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排序方式: 共有591条查询结果,搜索用时 43 毫秒
41.
Hitoshi Kubota Takahide Doi Shoichiro Yamamoto Seiichi Watanabe 《Fisheries Science》2007,73(2):270-284
ABSTRACT: Stocking of exogenous, hatchery-reared white-spotted charr Salvelinus leucomaenis has been conducted throughout much of their range in Honshu Island, Japan, to increase angling opportunities. Although the native charr populations are thought to have declined because of hybridization with introduced fish, their distribution and genetic status have been uncertain. Fine population structures of charr in the upper Tone River drainage were examined using mitochondrial DNA and microsatellite analyses so as to clarify the presence of native populations. One common mtDNA haplotype was detected in all populations in the Ohashi River and Watarase River, and four and one tributary populations were monomorphic for such haplotypes, respectively. However, several haplotypes, considered to have originated from stocked hatchery fish, were observed in the stocked and the remaining populations. Judging from the genetic integrity over a fine geographic scale, the former were considered as indicative of native populations and the latter as admixtures with hatchery fish. Comparisons of genetic diversity, deviations from the Hardy–Weinberg equilibrium, principal component analysis, and relatedness estimations based on microsatellite DNA can also provide evidence for distinguishing native populations from those influenced by hatchery fish. 相似文献
42.
[目的]为明确枣棉间作模式下不同施氮量对棉花根际微生物的影响。[方法]通过田间小区试验,研究0、150、300、450、600、750 kg/hm26种施氮水平对枣树‖棉花模式中棉花根际土壤中细菌、真菌和放线菌数量的变化动态。[结果]300和450 kg/hm2施氮量能显著增加蕾期、花期和吐絮期微生物总数量。细菌和放线菌在整个生育期中蕾期数量最少,铃期和花期较高,吐絮期次之。真菌数量各个时期变化不大。适宜施氮量能增加铃期枣棉间作交际行棉花根际土微生物数量。[结论]该研究可为枣棉间作系统合理施用氮肥提供科学依据。 相似文献
43.
Abstract The ormer, Haliotis tuberculata L., is the only abalone species found on the coasts of western Europe, its northern most limit of distribution being the Channel Islands. Previous Guernsey ormer population studies were based upon a form of catch-per-unit-effort sampling where the unit of effort was one diver, searching the substrate for 5 min continuously. An ormer population survey was carried out in the waters around Guernsey, using this former method concurrent with an alternative system of sampling by area using 10 m2 quadrats at randomly selected locations. The published results of a series of earlier surveys include a measure of ormer density m-2 which, along with knowledge of the extent of suitable substrate, allows tentatively for absolute abundance to be estimated. This study demonstrates that an estimate obtained in this way may be unreliable. Statistical comparison of the population size structures derived from the two different sampling methods also showed considerable inconsistency. The implications of this for management of the Guernsey ormer stock are considered. 相似文献
44.
Chenghui Wang Sifa Li Zoltn Tams Nagy Istvn Lehoczky Len Huang Yan Zhao Xiao Song Zsigmond Jeney 《Aquaculture Research》2010,41(9):1339-1347
China and Hungary are major providers of the common carp (Cyprinus carpio L.) in East Asia and Europe respectively. However, the genetic variation and relationship of this species in the two countries have been poorly understood. In this study, mitochondrial COII‐tRNALys and D‐loop sequences were analysed to investigate the genetic structure and relationships of the representative wild and domesticated common carps distributed in China and Hungary. The results indicated that the genetic diversities of the Chinese common carps are higher than those of Hungarian common carps, and the diversities of the wild common carps are higher than those of domesticated common carps in both the countries. Analysis of molecular variance and pairwise FST demonstrated a significant genetic divergence between the Chinese and the Hungarian common carps, and between the wild and the domesticated common carps. Bayesian phylogenetic analysis and statistical parsimony network showed an obvious genetic differentiation between the Chinese and the Hungarian common carps, between the wild and the domesticated common carps. However, a few specimens and haplotypes from the Chinese wild common carps appeared in the Hungarian common carps, demonstrating that there was no absolutely isolated and possible genetic linker between the Chinese and the Hungarian common carps. 相似文献
45.
Based on polyacrylamide gel electrophoresis, nine natural populations of Atriplex halimus L., a perennial shrub, collected in different regions of Morocco, were studied for their genetic variation using isoenzyme
polymorphism of the highly active enzyme systems: esterases (EST), acid phosphatases (ACP) and glutamate oxaloacetate transaminase
(GOT). Different allozyme frequencies from 7 different loci were obtained for all populations of this halophyte species. High
levels of genetic diversity were revealed. The mean number of alleles per locus (A = 1.9–2.0), the percentage of polymorphic
loci (p = 71.4–85.7) and the mean expected heterozygosity (He = 0.339–0.385) showed an important variability in all populations. Gene diversity was essentially explained by the within
population component. The between populations differentiation accounted for 8% of the whole diversity (FST, averaged over all loci, is 0.08). The relationships among the 9 populations were inferred from the Nei’s genetic distances.
Four major groups were formed. The northern population ‘Tanger’, forming a unique group, was highly divergent from the other
groups. It appeared that the genetic distance between all groups was related to the geographic distance that separates them.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
46.
Although the Advanced Backcross strategy has proven very useful for QTL detection in tomato, it has been used mainly in identifying
QTL for agronomic traits such as yield, color, etc. Tomato flavor is an important quality characteristic, yet it has been
difficult to assess flavor or traits that affect it. In this study the AB-QTL strategy was applied to four advanced backcross
populations to identify QTL for biochemical properties that may contribute to the flavor of processed tomatoes, such as sugars
and organic acids. A total of 222 QTL were identified for 15 traits, including flavor as assessed by a taste panel. Correlations
of certain biochemicals with flavor and possible methods of assessing and improving flavor are discussed. In particular, QTL
with very significant effects associated with the ratio of sugars/glutamic acid, a trait highly correlated with improved flavor,
have been identified as good targets for future work in improving the flavor of tomatoes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
47.
S. P. Singh 《Plant Breeding》1995,114(3):269-271
The objective of this study was to compare the seed yield, seed weight, and maturity of random lines derived from two contrasting populations of common bean ( Phaseolus vulgaris L.): Middle American (TR 7790) and Andean × Middle American (TR 7791). TR 7790 involved crosses between common-bean races of Middle American origin only (Mesoamerica and Durango), whereas TR 7791 involved crosses between races of Middle American and Andean origin (Mesoamerica and Nueva Granada). A total of 85 random lines from each of these two double-cross, interracial populations, a bulk sample of both populations, and all parents were evaluated in a replications-in-set design in eight environments in Colombia between 1991 and 1993. The mean yields of parents, population bulk, and lines from TR 7790 were significantly higher (P < 0.05) than those of TR 7791. Six lines in TR 7790 and nine lines in TR 7791 yielded significantly higher (P < 0.05) than the mean of their parents. Four lines from TR 7790 out-yielded the highest-yielding line from TR 7791. Moreover, while three lines from TR 7790 out-yielded its best parent, none of the lines from TR 7791 out-yielded its highest yielding parent. Thus, substantial yield gains should be expected from interracial populations within the Middle American group of common beans, whereas selection for higher seed yield from Andean × Middle American populations would seem problematic. 相似文献
48.
Morphological variation in Astragalus hamosus L. and Coronilla scorpioides L. populations of Tunisia
Morphological variation between Astragalus hamosus and Coronillascorpioides populations was studied using local germoplasm collected in northern and central Tunisia. Twenty-one morphological traits
were recorded and data were analysed using complementary statistical analysis. Considerable variation based on morphological
and agronomical traits was found between populations and for both species. Pod and peduncle lengths as well as flowers number
were the most discriminant variables between populations. Differences were also found for variables like seed number per pod,
seed yield and dry matter production. Significant correlations were found between plant traits and the environmental parameters
of the origin sites. This study revealed enough variation among populations to initiate a selection programme for pasture
improvement in arid and semi-arid areas of Tunisia, where the two species are well adapted.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
49.
Genetical studies on mildew resistance were carried out with Hordem spontaneum derived lines. A total of 28 lines (66 %) showed monofactorial segregation for mildew resistance, For 14 lines, a bifactorial mode of inheritance was found. In total fifty six mildew resistance genes take part in the inheritance of mildew resistance of the H. spontaneum derived lines, while the presence of known genes for mildew resistance (i.e, Ml-a.9 and Ml-p) was established only in two cases. Independent segregation from the Ml-a locus was found in 10 mbnofaetorial segregating lines, The genes conditioning mildew resistance in barley lines derived from the accessions 1B-54B, RS 170-47, RS 20-1. 1B-86B, RS 145-39 and 1B–152B of H. spontaneum were closely linked or alleles to the Ml-a locus, but shown to be different from 15 previously identified Ml-a alleles. It is suggested that these genes should be designated Ml-a16, Ml-18, Ml-19 Ml-20 and Ml-a21 respectively. No recombinants were found in test crosses when both parents carried genes/alleles of the Ml-a locus. In addition, polymorphism has been observed also for the Ml-a locus. In 4 lines mildew resistance was conditioned by two dominant complementary genes. For one of the 2 genes, conditioning mildew resistance of line RS 42-8 × OrioL a new locus was found located near the centromere of the long arm of chromosome 5, and should be designated Ml-i The potential use of H. spontaneum genes for mildew resistance in barley breeding is discussed. 相似文献
50.
Eviatar Nevo Avigdor Beiles Yitzchak Gutterman Nurith Storch Diane Kaplan 《Euphytica》1984,33(3):717-735
Summary Populations of wild emmer wheat, Triticum dicoccoides, in Israel, originating from diverse habitats, and tested earlier for allozyme (Nevo et al., 1982) and disease resistance polymorphisms (Moseman et al., 1983a, 1983b; Nevo et al., 1984a, 1984b), were compared and contrasted for performance in agronomically important phenotypic traits. The traits compared involved 10 variables comparing germination, earliness, biomass and yield variables. The field experiments were conducted in 1980, 1981 and 1982 in two relatively standardized and contrasting environments: mesic (Mount Carmel, Haifa) and xeric (Acedat Farm, and Sede Boqer, in the northern Negev desert). The experimental design involved 12 population quadrangles at Avedat Farm in 1980, and rows of randomized genotypes of five populations in both Haifa and Sede Boqer in 1981 and 1982.The results indicate that the characters studied are partly genetically determined. Striking genetic variation was found between and, at least in some characters, also within populations in each site, whereas remarkable environmental variation including genetic-environmental interaction was found between the mesic and the xeric sites. We conclude that natural populations of wild emmer wheat in Israel vary not only in genetic polymorphisms of allozymes and disease resistance, but also in quantitative traits of agronomic importance. These traits are economically significant and should be conserved and utilized in wheat crop improvement. 相似文献