Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2006
Publication Date: 9/23/2006
Citation: Ma, X., Gustafson, J.P. 2006. Timing and rate of genome variation in triticale following allopolyploidization. Genome. 49:950-958. Interpretive Summary: Cereals contain enormous evolutionary diversity in genome organization and variation, which have resulted from genome changes throughout their evolution. A very important question is how has polyploidization affected the genome organization and evolution of cereals? The results suggested that different types of genome variation have significantly impacted the structure of various grass species and have significant effects when cereal species are subsequently combined to form a polyploid. Cytoplasm and the relationship between the parental genomes of an allopolyploid were the key factors determining the direction, amount, timing, and rate of sequence variation in the allopolyploid. This information will benefit plant breeders and molecular geneticists as they explore relationships among cereal species and attempt to move desirable traits between species.
Technical Abstract: Timing and rate of genome variation induced by allopolyploidization in the wheat/rye hybrid triticale (X Triticosecale Wittmack) were studied using amplified fragment length polymorphism (AFLP) analyses with two kinds of primers, EcoRI/MseI (E/M) and PstI/MseI (P/M), which primarily amplify repetitive and low-copy sequences, respectively. The overall results not only confirmed earlier observations that massive sequence variations occurred during allopolyploidization in triticale, but also indicated that a great degree of the genome variation occurred immediately following wide hybridization. Specifically, about 46.3% and 36.2% of the wheat (Triticum spp.) parental band loss and 74.5% and 68.4% of the rye (Secale cereale L.) parental band loss occurred in the F1 hybrids (before chromosome doubling) for E/M and P/M primers, respectively. The sequence variation (modification/elimination) events occurring after chromosome doubling were continuous modifications at a very small rate compared to the variation that occurred before chromosome doubling. However, the rate of sequence variation involving the rye parental genome was much higher in about the first five generations following chromosome doubling. The data also indicated that the rate of variation in repetitive sequences was much higher than that in low-copy-number sequences. Compared to other species, the present study suggested cytoplasm and the relationship between the parental genomes of an allopolyploid were the key factors determining the direction, amount, timing, and rate of sequence variation in the allopolyploid.