Chromosome locations of leaf rust resistance genes in selected tetraploid wheats through substitution lines     

Shimelis?HusseinEmail author  Johan?J.?Spies  Zakkie?A.?Pretorius  Maryke?T.?Labuschagne 《Euphytica》2005,141(3):209-216

Langdon durum D-genome disomic substitution lines were used to study the chromosome locations of adult-plant leaf rust resistance genes identified from tetraploid wheat accessions. The accessions are 104 (Triticum turgidum subsp. dicoccum var. arras) and 127 (T. turgidum subsp. durum var. aestivum). The complete sets of the substitution lines were crossed as female parents with the accessions and F₁ double monosomic individuals selected at metaphase I. Segregating F₂ individuals were inoculated during the flag leaf stage with pathotype UVPrt2 of Puccinia triticina. The substitution analysis involving accession 104 showed that the gene for leaf rust resistance is located on chromosome 6B. The analysis with accession 127 indicated that chromosome 4A carries a gene for leaf rust resistance. The two novel genes are temporarily designated as Lrac104 and Lrac127, respectively from accessions 104 and 127.  相似文献   

Characterization of fungi (Fusarium and Rhizoctonia) and oomycetes (Phytophthora and Pythium) associated with apple orchards in South Africa     

Yared Tesfai Tewoldemedhin  Mark Mazzola  Wilhelm J. Botha  Christoffel F. J. Spies  Adéle McLeod 《European journal of plant pathology / European Foundation for Plant Pathology》2011,130(2):215-229

Several species of fungi and oomycetes including Fusarium, Rhizoctonia, Phytophthora and Pythium have been reported as root pathogens of apple where they contribute to a phenomenon known as apple replant disease. In South Africa, little is known about specific species in these genera and their pathogenicity toward apple. Therefore, these aspects were investigated along with the development and optimization of qPCR tests for detection and quantification of the most virulent oomycete species. In eight investigated orchards, the oomycete Phythophthora cactorum was widely distributed, while nine Pythium species were differentially distributed among the orchards. Pythium irregulare was the most widely distributed and the most virulent species along with P. sylvaticum, P. vexans and Ph. cactorum. Seven binucleate Rhizoctonia anastomosis groups (AGs) were also differentially distributed among the orchards, with the majority appearing to be non-pathogenic while certain AG-I and AG-F isolates exhibited low virulence on apple. In the genus Fusarium, F. oxysporum was widely distributed, but isolates were non-pathogenic. Fusarium solani and F. avenaceum were less frequently encountered, with only some isolates having low virulence. qPCR data obtained from seedling roots inoculated with the most virulent Pythium species (P. irregulare, P. sylvaticum and P. vexans) and the genus Phytophthora were not always reproducible between trials, or isolates of the same species. In general, seedling growth inhibition was associated with the presence of a low amount of pathogen DNA (±40 fg μl⁻¹ to 2 pg μl⁻¹) in roots. Pythium irregulare, although having the lowest DNA concentrations in roots, was the only species for which a significant negative correlation was found between seedling weight and pathogen DNA concentration.  相似文献   

Relationships of dead wood patterns with biophysical characteristics and ownership according to scale in Coastal Oregon,USA   总被引：1，自引：0，他引：1  

Rebecca S. H. Kennedy  Thomas A. Spies  Matthew J. Gregory 《Landscape Ecology》2008,23(1):55-68

Dead wood patterns and dynamics vary with biophysical factors, disturbance history, ownership, and management practices; the relative importance of these factors is poorly understood, especially at landscape to regional scales. This study examined current dead wood amounts in the Coastal Province of Oregon, USA, at multiple spatial scales. Objectives were to: (1) describe current regional amounts of several characteristics of dead wood; (2) compare dead wood amounts across ownerships; (3) determine the relative importance, according to spatial scale, of biophysical and ownership characteristics, to regional dead wood abundance. Dead wood plot data were evaluated with respect to explanatory variables at four spatial scales of resolution: plots, subwatersheds, watersheds and subbasins. The relationships of dead wood characteristics with biophysical attributes and ownership were diverse and scale-specific. Region-wide dead wood abundance and types varied among ownerships, with public lands typically having higher amounts of dead wood and more large dead wood than private lands. Regression analysis of total dead wood volume indicated that ownership was important at the subbasin scale. Growing season moisture stress was important at plot, subwatershed, and watershed scales. Topography was important at the two coarser scales. Multivariate analysis of dead wood gradients showed that ownership was important at all scales, topography at the subbasin scale, historical vegetation at watershed and subbasin scales, and current vegetation at plot and subwatershed scales. Management for dead wood and related biodiversity at watershed to landscape scales should consider the distinct dynamics of snags and logs, the importance of historical effects, and the relevance of ownership patterns.  相似文献   

Influence of landscape structure,topography, and forest type on spatial variation in historical fire regimes,Central Oregon,USA     

Andrew G. Merschel  Emily K. Heyerdahl  Thomas A. Spies  Rachel A. Loehman 《Landscape Ecology》2018,33(7):1195-1209

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Phytophthora species distribution in South African citrus production regions     

J. C. Meitz-Hopkins  M. C. Pretorius  C. F. J. Spies  L. Huisman  W. J. Botha  S. D. Langenhoven  A. McLeod 《European journal of plant pathology / European Foundation for Plant Pathology》2014,138(4):733-749

Several Phytophthora spp. are known to cause a range of symptoms on citrus, resulting in significant crop losses worldwide. In South Africa, Phytophthora remains a destructive citrus disease, but the species and their distribution have not been well documented. A total of 162 Phytophthora isolates was collected from 60 citrus orchards in seven provinces of South Africa (Eastern Cape, Kwazulu-Natal, Limpopo, Mpumalanga, Northern Cape, North West and Western Cape). Isolates were identified to the species level through PCR-RFLP (restriction fragment length polymorphism) analyses of the internal transcribed spacer region. The identity of a subset of the isolates was confirmed using morphological and sequence analyses. Phytophthora nicotianae was the predominant species (76 % of isolates) and occurred in 80 % of the orchards in all of the provinces, followed by P. citrophthora (22 % of isolates in 28 % of orchards). The P. citrophthora isolates were further subdivided into two previously identified subgroups, G1 and G2, with most (69 %) of the isolates belonging to the G1 subgroup. Other Phytophthora species included P. multivora in the Western Cape Province, and an unknown species in the Eastern Cape Province with high sequence similarity (98 %) to a putative new species submitted to GenBank as Phytophthora taxon Sisuluriver. Phytophthora palmivora, a known citrus pathogen, was not identified. Most of the P. nicotianae isolates (79 %) were of the A1 mating type. The P. citrophthora isolates were mostly sterile (64 %), including most of the G1 isolates (81 %). The remaining G1 isolates (19 %) belonged to the A1 mating type, whereas almost all G2 isolates belonged to the A2 mating type except for one isolate that was sterile.  相似文献   

Evaluation of genetic variation in Lachenalia bulbifera (Hyacinthaceae) using RAPDs     

Riana Kleynhans  Johan J. Spies 《Euphytica》2000,115(2):141-147

RAPD (randomly amplified polymorphic DNA) analyses were carried out on 21 accessions of Lachenalia bulbifera (Cyrillo) Engl. Five pre-selected primers produced an average of 88% polymorphisms. Fifteen of the 21 accessions could be identified using the five primers. In a pairwise comparison genetic distance values ranging from 0.11 to 1.08 were obtained. These values reveal a high amount of variation within the species. The genetic distance values within the tetraploid and hexaploid groups on the south coast were low, but values were high between the groups on the south coast and those on the west coast. A dendogram was constructed from the RAPD banding profiles, using UPGM cluster analysis. The dendogram clusters certain accessions together. These clusters are supported by their geographical locality and chromosome data. The hexaploid group, tetraploid group and octoploid group on the south coast are respectively clustered together. It is concluded that RAPDs can be used to assess the genetic variation at an intra-specific level in Lachenalia. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Restoring fire-prone Inland Pacific landscapes: seven core principles     

Paul F. Hessburg  Derek J. Churchill  Andrew J. Larson  Ryan D. Haugo  Carol Miller  Thomas A. Spies  Malcolm P. North  Nicholas A. Povak  R. Travis Belote  Peter H. Singleton  William L. Gaines  Robert E. Keane  Gregory H. Aplet  Scott L. Stephens  Penelope Morgan  Peter A. Bisson  Bruce E. Rieman  R. Brion Salter  Gordon H. Reeves 《Landscape Ecology》2015,30(10):1805-1835

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Gonadotropin-releasing hormone receptor binding and pituitary responsiveness in estradiol-primed monkeys     

T E Adams  R L Norman  H G Spies 《Science (New York, N.Y.)》1981,213(4514):1388-1390

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Canopy damage to conifer plantations within a large mixed-severity wildfire varies with stand age   总被引：1，自引：0，他引：1  

Jonathan R. Thompson  Thomas A. Spies  Keith A. Olsen 《Forest Ecology and Management》2011,262(3):355-360

The 2002 Biscuit Fire burned at mixed-severities encompassing over 200,000 ha of publicly owned forestland, including more than 8300 ha of conifer plantations. We used pre- and post-fire digital aerial photography to examine how the level of canopy damage varied within these plantations in relation to topography, weather, vegetation-cover, and management history, with an emphasis on the age of the plantation. We examined 198 plantations that varied widely in age (5-47 years), size (1.25-47 ha), and landscape context. The average level of canopy damage within the plantations was 77%. Based on Random Forest variable importance values, plantation age was the best predictor of canopy damage. Average annual precipitation, elevation and topographic position were ranked second, third, and fourth, respectively. A model selection procedure, using geo-statistical regression models and Akaike’s information criterion, corroborated the importance of plantation age relative to the other predictors tested and also suggested that the influence of age varied over time. The top ranked regression model indicated that the level of canopy damage reached its maximum around age 15 and stayed relatively high until age 25 before declining.  相似文献   

Vegetation and weather explain variation in crown damage within a large mixed-severity wildfire   总被引：1，自引：0，他引：1  

Jonathan R. Thompson  Thomas A. Spies   《Forest Ecology and Management》2009,258(7):1684-1694

The 2002 Biscuit Fire burned through more than 200,000 ha of mixed-conifer/evergreen hardwood forests in southwestern Oregon and northwestern California. The size of the fire and the diversity of conditions through which it burned provided an opportunity to analyze relationships between crown damage and vegetation type, recent fire history, geology, topography, and regional weather conditions on the day of burning. We measured pre- and post-fire vegetation cover and crown damage on 761 digital aerial photo-plots (6.25 ha) within the unmanaged portion of the burn and used random forest and regression tree models to relate patterns of damage to a suite of 20 predictor variables. Ninety-eight percent of plots experienced some level of crown damage, but only 10% experienced complete crown damage. The median level of total crown damage was 74%; median damage to conifer crowns was 52%. The most important predictors of total crown damage were the percentage of pre-fire shrub-stratum vegetation cover and average daily temperature. The most important predictors of conifer damage were average daily temperature and “burn period,” an index of fire weather and fire suppression effort. The median level of damage was 32% within large conifer cover and 62% within small conifer cover. Open tree canopies with high levels of shrub-stratum cover were associated with the highest levels of tree crown damage, while closed canopy forests with high levels of large conifer cover were associated with the lowest levels of tree crown damage. Patterns of damage were similar within the area that burned previously in the 1987 Silver Fire and edaphically similar areas without a recent history of fire. Low-productivity sites on ultramafic soils had 92% median crown damage compared to 59% on non-ultramafic sites; the proportion of conifer cover damaged was also higher on ultramafic sites. We conclude that weather and vegetation conditions — not topography — were the primary determinants of Biscuit Fire crown damage.  相似文献