Molecular cytogenetics, cytology and genomic comparisons in the Triticeae

• Published in: Hereditas Vol. 116; no. 1‐2; pp. 93 - 99
• Main Author: HESLOP‐HARRISON, J. S.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.1992
• Subjects: Triticeae
• ISSN: 0018-0661; 1601-5223
• DOI: 10.1111/j.1601-5223.1992.tb00210.x

Within the Triticeae, many useful genes have been transferred between genera, and the transferred characters are found widely in cereal crops. The subject matter of this talk has provided the basis for our understanding of gene transfer and chromosome behaviour. Genomes can be studied by cytogenetic examination of the chromosomes in species, natural and synthetic hybrids. Work on the molecular biology can demonstrate directly differences between their DNA sequences – in the code itself, and in the length and copy number of particular sequences. Molecular cytogenetics, particularly using DNA:DNA in situ hybridization, enables the two technologies to be linked by allowing direct observation of the dispersal of different types of DNA within chromosomes. Co‐evolution of sequence families within genomes is a major feature of species evolution and divergence within the tribe. Thus, genome‐specific sequences can be isolated and cloned relatively easily. Many such sequences are tandemly repeated and co‐localize with C‐bands on chromosomes; each C‐band may consist of several different sequence classes. Information about band sizes and their constitution assists genome studies. Other families of middle and highly repeated DNA sequences are dispersed within a genome, and may show retrotransposon‐like modes of co‐evolution. I plan to show examples of the types of difference between chromosomes in various species, and to relate the differences to DNA sequence, chromosome morphology and behaviour. Despite, or perhaps because of, the wide range of aneuploids, hybrids and translocations that can be made within the Triticeae, in natural populations, the basic chromosome number and morphology is remarkably stable; even translocations are uncommon. What constraints may restrict genome evolution? What limits, or can advance, the manipulation and transfer of genes within the Triticeae?