Mutation-selection equilibrium as a possible cause of an interchange chromosome polymorphism in a cultivar of rye,Secale cereale L.

Summary A persistent chromosomal polymorphism exists in a population of cultivated rye, Secale cereale (Candela et al. 1979). In order to ascertain the possible causes that maintain it, we have estimated the fitness values of structurally homozygous and heterozygous plants and the mutation rate of spontaneous interchange. The estimates of the selection coefficient against heterozygotes (s=0.15-0.40) and of the mutation rate u=6.12×10^–2 support a mutation-selection equilibrium as a likely cause of the interchange chromosome polymorphism.