COMBINING ABILITY IN SUGAR-BEET INBREDS AFTER MALE GAMETOPHYTE SELECTION

Five cycles of male gamete selection were directed to increase the fre quency of the mutant semilethal alcohol dehydrogenase Adh1-S allele in the sugar beet inbred family C257. In the fourth generation of this s election, the SS-homozygotes began to survive. In crosses with tester male sterile plant, the combining ability of these plants was higher t han the combining ability of FS-heterozygotes and FF-homozygotes. This increase in combining ability was not related to monogenic heterosis for the Adh1 locus. The formation of a complex of genes compensating t he lethal effect of the mutant allele can be responsible for this incr ease. Male gamete selection is discussed as one of the possible source s to obtain genotypes with increased combining ability.