Polyploidization Facilitates Biotechnological In Vitro Techniques in the Genus Cucumis

Prezygotic interspecific crossability barrier in the genus Cucumis is related to the ploidy level of the species (cucumber (C. sativus), x = 7; muskmelon (C. melo) and wild Cucumis species, x = 12). Polyploidization of maternal plants helps hybridization among other Cucumis species by overcoming prezygotic genetic barriers. The main objective of this paper is to compare the results of several methods supporting interspecific crosses in cucumber without and with polyploidization (comparison between diploid (2x) and mixoploid (2x/4x) cucumber maternal plants). Mixoploid plants were obtained after in vivo and in vitro polyploidization by colchicine and oryzalin. Ploidy level was estimated by flow cytometry. Embryo rescue, in vitro pollination, and isolation of mesophyll protoplast were tested and compared. Positive effect of polyploidization was observed during all experiments presented by higher regeneration capacity of cultivated mixoploid cucumber embryos, ovules, and protoplasts. Nevertheless, the hybrid character of putative hybrid accessions obtained after cross in vivo and in vitro pollination was not confirmed

Haploid and mixoploid cucumber (Cucumis sativus L.) protoplasts – isolation and fusion

This paper reports on the isolation of haploid and mixoploid protoplasts in the genus Cucumis. The cucumber mixoploid plants (C. sativus L., 2x/4x; 2x = 14) were obtained after oryzalin treatments and the mesophyll protoplasts (2x/4x/8x) were isolated and cultivated by well known in vitro methods. The influence of oryzalin pretreatment on the average viability and density of  protoplasts was tested. The average viability as well as the density is signifi cantly influenced by the oryzalin concentration, whereas the time-span of the treatment doesn’t have significant impact on the density and the viability. Callus formation was the highest level of regeneration in the experiments described in our study. Furthermore the isolation and cultivation of the cucumber and muskmelon (C. melo L.; 2x = 24) haploid protoplasts from young-stage pollen grains were improved. Subsequently, somatic hybridization between mixoploid cucumber protoplasts and muskmelon mesophyll and callus protoplasts, and kiwano (C. metuliferus E. Meyer ex Naudin; 2x = 24) mesophyll protoplasts, by chemical fusion with polyethylene glycol (PEG) 6000 was performed for the first time. Heterofusants were observed and developed into micro colonies. Additionally, the gametosomatic hybridization between mixoploid cucumber protoplasts and pollen muskmelon protoplasts was performed for the first time. Heterofusants and the first cell division were observed, however, the regeneration stopped in this stage. In conclusion, the different ploidy, especially the mixoploid character of isolated protoplasts, has positive influence on protoplasts isolation and the following fusion as represented by a higher regeneration capacity. In addition, both types of protoplasts, haploid and mixoploid, represent a unique systems for biochemical, molecular and genetic experiments. Especially, the haploid protoplasts could be used during in vitro fertilization

Vyjadřování osobní a sociální identity dospívajících v podmínkách společenských změn

Katedra psychologieFilozofická fakult

Porovnání mikrostruktury TRIP ocelí s izotermálními anizotermálními deformačními kroky po tepelně-mechanickém zpracování

The processing strategy of thin-walled hollow parts was verified in this work by physical-material modelling using C-Mn-Si transformation induced plasticity (TRIP) steel microalloyed with Niobium. The specimens were processed by a thermo-mechanical simulator to simulate real processing conditions. Different processing methods were applied to the specimens during subsequent cooling. The influence of intensive forming which was carried out during a continual decrease of temperature was compared with the influence of deformation steps applied at chosen temperatures during cooling. The effect of deformation parameters on ferrite development, grain refinement and phase distribution was investigated. Resulting microstructures were characterized with the use of light optical microscopy, transmission electron microscopy of extraction carbon replicas and a new method of confocal laser scanning microscopy

Biotechnologické in vitro metody u ohrožených druhů vrb =Biotechnological in vitro methods with endangerred willow species

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