Aneuploidy and inbreeding depression in random mating and self-fertilizing autotetraploid populations.

Almost all autotetraploids produce aneuploid progeny because of irregularities at meiosis. Aneuploid plants produce high frequencies of aneuploids. If it were not for selection against aneuploid gametes and sporophytes the amount of aneuploidy would increase every generation. Most experimental and theoretical studies on population genetics and heterosis in autotetraploids have neglected aneuploidy as a factor. To take aneuploidy into account experimentally requires the cytological identification of all chromosomes and to consider it theoretically requires a huge amount of computations. Consequently, microcomputer programs have been devised to show the effects of random mating and self-fertilization in autotetraploid populations. According to the model aneuploidy rapidly increases in randomly mated and self-fertilized autotetraploid populations until they achieve an equilibrium where the amount of aneuploidy introduced into the population is balanced by the amount of aneuploidy removed from the population by selection. The model suggests that self-fertilized populations have greater frequencies of aneuploid gametes and zygotes than do randomly mated populations and therefore aneuploidy may be a significant cause of the great inbreeding depressions found in autotetraploids.