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.

The aim of this research is to evaluate the variability of the martagonlily (Lilium martagon L.) found in the wild in the west of Latvia. Latvia is situated in a nature zone between the vegetation of Northern and Central Europe. The country distinguishes itself with a large variety of flora and fauna (total approx. 27, 7 thousand species). The genus Lilium L. includes approximately a hundred species, subspecies and varieties of species. In northern Europe, one of the best known and longest cultivated of lilies is L. martagon L. It is distributed across the largest growing area of most species - from western Portugal throughout Europe and Asia. To evaluate the survival potential of L. Martagon L. in Latvia, research was carried out in locations at Kurzeme - districts of Ventspils, Kuldiga, and Tukums. The results indicate that the diversity in genotypes varies according to location and distribution. There are differences in phenotypes and colour variability from pale to bright violet-pink. Diameter of flower varies between of 3.5 to 6.0 cm. The height of these plants varies up to 114 - 130 cm. The flowering time is in June and July. Wild martagonlily found in these regions is growing in calcareous soils among shrubs in river valleys and semi-shaded deciduous forests. This particular martagonlily is hardy and disease resistant and is recommended as a donor in breeding programs.

This study was carried out in 2012 to determine the effects of different irrigation intervals and irrigation water amounts on the cut flower performance of oriental lilium (Lilium L.) ‘Casa Blanca’ cultivated in greenhouse conditions. Different ratios of the plant water consumption (Tr) calculated using exterior radiation values of the greenhouse were applied to the plants as irrigation water. Irrigation water amounts varied between 199.3-589.0 mm, whereas measured plant water consumption (ETa) varied between 314.9-613.8 mm according to the treatments. Different irrigation water amounts and irrigation intervals had statistically significant effects on flower stem length, flower stem diameter, stem weight and number of flowers. In the study the stem length varied between 26.4-74.7 cm, stem weight varied between 72-175 g, stem diameter varied between 5.0-9.5 mm and the number of flowers buds varied between 3.6 and 8.0. The experimental treatment on which about 1.25 times of the potential plant water consumption calculated in two day intervals and the experimental treatment on which about 1.50 times of the potential plant water consumption calculated in four day intervals were selected as irrigation program.