Pairing affinities of the B- and G-genome chromosomes of polyploid wheats with those ofAegilops speltoides

Abstract

Chromosome pairing at metaphase I was studied in different interspecific hybrids involving Aegilops speltoides (SS) and polyploid wheats Triticum timopheevii (AtAtGG), T. turgidum (AABB), and T. aestivum (AABBDD) to study the relationships between the S, G, and B genomes. Individual chromosomes and their arms were identified by means of C-banding. Pairing between chromosomes of the G and S genomes in T. timopheevii x Ae. speltoides (AtGS) hybrids reached a frequency much higher than pairing between chromosomes of the B and S genomes in T. turgidum x Ae. speltoides (ABS) hybrids and T. aestivum x Ae. speltoides (ABDS) hybrids, and pairing between B- and G-genome chromosomes in T. turgidum x T. timopheevii (AAtBG) hybrids or T. aestivum x T. timopheevii (AAtBGD) hybrids. These results support a higher degree of closeness of the G and S genomes to each other than to the B genome. Such relationships are consistent with independent origins of tetraploid wheats T. turgidum and T. timopheevii and with a more recent formation of the timopheevi lineage.

Fate of <i>Aegilops speltoides</i>-Derived, Repetitive DNA Sequences in Diploid <i>Aegilops</i> Species, Wheat-<i>Aegilops</i> Amphiploids and Derived Chromosome Addition Lines

“…speltoides , suggesting that the S genome of Ae. speltoides is more closely related to the G genome of T. timopheevii than to the B genome of T. turgidum, which is in agreement with previous studies [Dvorak and Zhang, 1990;Tsunewaki, 1996;Rodriguez et al, 2000;Zhang et al, 2002].…”

Wheat Evolution, Domestication, and Improvement

“…The present-day B genome of wild and cultivated wheat carries from zero to two Spelt 1 clusters per haploid genome in contrast to the G genome of existing allopolyploids, which contains up to six Spelt 1 clusters (Salina et al, 2006). These data are in accordance with the purported independent origin of the B and G genomes of allopolyploid wheat (Jiang and Gill 1994b;Rodríguez et al, 2000a).…”

The use of cytogenetic tools for studies in the crop-to-wild gene transfer scenario

“…Thus, chromosome counting by any conventional staining method is the easiest cytogenetic tool if the parental species possesses different 2n values (for instance, diploid versus polyploid, or two diploids with different basic numbers) or show remarkably distinct chromosome morphologies (Eber et al, 1994;Mariam et al, 1996;Chen et al, 1997;Hussain et al, 1997). However, when the karyotypes of the parental species are similar, techniques that provide cytological discrimination between both chromosome complements such as GISH (Karlov et al, 1999;Piperidis et al, 2000), FISH with appropriate labelled probes (Lan et al, 2006) and, in some cases, C-banding (Rodriguez et al, 2000) are the only reliable methods for mitotic assessments on the hybrid nature of a plant ( Figs. 3 , 7).…”

“…2 ). During the 80's and 90's, Naranjo and co-workers authored thorough reports where the meiotic pairing pattern was determined for individual wheat and related homoeologous partners in several interspecific hybrid combinations (Naranjo et al, 1987;Naranjo and Maestra, 1995;Maestra and Naranjo, 1997;Rodriguez et al, 2000). In most other cases, the C-banding technique was employed to differentiate wheat and alien genomes but further discrimination of specific chromosomes was not attempted (Hutchinson et al, 1983;Cuñado et al, 1986;Jouve and Giorgi, 1986;Fernandez-Calvin and Orellana, 1992;Fernandez-Calvin et al, 1995).…”