Genetic Variation in Quantitative Characters in Maize Inbred Lines, II. Effects on Performance in Single‐Cross and Double‐Cross Hybrids¹

Abstract

Six inbred lines and seven single crosses involving these lines were obtained from four Corn Belt foundation seed stock organizations and the Iowa Agriculture Experiment Station. The genetic variation among the strains within inbred lines and among single crosses of the same pedigree was investigated. The inbred strains were compared in testcrosses with three unrelated inbred lines and the single crosses were compared in nine double‐cross hybrids. Tests in 10 environments, five locations for two years, revealed significant differences for percentage moisture among strain testcrosses within all inbreds and for yield in all except two of the inbreds. Strains included pollen restorer (Rf) and nonrestorer (rf) versions, except for two lines in which only rf versions were available. Significant variations were obtained for Rf vs. rf strain testcrosses, among Rf strain testcrosses, and among rf strain testcrosses. The Iowa Rf strain testcrosses were not different from the remaining Rf strain testcrosses for yidd, but the Iowa rf strain testcrosses compared with the remaining rf strain testcrosses were significantly different for yield within three of the six inbreds and for moisture within five of the six inbreds. Among strains within double crosses there were significant differences for percentage moisture in eight hybrids and for yield in four hybrids. Yield differences were great enough to be of practical importance in some cases, whereas moisture differences were not considered of practical importance even though many were statistically significant.

Conservation Breeding of Elite Cultivars

“…Even since the 1950s, studies in maize have indicated significant phenotypic variation within inbred lines (Schuler, 1954; Hooker, 1955; Sprague et al, 1960; Russell et al, 1963; Busch and Russell, 1964; Fleming et al, 1964; Fleming, 1971; El‐Eryani and Fleming, 1966, 1968; Higgs and Russell, 1968a,b; Grogan and Francis, 1972; Russell and Vega, 1973; Bogenschutz and Russell, 1986; Tokatlidis, 2000). The variation was mainly searched by comparing sister lines obtained via selection within inbred lines, and was found to be transmissible to the hybrids.…”