Index, Individual Trait, and Tandem Selection to Improve a Maize Synthetic for Yield, Corn Borer, and Disease Traits
Miller, Robert Lynn
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https://hdl.handle.net/2142/71580
Description
Title
Index, Individual Trait, and Tandem Selection to Improve a Maize Synthetic for Yield, Corn Borer, and Disease Traits
Author(s)
Miller, Robert Lynn
Issue Date
1982
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Agriculture, Plant Pathology
Abstract
Genetic variance and covariance estimates from replicated trials of 120 to 200 half-sib families of a maize (Zea mays L.) synthetic were obtained in one to three years for grain yield (measured on uninoculated plants), quantitative resistance to four common leaf and stalk diseases evaluated separately, the aggregate effect of several common leaf and stalk diseases, and first generation European corn borer (CB) {caused by Ostrinia nubilalis (Hubner)}. These data were used to estimate genetic correlations between pairs of traits, to construct two selection indexes designed to improve the synthetic for yield and resistance to CB and common Illinois maize diseases simultaneously, to predict gain from selection, and to determine adequate numbers of replicates and plants per plot for half-sib and S(,(PERP)) family selection for each disease trait. Two sequential cycles of divergent selection for the indexes were completed and compared with one cycle of tandem selection which involved high intensity mass selection for aggregate leaf and stalk rot resistance, followed by recombination and half-sib family selection for yield. One cycle of divergent half-sib family selection for each trait per se was also completed and evaluated.
Tandem selection led to significant improvement for all disease traits evaluated. This response was generally superior to response for disease traits from two cycles of positive index selection. Progress from index selection agreed reasonably well with prediction for index score and for individual component traits.
Divergent response to half-sib family selection for individual disease and CB traits was in good agreement with prediction. In general, favorable realized correlations among leaf disease traits and among stalk disease traits were observed, but there was no consistent realized correlation between leaf and stalk disease traits. Tandem selection was equal to or more effective than direct selection for any disease trait. Tandem selection was more effective than other selection schemes in improving the average resistance over all disease traits measured.
Selection for disease traits led to either no effect or a favorable effect on yield (under uninoculated conditions). Positive selection for disease resistance did not change maturity, except mass selection for multiple disease resistance delayed silk date one day.
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