Nuclear DNA content in F1 hybrids of maize

Abstract

The nuclear DNA content was determined in two separate experiments for 19 maize inbred lines and 26 maize F1 hybrids. Ten inbred lines were initially screened in the first experiment. An 11 per cent difference in nuclear DNA amount was observed between the two lines with the lowest amounts of DNA and two lines with the largest genome sizes. All possible hybrid combinations were made among these four lines. In all cases, the genome sizes of the F1 hybrids were not significantly different from their expected parental means. In several cases, however, F1 plants of specific crosses were not uniform in genome size. In these crosses, genome sizes observed ranged from the genome size of the low parental genome to the largest parental genome. These results indicate an instability in F1 genome sizes in certain maize crosses. In order to corroborate this hypothesis, a second experiment was performed. To remove any biases with respect to genome size, 14 F1 maize hybrids were selected solely on the basis of their heterotic response with no regard for their genome sizes or the genome sizes of their parental inbred lines. The nuclear DNA content of the nine parental lines and 14 hybrids was determined. In most of the crosses, the nuclear DNA content of the F1 hybrids was not significantly different from their respective parental means. However, in five parental combinations, the mean nuclear DNA content of the F, hybrids was significantly higher than their respective parental means. The combined results of this study support the hypothesis of instability in nuclear DNA content in F1 hybrids of maize. This instability appears not to be universal in all maize hybrids but is restricted to specific parental combinations.