Synteny between bulb onion and bunching onion based on linkage maps.

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Linkage maps have been developed for bulb onion(Allium cepa L.) and bunching onion(A. fistulosum L.). It is considered that a high level of macrosynteny exists between these 2 species since they belong to the section Cepa and have the same chromosome number(2n=16). However, a detail comparison has not evaluated because there are few common markers onto the maps of both species. The objective of this study was to evaluate synteny at the genome-wide level between bunching onion and bulb onion. As a first step, we developed a basal linkage map in F_2 population between yellow bulb onion and red shallot. Linkage map consists of 11 linkage groups with 164 markers covering 1, 040 cM. Ten linkage groups were assigned to eight chromosomes with 65 markers. Although both SNP markers(F3' H and DFR) were located on the Chr. 7, two trait markers, Pg and Ant1, were closely linked to DFR. A QTL for bulb pigmentation was also detected on the Chr. 7.All individuals homozygous for onion allele at DFR loci showed no pigmentation in F_2 individuals. The degree of red pigmentation became significantly darkened by replacing shallot allele at DFR in both F_2 and F_<2 : 3>. Therefore, DFR is one of key genes involved in bulb color in this population.