The Frequencies of Seed and Seedling Abnormalities in Maize.

T HE fact that cross-fertilizing species carry relatively large numbers of deleterious recessives in a heterozygous condition has been demonstrated by various investigators and for several species. The results obtained have been used to make inferences or to provide a critical interpretation relative to population structure and size, types of gene action, mutation rates, selective advantage, and other attributes which contribute to the description of a population in genetic terms. Relatively little information is available, however, for the subsequent behavior of populations that have been experimentally purged of deleterious recessives. The purpose of the present paper is to provide information about one such case in maize. Information on the frequency of deleterious recessives is most extensive for Drosophila species. Less information is available for many other species of animals and plants. We shall be concerned here with only the pertinent information available for maize. JENKINS (1924) reported a range of 0.0 to 35.5 percent for chlorophyll-defective types in first selfed-generation progenies derived from 16 open pollinated varieties. In samples representing six varieties, HAYES and BREWBAKER (1924) reported frequencies of chlorophyll-deficient types ranging from 10.0 to 39.4 percent. WENTZ and GOODSELL (1929) sampled 19 varieties which had been included in the Iowa State yield test for 1924 and 1925. The observed range for percentage of chlorophyll deficiencies was 3.6 to 42.8. In three varieties, WOODWORTH (1929) observed the percentage of self-pollinated ears segregating for chlorophyll deficiencies to range from 10.0 to 28.9. In a later summary WOODWORTH and MUMM (1931) reported 17.7 percent of self-pollinated ears of the variety Reid segregated for chlorophyll deficiencies and 3.9 percent for defective seeds. This report is of particular interest since a reconstituted Reid was produced by compositing remnant seed of all selfed ears whose progeny were free from detectable segregations. This reconstituted variety was propagated under open-pollination