A cytogenetic ladder-map of the wheat homoeologous group-4 chromosomes

Abstract

We report the results of chromosome maps of wheat homoeologous chromosomes 4A, 4B, and 4D using 40 RFLP markers and 39 homozygous deletion lines. Deletion breakpoints divide the chromosomes into 45 subarm intervals with 32 intervals distinguished by molecular markers. The chromosome maps confirm the homoeology of arms 4AS to 4BL and 4DL, and 4AL to 4BS and 4DS. The chromosome map of 4A reveals novel information concerning the 4AL-5AL-7BS cyclical translocation. The presence of homoeologous group-4 long-arm markers, Xksu G10 and Xpsr 1051, intervening between the translocated 5AL and 7BS chromosome segments in 4AL suggests that the translocation events are more complex than was earlier believed. Chromosome maps confirm a pericentric inversion in Chinese Spring chromosome 4B. The consensus chromosome map is compared to the genetic map of wheat to construct a cytogenetic ladder-map (CLM). The CLM reveals an unequal distribution of recombination along the length of the chromosome arms. Recombination is highest in the distal half, and low in the proximal half, of the chromosome arms.

Single-copy gene fluorescence in situ hybridization and genome analysis: Acc-2 loci mark evolutionary chromosomal rearrangements in wheat

“…Chromosome 4A of T. monococcum, T. turgidum, and bread wheat is known to have a rearranged structure that resulted from a 4AL/5AL translocation, which occurred at the diploid level. Further rearrangements involving chromosome arms 7BS, a paracentric and two pericentric inversions, took place at the tetraploid level (Naranjo et al 1987;Devos et al 1995;Mickelson-Young et al 1995;Miftahudin et al 2004). Our results confirm the presence of the A-genome-specific translocation T4AL/5AL that is shared by several related species and is also present in the derived A genomes of allopolyploid species Rodriguez et al 2000) (Fig.…”

Gene evolution at the ends of wheat chromosomes

“…Nonterminal regions of NSH EST concentration along the chromosome length might be explained by recombination hot spots (41). Increased frequency in the nonterminal 4AL5 deletion bin could be explained by the 4A, 5A, 7B cyclic translocation (42,43) that moved the 5AL terminal segment to this site.…”

Genetic mapping of 66 new microsatellite (SSR) loci in bread wheat

“…Despite this, detailed RFLP genetic maps with more than 1,500 mapped loci spanning a genetic distance of over 3,700 cM (a density of 4.4 Mb per cM) are now available for bread wheat, due to concerted efforts made by several laboratories, coordinated by the ITMI (see Communicated by P. Langridge Gupta et al 1999 for a review). Physical maps for all 21 chromosomes involving a sizable proportion of the genetically mapped loci are also available Kota et al 1993;Hohmann et al 1994;Ogihara et al 1994;Delaney et al 1995a, b;Mickelson-Young et al 1995;Varshney et al 2001). These genetic and physical maps, however, are still far from the ultimate objective of getting a map as saturated as those available for the tomato and rice genomes.…”