Some of best varieties of plants, especially ornamentals and fruits, were polyploid. Polyploids have larger flowers and stems than diploids. In the production of polyploid forms, different types of crosses were made. In present study a cross of diploid (2n = 2x = 24) and tetraploid (4n = 4x = 48) varieties resulted in the production of highly viable seeds 89.3% on average, but a cross of tetraploids and diploids – of 39.5% on average, with fluctuating results between cross combinations. Treating seeds and bulb scales with colchicine solutions can change chromosome number of 9 varieties. These results demonstrated that optimal concentration of colchicine was 1 g kgE-1 for chromosome doubling of seeds. A high concentration (2 g kgE-1) showed phytotoxicity that is detrimental for plant regeneration. The scales of bulbs treated with 1 g kgE-1 colchicine have resulted in the production of lily polyploid forms. The polyploid plants regenerated after pre-treatment by colchicine may be selected in early stage by phenotype of young bulblets. Broad, fleshy bulb scales setting right angle to growth axis were characteristic for regenerated tetraploids. The produced polyploid plants, in comparison with diploids, had a larger diameter of the flower (+2 up to 2.5 cm), more extended plant height (+10 up to 20 cm), increased flower count (+2) and was coming into bloom 4-10 days later than diploids of the same variety.

The lily (Lilium L.), a vegetative propagated perennial crop, is one of the economically most important flower bulb plants. It is cultivated worldwide as a cut flower, garden plant and pot plant. Lilies, 'the aristocrats of the garden', are very popular for their elegant flowers and stately habit, and offer the gardener an enormous range of colours, forms, and fragrances. The aim of this research was to evaluate the parent plants with the hybrids according to their morphological characteristics: plant height, flower diameter and inflorescence: number of flowers. In a trial, fourteen cross combinations were analyzed in 2006 – 2007. The evaluation was conducted in a lily breeding and growing farm 'Puķulejas', located in Saulkrasti, region of Riga, Latvia. The results showed that, if there were no significant differences in plant height between the parent plants, the hybrids were shorter than their parents. Male parents with short stems produced hybrids with shorter stems. Parental selections of medium and large number of flowers produced hybrids with comparatively large numbers of flowers on a stem, but if parents of different number of flowers were selected, in hybrids the smaller count dominated or prevailed.

Black alder wood is suitable for production of high quality veneer and other uses, but doe to its small share in total forest area (3%) in Latvia its genetic improvement have not been a priority. Set of progeny tests, together 22.8 ha, have been established only in the last decade. First of them have reached the age of 8 to 10 years and are suitable for first assessment. Aim of our study was to evaluate potential of improvement of black alder using selection, based on progeny testing. Data from 4 open pollinated progeny tests of phenotypically selected black alder plus trees, located in central part of Latvia, each containing from 15 to 21 families, are evaluated, using breeding value as a criterion. Results reveal that selection of parent trees with the practically possible intensity (10%) yields notable improvement in height at the age of 8 to 10 years: from 10 to 32%. Parent trees of open-pollinated families S9, S14, S16 and 84115 that have superior productivity and above-average quality can be recommended for establishment of second-round seed orchard. Estimates of genetic parameter suggest that selection in black alder trials could be carried out with high accuracy and improvements are possible both in productivity and quality (branch thickness, stem straightness, occurrence of spike knots).

Economic importance of Silver birch in Latvia has been increasing in last decade, triggering scientific research, dedicated to improvement of this species, including tree breeding. Bulk of progeny trials will reach the evaluation time in next few years; therefore, decisions for further tree breeding activities have to be made. The aim of our study is to evaluate profitability of silver birch breeding, based on current situation in the year 2010 and circumstances in Latvia and assess the factors that might notably influence the result. Analysis considers all available breeding material and links between tree breeding, seed orchards and end product – forest stand, regenerated with improved plants in order to evaluate profitability of different alternatives based on differential approach. Results reveal that differential benefits from forest regeneration with selected birch material in comparison to natural regeneration, in areas with highest site indexes (Ia-II) with 3% interest rate and at least part of the stands managed in order to maximize yield of large diameter trees at age of final felling, are positive. The highest profitability can be reached if selection of best individuals is done based on clonal testing, genetic gain is maximized and combined with proper silvicultural praxis and annual planting area (utilization of seeds from selected trees) are maximized.

Breeding work on Ribes species has been started at the National University of Life and Environmental Sciences of Ukraine in Kyiv since 1984 by Petro Sherenhovyj. The breeding programme has been focused on fruit quality, yield, resistance to diseases and pests, as well as on adaptive responses to environmental conditions. As a result of the long-term work, 18 new cultivars were included in the State Register of Plant Varieties of Ukraine in 1999– 2016. The aim of this paper is to describe these varieties: 10 blackcurrant (‘Dochka Vorskly’, ‘Hovtva’, ‘Pam`yati Leonida Mykhalevskoho’, ‘Universytetska’, ‘Aspirantska’, ‘Didorivska’, ‘Poltava 584’, ‘Petrivska’, ‘Yuvileina Sherenhovoho’, and ‘Leleka’), 5 redcurrant (‘Kyianochka’, ‘Poliana Holosiivska’, ‘Buzhanska’, ‘Malva’, and ‘Olha’), 1 whitecurrant (‘Lebidka’), and 2 gooseberry (‘Vasylko’, and ‘Tikych’). The varieties described give farmers and scientists the best knowledge about these cultivars with good level of commercial traits, suitable for dissemination in Ukraine.

Due to large diversity of site conditions suitable for Scots pine growth in Latvia, it is important to evaluate their influence on growth and survival of particular Scots pine families. To do so, open pollinated progenies from phenotypically selected plus trees of 35 at the age of 32 years have been evaluated in 2 forest types (Cladinosa-callunosa and Hylocomyosa). Investigation revealed that forest type and family influence had a great significance to height, diameter at breast height, and diameter of thickest branch up to 2 meters' height (alpha is less than 0.001), but clone influence had lower significance (alpha=0.008). Proportion of influence to height growth caused by tree family was 70% at the age of 6 years and 17% at the age of 32 years. Proportion of influence on survival caused by tree family was 57% and 44% respectively. The corresponding influence of forest type was 12% and 28% to height, 15% and 39% to survival. Diameter at breast height at the age of 32 years was equally influenced by forest type and family (~11%). Equal breeding effect - but not with the same families - can be reached both in fertile and poor soils. In group (20%) selection this effect was ~8% for height, 11% for diameter, and 30% for survival; in individual selection ~10% for height, and ~17% for diameter.