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排序方式: 共有478条查询结果,搜索用时 15 毫秒
21.
S C Harvey S F Powell D D Kennedy B J McAndrew & D J Penman 《Aquaculture Research》2002,33(5):339-342
The karyotypes of both Oreochromis mortimeri (Trewavas) and Sarotherodon melanotheron (Rüppell) are shown to consist of 22 pairs of chromosomes (2n = 44). In O. mortimeri, the karyotype is composed of 9 sm/st and 13 t chromosomes. In the case of S. melanotheron, the karyotype is composed of 15 sm/st, 2 m and 5 t chromosomes. The karyotypes of these species are therefore similar to those of the majority of other tilapia species, with that of S. melanotheron being considerably different from that previously reported for this species. 相似文献
22.
23.
Lerat S Gulden RH Hart MM Powell JR England LS Pauls KP Swanton CJ Klironomos JN Trevors JT 《Journal of agricultural and food chemistry》2007,55(25):10226-10231
The presence of the recombinant cp4 epsps gene from Roundup Ready (RR) corn and RR soybean was quantified using real-time PCR in soil samples from a field experiment growing RR and conventional corn and soybean in rotation. RR corn and RR soybean cp4 epsps persisted in soil for up to 1 year after seeding. The concentration of recombinant DNA in soil peaked in July and August in RR corn and RR soybean plots, respectively. A small fraction of soil samples from plots seeded with conventional crops contained recombinant DNA, suggesting transgene dispersal by means of natural process or agricultural practices. This research will aid in the understanding of the persistence of recombinant DNA in agricultural cropping systems. 相似文献
24.
Summary The regular meiotic behaviour of the cultivated oat Avena sativa (2n=6x=42) is genetically controlled. The factors which control the diploid-like meiotic behaviour also restrict the amount of pairing that occurs between alien chromosomes and their homoeologues in A.sativa, and hence increases the difficulties of introducing desirable variation from wild species into the cultivated oat. A genotype of the diploid species A.longiglumis which interferes with the regular meiotic behaviour of A. sativa can be used to induce pairing between alien chromosomes and their corresponding chromosomes in A. sativa. Using this procedure the dominant gene conferring mildew resistance has been transferred from the tetraploid weed species A. barbata into the cultivated oat. 相似文献
25.
The extent of genetic diversity and the genetic relationships among 94 coconut varieties/populations (51 Talls and 43 Dwarfs)
representing the entire geographic range of cultivation/distribution of the coconut was assessed using 12 pairs of coconut
micro satellite primers. A high level of genetic diversity was observed in the collection with the mean gene diversity of
0.647±0.139, with that of the mean gene diversity of Talls 0.703±0.125 and 0.374±0.204 of Dwarfs. A phenetic tree based on
DAD genetic distances clustered all the 94 varieties/populations into two main groups, with one group composed of all the Talls
from southeast Asia, the Pacific, west coast of Panama, and all Dwarfs and the other of all Talls from south Asia, Africa,
and the Indian Ocean coast of Thailand. The allele distribution of Dwarfs highlighted a unique position of Dwarf palms from
the Philippines exhibiting as much variation as that in the Tall group. The grouping of all Dwarfs representing the entire
geographic distribution of the crop with Talls from southeast Asia and the Pacific and the allele distribution between the
Tall and Dwarf suggest that the Dwarfs originated from the Tall forms and that too from the Talls of southeast Asia and the
Pacific. Talls from Pacific Islands recorded the highest level of genetic diversity (0.6±0.26) with the highest number of
alleles (51) among all the regions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
26.
A.H. Marshall T.P.T. Michaelson-Yeates M.T. Abberton A. Williams H.G. Powell 《Euphytica》2002,126(2):195-201
Interspecific hybridisation with Trifolium nigrescens Viv. is a possible strategy to improve the reproductive potential of white clover (Trifolium repens L.). Following the development of a fertile F1 hybrid, three generations of backcrossing have been carried out usingT. repens as the recurrent parent. Vegetative characteristics, stolon growth and seed yield components of the backcross (BC) 2 and
3 generations, as well as the parental species were measured on spaced plants grown in the field. Leaf size and plant spread
of the BC2 and BC3 generations were less than T. repens but there was no difference in plant fresh weight. Numbers of inflorescences per plant and florets per inflorescence of the
backcrosses were greater than T. repens however this was not reflected indifferences in seed yield per plant asT. repens had more seeds per floret and per plant than the backcrosses. Differences in stolon length, the proportion of flowering nodes
and the pattern of axillary bud development were observed between T. repens and the backcrosses. Significant variation among the BC 3 generation for vegetative and reproductive traits was observed.
Individual plants among the BC 3 generation were identified that combine high forage yield, substantial inflorescence production
and good fertility, and these will form the basis of further selection.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
27.
Quantitation of transgenic plant DNA in leachate water: real-time polymerase chain reaction analysis
Gulden RH Lerat S Hart MM Powell JR Trevors JT Pauls KP Klironomos JN Swanton CJ 《Journal of agricultural and food chemistry》2005,53(15):5858-5865
Roundup Ready (RR) genetically modified (GM) corn and soybean comprise a large portion of the annual planted acreage of GM crops. Plant growth and subsequent plant decomposition introduce the recombinant DNA (rDNA) into the soil environment, where its fate has not been completely researched. Little is known of the temporal and spatial distribution of plant-derived rDNA in the soil environment and in situ transport of plant DNA by leachate water has not been studied before. The objectives of this study were to determine whether sufficient quantities of plant rDNA were released by roots during growth and early decomposition to be detected in water collected after percolating through a soil profile and to determine the influence of temperature on DNA persistence in the leachate water. Individual plants of RR corn and RR soybean were grown in modified cylinders in a growth room, and the cylinders were flushed with rain water weekly. Immediately after collection, the leachate was subjected to DNA purification followed by rDNA quantification using real-time Polymerase Chain Reaction (PCR) analysis. To test the effects of temperature on plant DNA persistence in leachate water, water samples were spiked with known quantities of RR soybean or RR corn genomic DNA and DNA persistence was examined at 5, 15, and 25 degrees C. Differences in the amounts and temporal distributions of root-derived rDNA were observed between corn and soybean plants. The results suggest that rainfall events may distribute plant DNA throughout the soil and into leachate water. Half-lives of plant DNA in leachate water ranged from 1.2 to 26.7 h, and persistence was greater at colder temperatures (5 and 15 degrees C). 相似文献
28.
Precipitation of sulfide ores and organic matter: sulfate reactions at pine point, Canada 总被引:1,自引:0,他引:1
Bitumen is a common associate of carbonate-hosted lead-zinc deposits. On the Pine Point lead-zinc property, Northwest Territories, Canada, there are two forms of bitumen. Unaltered bitumens have atomic hydrogen/carbon ratios of about 1.4, sulfur contents of about 7.8 percent, and sulfur isotope ratios ( section sign(34)S) of approximately +4.6 per mil. Altered bitumens occur in proximity to sulfide ore bodies and white sparry dolomite. Their hydrogen/carbon ratios are about 1.02, the sulfur contents average 22 percent, and the section sign(34)S values are about +12.4 per mil. These data indicate that some bitumen has participated in the thermochemical reduction of sulfate to produce hydrogen sulfide required to precipitate the ores. Mass balance considerations show that the amount and degree of alteration of bitumen is more than adequate to account for the reduced sulfur species (lead, zinc, and iron sulfides) deposited at Pine Point. These reactions may provide an important means of generating the large volumes of sulfide necessary to precipitate ore bodies in carbonate rocks. 相似文献
29.
Sulfur difluioride has been identified and characterized from its microwave spectrum. The analysis of rotational transitions for both sulfur difluoride-32 and sulfur difluoride-34 shows that this molecular species has C(2v) symmetry with a bond length of 1.589 angstroms, a bond angle of 98 degrees 16', and a dipole moment of 1.05 Debye. 相似文献
30.
Induction of HTLV-III/LAV from a nonvirus-producing T-cell line: implications for latency 总被引:42,自引:0,他引:42
T Folks D M Powell M M Lightfoote S Benn M A Martin A S Fauci 《Science (New York, N.Y.)》1986,231(4738):600-602
When the human T-cell line A3.01 is infected with HTLV-III/LAV, the virus associated with the acquired immune deficiency syndrome (AIDS), most of the cells are killed. However, a small number of cells that lack the Leu-3 surface marker survive. Under normal conditions these surviving cells do not produce virus, nor can they be infected by the virus, but they can be induced to produce virus by treatment with 5-iodo-2'-deoxyuridine. This response can be induced for as long as 3 months after the initial infection, suggesting that the cells may harbor a latent form of HTLV-III/LAV. 相似文献