Molecular genetic maps in wild emmer wheat, Triticum dicoccoides: Genome-wide coverage, massive negative interference, and putative quasi-linkage

The main objectives of the study reported here were to construct a molecula r map of wild emmer wheat, Triticum dicoccoides, to characterize the marker -related anatomy of the genome, and to evaluate segregation and recombinati on patterns upon crossing T. dicoccoides with its domesticated descendant T riticum durum (cultivar Langdon). The total map length exceeded 3000 cM and possibly covered the entire tetraploid genome (AABB). Clusters of molecula r markers were observed on most of the 14 chromosomes. AFLP (amplified frag ment length polymorphism) markers manifested a random distribution among ho mologous groups, but not among genomes and chromosomes. Genetic differentia tion between T. dicoccoides and T. durum was attributed mainly to the B gen ome as revealed by AFLP markers. The segregation distorted markers were mai nly clustered on 4A, SA, and 5B chromosomes. Homeoalleles, differentially c onferring the vigor of gametes, might be responsible for the distortion on 5A and 5B chromosomes. Quasilinkage, deviation from free recombination betw een markers of nonhomologous chromosomes, was discovered. Massive negative interference was observed in most of the chromosomes (an excess of double c rossovers in adjacent intervals relative to the expected rates on the assum ption of no interference). The general pattern of distribution of islands o f negative interference included near-centromeric location, spanning the ce ntromere, and median/subterminal location.