Date of this Version
Thesis (M.S.)—University of Nebraska—Lincoln, 1971. Department of Agricultural Engineering.
The economic value of a plant is usually determined by several traits which may or may not be equally important.Consequently, plant breeders have to consider several traits in deciding which individuals or families are the most valuable to select.
The usual method of “eye-ball” selection is hard to employ when several traits are being considered because of the masking effects of the environment and the inability to efficiently utilize the information on the relationship between the traits.What is needed is a method that will objectively determine the genotypic worth of the individuals or families.Selection, indices, theoretically, may accomplish the above goal and have been reported to give good results in cotton, soybeans and alfalfa.However, the application of such indices has been limited.This is probably due to difficulties in giving the proper economic weight to contributing traits and the labor involved in the construction of the indices.Therefore, simple indices that may be useful in selection work are needed.
The objective of this study is to compare the efficiency of some weighted and un-weighted selection indices that might be useful in corn breeding.
The maize populations used in this study were the Nebraska B synthetic, Stiff Stalk synthetic (SS) and the open pollinated variety Krug (K).
Five selection indices involving yield, lodging and dropped ears were constructed in two variety crosses of corn, B x SS and B x K.The relative efficiencies of those indices and individual traits as criteria of selection were compared.
The relative economic importance was assigned to each character by assuming that 1 percent of either lodging or dropped ears cases a loss of 1 percent of the yield.The selection differential of the indices and the individual traits was 9.6% and 10.1% in each of the two populations.
The bases for comparison was the expected total gain from selection in terms of yield and the ease of an index to apply.
Advisor: William A. Compton