Nebraska Agricultural Exy. Station , Research Bui. 20 Many of the plant characters which are involved in adaptation are not inherited singly, but commonly go in groups of associated characters. As a consequence the selection for some single specific character is frequently attended by the indirect selection of a group of characters. Some of the adaptive characters which tend strongly to be associated or transmitted in groups are early maturity, small stature, ears low on the stalk, small leaf area, slender ears, and smooth, shallow kernels with horny endosperm. Selection toward the opposite extreme of any of these characters tends to result in a rather corresponding transition in all of the other associated characters. Exceptions occasionally occur to these groupings of plant characters. 2. Continuous selection within a commercial variety at this Station during four years for opposite extremes in the ratio of leaf area to dry plant substance resulted in seven "high leaf area" and nine "low leaf area" strains of corn, in which the former, in comparison with the latter, averaged 23 per cent more leaf area per unit dry matter, 29 per cent greater actual leaf area, and five days later maturity. The high leaf area selections had ears of larger circumference, and deep, rough, starchy grain, whereas the low leaf area strains had more slender ears, with smooth, shallow, horny kernels. In a succeeding seven-year yield test, the low leaf area yielded 7 per cent more shelled corn per acre than the high leaf area type, but produced 4 per cent less than the original corn from which it was selected. An F 1 cross between these two leaf area types yielded 2 per cent more than the original corn during the seven years. The data suggest superiority of the low leaf over the high leaf area strains but also that some reduction in yield has resulted from narrow breeding brought about by too restricted type selection. 3. Annual selections of various ear types of a standard local variety, Nebraska White Prize, during a six-year period, indicate that long, slender, smooth seed ears with a relatively short and flinty kernel excelled large, rough, deep, and starchy grained seed ears by 9 per cent and the original unselected corn by 1.4 per cent. In another six-year test with standard Iveid'ŝ ellow Dent in which continuous selection was practiced, the long, smooth type of ears surpassed the standard medium, rough type 7 per cent. In a two-year test with local Hogue's Yellow Dent corn, long, slender ears with a rather smooth, shallow kernel excelled ears with deep, rough kernels 9 per cent and the original corn «S per cent in yield of grain. While complete notes descriptive of the plant development resulting from these ear Corn Investigations < type selections were not taken thruout the entire period of the tests, the measurements and observations made lead to the conclusion that ear type selections indirectly result in a selection of correlated plant characteristics which differ in their adaptation to various environmental conditions. Select...
