Submitted to: Annals Of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2007
Publication Date: 4/5/2008
Citation: Ma, X., Gustafson, J.P. 2008. Allopolyploidization Accommodated Genomic Sequence Changes in Triticale. Annals Of Botany. 101(6):825-832. Interpretive Summary: The wheat and rye genomes contain an enormous DNA diversity in organization and variation, which can play a role in our ability to manipulate the wheat and rye genomes for wheat improvement. A very important question is how the polyploid nature of wheat and rye influence the genome organization and evolution of triticale, the wheat/rye hybrid. An analysis of the rate of genome evolutionary changes occurring in hybrids between wheat and rye was analyzed. A study was designed to compare the genome structure of existing triticale, its original wheat and rye parents, and newly developed hybrids. The approach was designed to make use of existing molecular markers and marker systems to analyze genome changes in the triticale compared to the parents and the hybrid. The results showed that during polyploid formation, non-coded repeated, low-copy, and coded wheat and rye sequences can be rearranged or even deleted when they were placed together in a triticale. The results also demonstrated that, in triticale, rye non-coded repeated, low-copy, and coded sequences showed a significantly larger degree of change than did those of wheat. The results will enable scientists to better understand the evolutionary processes involved in polyploid creation and stabilization.
Technical Abstract: Allopolyploidization is one of the major evolutionary modes of plant speciation. Recent interest in studying allopolyploids has provided significant novel insight into the mechanisms shaping allopolyploid formation. Triticale (X Triticosecale Wittmack) is a good species to study the evolutionary course of allopolyploids due to its recent origin, and high genome complexity and diversification. Here we review recent progress involving allopolyploid formation in triticale. Studies have indicated extensive non-Mendelian sequence changes or modifications, and the degree of variation appeared to be higher than in previous allopolyploid species studied. The data indicated that sequence changes were non-random, and appeared to be a function of genome syntenic relation, ploidy level and sequence type. Specifically, the rye parental genome contained a higher level of changes than the wheat genome. The frequency of lost parental bands was much higher than the frequency of gained novel bands, suggesting that sequence elimination might be a major force causing genome variation in triticale. It was also shown that 68% of the total changes occurred immediately following wide hybridization, but before chromosome doubling. The modification variations occurred slowly following chromosome doubling, but occurred at a very small rate and the changes were mainly observed in the first five or so generations. The data suggested that cytoplasm and relationship between parental genomes were the key factors in determining the direction, amount, timing, and rate of genomic sequence variation occurring during inter-generic allopolyploidization.