Annals of Botany 70: 111-118, 1992
© 1992 Annals of Botany Company
RESEARCH-ARTICLE |
Spatial Separation of Ancestral Genomes in the Wild Grass Milium montianum Parl.
Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey TW9 3DS, UK
Accepted: 20 February 1992
Previous work showed a strong tendency for genomes from two different parents to be spatially separated in cell nuclei of several man-made F1 hybrids between grass species. An important question therefore is whether similar nonrandom genome disposition occurs in wild species. Milium montianum Parl. (2n = 22) is a naturally occurring allopolyploid grass combining two genetically dissimilar chromosome sets (V and M genomes), each originating from a different ancestral species. These two ancestral genomes were easily discriminated as all V genome chromosomes were larger than all M genome chromosomes. In two-dimensional spread preparations, the V genome derived from M. vernale Bieb. (2n = 8), and the M genome (of different but uncertain origin) showed a highly significant tendency to lie apart. Generally, the V chromosomes tended to surround the M chromosomes in both mitotic and meiotic nuclei suggesting that this arrangement persists throughout plant development. Such nuclear organization is probably under genetic control and may facilitate some independent behaviour of ancestral genomes in allopolyploids. Indeed it may play a significant role in plant evolution and speciation, especially if different intranuclear positions (e.g. central or peripheral) are correlated with preferential phenotypic expression of ancestral genes.
Milium montianum Parl., Gramineae, allopolyploid, spatial chromosome disposition, ancestral genome separation, plant speciation and evolution
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