Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2005
Publication Date: 2/1/2006
Citation: Jauhar, P.P., Peterson, T.S. 2006. Cytological analyses of hybrids and derivatives of hybrids between durum wheat and Thinopyrum bessarabicum, using multicolor fluorescent GISH. Plant Breeding 125:19-26. Interpretive Summary: Several wild grasses, some close or distant relatives of wheat, are important sources of genes for superior traits, such as resistance to diseases like scab, which can be transferred into durum wheat cultivars via hybridization. We crossed two durum cultivars, Lloyd and Langdon, with a wheatgrass, which is diploid (i.e., with only two sets of chromosomes) and produced several hybrids with and without a gene called Ph1. This gene permits pairing only among very similar or identical chromosomes (rod-like structures in the cell that carry genes), helping to identify sets of chromosomes (genomes) that are closely related. Using appropriate genetic stocks of durum, we synthesized several hybrids without the Ph1 gene. In the absence of this gene, pairing between wheatgrass chromosomes and durum chromosomes was enhanced mani-fold. We used a specialized technique of staining chromosomes, called fluorescent genomic in situ hybridization (fl-GISH), and studied the specificity of chromosome pairing. We confirmed pairing between wheat and grass chromosomes, which is the key to transfer of desirable genes into durum cultivars. This information on chromosome pairing relationships will help gene introgression work in durum wheat.
Technical Abstract: The wheat progenitors and other wild relatives are important sources of genes for agronomically desirable traits, which can be transferred into durum wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) cultivars via hybridization. Two durum cultivars, Lloyd and Langdon, were crossed with diploid wheatgrass, Thinopyrum bessarabicum (2n = 2x = 14; JJ) to synthesize F1 hybrids (2n = 3x = 21; ABJ) with the homoeologous chromosome pairing suppressor gene, Ph1. Langdon disomic substitution 5D(5B) was used as female parent to raise F1 hybrids without Ph1. The F1 hybrids were backcrossed to respective parental cultivars and BC1 progenies were raised. Langdon 5D(5B) substitution ´ Th. bessarabicum F1 hybrids were crossed with normal Langdon to raise BC1. Chromosome pairing relationships were studied in F1 hybrids and BC1 progenies using both conventional staining and fluorescent genomic in situ (fl-GISH) techniques. Chromosome pairing in durum x alien species hybrids in the presence of Ph1 provides a valuable understanding of genome relationships between durum wheat and potential wild donors. Multicolor fl-GISH proved to be an excellent tool for characterizing the nature and specificity of chromosome pairing: A-B, A-J, and B-J pairing. Some pairing occurred between durum and the grass chromosomes but it was limited to B-J pairing; no A-J pairing was observed. This information on chromosome pairing relationships will help gene introgression work in durum wheat.