Allozyme Diversity in Cultivated Crops

Estimates of genetic diversity maintained by plant species and its distribution within and among populations allows plant geneticists to predict, in a general way, the evolutionary potential of species. Single‐gene markers, particularly allozymes, have been used to measure the genetic diversity of species. In this paper, the plant allozyme literature was reviewed to compare levels of genetic variation maintained by crop and non‐crop species. Crop species (plant species intentionally cultivated by humans) have more allozyme diversity as a whole than other seed plant species, although the mean genetic diversity partitioned within populations of crop species was similar to that of other plant species. Populations of crop species were more genetically heterogeneous, an observation that was probably due to the higher proportion of crops that reproduce by self fertilization. Dicotyledonous crops have much less genetic diversity than monocotyledonous crops at the species and the population level and exhibit more inter‐population genetic differentiation. Annual and perennial crop species had similar levels of genetic diversity and partitioned genetic diversity in similar ways. Predominantly selflng crops had somewhat less genetic diversity than outcrossing or mixed‐mating species. Selflng crops exhibited more population‐to‐population variation in genetic diversity and allele frequency differences were much greater among their populations. High population‐to‐population variation in genetic diversity increases the importance of empirical data for the design of sampling protocols.