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The aim of the research was to make a preliminary determination of the effectiveness of the in duc tion of haploids in Capsicum frutescens L. In order to induce androgenesis red and yellow fruit forms of species were used, each bred by the re searchers on their own. The experiment was per formed in October. An ther cultures were conducted according to a modified me - thod developed by Dumas et al. (1981) for C. annuum L. The anthers were laid on CP medium con taining 0.01 mg·dm⁻³ 2.4-D and 0.01 mg·dm⁻³ kinetin, with the addition of 0.5 g·dm⁻³ of activated carbon and 5 mg×dm⁻³ of silvernitrate, solidified with 8 g·dm⁻³ of agar. The cul tures were in cu bated in the dark at 35 deg C for 8 days. Next they were trans ferred to 25 deg C under a 12-hour photoperiod. After 14 days of induction, anthers were trans ferred to R₁ medium supplemented with 0.1 mg·dm⁻³ kinetin. Obtained embryos were subsequently transplanted onto V₃ hormone-free me dium and well growing plants were planted in green houses. The efficiency of androgenesis for both C. frutescens L. forms was relatively low and it did not exceed 5 %. The ploidy level of the result ing plants was determined by flow-cytometric analysis. The regenerants con sisted of about equal numbers of haploids and diploids. Additionally, among plants regenerated from anthers of yellow fruit forms, two mixoploids were observed.
Haploid plants after doubling the chromosomes can give rise to diploid homozygote lines, which can be used as DH lines in breeding new varieties or as initial plant material in creating F1 hybrids. This work studied natural polyembryony and the effect of growth regulators on induction of polyembryonic seeds and haploid embryogenesis in five species of the genus Capsicum. Water solutions of the following growth regulators were used: 2,4-D (2,4-dichlorophenoxyacetic acid) and BNOA (beta-naphthoxyacetic acid) at 0.001% used separately or combined with BAP (benzylamino-purine). Twin seed frequency was highest in C. chinense and lowest in C. baccatum var. pendulum. In C. annuum the share of twin embryos was highest in the 'Corno di toro' variety; 2,4-D clearly increased the number of twin plants only in 'Corno di toro' seeds. Treatment with combinations of 2,4-D or BNOA with BAP increased the frequency of polyembryonie seeds in the 'ATZ1' line. In C. frutescens the frequency of polyembryony increased following application of BNOA with BAP. Of all the seeds tested, seven haploid plants were obtained, representing C. frutescens, C. chacoense and C. baccatum var. pendulum. The differences in the frequency of polyembryony in the studied genotypes points to genetic control of this phenomenon. The presence of monoploid plants definitely depends on the genotype, as a high frequency of polyembryony is not always accompanied by a high share of haploid plants. For most genotypes evaluated, the effect of growth regulators was disadvantageous, resulting in a considerable decrease in the share of twin plants among germinated seeds.
Results of crosses between Hordeum bulbosum (2x) and H. vulgare (2x) are presented. Nine H. vulgare genotypes of different crossability with H. bulbosum were treated both as female and male parents. Immature embryos were cultured in vitro according to ADAMSKI and SURMA (1994). Seeds set, embryo development and obtained haploid plants were recorded. It was shown that seed setting and haploid plant efficiency (haploids/100 florets) were about ten times lower in H. bulbosum x H. vulgare than in H. vulgare × H. bulbosum The cvs. Vada, Apex and the doubled haploid line KA7/3 (related to Apex) which showed a low crossability in H. vulgare × H. bulbosum, gave a relatively high seed setting in reciprocal crosses. The obtained results indicate that partial incompatibility of some H. vulgare genotypes with H. bulbosum could be cytoplasmatically influenced.
The utility of haploids and DH lines for breeding programmes and basic research is discussed here. High effectiveness of haploid induction from random responding gametes and from valuable donor plants is not sufficient to ensure success in breeding. DH lines often appeared inferior to conventionally obtained inbred lines. One of the causes may be a very high level of homozygosity, in this paper referred to as excessive homozygosity. Besides, colchicine treatment as well as gametoclonal and somaclonal variation could have a negative effect on the agronomic performance of DH plants. Lack of natural selection in the first stages of haploid development is another important factor, negatively influencing haploid utility. On the other hand, there is a wide range of possibilities of using haploids as model plants for basic research. Among different applications, including mapping, genetic analysis, mutations, transformation, somatic hybridisation, biochemical and physiological studies, artificial seed production and germplasm storage, the first seems to be explored most effectively and give promising results.
The investigated material involved three pungent soft-flesh forms selected from a Capsicum frutescens L. x C. annuum L. hybrid. Capsaicinoid contents, determined by the HPLC technique in the fruit pericarp, amounted to 100 mg. kg-1. The anthers were cultured in vitro employing the method described by Chambonnet (1988) for C. annuum L. with modification involving an increase in kinetin content in R1 medium to 0.2 mg. dm-3. The efficacy of embryogenesis ranged between 0.25% and 4.12%, related to the ratio of the number of obtained plants to the number of cultured anthers, depending on genotype and the employed medium. Conversion of the embryos into plants and the general efficacy of androgenesis were highest in one line. In all of them, cytometrically determined DNA content in cells of leaves in the obtained regenerates amounted 1C.
The use of 2,4-D as a post pollination treatment to fertilize florets instead of GA₃ provided a two-fold improvement in seed set, culturable embryos and hence green plant production from wheat and maize pollination. The efficiency of the wheat by maize pollination method for haploid production was equal to the anther culture method in F₁ hybrid combinations that were responsive to anther culture. However, in recalcitrant combinations obtained from non-responsive genotypes the maize pollination method was far superior.
Haploid wheat plants have been produced by a new method of zygote rescue carried out after distant pollination. Wheat stigmas were pollinated with maize pollen and subsequently the activated egg cells from the elongated ovaries were rescued for in vitro plant development in single cell culture. As the control, 2-week-old embryos were also dissected and then cultured. The efficiency of both techniques was comparable. Wheat was also pollinated with rice, and the further development of rescued zygotes into multicellular structures is reported here for the first time. Because the lack of a normal endosperm hampers embryo development even in the early stages, early zygote rescue (two days after distant pollination) may represent a more efficient way of producing double haploid (DH) plants in cultivars that are recalcitrant in androgenic cultures, after further optimization of in vitro culture of isolated single cells.
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