KORPELAINEN, HELENA. Department of Biosciences, Division of Genetics, P.O. Box 56, FIN-00014 University of Helsinki, Finland. - A genetic method to resolve gender before sexual maturity complements investigations on sex ratios in dioecious Rumex acetosa.
Rumex acetosa (Polygonaceae) is a perennial dioecious weed and
one of the few plant species which possess well-differentiated sex
chromosomes (2n=12+XX in females and 2n=12+XY1Y2 in males). Such a
chromosomal sex determination system constrains the average primary
sex ratios to a 1:1 ratio. Yet, the operational sex ratios (the number
of males per female at sexual maturity) may become biased due to
differential mortality, longevity or vegetative vigor between the
sexes. Although time-consuming cytological analyses would allow
studies on sex ratios among seedlings in dioecious species that have
distinguishable sex chromosomes, investigations on sex ratios have
mostly relied on information obtained at sexual maturity. A genetic
method has now been applied to resolve gender among nonflowering
plants of R. acetosa. The method involves amplification of a Y
chromosome specific DNA sequence by PCR. To detect the mechanisms
responsible for the observed sex ratio variation, a combination of
methods is used to examine the patterns of seasonal sex ratio
variation observed in populations of R. acetosa living in
different habitats.
Key words: Polygonaceae, Rumex acetosa, sex ratio variation, sex specific DNA marker