Tomato chromosome 6: effect of alien chromosomal segments on recombinant frequencies

Abstract

Variation in recombinant frequencies at two adjacent intervals on chromosome 6 of tomato (Lycopersicon esculentum Mill.) has been studied in seven lines that differ in the amount and origin of introgressed segments from wild species. These lines were all crossed to a genotype homozygous recessive for the markers tl, yv, and c, which define the centromere spanning region tl-yv and the long arm region yv-c. Recombinants were identified in large F2, populations consisting of over 30 000 plants in total. Application of molecular markers provided additional information on the distribution of crossover events within the centromere-containing interval tl-yv. A decrease in recombination at the marked intervals correlated with the presence of an alien segment. Suppression of recombination was up to sixfold in the centromere spanning interval tl-yv depending on the source and size of the introgression, and was restricted to the alien segments with no strong effect on the neighbouring intervals. Key words : recombinant frequency, Lycopersicon esculentum, morphological markers, introgressions, centromere.

Using SNP markers to dissect linkage disequilibrium at a major quantitative trait locus for resistance to the potato cyst nematode Globodera pallida on potato chromosome V

“…The existence of a 70-kbp inversion between S. demissum and S. tuberosum in this genome segment has been demonstrated (Ballvora et al 2007). Suppression of recombination depending on the source and size of the introgression from wild species has been shown in tomato (Liharska et al 1996;Kaloshian et al 1998). Linkage disequilibrium extending over several centimorgan has also been observed by Simko et al (2006) and Li et al (2008) in diVerent populations of tetraploid and diploid potato genotypes.…”

TheMi-9Gene fromSolanum arcanumConferring Heat-Stable Resistance to Root-Knot Nematodes Is a Homolog ofMi-1

“…The presence of this inversion partly explains the lack of recombination in this region in crosses between root-knot nematode susceptible tomato and resistant tomato that contains S. peruvianum-introgressed region Seah et al, 2004). Although the suppression of recombination is partly attributed to the presence of the S. peruvianum-introgressed genome, the suppression is more pronounced in the region spanning the inversion (Liharska et al, 1996;Kaloshian et al, 1998;Seah et al, 2004). While several recombination events were identified in close proximity to the Mi locus, no recombination between C264.2 and Rex-1 was previously reported .…”

Chromosome ‘speed dating’ during meiosis of polyploid <i>Brassica</i> hybrids and haploids

“…At first sight, these conclusions seem straightforward as they illustrate the fact that (sequence) divergence between the two partners involved in a recombination event has a detrimental effect on the frequency of genetic exchanges (Datta et al, 1996;Liharska et al, 1996;Vulic et al, 1997;Lukacsovich and Waldman, 1999;Opperman et al, 2004;Li et al, 2006). However, a much closer look at the variations of CO frequency among the different partners reveals that they are also influenced by the chromosome composition of the plants that undergo meiosis (see below).…”