ISHS Acta Horticulturae 407: ISHS Brassica Symposium - IX Crucifer Genetics Workshop
GENOME VARIATION AND EVOLUTION OF BRASSICA AMPHIDIPLOIDS |
| Authors: | K. Song, K. Tang, Thomas C. Osborn, P. Lu |
| Keywords: | B. carinata, B. juncea, B. napus, RFLP, molecular evolution, synthetic polyploid, genome change |
| Abstract:
Genome variation among natural and synthetic Brassica amphidiploid species have been studied by RFLP analyses. Large genetic diversity was found among and within the three cultivated amphidiploid species. Based on genetic diversity, B. napus seems to be the most ancient amphidiploid, followed by B. juncea and B. carinata. Two major factors are responsible for the genetic diversity within amphidiploids: one is multiple hybridizations between different diploid parents, and the other is genome modifications after polyploidization. A good example for multiple hybridizations was found in B. napus. Four cytoplasmic types were observed in a group of representative B. napus accessions, which matched with different parental diploid cytoplasms. Direct evidence for genome changes after polyploidization were obtained from synthetic amphidiploids. Genome changes, maily involving loss and/or gain of parental fragments and novel fragments, were observed in the early generations of four synthetic amphidiploids. The frequency of genome change and the direction of genome evolution in the synthetics appeared to be associated with the genome divergence between the parental diploid species. Rapid genome changes resulted in fast genetic divergence among the derivatives of synthetic amphidiploids, which, by providing raw materials for seletion, might have played an important role in the evolutionary success of Brassica amphidiploids and many polyploid lineages. | |
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