The effects of sugars and growth regulators on embryo- and callusogenesis in isolated ovules culture of beetroot, Beta vulgaris L.

Haploid techniques have risen interest among researchers and breeders as they significantly reduce the time of creating pure lines in breeding programs, especially for biennial vegetable crops. The only way to produce doubled haploids used in representatives of the genus Beta is in vitro culture of non-pollinated ovules. This is a rather laborious method that requires manual labor to isolate beet ovules from flower buds, followed by their inoculation onto a culture medium. This method also has its drawback - the development of clones from the somatic tissues surrounding the embryo sac. At the same time, the yield of embryoids and subsequent regenerations is on average 12-14% of isolated ovules introduced into in vitro culture in the most responsive genotypes of sugar beet and 8% in beetroot. The selection of the optimal cultivation conditions for each genotype makes it possible to maximize the yield of regenerant plants in the culture of isolated ovules. This research is devoted to study the effect of various types of carbohydrates and growth regulators in the culture media on embryogenesis and callusogenesis in isolated ovules culture of five beetroot genotypes. We obtained embryoids and callus in isolated ovules culture of all studied genotypes using sucrose-based culture medium, while on a glucose- and fructose-based culture media or their combination, the number of callus and embryoids was much lower. Additionally, it has been shown that glucose has more negative effect on embryo- and callusogenesis than fructose. The addition of mannitol to the culture medium had a stimulatory effect on the ovules for one genotype only. The study of various combinations of phytohormones on 5 beetroot genotypes showed that gibberellic acid reduces the embryogenesis response of ovules in all genotypes.