Repeated DNA sequences and ribulose bisphosphate carboxylase/oxygenase as tools for the study of rice evolution

Abstract

The phylogenetic relationships of the cultivated rices, O. sativa and O. glaberrima, to the complex of species grouped under the heading of O. perennis is far from clear. We have analyzed a series of accessions from each of these species for the isoelectric focusing patterns of ribulose bisphosphate carboxylase/oxygenase (rubisco), and for the presence and organization of a number of coding and noncoding repeated sequence families. The results of these studies indicate a very close relationship between O. sativa, O. glaberrima, and O. perennis accessions from Africa, Asia, and South America. Two South American accessions of O. perennis differed from the others and from the cultivated rices, indicating that O. sativa and O. glaberrima must have diverged from the O. perennis complex more recently than some species that have been hitherto considered to be members of the complex. The results are certainly not consistent with the view that the cultivated rices have been isolated from one another and from their wild progenitors since the time of continental drift.