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Breeding of perennial legumes and initial seed production have been carried out at the Research Institute of Agriculture in Skriveri for nearly 70 years. Eight red clover varieties, two varieties of alsike clover and two varieties of alfalfa have been developed. The varieties are included in the perennial grass seed mixtures and widely used in formation of highly productive meadows and pasture swards. They are characterized by different longevity, ripening time, productivity level, number of sward cuttings per season. There are both diploid and tetraploid varieties, which are suitable for different forage production ways. These varieties are included in the European Common Catalogue of plant varieties and they are grown and multiplied in seed production fields in European countries and Canada. [ABSTRACT FROM AUTHOR]

The papilionaceous plants have a high value of biomass, they are the excellent source of proteins and an indispensable part of improving the soil with nitrogen, in particular it is important in ecological agriculture. The expanding of those plants sowing area nowadays is a prior task of agriculture in many European countries, including Latvia. Trifolium family include more than 300 species. In Latvia mainly used in agriculture is red clover (Trifolium pratense L.), where most of red clover sowing area (meadows and pasture) is covered with diploid (2n=14) varieties. But in last year's more importance is paid to tertraploid varieties (4n=28) breeding. The aim of red clover breeding program is offering varieties with high adaptation potential - able to grow in various types of soil, better photosynthesis activity for more competitiveness with weeds and higher biomass and seeds harvest, winter-hardy, long-term, durable against sicknesses and pests. Historically (since the 60 years of the last century) the main red clover breeding method is the free intervarietal hybridization and following individual and mass selection. For obtaining of tetraploid breeding source material the most common method is the chromosome number doubling using colchicine. In result of cooperation between LLU Research Institute of Agriculture, and Latvia Plant Genetics laboratory of Institute of Biology (University of Latvia) the group of biotechnology methods for enhancing of tetraploid red clover breeding source material obtaining was elaborated. The in vitro method for chromosome doubling of plantlets and in vitro cultivation of the tetraploid plantlets were developed. For ploidy determination the BD FACSJazz cell sorter with the flow cytometer function was used. The high percentage of cells with different ploidy plantlets after incubation in colchicine were found. The influence of genotype were observed on tetraploid cell development and plantlets surviving after colchicine treatment. 176 plantlets with well-developed roots in 2-3 leaves stage were planted in soil and grown in a greenhouse for about a month, then replanted in the soil in field conditions and grown till the maturity. After the evaluation 30 plants were chosen for including in further breeding program. In the next progeny of red clover 60% of stable tetraploid plants were establish. [ABSTRACT FROM AUTHOR]