Genetic Analysis of Crosses among Corn Strains Divergently Selected for Percent Oil and Protein¹

Abstract

All possible crosses, excluding reciprocals, among the nine strains [Illinois high oil (IHO), reverse high oil (RHO), switchback high oil (SHO), low oil (ILO), reverse low oil (RLO), high protein (IHP), reverse high protein (RHP), low protein (ILP), and reverse low protein (RLP)] in the Illinois long term selection experiment for percent oil and protein in corn ( Zea mays L.) were grown to measure their performance and to study; 1) the effects of oil and protein percentage on grain yield and other agronomic traits, 2) the effects of selection for percent protein on components of percent protein, 3) the relationship of percent oil and protein to calorie production, and 4) the importance of genetic effects for several traits. Results obtained suggest that; 1) grain yield is negatively correlated with percent oil and percent protein, 2) percent protein in the kernel is primarily determined by percent protein in the endosperm, 3) calories per g dry matter are largely determined by percent oil while calories per kernel or ha are largely determined by kernel weight or grain yield, 4) the sum of squares (s.s.) due to heterosis accounted for only 5 and 7%, respectively, of the entry s.s. for percent oil and percent protein but over 50% of the entry s.s. for yield of grain and protein, and 5) evidence was obtained of dominance for both high and low percent oil.