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In nature, the tree fern Cyathea smithii lacks meristem multiplication; therefore, a system of vegetative propagation in vitro is required to protect the species' gene resources. Experiments were carried out on the apical dome of C. smithii J. D. Hooker (soft tree fern, Katote) to determine its morphogenic potential using 1/2 strength of Murashige and Skoog medium containing various concentration of thidiazuron [TDZ; 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea)] (0.01, 0.1, 1.0, and 5.0 µM) supplemented with naphthalene acetic acid (0.25 µM). The success of the treatments was determined by the number of regenerants per explant, level of regenerant development, and nuclear DNA content in the green mesophyll cells. The highest number of regenerants was achieved in the presence of 5.0 µM TDZ and the lowest at 0.01 µM TDZ. The quality of development of the regenerants was expressed as the number of formed leaves and their growth per individual plantlet. The highest growth and development of regenerants occurred at the lowest concentration of TDZ (0.01 µM), and the lowest growth and development of regenerants occurred at the highest TDZ concentration (5.0 µM); however, the number of regenerants showed the opposite. In gametophytes, the nuclear DNA content ranged from 4.74-4.78 pg representing haploid level, whereas in sporophytes it ranged from 8.45-9.13 pg and was diploid. These results prove the stability of the regenerant genome after TDZ treatment of meristematic cells. [ABSTRACT FROM AUTHOR]

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In Brassica, interspecific hybridisation plays an important role in the formation of allopolyploid cultivars. In this study, the ploidy of F1 and F2 generations resulting from interspecific hybridisation between B. oleracea inbred lines of head cabbage (B. oleracea L. var. capitata) (2n = 18) and kale (B. oleracea L. var. acephala) (2n = 18) with inbred lines of rapeseed (B. napus L.) (2n = 38) was examined by flow cytometry analysis and chromosome observation. Furthermore, the effect of meiotic polyploidisation on selected phenotypic and anatomical traits was assessed. The F1 hybrids of head cabbage × rapeseed (S3) and kale × rapeseed crosses (S20) were allotriploids with 2n = 28 chromosomes, and nuclear DNA amounts of 1.97 (S3) and 1.99 pg (S20). These values were intermediate between B. oleracea and B. napus. In interspecific hybrids of the F2 generation, which were derived after self-pollination of F1 hybrids (FS3, FS20) or by open crosses between F1 generation hybrids (FC320, FC230), the chromosome numbers were similar 2n = 56 or 2n = 55, whereas the genome sizes varied between 3.81 (FS20) and 3.95 pg 2C (FC230). Allohexaploid F2 hybrids had many superior agronomic traits compared to parental B. napus and B. oleracea lines and triploid F1 hybrids. In the generative stage, they were characterised by larger flowers and flower elements, such as anthers and lateral nectaries. F2 hybrids were male and female fertile. The pollen viability of F2 hybrids was comparable to parental genotypes and varied from 75.38% (FS3) to 88.24% (FC320), whereas in triploids of F1 hybrids only 6.76% (S3) and 13.46% (S20) of pollen grains were fertile. Interspecific hybrids of the F2 generation derived by open crosses between plants of the F1 generation (FC320, FC230) had a better ability to set seed than F2 hybrids generated from the self-pollination of F1 hybrids. In the vegetative stage, F2 plants had bigger and thicker leaves, larger stomata, and significantly thicker layers of palisade and spongy mesophyll than triploids of the F1 generation and parental lines of B. oleracea and B. napus. The allohexaploid F2 hybrids analysed in this study can be used as innovative germplasm resources for further breeding new vegetable Brassica crops at the hexaploid level. [ABSTRACT FROM AUTHOR]

The aim of this work was to find an effective protocol for in vitro propagation and to perform the in vitro polyploidization of diploid Thymus vulgaris (2n = 30) using two experimental methods based on the use of oryzalin, an antimitotic agent. The ploidy level of the obtained shoots was checked by flow cytometric analysis. The most efficient conditions for inducing polyploidy were oryzalin concentrations of 0.346 and 1.73 mg L−1 present in the medium for two weeks. The vital polyploid shoots were multiplied for further evaluation, rooting and final transfer to nonsterile glasshouse and field conditions. The chemical compositions of the essential oils (EOs)—which were obtained from dried field grown plants by steam distillation—were analyzed by gas chromatography/mass spectrometry (GC/MS). The identified substances contributed approximately 95% to the total peak area. Statistical analysis revealed that the tetraploid subclone and the diploid reference plant do not differ in total terpene content, but they do differ in the relative proportions of all the individual terpenes with the exception of α-pinene and UN5, indicating that both clones produce EOs of different quality. The obtained results showed the possibility of developing more efficient botanical insecticides based on EOs obtained from the tetraploid plants. [ABSTRACT FROM AUTHOR]