Abstract
Ionizing radiation combined with in vitro tissue culture has been used for development of new cultivars in diverse crops. The effects of ionizing radiation on mutation induction have been analyzed on several orchid species, including Cymbidium. Limited information is available on the comparison of mutation frequency and spectrum based on phenotypes in Cymbidium species. In addition, the stability of induced chimera mutants in Cymbidium is unknown. In this study, we analyzed the radiation sensitivity, mutation frequency, and spectrum of mutants induced by diverse γ-ray treatments, and analyzed the stability of induced chimera mutants in the Cymbidium hybrid cultivars RB003 and RB012. The optimal γ-irradiation conditions of each cultivar differed as follows: RB003, mutation frequency of 4.06% (under 35 Gy/4 h); RB012, 1.51% (20 Gy/1 h). Re-irradiation of γ-rays broadened the mutation spectrum observed in RB012. The stability of leaf-color chimera mutants was higher than that of leaf-shape chimeras, and stability was dependent on the chimera type and location of a mutation in the cell layers of the shoot apical meristem. These results indicated that short-term γ-irradiation was more effective to induce mutations in Cymbidium. Information on the stability of chimera mutants will be useful for mutation breeding of diverse ornamental plants.
Highlights
The Orchidaceae is among the largest families of angiosperms, and is composed of approximately736 genera and about 28,000 species [1]
We evaluated the optimal γ-ray dose to induce mutations in Cymbidium, and compared the mutation frequency and spectrum of leaf mutants induced by diverse γ-ray treatments
RB003 and RB012 gradually decreased with increase in γ-ray dose
Summary
The Orchidaceae is among the largest families of angiosperms, and is composed of approximately. 736 genera and about 28,000 species [1]. Among the diverse genera in the family, Dendrobium, Phalaenopsis, Oncidium, and Cymbidium are important floricultural crops in Asian countries [2]. Cymbidium species are conveniently divided into two groups on the basis of the native habitat and climate region, i.e., temperate and subtropical or tropical regions [4,5]. There is continuous demand for development of new Cymbidium cultivars on account of the attractiveness of the foliage as well as the flower colors and fragrance. Many Cymbidium cultivars have been developed via natural selection or artificial cross-breeding, transformation has been applied in Cymbidium
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