Molecular Genetic Maps in Wild Emmer Wheat, Triticum dicoccoides: Genome-Wide Coverage, Massive Negative Interference, and Putative Quasi-Linkage

Abstract

The main objectives of the study reported here were to construct a molecular map of wild emmer wheat, Triticum dicoccoides, to characterize the marker-related anatomy of the genome, and to evaluate segregation and recombination patterns upon crossing T. dicoccoides with its domesticated descendant Triticum durum(cultivar Langdon). The total map length exceeded 3000 cM and possibly covered the entire tetraploid genome (AABB). Clusters of molecular markers were observed on most of the 14 chromosomes. AFLP (amplified fragment length polymorphism) markers manifested a random distribution among homologous groups, but not among genomes and chromosomes. Genetic differentiation between T. dicoccoidesand T. durum was attributed mainly to the B genome as revealed by AFLP markers. The segregation-distorted markers were mainly clustered on 4A, 5A, and 5B chromosomes. Homeoalleles, differentially conferring the vigor of gametes, might be responsible for the distortion on 5A and 5B chromosomes. Quasilinkage, deviation from free recombination between markers of nonhomologous chromosomes, was discovered. Massive negative interference was observed in most of the chromosomes (an excess of double crossovers in adjacent intervals relative to the expected rates on the assumption of no interference). The general pattern of distribution of islands of negative interference included near-centromeric location, spanning the centromere, and median/subterminal location.[An appendix describing the molecular marker loci is available as an online supplement athttp://www.genome.org.]

Detailed Recombination Studies Along Chromosome 3B Provide New Insights on Crossover Distribution in Wheat (Triticum aestivum L.)

“…We confirmed this interference in a different cross where the screening of .1400 F 2 CsRe using two markers separated by 12 cM and localized in the distal part of the short arm showed an absence of double COs (P-value ¼ 0.015, data not shown). In wheat and barley, Peng et al (2000) and Esch and Weber (2002) reported negative interference within short distances. However, in contrast to our study that is based on doubled-haploid populations, Peng et al (2000) used F 2 plants.…”

“…In wheat and barley, Peng et al (2000) and Esch and Weber (2002) reported negative interference within short distances. However, in contrast to our study that is based on doubled-haploid populations, Peng et al (2000) used F 2 plants. Estimation of the coefficient of coincidence with this type of population is biased because two independent gametes are considered as one.…”

“…In any case, using an F 2 population results in substantial loss of statistical power to detect interference compared to DH populations in which individual gametes are considered. Moreover, in their studies, Peng et al (2000) and Esch and Weber (2002) considered intervals with very small numbers of recombinants (,10), thereby introducing another bias in the measurement of the coefficient of coincidence and leading to potentially large overestimations (Martin and Hospital 2006). Thus using an F 2 population and analyzing small intervals result in an overestimation of double recombination events, in high values for the coefficient of coincidence (C .…”

Cytonuclear Genic Incompatibilities Cause Increased Mortality in Male F2 Hybrids of Nasonia giraulti and N. vitripennis

“…To minimize the effect of negatively interacting loci causing mortality on the linkage map reconstruction due to a phenomenon commonly referred to as quasi-or pseudolinkage (Korol et al 1989;Lorieux et al 1995a,b;Liu 1998;Weston et al 1999;Peng et al 2000), we considered only F 2 hybrid embryos for linkage analysis. We first evaluated the mapping population (N ¼ 225) by analyzing markers for missing information and MTRD.…”

Genetic effects on microsatellite diversity in wild emmer wheat (Triticum dicoccoides) at the Yehudiyya microsite, Israel

“…The last assumption is especially supported by allele distribution at GWM537 (Figure 1). (1998), the distance of GWM 218 also referred to the map of Peng et al (2000). c m, n, and k symbolize repeat number.…”