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排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
Xiao-Hua Qi Ming-Fang Zhang Jing-Hua Yang 《Genetic Resources and Crop Evolution》2007,54(8):1709-1716
Sequence variation of nuclear internal transcribed spacer regions of ribosomal DNA (ITS1, 5.8S rRNA and ITS2) from Chinese
vegetable mustards (AB-genome) and its putative parents Brassica rapa (the A-genome) and Brassica nigra (the B-genome) were used to investigate the molecular phylogeny and the probable evolutional pattern of this amphidiploid
species that uniquely formed in China. Totally, 16 accessions of Chinese vegetable mustard those covering nearly all the diverse
variations were included in this study, and together with three accessions of B. rapa and one accession of B. nigra. The results disclosed two strongly supported clades, one containing four accessions of vegetable mustard which have closer
relationship with B-genome species “B.nigra” lineage and the other containing 12 accessions of B. juncea and three A-genome accessions. This classification was in disagreement with the evidence from chloroplast DNA, mitochondrial
DNA, nuclear DNA restriction fragment length polymorphism (RFLP), which suggested that B. juncea was closely related to the A-genome type. For the incongruence, we speculated that the B. juncea crops derived from Chinese have evolved through different recombined events of the diploid morphutypes and evolved unidirectional
concerted evolution. The traditional phenotypic classification of B. juncea was not wholly supported by ITS results, and hence the phylogenetic relationships among these subspecies need to be reconsidered
on molecular level. 相似文献
992.
A study was conducted with the objective of obtaining a profile of farmers who have participated in the Farm Partnership Scheme
in Ireland. This scheme is a joint venture between Coillte (The Irish Forestry Board) and farmers. Under the terms of the
scheme, Coillte is responsible for the establishment, management and harvesting of the forest plantation on the farmer’s land.
The farmer retains ownership of the land, receives premium payments and shares in the harvesting profits. Fifty farmers who
joined the Farm Partnership Scheme between 1993–1997 were interviewed in 1999 and a detailed questionnaire was completed.
Survey results indicate that the typical farm partner was male, married and aged 50 years or older. Over half of those surveyed
had an off-farm job. The most popular reason for farmers opting to participate in the Farm Partnership Scheme was that they
did not have sufficient time to undertake the establishment and management of a forest plantation themselves. The average
size of forest established under the scheme was 23.7 ha, with Sitka spruce the most popular species planted. The average annual
payment under the scheme was €8077. For 46% of those surveyed, the returns from the Farm Partnership Scheme comprised all
of their farm income. 相似文献
993.
In landlocked countries, the role of fish is often poorly known and/or propagated. In many countries fish represent the biggest and qualitatively most valuable protein source (24% of the worldwide available animal protein) for human consumption. At present the economic significance of the production and trade of fish is already very high. However, according to FAO, the future demand of proteins can only be covered by a considerable expansion of the aquaculture production, in particular because of a stagnated fish catch and a continuous reduction of the agricultural production. The ideational value of ornamental fish appears obvious however pet fish keeping represents also a value worth of many millions US dollars worldwide. Finally the importance of fish will not only increase for economic, but certainly also for ecological reasons, because it is well established as an incorruptible bioindicator of our environment. 相似文献
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H W Hannah 《Journal of the American Veterinary Medical Association》1970,157(10):1299-1300
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