INTERMATING SCHEMES USED TO SYNTHESIZE A POPULATION ARE EQUAL IN GENETIC CONSEQUENCES

Several crossing arrangements can be used to synthesize base populations for recurrent selection. This study compared four intermating methods (chain cross, convergent cross, diallel cross following pair crossing, and pair crosses following a diallel) with regard to the maintenance of alleles, the amount of recombination, and the genetic variability available in each population. Base populations were produced by intermating 10 soybean [Glycine max (L.) Merr.] isolines that differ in alleles at 12 loci. A 12-gene additive trait was simulated by designating a favorable allele at each locus, following the fate of these favorable alleles during intermating, and summing the number of favorable alleles present at all loci to obtain genotypic scores. No alleles were lost during the population synthesis. All allele frequencies in all populations fell within the confidence intervals of the expected values associated with genetic drift. No significant differences were found among populations for genetic variability or recombination. This study indicates that the intermating method can be chosen on the basis of resources required for its implementation. The chain cross or pair crosses followed by a diallel were most appropriate in our case.