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Cultivation of sunflower (Helianthus annuus L.) is strongly affected by Sclerotinia sclerotiorum. To identify new sources of genetic diversity for sunflower breeding 25 sunflower inbred lines were analysed using eight Amplified Fragment Length Polymorphism (AFLP) primer combinations and their genetic similarities (GS) were estimated. Data were used to develop a Unweighted Pair Group Method using Arithmetic Averages (UPGMA) dendrogram. GS values of 0.58‐0.98 were observed but with no separate groupings dependant on oil quality. The inbred lines were screened for their reaction to inoculation with Sclerotinia sclerotiorum (Lib.) de Bary. Sunflower heads were artificially inoculated with S. sclerotiorum in three environments. Head infection was monitored after 1 week (lesion length) and 2 weeks (head rot). The F5 generation of a cross between a resistant (SWS‐B‐04) and a susceptible inbred line (SWS‐B‐01) was also tested for sclerotinia reaction across three environments. Significant differences in sclerotinia resistance, moderate heritabilities and a high correlation between the two assessments were observed. Inbred lines with a high level of resistance could be identified. These lines can be used for further breeding to improve sunflower sclerotinia resistance and to develop superior new hybrids. 相似文献
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S. Rönicke V. Hahn R. Horn I. Grone L. Brahm H. Schnabl W. Friedt 《Plant Breeding》2004,123(2):152-157
Sclerotinia sclerotiorum is considered the most devastating pathogen of sunflower grown in humid environments. In this study, progenies of partial hybrids between Helianthus maximiliani, a wild species that has been shown to be resistant to S. sclerotiorum, and H. annuus were characterized by amplified fragment length polymorphism (AFLP) analysis to identify whether there are introgressions from H. maximiliani into the cultivated sunflower at the molecular level. Wild species‐specific fragments as well as fragments not found in either parent were detected. Progenies tended to cluster together according to the original partial hybrids in the dendrogram by the use of bootstrap procedures. The progenies were studied for their reaction to S. sclerotiorum using artificial inoculation of sunflower heads. Some of the progenies showed a higher level of resistance compared with resistant inbred lines. It was possible to identify two AFLP‐fragments which seem to be linked to Sclerotinia resistance. 相似文献
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Sclerotinia sclerotiorum (Lib.) de Bary is a major limiting factor for sunflower (Helianthus annuus) production. This study was conducted to (1) evaluate a large number of current sunflower lines for their reaction to Sclerotinia, and (2) determine the optimum allocation of resources for their selection. A set of 85 inbred lines was screened under artificial leaf infection in three environments. The test revealed ample variation for all resistance traits in the current germplasm. A line selected from NDBLOS, an oilseed sunflower germplasm poo, and its derivatives were most resistant to Sclerotinia. Lines derived from interspecific crosses with the wild species Helianthus tuberosus and Helianthus argophyllus also showed satisfactory Sclerotinia resistance. The evaluation of five plants per plot in two replications and four environments appears to be a reasonable allocation of resources in order to optimize the selection response. 相似文献
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Genetic variation in HTLV-III/LAV over time in patients with AIDS or at risk for AIDS 总被引:89,自引:0,他引:89
B H Hahn G M Shaw M E Taylor R R Redfield P D Markham S Z Salahuddin F Wong-Staal R C Gallo E S Parks W P Parks 《Science (New York, N.Y.)》1986,232(4757):1548-1553
In a study of genetic variation in the AIDS virus, HTLV-III/LAV, sequential virus isolates from persistently infected individuals were examined by Southern blot genomic analysis, molecular cloning, and nucleotide sequencing. Four to six virus isolates were obtained from each of three individuals over a 1-year or 2-year period. Changes were detected throughout the viral genomes and consisted of isolated and clustered nucleotide point mutations as well as short deletions or insertions. Results from genomic restriction mapping and nucleotide sequence comparisons indicated that viruses isolated sequentially had evolved in parallel from a common progenitor virus. The rate of evolution of HTLV-III/LAV was estimated to be at least 10(-3) nucleotide substitutions per site per year for the env gene and 10(-4) for the gag gene, values a millionfold greater than for most DNA genomes. Despite this relatively rapid rate of sequence divergence, virus isolates from any one patient were all much more related to each other than to viruses from other individuals. In view of the substantial heterogeneity among most independent HTLV-III/LAV isolates, the repeated isolation from a given individual of only highly related viruses raises the possibility that some type of interference mechanism may prevent simultaneous infection by more than one major genotypic form of the virus. 相似文献
40.
Mouse erythrocytes, parasitized by chloroquine-sensitive plasmodia, concentrate this drug in vivo to levels over twice as high as erythrocytes parasitized by chloroquine-resistant plasmodia; nonparasitized red cells accumulate little chloroquine. Selective toxicity of this drug may depend upon a special drug-concentrating mechanism of plasmodic impairment of such mechanism. 相似文献