Predicted and actual responses during long-term selection for chemical composition in maize

Selection for higher and lower levels of protein and oil content in maize has been conducted for 61 generations. Response to selection has been irregular, and prediction of response by extrapolation of regression trend lines proved seriously inaccurate in at least 9 of 12 predictions. Application of a selection response formula also yielded generally unsatisfactory predictions. Analysis of the morphological components of oil content led to very accurate prediction of response in the High Oil strain and to a reasonably satisfactory prediction in Low Oil. It was apparent that in the last 55 generations of selection, selection response for oil content was concentrated in two separate morphological characters — germ size in the high selection and oil content of the germ in selection for lower oil content. A satisfactory analysis of the character protein content could not be made from data available.Prepared as part of a research project while the author was a Fulbright senior research fellow at the Max-Planck-Institut für Züchtungsforschung, Köln-Vogelsang, Germany, March–July, 1961.