Selection response, genetic variation, and combining ability of high oil maize genotypes

High maize oil has several advantages as an important source for human foods and animal feeds. Therefore, improvement of several value-added maize traits including higher oil concentration along with increased grain yield would add considerable value to maize hybrids and additional return to growers. The production of high yielding maize hybrids with high oil concentration could be accomplished by using a comprehensive breeding program through population improvement, inbred line selection, and hybrid development. The University of Illinois has developed high oil maize synthetics, Alexho Elite (AE) and Ultra High Oil (UHO), selected for increased grain yield using recurrent selection. To obtain additional information on these maize synthetics along with inbreds developed from AE, UHO, and other synthetics, three experiments have been conducted.; The first experiment was Selection Response for Increased Grain Yield in Two High Oil Maize Synthetics. Results of the study showed six cycles of recurrent selection using an inbred tester B73 for increased grain yield in AE and UHO did increase grain yield of AE testcrosses without changing both oil and protein concentrations. However, there was no change in grain yield and oil concentration of both AE and UHO cycles. AE testcrosses (having lower oil concentration) produced higher grain yields and greater selection response for grain yield than UHO testcrosses. AE and UHO testcrosses with LH185 gave the highest grain yield among testcrosses to three testers. An increase in grain yield from cycle-0 to cycle-6 in AE testcrosses was associated with increases in grain weight ear−1, kernel weight, and starch concentration.; The second experiment was Genetic Variation in Alexho Elite High Oil Maize Synthetic Selected for Increased Grain Yield. The study showed significant genetic variability estimates were available for grain weight plant −1 in AEC₆S₃ lines and for grain yield in AEC₆S₂ x LH185 testcrosses. Due to significant negative genotypic correlation between oil concentration and grain weight plant −1 in AEC₆ lines, breeding for increased grain weight plant−1 could reduce oil concentration. Based on adequate levels of additive genetic variance available and high narrow sense heritability estimates for grain yield and other traits in the AEC₆S₂ x LH185 testcrosses, further improvement for grain yield in testcrosses should be achieved by recurrent selection using inbred LH185 as the tester without a great reduction in both oil and protein concentrations.