title: Efficient callus formation and plant regeneration are heritable characters in sugar beet (Beta vulgarisL.).
abstract: BACKGROUND
  Obtaining dedifferentiated cells (callus) that can regenerate into whole plants is not always feasible for many plant species. Sugar beet is known to be recalcitrant for dedifferentiation and plant regeneration. These difficulties were major obstacles for obtaining transgenic sugar beets through anAgrobacterium-mediated transformation procedure. The sugar beet line 'NK-219mm-O' is an exceptional line that forms callus efficiently and is easy to regenerate, but the inheritance of these characters was unknown. Another concern was whether these characters could coexist with an annual habitat that makes it possible to breed short life-cycle sugar beet suitable for molecular genetic analysis.
  
  
  RESULTS
  Five sugar beet lines including NK-219mm-O were crossed with each other and subjected to in vitro culture to form callus. F1s with a NK-219mm-O background generally formed callus efficiently compared to the others, indicating that efficient callus formation is heritable. The regeneration potential was examined based on the phenotypes of calli after placement on regeneration medium. Five phenotypes were observed, of which two phenotypes regenerated shoots or somatic embryo-like structures. Vascular differentiation was evident in regenerable calli, whereas non-regenerable calli lacked normally developed vascular tissues. In a half-diallel cross, the callus-formation efficiency and the regeneration potential of reciprocal F1s progeny having a NK-219mm-O background were high. Finally, we crossed NK-219mm-O with an annual line that had a poor in vitro performance. The callus-formation efficiency and the regeneration potential of reciprocal F1were high. The regenerated plants showed an annual habitat.
  
  
  CONCLUSIONS
  Efficient callus formation and the high plant regeneration potential of NK-219mm-O were inherited and expressed in the F1. The annual habitat does not impair these high in vitro performances.
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8589 Japan.
authors.forename: Hiroyo
authors.initials: H
authors.lastname: Kagami
authors.affiliation: Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization, Memuro, 082-0081 Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Taguchi
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8589 Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Arakawa
authors.affiliation: Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization, Memuro, 082-0081 Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Kuroda
authors.affiliation: Central Agricultural Experimental Station, Agriculture Research Department, Hokkaido Research Organization, Takikawa, 073-0013 Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Tamagake
authors.affiliation: Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8589 Japan.
authors.forename: Tomohiko
authors.identifier: 0000-0001-6045-0167
authors.initials: T
authors.lastname: Kubo
mesh_terms: D027461:Beta vulgaris / Q000235:genetics* / Q000254:growth & development*; D003433:Crosses, Genetic; D005838:Genotype; D040582:Inheritance Patterns; D010641:Phenotype; D000069600:Plant Breeding; D012038:Regeneration / Q000235:genetics*
keywords: DNA marker; Dedifferentiation; F1 hybrid; Somatic embryo; in vitro culture