Chromosome Engineering Techniques Modify Contents and Constituents of Fructans in Cultivated Allium Species

摘要

Onion (Allium cepa L.) and shallot (A. cepa Aggregatum group) exhibit wide variation in bulb fructan content and the Frc locus on chromosome 8 conditions much of this variation. To understand the biochemical basis of Frc we conducted biochemical and genetic analyses of Allium fistulosum (FF) - shallot alien monosomic addition lines (AALs; FF+1A-FF+8A), onion mapping populations and shallot - A. fistulosum addition lines. Sucrose and fructan levels in leaves of FF+2A were significantly lower than FF throughout the year. FF+8A showed significantly higher winter sucrose accumulation and sucrose phosphate synthase (SPS) activity. Markers for additional candidate genes for sucrose metabolism were obtained by cloning a major SPS expressed in onion leaf and exhaustively mining onion EST resources. SPS and sucrose synthase (SuSy) loci were assigned to chromosome 8 and 6 respectively using AALs and linkage mapping. Further loci were assigned, using AALs, to chromosomes 1 (sucrose phosphate phosphatase), 2 (SuSy and 3 invertases) and 8 (neutral invertase). The shallot - A. fistulosum AAL (AA+8F) also showed the high fructan accumulation. The concordance between chromosome 8 localization of SPS and elevated leaf sucrose levels conditioned by high fructan alleles at the Frc locus in bulb onion or alien monosomic additions of chromosome 8 in A. fistulosum and in A. cepa suggest that the Frc locus may condition variation in SPS activity.