Comparison of haploid and doubled haploid sugar beet clones in their ability to micropropagate and regenerate
Background: Haploid plant material is considered as recalcitrant to organogenesis, propagation, and maintenance in vitro. However, sugar beet (Beta vulgaris L.) breeders utilizing doubled haploid (DH) technology in their breeding programs indicate that sugar beet haploids may be cultured in vitro as well as diploids. Thus in this paper the in vitro performance of haploid and the doubled haploid sugar beet of various origin was evaluated. The DHs were derived from haploids by diploidization and twelve such haploid and corresponding DH clone pairs were obtained thus the comparison included haploid and DH clones that had identical allelic composition and differed only in their ploidy level. Results: The genotypes differed in shoot morphology and susceptibility to blackening during culture in vitro, but no significant differences were observed between the haploids and DHs. The micropropagation rate was, on average, higher for the haploids than DHs. Viability of the midrib and petiole explants after a 6-week culture was highly genotype dependent, but not affected by explant ploidy level. However, regeneration efficiency depended on both the genotype and ploidy level. The explants of several haploids regenerated more frequently and developed more adventitious shoots than the corresponding DHs thus overall efficiency was higher for haploids. Conclusions: The results obtained indicate that most of the haploids used in the comparison performed similar to or even better than DHs. This suggests that sugar beet haploid material can be successfully used not only for the production of DHs, but also maintained in vitro and utilized in projects requiring haploid tissues as the source material.