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Gooseberry (Ribes grossularia L.) is a small fruit crop producing valuable fruits, which is constantly gaining importance. In vitro propagation of this species can significantly support the production of virus-free planting material and accelerate the introduction of new cultivars to the market. The aim of presented study was to assess field performance and genetic stability of micropropagated plants (MPs) of four gooseberry cultivars, &ldquo, Captivator&rdquo, &ldquo, Hinnonmaki Rot&rdquo, Invicta&rdquo, and &ldquo, Resika&rdquo, The growth vigor and yield of MPs and plants propagated by standard methods from softwood cuttings (ST) were evaluated in a field experiment. Microscopic observations of the number and length of the stomata of MP and ST plants were carried out. Two DNA-based techniques, amplified fragment length polymorphism (AFLP) and inter simple sequence repeat (ISSR), were used to assess genetic stability of MP plants. For analysis of genetic stability of ST plants, the ISSR technique was applied. For three cultivars, Captivator, Hinnonmaki Rot, and Invicta, the plants&rsquo, growth vigor and fruit yield were greater in MP plants than in ST plants. In the case of Resika, most of these parameters were higher in ST plants. Microscopic observations of the stomata indicated a lack of differences in the length between MP and ST plants, while the stomata frequency on leaves of MP plants was higher than that of ST plants. The genetic variability of MP plants, assessed by AFLP, ranged from 0.35% for Hinnonmaki Rot to 2.12% for Resika. The results of ISSR analysis of MP plants showed variability from 0% in the case of Hinnonmaki Rot and Resika to 4% and 8.69% for Captivator and Invicta, respectively. No polymorphism was detected among ST plants of all analyzed gooseberry cultivars.

The goal of this study was to evaluate whether Rubus genotypes could be selected in vitro for tolerance to drought stress. Drought conditions were simulated by introducing polyethylene glycol 6000 (PEG) into proliferation or growth regulator free media. The ability to produce axillary shoots, dry weight and proline content were used for evaluation of the stress reaction. All the cultivars reacted to PEG in the medium with a decrease in the axillary shoot number and an increase in proline content. The reaction differed in strength depending on the concentration of the stressor in the medium, the length of the stress period, and the genotype. To yield a practical value for breeding, the results obtained in vitro will be compared with results from in vivo experiments which are underway.

Shoots of Codiaeum variegatum 'Excellent' produced in vitro on defoliated explants were rooted on the MS medium with I mg 1 -1 indole-3-butyric acid (IBA). Almost all shoots, even the smallest one (5 mm long) rooted and doubled their length in the course of 4 weeks. In order to stimulate more shoot elongation during in vitro rooting, we decreased the IBA concentration to 0.5 mg 1 -1 , excluded IBA from the medium with 3 g 1 -1 activated charcoal (AC) or supplemented AC medium with gibberellic acid (GA 3 ). GA 3 incresed shoot length insignificantly but also decreased the number of rooted shoots. Diluting the MS medium by half stimulated root growth when combined with 2 mg 1 -1 Gelrite instead of 7 g 1 -1 agar.

The removal of all developed leaves from 1 to 1.5 cm shoots of Codiaeum variegatum Blume var. pictum Muell. Arg. ‘Excellent’, cultured on the Murashige–Skoog medium containing 4.4 μM (1 mg l−1) 6-benzylamino-purine (BAP) and 5.8 μM (2 mg l−1) gibberellic acid (GA3), doubled the number of axillary shoots in comparison to non-defoliated controls. An additional increase in shoot numbers was achieved when the shoots were placed on the medium horizontally or vertically in an inverted position with the shoot tip down. Shoot tip removal slightly improved axillary branching, and additional defoliation strengthened this effect. Exogenous indole-3-acetic acid (IAA) decreased shoot numbers, and 2,3,5-triiodobenzoic acid (TIBA) did not replace defoliation nor diminish the size of callus formed at the base of the shoots. Almost all the shoots obtained were able to root on the medium with 4.9 μM (1 mg l−1) indole-3-butyric acid (IBA), and acclimatize in the greenhouse.

An effective system for in vitro regeneration of adventitious shoots from callus for the transformation or mutation of gerbera was developed. Callus was produced from petioles of the youngest 3–4 leaves detached from auxillary shoots produced in vitro. Induction medium, on which leaves were incubated over 3 or 6 days, contained 2.3 μM thidiazuron and 0.53 μM α-naphthaleneacetic acid. Explants were than transferred to one of three regeneration media with lower levels of growth regulators. Regeneration was quantified over four (4-weeks each) passages at the time of explant transfer to fresh medium. Direct shoot regeneration occurred during the first 4 weeks, and after these shoots were discarded a semi-compact organogenic callus was produced. Effectiveness of shoot regeneration depended on four criteria: the cultivar (three cultivars were tested), the sequence of passage on regeneration medium, the growth regulators in regeneration medium and the duration of the induction period. Regeneration potential from calli of all cultivars increased from the first to the fourth passage. Duration of the incubation period on induction medium (3 or 6 days) influenced regeneration to varying degrees, depending on the cultivar used and the regeneration medium contents. There were no differences between two of the regeneration media – B, containing 2.2 μM 6-benzyladenine and 0.3 μM indole-3-acetic acid and C, containing 4.4 μM 6-benzyladenine, 4.6 μM zeatin and 0.6 μM indole-3-acetic acid. Cultivar Mariola was the most productive and regenerated more than seven shoots per callus in the fourth passage. Regeneration on medium B was further evaluated on four additional gerbera cultivars.

The pattern of regeneration from tissues of Paeonia mlokosewitschii and P. tenuifolia cultured in vitro in the same chemical conditions depended on the initial explant. Direct shoot regeneration was obtained from the bases of petioles and petals, and leaf veins. Vegetative initial buds and regenerated in vitro shoots produced on their bases slowly growing nodular callus which was very productive in repetitive shoot regeneration. The tops of stems, flower bases, sepals, petals and ovary walls produced small callus which regenerated white and red spherical structures within 1.5 years. After that time also from those cultures arised nodular, shoot regenerating callus developed.