Doubled haploids in sugar beet: Spontaneous and colchicine-induced polyploidization

In vitro techniques were used to obtain haploid lines of ovule origin in different sugar beet genotypes. Rate of spontaneous polyploidization, observed in vitro, depended on the type of gynogenetic regeneration (embryogenesis or organogenesis) and culture conditions. Embryogenic shoots remained haploid longer than organogenic shoots. After prolonged culture, cells with spontaneously doubled chromosome numbers were observed in all haploid gynogenetic lines and the amount of such cells increased. This has never been observed in diploid control sugar beet plants, micropropagated in vitro by adventitious shoot formation without calli. Homozygous diploid lines were also obtained by colchicine-treatment. One-year-old plants of spontaneously doubled haploids in the field showed better technological characteristics than colchicine doubled plants of the same origin.