated elk evapotranspiration (ET) on 3 d weekly. About 200% more water was applied to daily irrigated turf than to turf irrigated based on atmometer-estimated ET. Similar amounts of active ingredient were used on both fungicide schedules in 1995. In 19%, a curative fungicide schedule resulted in application of 64% less active ingredient than a preventive schedule. Daily irrigation suppressed brown patch (Rhizoctonia solani Kuhn) injury by 901, in 1995 and 2% in 1996 but resulted in more than twice as many dollar spot (Sclerotinia homoeocarpa F.T. Bennett) infection centers in 1996. Irrigation treatment had no effect on smooth crabgrass [Digitaria ischaemum (Schreb.) Muhl.] or dandelion (Taraxacum officinale Weber) incidence., Golf courses are often publicly scrutinized, in part, because of high summer water usage during peak demand periods in urban areas and fear of potential health and environmental problems posed [...]

Abstract Background Pythium species are an agriculturally important genus of plant pathogens, yet are not understood well at the molecular, genetic, or genomic level. They are closely related to other oomycete plant pathogens such as Phytophthora species and are ubiquitous in their geographic distribution and host rage. To gain a better understanding of its gene complement, we generated Expressed Sequence Tags (ESTs) from the transcriptome of Pythium ultimum DAOM BR144 (= ATCC 200006 = CBS 805.95) using two high throughput sequencing methods, Sanger-based chain termination sequencing and pyrosequencing-based sequencing-by-synthesis. Results A single half-plate pyrosequencing (454 FLX) run on adapter-ligated cDNA from a normalized cDNA population generated 90,664 reads with an average read length of 190 nucleotides following cleaning and removal of sequences shorter than 100 base pairs. After clustering and assembly, a total of 35,507 unique sequences were generated. In parallel, 9,578 reads were generated from a library constructed from the same normalized cDNA population using dideoxy chain termination Sanger sequencing, which upon clustering and assembly generated 4,689 unique sequences. A hybrid assembly of both Sanger- and pyrosequencing-derived ESTs resulted in 34,495 unique sequences with 1,110 sequences (3.2%) that were solely derived from Sanger sequencing alone. A high degree of similarity was seen between P. ultimum sequences and other sequenced plant pathogenic oomycetes with 91% of the hybrid assembly derived sequences > 500 bp having similarity to sequences from plant pathogenic Phytophthora species. An analysis of Gene Ontology assignments revealed a similar representation of molecular function ontologies in the hybrid assembly in comparison to the predicted proteomes of three Phytophthora species, suggesting a broad representation of the P. ultimum transcriptome was present in the normalized cDNA population. P. ultimum sequences with similarity to oomycete RXLR and Crinkler effectors, Kazal-like and cystatin-like protease inhibitors, and elicitins were identified. Sequences with similarity to thiamine biosynthesis enzymes that are lacking in the genome sequences of three Phytophthora species and one downy mildew were identified and could serve as useful phylogenetic markers. Furthermore, we identified 179 candidate simple sequence repeats that can be used for genotyping strains of P. ultimum. Conclusion Through these two technologies, we were able to generate a robust set (~10 Mb) of transcribed sequences for P. ultimum. We were able to identify known sequences present in oomycetes as well as identify novel sequences. An ample number of candidate polymorphic markers were identified in the dataset providing resources for phylogenetic and diagnostic marker development for this species. On a technical level, in spite of the depth possible with 454 FLX platform, the Sanger and pyro-based sequencing methodologies were complementary as each method generated sequences unique to each platform.

The walnut twig beetle (WTB), Pityophthorus juglandis Blackman (Coleoptera: Curculionidae), vectors a fungus, Geosmithia morbida Kolařík, Freeland, Utley, and Tisserat (Ascomycota: Hypocreales), which colonises and kills the phloem of walnut and butternut trees, Juglans Linnaeus (Juglandaceae). Over the past two decades, this condition, known as thousand cankers disease (TCD), has led to the widespread mortality of Juglans species in the United States of America. Recently the beetle and pathogen were discovered on several Juglans species in northern Italy. Little is known about the extra-generic extent of host acceptability and suitability for the WTB. We report the occurrence of both the WTB and G. morbida in three species of wingnut, Pterocarya fraxinifolia Spach, Pterocarya rhoifolia Siebold and Zuccarini, and Pterocarya stenoptera de Candolle (Juglandaceae) growing in the United States Department of Agriculture-Agricultural Research Service, National Clonal Germplasm Repository collection in northern California (NCGR) and in the Los Angeles County Arboretum and Botanic Garden in southern California, United States of America. In two instances (once in P. stenoptera and once in P. fraxinifolia) teneral (i.e., brood) adult WTB emerged and were collected more than four months after infested branch sections had been collected in the field. Koch’s postulates were satisfied with an isolate of G. morbida from P. stenoptera, confirming this fungus as the causal agent of TCD in this host. A survey of the 37 Pterocarya Kunth accessions at the NCGR revealed that 46% of the trees had WTB attacks and/or symptoms of G. morbida infection. The occurrence of other subcortical Coleoptera associated with Pterocarya and the first occurrence of the polyphagous shot hole borer, a species near Euwallacea fornicatus Eichhoff (Coleoptera: Curculionidae), in Juglans are also documented. [ABSTRACT FROM PUBLISHER]

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