POLYPLOIDY AND THE EVOLUTION OF DOMESTICATED PLANTS

Polyploidy and domestication are common features of plant evolution. A number of selective advantages conferred by polyploidy appear relevant to domestication. Surprisingly, the correlation between the two has not previously been examined. Anderson (Plants, man and life. University of California Press, Berkeley, CA, 1969) asserted that we do not yet know exactly what percentage of cultivated plants and weeds are polyploid, but it must be high. Heiser (Seeds to civilization, the story of food, 2d ed., W. H. Freeman, San Francisco, CA, 198 1) stated that a large number of the major food crops are polyploids, giving wheat, sugar cane, potatoes, sweet potatoes, and bananas as examples. In this study, the distribution of polyploidy in 244 crop species was compared to the estimates of polyploidy in their respective higher categories. The proportion of polyploidy in crop plants was considered in relation to taxonomic origin, habitat, and reproductive strategies of the crops. The study showed that the crop species were a random selection as far as ploidy level is concerned and that domestication did not appear to have favored polyploid over diploid genomes or vice versa. Vegetative, seed, and tree crops were statistically homogenous in their polyploid composition. The distribution of polyploidy in annual and perennial crops did not differ statistically. The data imply that polyploid genomic constitution neither facilitated nor hindered the ability of wild species for domestication.