Identification of resistance genes to Puccinia striiformis in seedlings of Ethiopian and CIMMYT bread wheat varieties and lines

In a controlled environment, the reaction was observed of 42 bread wheat varieties and lines inoculated with 19 isolates of yellow rust differing in their virulence to 20 differential varieties. Five varieties and lines showed resistance to all isolates. The remaining ones appeared to have the genesYr2, Yr3, Yr4, Yr6, Yr7, Yr9 andYrA, either singly or in combination.Yr9 derived from rye was present in 67% of the varieties and lines.Yr4 is the only effective gene in that material as, in Eastern and Central Africa, yellow rust has virulence to the otherYr genes. Recognition of virulence toYr genes is enhanced by the use of a supplemental set of differential varieties supposedly carrying a single gene.Samenvatting Onder geconditioneerde klimaatsomstandigheden zijn 42 Ethiopische en CIMMYT rassen en lijnen van broodtarwe (Triticum aestivum) in het kiemplantstadium geïnoculeerd met 19 isolaten van gele roest die onderling verschilden in hun pathogeniteit voor 20 differentiërende tarwerassen waarvan de resistantie-achtergrond bekend is. De genom-gen relatie is toegepast om resistentiegenen te identificeren. Vier rassen en lijnen bleken resistent te zijn tegen alle isolaten. Verondersteld wordt dat hun resistentie berust op genen die niet eerder herkend waren of op een combinatie van bekende genen die niet compatibel was met de gebruikte isolaten. In het overige tarwemateriaal kon de aanwezigheid worden aangegeven van de resistentiegenenYr2, Yr3, Yr4, Yr6, Yr7, Yr9 enYrA. Het van rogge afkomstige en door het CIMMYT veel gebruikte resistentiegenYr9 was in 28 rassen en lijnen (67%) aanwezig. In het onderzochte tarwemateriaal isYr4 het enige voor Oost en Centraal Afrika effectieve resistentiegen omdat de daar voorkomende gele roest pathogeniteit bezit voor de overige genen. Het herkennen van pathogeniteit van gele roest voor bepaalde resistentiegenen is verbeterd door het toevoegen van tarwerassen met monogene resistentie aan het internatinale gebruikte tarwesortiment voor de determinatie van gele-roestfysio's.     

Rapid detection of stand density,tree positions,and tree diameter with a 2D terrestrial laser scanner

Harvester operators that decide about tree removal during thinnings have currently no instruments to measure stand density continuously before and after the operation. We tested whether basal area can be measured rapidly for this purpose with a 2D terrestrial laser scanner. An algorithm was developed, which automatically detects trees from laser scanner point clouds, measures their position and diameter, and calculates basal area. A field test included 18 laser scans in two Norway spruce stands with a wide range of stand densities, representing situations before and after thinning. Occlusion is a problem of single laser scans, and about one-third of the trees within the scanning range were not detected. Occlusion varies with stem density and branchiness. We therefore applied a flexible scanning range, which is detected automatically based on the laser hit density distribution for each scan. Scanning ranges were between 5.5 and 8.4 m (mean = 7.3 m) in the test scans, which is below the reach of the harvester crane, but still large enough to estimate local stand density. Basal area measured with the laser scanner was unbiased only in one of the two stands. Trees not detected or trees falsely detected caused only small bias of the basal area measurement in one of the two stands. Measurement errors for individual scans were, however, often around 10 m² ha^?1.     

Gastrointestinal nematodes in dogs from Debre Zeit, Ethiopia

The study was conducted during the period between January 2005 and June 2006 to determine the frequency of gastrointestinal (GI) nematode infections of dogs in and around Debre Zeit, using qualitative and quantitative coprological (N = 100) and postmortem examinations (N = 20). By coproscopy 51% dogs were positive for different types of nematodal eggs, out of which 23.5% were with mixed infections. On necropsy 95% animals were found positive for adult parasites, of which 31.6% were showing more than one species of adult nematodes. The coproscopical examination revealed 32% infection with Ancylostoma caninum followed by Toxocara canis (21%), Spirocerca lupi (7%) and Trichuris vulpis (3%), while postmortem examination showed 70, 45, 23.5 and 5% infection, respectively. The study further indicated significant difference (P < 0.05) in overall frequency of GI nematode infections among different age groups but no difference (P > 0.05) between sexes.     

Woody plant diversity,structure and regeneration in the Ambo State Forest,South Gondar Zone,Northwest Ethiopia

For this study in the Ambo State Forest on woody plant diversity, structure and regeneration, 70 quadrats, each 25 m by 25 m, were selected using a systematic random sampling technique and intervals of 100 m along a transect line. For assessing seedlings and saplings,two 2 × 10 m sub quadrats were set upon opposite sides of each main quadrat. Data on species diversity, abundance,structure, basal area, density, frequency and regeneration status were collected and analyzed using standard procedures and programs. Of 58 woody plant species identified,69 % were trees, 16 % were shrubs, 12 % were tree/shrubs and 4 % were climbers. Fabaceae was the most speciesrich family comprising 17 species. The Shannon–Weiner diversity index was 2.73, and evenness was 0.67. The population structure in the cumulative diameter class frequency distribution revealed an interrupted and inverted J-shape with a very high decrease in higher diameter class.Acacia lahai(49 %) was the most important woody species with the highest importance value index. To maintain balanced structure, enhanced regeneration and protecting the forest from selective cutting are recommended.     

Genetic diversity in tef [Eragrostis tef (Zucc) Trotter] and its relatives as revealed by Random Amplified Polymorphic DNAs

Tef is one of the staple cereal crops in Ethiopia. To evaluate genetic diversity of tef and its relatives, 47 accessions of tef, three accessions of E. pilosa, and six accessions of E. curvulawere analyzed using random amplified polymorphic DNA (RAPD) markers. The level of polymorphism among the wild species was extremely high, while low polymorphism was detected among tef accessions. All cultivars and wild species under study could be distinguished with the help of different primers, thereby indicating the potential of RAPD in the genetic fingerprinting of tef. Accessions from E. curvula and E. pilosa can be differentiated by a single selected primer. In spite of low polymorphism within tef, accessions under study could be distinguished by a combination of selected primers. Cluster analysis indicated that tef is a very closely related species to E. pilosa with 45%similarity, supporting the hypothesis that tef originated from E. pilosa based on morphological data. Given that RAPD are relatively quick, simple to use, and are not subjected to environmental influences, they provide a valuable new approach for the genetic fingerprinting and study of genetic diversity in tef. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of amplified fragment length polymorphism markers in tef, Eragrostis tef (Zucc.) Trotter, and related species

Tef is an important cereal crop in Ethiopia. This study was conducted to investigate (1) genetic diversity within and among three Eragrostis species (E. tef, E. pilosa and E. curvula), and (2) the relationship between E. tef, E. pilosa and E. curvula. A total of 529 AFLP markers were obtained, out of which 58% (368) were polymorphic, using 10 primer, combinations. The three species were separated distinctly using amplified fragment length polymorphism (AFLP), However, diversity revealed at the morphological trait level was not commensurate with that observed for AFLP. This was due to the small number of morphological traits available and their interaction with the environment. Within tef, ‘Rubicunda’ and DZ‐01‐1093 were found to be distantly related to the rest of the tef accessions. The diversity within species was such that E. pilosa was the most diverse followed by E. curvula and E. tef. Moreover, E. pilosa was more closely related to E. tef than E. curvula. Therefore, further study is needed of E. pilosa accessions and of ‘Rubicunda’ and DZ‐01‐1093 in a crossing programme to generate a population for selection and/or genetic mapping. A total of 19 cultivars or accessions had one or more unique fragments using one or more AFLP primers, indicating the potential of the technology in fingerprinting tef in a breeding or seed multiplication programme.     

Epidemiology of paratuberculosis in wild ruminants studied by restriction fragment length polymorphism in the Czech Republic during the period 1995-1998

In two studies carried out during the period 1995-1998, paratuberculosis was diagnosed in domestic and wild ruminants in the Czech Republic. The isolated Mycobacterium avium subspecies paratuberculosis strains were analysed by standardised restriction fragment length polymorphism (RFLP) [Pavlik, I., Horvathova, A., Dvorska, L., Bartl, J., Svastova, P., du Maine, R., Rychlik, I., 1999. J. Microbiol. Methods 38, 155-167]. In December 1992, 19 late pregnant Charolais heifers were imported to the Czech Republic from Hungary (original import from France to Hungary). One 11-month-old heifer roamed in the wild in a range of approximately 15-20km for 7 months from November 1993 to May 1994. Upon capture, the animal showed clinical signs of paratuberculosis (emaciation and diarrhoea). Seven other animals from the same herd were infected with the identical RFLP type B-C1 of M. paratuberculosis. During the period 1995-1996, samples were taken and examined from the small intestine and corresponding lymph nodes of 84 wild ruminants: 19 red deers (Cervus elaphus) and 65 roe-deers (Capreolus capreolus). These wild ruminants originated from 44 different locations within the same district from as the infected escaped heifer. Five M. paratuberculosis strains were isolated: one strain of RFLP type B-C1 from a stag and three strains of RFLP type B-C1 and one strain of RFLP type B-C9 from roe-deer. The three wild ruminants (one stag and two roe-deer) infected with the same RFLP type B-C1 were detected in the same area as the heifer, suggesting that this was the likely infection source. However, the infection source of the roe-deer infected with strain of RFLP type B-C9 was obviously different, and the stags that escaped from the farm were purchased from an area infected with this RFLP type. In the second study carried out during 1997-1998 in the whole Czech Republic (divided into 76 districts), 718 wild ruminants were examined from 90% of the districts. M. paratuberculosis was isolated from 25 (3.5%) animals from the wild, from farms and from game parks: 7.1% of 132 red deers, 1.5% of 336 roe-deers, 3.9% of 178 fallow deers (Dama dama), and 4.2% of 48 moufflons (Ovis musimon). This study discovered three RFLP types (B-C1, D-C12 and M-C16). A surprising finding was that of M. paratuberculosis (RFLP type B-C1) infection in roe-deer and a fallow deer in their natural habitat. The infection source was determined to have originated from two imported Holstein and Limousine cattle herds infected with the same strain. In the case of a mother and daughter roe-deer infected with RFLP type M-C16 and a fallow deer infected with RFLP type D-C12, all roaming in their natural habitat, the infection source was not discovered. The highest incidence of clinically ill wild ruminants was found in farmed red deer, and no relationship was found between the RFLP type or ruminant species and clinical status of animal.     

Phenotypic diversity for qualitative and phenologic characters in germplasm collections of tef (Eragrostis tef)

A total of 3600 entries of tef [Eragrostis tef (Zucc.) Trotter] germplasm collections representing 36 populations from six regions of Ethiopia were evaluated for phenotypic diversity in six qualitative and phenologic characters. High values of Shannon–Weaver diversity index ( ) were recorded for most characters in each population. Monomorphism was high for anther color (purple) and panicle form (loose). Larger variances for were obtained among regions than among populations within a region from hierarchical analysis of variance. Significant (P<0.05) to highly significant (P<0.01) t-values were observed among values of some regions for seed color, panicle form and days to maturity. A substantial level of variance (P<0.05) was obtained for populations within altitudinal zones only for days to maturity. Altitudinal zones exhibited similar levels of diversity across characters for these collections. Generally, considerable variations important for tef improvement work have been observed and regions with highest diversity for some traits have been suggested for future in situ or ex situ germplasm conservation works. Although similar mean diversity indices were obtained among regions, they were non overlapping.     

Sources of Resistance to Stem Rust (<Emphasis Type="Italic">Puccinia graminis</Emphasis> f. sp. <Emphasis Type="Italic">tritici</Emphasis>) in Ethiopian Tetraploid Wheat Accessions

Seedlings of 41 emmer (Triticum dicoccon Schrank) and 56 durum (T. durum Desf.) wheat accessions were evaluated for their response to stem rust (Puccinia graminis f. sp. tritici) infection under greenhouse condition at Kulumsa Agricultural Research Center, Ethiopia. The objectives were to identify tetraploid wheat accessions that could serve as sources of resistance to stem rust, and postulate the stem rust (Sr) resistance genes through multipatotype testing. The test included screening of accessions for stem rust resistance and multipatotype testing. To ensure vigorous screening, a mixture of six isolates (Si-1a, Am-2, Ku-3, Dz-4a, Ro-4 and Na-22) that were collected from severely infected emmer, durum, and bread wheat (Triticum aestivum L.) varieties of major wheat growing areas of Ethiopia was used as inocula. Out of the tested accessions, 18 emmer and 6 durum accessions exhibited low infection types (0–2) response and hence selected as a source of resistance to stem rust infection. Multipatotype testing was done to postulate Sr genes in the selected accessions. In the test, 10 different stem rust races (A2, A9, A11, A14, A16, A17, B3, B7, B15, and B21), 33 stem rust differential lines, and a universal susceptible check variety, Morocco were used, The high (3–4) and low infection type reaction patterns of the tested accessions and differential lines were used to postulate the genes that exhibit gene-for-gene relationship. The presence of Sr 7b, 8b, 9a, 9b, 10, 14, 24, 27, 28, 29, 30, 31, 32 and Tt-3+10 genes were postulated in 16 selected emmer and 5 durum wheat accessions. Efforts to transfer these valuable Sr genes from cultivated tetraploid wheats could be rewarding to get stem rust resistant varieties and boost wheat production.     

Surfactant-Enhanced Soil Washing for Removal of Petroleum Hydrocarbons from Contaminated Soils: A Review

An increase in energy demand leads to further exploration, transportation, and utilization of petroleum, which creates severe soil contamination because of recurrent accidents and oil spills. Remediation of these contaminated soils is challenging. Among many treatment methods practiced for remediation of petroleum-contaminated soils, surfactant-enhanced soil washing has been widely practiced as a preferred treatment option, as it is a fast and environmentally accepted method. In this paper, we review research undertaken on various anionic, nonionic, cationic, biological, and mixed surfactants for the remediation of petroleum hydrocarbon-contaminated soils. Upcoming surfactants like gemini and switchable surfactants are summarized. We assess the challenges and opportunities of in-situ and ex-situ soil washing, the mechanisms of surfactant-enhanced soil washing, and the criteria to follow for surfactant selection. Furthermore, we briefly discuss the operational and environmental factors affecting soil washing efficiency and soil and surfactant properties affecting surfactant adsorption. We also describe the advantages of coupling soil washing with effluent treatment and surfactant reuse challenges and opportunities. Moreover, challenges and possible new directions for future research on surfactant-enhanced soil washing are proposed.