Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2000
Publication Date: 2/15/2001
Citation: Altuntepe, M.D., Jauhar, P.P. 2001. Production of durum wheat substitution haploids from durum x maize crosses and their cytological characterization. Genome 44:137-142.
Interpretive Summary: Haploid plants with half the chromosome number (rod-like structures in the cell that carry genes for various traits) are of great importance in basic research in cytogenetics and in practical plant breeding. Although haploids have been produced in common bread wheat, only a few systematic studies have been conducted on haploid production in durum wheat. We studied the effect of individual chromosomes on production of haploids from durum x maize crosses. We analyzed a complete set of D-genome (the set of chromosomes that came from a wild grass) substitution lines in which each of the 14 durum chromosomes was substituted by a D-genome chromosome (one at a time). We found that chromosome 5D (of bread wheat) substituted for chromosome 5B (of durum) confers on durum wheat a greater ability to produce haploids. Using a specialized technique (fluorescent genomic in situ hybridization), we elucidated the translocation involving chromosomes 4A and 7B that occurred some 10,000 years ago at the time of evolution of durum wheat. We also confirmed the genomic constitution of the haploids produced. These findings may accelerate the production of durum haploids and hence have significance in durum wheat breeding.
Technical Abstract: We showed earlier that maize-mediated chromosome elimination provides the best method for haploid production in durum wheat. Successful durum wheat x maize hybridization resulting in the formation of hybrid embryos is a prerequisite for durum haploid production. The objective of this study was to investigate the effect of individual chromosomes on crossability with maize and to do cytological characterization of haploids recovered. Nine Langdon (LDN) D-genome disomic substitution lines [1D(1A), 1D(1B), 2D(2A), 2D(2B), 3D(3A), 4D(4A), 6D(6A), 7D(7A), 7D(7B)]; five LDN D-genome disomic substitution lines maintained with either a complete monosome [3D(3B)+3B, 4D(4B)+4B, 5D(5A)+5A, 5D(5B)+5B] or a telosome [6D(6B)+6BS]; a LDN Ph mutant (Ph1b ph1b); and normal Langdon were pollinated with three commercial maize cultivars. After pollination, hormonal treatment was given daily for up to 14 days. Haploid embryos were obtained from all lines and were aseptically cultured. From a total of 55,358 pollinated florets, 895 embryos were obtained, only 14 germinated and developed into healthy plants. The substitution 5D(5B) gave the highest yield of embryos and haploid plants. These results indicate that the substitution of 5D for 5B confers on durum wheat a greater ability to produce haploids. Fluorescent genomic in situ hybridization (GISH) showed that the substitution haploids consisted of 7 A-genome chromosomes, 6 B-genome chromosomes, and 1 D-genome chromosome. Triticum urartu genome was efficient in probing the 7 A-genome chromosomes, although the D-genome chromosome also showed intermediate hybridization. This shows a close affinity between the A genome and D genome.