RFLP linkage map of asparagus

A population resulting from a double pseudotestcross of two outbred-derived asparagus (Asparagus officinalis L.) clones was evaluated by RFLP (restriction fragment length polymorphism) analysis to produce individual maps of the male and female parents. An asparagus PstI genomic library was created and used as the source of probes. Scoring of bands was done by examining SDRFs (single dose restriction fragments) that are present in one parent and absent in the other and segregate 1:1 in the progeny. The data were analyzed as a backcross population; inversion or recoding allowed for the detection of repulsion phase linkage. The male parent map consisted of 33 loci in 10 groups, while the female parent map had 48 loci arranged in 14 groups. Segregation distortion was minimal (5%), and 17% of the markers were found to be unlinked. Loci of the configuration a/b x a/b and a/c x b/c were used to bridge seven homologous linkage groups between the two parents. The sex locus was not found to be associated with any linkage group. Key words : RFLP, bridge loci, repulsion phase linkage, double pseudotestcross.