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Performance of Single and Double Cross Autotetraploid Maize Hybrids with Different Levels of Inbreeding

Garst Seed Co. Res. Dep., Highway 210 P. O. Box 500 Slater, IA 50244
Dep. of Agronomy, Univ. of Illinois, 1102 S. Goodwin Aven., Urbana, IL 61801

^* Corresponding author.

In autotetraploids (4N's), theory suggests that double crosses (DC) should outperform single crosses (SC) if the parents of the SC's are inbred. To evaluate the importance of this theory, experiments using 4N maize (Zea mays L.) were designed to determine the relative performance of 4N SC's and DC's from parents with different levels of inbreeding. The parental lines were derived from three 4N maize synthetics (B,CD, and OP). The study was divided into three experiments grown in central Illinois in from 2 to 4 environments. In one experiment grown at 2 locations in 1986, between population SC's (B x OP, B x CD, CD x OP)and DC's [(B x OP)(BOP), (B x CD)(B x CD), (CD x OP)(CD x OP)] produced S₁ parentalines were compared to within population SC's (B x B, CD x CD, OP x OP) and their between population DC's [(B B)(CD x CD), (B x B)(OP x OP), (CD x CD)(OP a second experiment grown at 2 locations in 1987, the within population SC's and between population DC's produced from S₁ lines were compared to the same SC's and DC's produced from S₃ parental lines. In a third experiment, within population SC's and DC's produced from 16 essentially homozygous lines from Syn. OP were evaluated. Double cross yields from S₂, S₃, and homozygous parents were similar, but SC yields decreased as the parents became more inbred. Thus, it may be possible to use relatively inbred parents to produce autotetraploid maize DC's without significant loss of productivity. Results agreed with theory in that for most traits DC's outperformed SC's, the performance was linearly related to the inbreeding coefficient (F), and genetic variancestimates among SC's were larger than among DC's.

Received for publication July 27, 1988.