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1.
Spirulina platensis (= Arthrospira fusiformis) was isolated from Lake Chitu, a saline, alkaline lake in Ethiopia, where it forms an almost unialgal population. Optimum growth conditions were studied in a turbidostat. Cultures grown in modified Zarrouk's medium and exposed to a range of light intensities (20–500 µmol photons m–2s–1) showed a maximum specific growth rate (µmax) of 1.78 d–1. Quantum yield for growth (µ) was 3.8% at the optimum light for growth of 330 µmol photons m–2s–1, and ranged from 2.8 to 9.4%. With increase in irradiance, the chlorophyll a concentration decreased, and the carotenoids/chlorophyll a ratio increased by a factor of 2.4. The phosphorus to carbon ratio (P/C) showed some variation, while the nitrogen to carbon ratio (N/C) remained relatively constant, thus causing fluctuations in the N:P ratio (7–11) of cells. An optimum N:P ratio of about 7 was attained in cells growing at the optimum light for growth. Results from the continuous culture experiments agreed well with maximum values of photosynthetic efficiency given in the literature for natural populations of S. platensis in the soda lakes of East Africa, Lake Arenguade (Ethiopia), and Lake Simbi (Kenya). 相似文献
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R.B. Linke G. Kebede D. Mushi A. Lakew D.S. Hayes W. Graf A.H. Farnleitner 《Letters in applied microbiology》2021,72(4):458-466
This study tested genetic microbial source tracking (MST) methods for identifying ruminant- (BacR) and human-associated (HF183/BacR287, BacHum) bacterial faecal contaminants in Ethiopia in a newly created regional faecal sample bank (n = 173). BacR performed well, and its marker abundance was high (100% sensitivity (Sens), 95% specificity (Spec), median log10 8·1 marker equivalents (ME) g−1 ruminant faeces). Human-associated markers tested were less abundant in individual human samples (median: log10 5·4 and 4·2 (ME + 1) g−1) and were not continuously detected (81% Sens, 91% Spec for BacHum; 77% Sens, 91% Spec for HF183/BacR287). Furthermore, the pig-associated Pig2Bac assay was included and performed excellent (100% Sens, 100% Spec). To evaluate the presence of MST targets in the soil microbiome, representative soil samples were tested during a whole seasonal cycle (n = 60). Only BacR could be detected, but was limited to the dry season and to sites of higher anthropogenic influence (log10 3·0 to 4·9 (ME + 1) g−1 soil). In conclusion, the large differences in marker abundances between target and non-target faecal samples (median distances between distributions ≥log10 3 to ≥log10 7) and their absence in pristine soil indicate that all tested assays are suitable candidates for diverse MST applications in the Ethiopian area. 相似文献
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Qian Zhang Eyob Kebede Chere Jingying Sun Feng Cao Keshab Dahal Shuo Chen Gang Chen Zhifeng Ren 《Liver Transplantation》2015,5(12)
Iodine‐doped n‐type SnSe polycrystalline by melting and hot pressing is prepared. The prepared material is anisotropic with a peak ZT of ≈0.8 at about 773 K measured along the hot pressing direction. This is the first report on thermoelectric properties of n‐type Sn chalcogenide alloys. With increasing content of iodine, the carrier concentration changed from 2.3 × 1017 cm?3 (p‐type) to 5.0 × 1015 cm?3 (n‐type) then to 2.0 × 1017 cm?3 (n‐type). The decent ZT is mainly attributed to the intrinsically low thermal conductivity due to the high anharmonicity of the chemical bonds like those in p‐type SnSe. By alloying with 10 at% SnS, even lower thermal conductivity and an enhanced Seebeck coefficient were achieved, leading to an increased ZT of ≈1.0 at about 773 K measured also along the hot pressing direction. 相似文献
5.
Phylogeography and conservation genetics of a giant lobelia (Lobelia giberroa) in Ethiopian and Tropical East African mountains 总被引:1,自引:0,他引:1
Lobelia giberroa is a giant rosette plant growing in the afro-montane belt of the afro-alpine environment, a unique and little-studied ecosystem occupying the high mountains of eastern Africa. We analysed amplified fragment length polymorphisms (AFLPs) from 11 mountain systems in Ethiopia and Tropical East Africa to infer the phylogeographical history of the species. A total of 191 individuals were investigated from 25 populations. Principal coordinate analysis and population structure analyses revealed three major phylogeographical groups: the Ethiopian mountains and one group on each side of the Rift Valley in Tropical East Africa, respectively: Elgon-Cherangani and Kenya-Aberdare-Kilimanjaro-Meru. Analysis of Molecular Variance showed 55.7% variance among the three groups, suggesting an old divergence. Together with a clear geographical substructure within the main groups, this pattern indicates gradual expansion and supports the montane forest bridge hypothesis, stating that the area occupied by forest was larger and more continuous in previous interglacials and earlier in the present interglacial. Genetic diversity was lower in Ethiopia than in the other two main groups, possibly due to an ancient founder effect when Ethiopia was colonized from the south. 相似文献
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Bonafoux D Abibi A Bettencourt B Burchat A Ericsson A Harris CM Kebede T Morytko M McPherson M Wallace G Wu X 《Bioorganic & medicinal chemistry letters》2011,21(6):1861-1864
The bioisosteric replacement of the indole core of CRTH2 antagonists using thienopyrroles was investigated, resulting in potent antagonists with good selectivity over DP1. Early ADME/PK assessment of this chemotype demonstrated bioavailability in mice. 相似文献
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Recycling of manure nutrients: use of algal biomass from dairy manure treatment as a slow release fertilizer 总被引:10,自引:0,他引:10
An alternative to land spreading of manure is to grow crops of algae on the N and P present in the manure and convert manure N and P into algal biomass. The objective of this study was to evaluate the fertilizer value of dried algal biomass that had been grown using anaerobically digested dairy manure. Results from a flask study using two soils amended with algal biomass showed that 3% of total algal nitrogen (N) was present as plant available N at day 0. Approximately 33% of algal N was converted to plant available N within 21 days at 25 degrees C in both soils. Levels of Mehlich-3 extractable phosphorus (P) in the two soils rose with increasing levels of algal amendment but were also influenced by existing soil P levels. Results from plant growth experiments showed that 20-day old cucumber and corn seedlings grown in algae-amended potting mix contained 15-20% of applied N, 46-60% of available N, and 38-60% of the applied P. Seedlings grown in algae-amended potting mixes were equivalent to those grown with comparable levels of fertilizer amended potting mixes with respect to seedling dry weight and nutrient content. These results suggest that dried algal biomass produced from treatment of anaerobically digested dairy manure can substitute for commercial fertilizers used for potting systems. 相似文献
8.
Quantitative trait loci influencing drought tolerance in grain sorghum (Sorghum bicolor L. Moench) 总被引:7,自引:0,他引:7
H. Kebede P. K. Subudhi D. T. Rosenow H. T. Nguyen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(2-3):266-276
Drought is a major constraint in sorghum production worldwide. Drought-stress in sorghum has been characterized at both pre-flowering
and post-flowering stages resulting in a drastic reduction in grain yield. In the case of post-flowering drought stress, lodging
further aggravates the problem resulting in total loss of crop yield in mechanized agriculture. The present study was conducted
to identify quantitative trait loci (QTLs) controlling post-flowering drought tolerance (stay green), pre-flowering drought
tolerance and lodging tolerance in sorghum using an F7 recombinant inbred line (RIL) population derived from the cross SC56×Tx7000. The RIL lines, along with parents, were evaluated
for the above traits in multiple environments. With the help of a restriction fragment length polymorphism (RFLP) map, which
spans 1,355 cM and consists of 144 loci, nine QTLs, located over seven linkage groups were detected for stay green in several
environments using the method of composite interval mapping. Comparison of the QTL locations with the published results indicated
that three QTLs located on linkage groups A, G and J were consistent. This is considered significant since the stay green
line SC56 used in our investigation is from a different source compared to B35 that was used in all the earlier investigations.
Comparative mapping has shown that two stay green QTLs identified in this study corresponded to stay green QTL regions in
maize. These genomic regions were also reported to be congruent with other drought-related agronomic and physiological traits
in maize and rice, suggesting that these syntenic regions might be hosting a cluster of genes with pleiotropic effects implicated
in several drought tolerance mechanisms in these grass species. In addition, three and four major QTLs responsible for lodging
tolerance and pre-flowering drought tolerance, respectively, were detected. This investigation clearly revealed the important
and consistent stay green QTLs in a different stay green source that can logically be targeted for positional cloning. The
identification of QTLs and markers for pre-flowering drought tolerance and lodging tolerance will help plant breeders in manipulating
and pyramiding those traits along with stay green to improve drought tolerance in sorghum.
Received: 2 June 2000 / Accepted: 15 November 2000 相似文献
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Naeela Qureshi Pakeerathan Kandiah Mesfin Kebede Gessese Vallence Nsabiyera Vanessa Wells Prashanth Babu Debbie Wong Matthew Hayden Harbans Bariana Urmil Bansal 《Molecular breeding : new strategies in plant improvement》2018,38(8):97
Stem rust of wheat, caused by Puccinia graminis f. sp. tritici (Pgt), is a threat to global food security due to its ability to cause total crop failures. The Pgt race TTKSK (Ug99) and its derivatives detected in East Africa carry virulence for many resistance genes present in modern cultivars. However, stem rust resistance gene Sr26 remains effective to all races of Pgt worldwide. Sr26 is carried on the Agropyron elongatum (syn. Thinopyrum ponticum) segment 6Ae#1L translocated to chromosome 6AL of wheat. In this study, a recombinant inbred line (RIL) population derived from a cross between the landrace Aus27969 and Avocet S, which carries Sr26, was used to develop co-dominant kompetitive allele-specific polymerase chain reaction (KASP) markers that co-segregate with Sr26. Four KASP markers (sunKASP_216, sunKASP_218, sunKASP_224 and sunKASP_225) were also shown to co-segregate with Sr26 in four additional RIL populations. When tested on Australian cultivars and breeding lines, these markers amplified alleles alternate to that linked with Sr26 in all cultivars known to lack this gene and Sr26-linked alleles in cultivars and genotypes known to carry Sr26. Genotypes WA-1 and WA-1/3*Yitpi carrying the shortest Sr26 translocation segment were positive only for markers sunKASP_224 and sunKASP_225. Our results suggest the four KASP markers are located on the original translocation and sunKASP_224 and sunKASP_225 are located on the shortened version. Therefore, sunKASP_224 and sunKASP_225 can be used for marker-assisted pyramiding of Sr26 with other stem rust resistance genes to achieve durable resistance in wheat. 相似文献
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