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Zjawisko chimeryzmu związane jest z hodowlą chryzantemy wielkokwiatowej na drodze mutagenezy. Chimery, zwłaszcza sektorialne i meryklinalne, u których zmiana barwy pojawia się tylko na niewielkim obszarze całego kwiatostanu, są interesującym źródłem dotychczas traconej zmienności. Ze względu na lokalizację mutacji i mały obszar tkanek objętych mutacją w kwiatostanie, nie można stosować znanych metod separacji genotypów składowych chimer. Jedyną możliwością wyizolowania zmienności jest regeneracja pędów lub zarodków przybyszowych z kwiatów języczkowatych lub ich fragmentów o zmienionej barwie pobieranych z kwiatostanów chimer. Praca przedstawia znaczenie kultur in vitro kwiatów języczkowatych w hodowli chryzantemy oraz opisuje czynniki wpływające na wydajność regeneracji pędów i zarodków przybyszowych.
Chryzantema, obok róży i gerbery, jest jedną z najpopularniejszych roślin ozdobnych na świecie. Chłonny rynek zbytu podlegający prawom mody nieustannie wykazuje zapotrzebowanie na nowe odmiany. Hodowcy podejmują wiele starań, aby zaspokoić wyrafinowane i często zmieniające się gusta klientów. Odmiany popularne w jednym roku są szybko zastępowane. Stąd też największym zainteresowaniem hodowców cieszą się metody pozwalające łatwo i w krótkim czasie uzyskać zmienność pojedynczych cech, jak barwa czy typ kwiatostanu, decydujących w głównej mierze o atrakcyjności nowych odmian. W porównaniu do innych metod, wymagania te najlepiej spełnia indukowana mutageneza. W pracy scharakteryzowano chryzantemę wielkokwiatową, opisano założenia i przebieg programów hodowlanych opartych na indukowaniu mutacji promieniowaniem X i gamma oraz przedstawiono najważniejsze osiągnięcia polskiej hodowli.
Chrysanthemum mutants can be chimeras. The regeneration in vitro of adventitious shoots from ligulate florets can lead to the separation of chimera components, resulting in producing a new cultivar. There was determined the effect of various factors on the number and length of shoots regenerating in vitro from ligulate florets of Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Cool Time’. The ligulate florets were inoculated on the MS [1962] medium supplemented with cytokinin (0; 4.44; 8.88; 13.32; 22.20 μM·dm-3 BAP; 4.65; 23.23; 46.47; 69.70 μM·dm-3 KIN) and auxin (0; 0.54; 1.08; 1.61; 2.69 μM·dm-3 NAA). Most shoots regenerate when 8.88; 13.32 μM·dm-3 BAP or 69.70 μM·dm-3 KIN and 2.69 μM·dm-3 NAA or 8.88 μM·dm-3 BAP and 1.61 μM·dm-3 NAA are supplemented. Adding 0.29; 1.44 or 2.89 μM·dm-3 GA3 to the MS medium with 8.88 μM·dm-3 BAP and 2.69 μM·dm-3 NAA limits the shoot regeneration efficiency and does not stimulate their elongation. An increase in the shoot number and length is affected by the subculture of regenerating ligulate florets from the MS medium containing 8.88 μM·dm-3 BAP and 2.69 μM·dm-3 NAA on the medium with 2.89 μM·dm-3 GA3 and 2.69 μM·dm-3 NAA. There were found no differences in the number and length of shoots regenerating on ligulate florets inoculated on solid or in liquid MS medium with 8.88 μM·dm-3 BAP and 2.69 μM·dm-3 NAA. The subculture of regenerating ligulate florets from the solid into liquid medium increases the number of regenerating shoots and stimulates their elongation growth, however these shoots are deformed.
In mutation breeding of chrysanthemum the regeneration in vitro of adventitious shoots from ligulate florets can lead to the separation of chimera components and, as a result, to producing a new original cultivar. The success of that method considerably depends on the result being the number of the shoots formed. The more is produced, the greater the chances for an effective separation of chimera components and creating a new stable cultivar. The present research defines the effect of such factors as the inflorescence development stage, the type of the explant as well as the position of its inoculation on the increase in the efficiency of adventitious shoots regeneration. The ligulate florets of Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Cool Time’ were inoculated on the Murashige and Skoog [1962] medium supplemented with 2 mg·dm-3 BAP and 0.5 mg·dm-3 NAA. There was shown no significant effect of the inflorescence development stage (incompletely open with a partially visible disk or with the entire visible disk in which tubular florets do not produce pollen or completely open in which two or half of the whorls of tubular florets produce pollen) on the shoot regeneration efficiency. Most shoots regenerate on transversely- or lengthwise-cut into half or on the entire pierced ligulate florets – horizontally inoculated, with the abaxial side on the medium.
Many chrysanthemum mutants are chimeras built from tissues of a varied genetic composition. Regeneration in vitro of somatic embryos from the whole mutated ligulate florets or only from their small mutated fragments can lead to the separation of chimera components and, as a result, producing a new original cultivar. There was determined the effect of growth regulators (2,4-D; KIN or BAP) and explant type (whole or transversely-cut-into-half ligulate florets) on the efficiency of somatic embryogenesis of Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Cool Time’. For the induction of the somatic embryogenesis ant the regeneration of somatic embryos the MS medium [Murashige and Skoog 1962] with 18.08 μM 2,4-D as well as with this auxin and 4.44; 8.88; 22.20 μM BAP or 4.65; 9.30; 23.25 μM KIN was used. The best results were obtained when transversely-cut-into-half ligulate florets were inoculated onto the medium with 4.65 μM KIN and 18.08 μM 2,4-D. This results may increase the probability of success in separation of chimera components in chrysanthemum breeding.
Ajania is closely related to the chrysanthemum, and may become an interesting alternative for it, the more that the cultivation of both species can be carried out simultaneously. The present study investigated the efficiency of micropropagation of three cultivars of Ajania pacifica (Nakai) Bremer et Humphries: ‘Bea’, ‘Bess’, ‘Silver and Gold’. The plants were propagated in vitro with single-node method on the modified MS medium without growth regulators. In all the three cultivars there was observed a similar propagation coefficient. After eight weeks of culture there were produced about 10 microcuttings from a single shoot. ‘Silver and Gold’ produced definitely shorter internodes than ‘Bea’ and ‘Bess’.
Induced mutagenesis allows to obtain in relatively short time new cultivars of chrysanthemum differing in single characteristic traits such as the colour or shape and size of inflorescence, which determines their decorative values. The traditional breeding methods as crossing, selection and techniques of genetic transformation face limitations in this species. The object of investigation were three cultivars of Chrysanthemum × grandiflorum (Ramat.) Kitam. –‘ Albugo’, ‘Alchimist’, ‘Satinbleu’. Gamma radiation in dose of 15 Gy was obtained from Co60 cobalt source generated by Theratron 780 C. The dose rate was 2.14 Gy × min-1. ‘Albugo’ and ‘Satinbleu’ microcuttings cultured on MS medium were exposed to irradiation. Following the irradiation, single-node explants and leaves were excised from plantlets and subcultured onto MS medium supplemented with 0.6 mg × dm-3 BAP and 2.0 mg × dm-3 IAA. In ‘Alchimist’ there were irradiated leaf explants with callus regenerated on petioles. A month earlier this explants were placed on the MS medium with 0.6 mg × dm-3 BAP and 2.0 mg × dm-3 IAA added. The regeneration of adventitious shoots was conducted without subculturing onto fresh medium. Newly formed shoots were transferred onto rooting medium 4 months after the irradiation. Gamma radiation effected the regeneration of shoots on explants. From the mutants obtained in vM2 generation the most interesting, worth introducing to cultivation five genotypes were selected: ‘Albugo Sunny’, ‘Alchimist Tubular’, ‘Alchimist Golden Beet’, ‘Satinbleu Minty’, ‘Satinbleu Honey’.
The use of flower tissue for the in vitro propagation of chrysanthemum (Chrysanthemum 9 grandiflorum (Ramat.) Kitam.), an ornamental plant, provides a specific and precious explant type for organogenesis (regeneration of adventitious shoots/roots) or somatic embryogenesis. This is of great importance for the breeding of this species. In vitro culture of flower tissue can lead to the separation of chimera components to obtain stable mutants. Moreover, regenerants derived from ray (ligulate) or disc (tubular) florets may present somaclonal variation. The ability to then regenerate such plant material can result in the production of plants with novel flower colour, modified architecture or other positive attributes, even more so after the application of physical mutagens such as gamma radiation. Although in vitro flowering is a rare phenomenon in chrysanthemum, the notion that it could be possible would allow for the formation of flower material that could serve as in vitro-disinfected material without the need to introduce explants, and possible contamination, from the ex vivo milieu. Regeneration protocols from flower tissue would allow for breeding using such tissues to be advanced while the process of in vitro flowering could also be better understood. This review provides an up-todate understanding of what is known in this field of research.
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