[Viable mutant homozygotes at Adh1 locus in sugar beet and their combination ablility]

Selection for an increased frequency of mutant semilethal allele Adh1-S of the gene for alcohol dehydrogenase (ADH) was conducted in inbred families of sugar beet. Starting from the fourth generation, viable plants of mutant Adh1-SS homozygotes appeared. In the sixth generation of selection, the combinative ability of mutant homozygotes SS, normal homozygotes FF, and heterozygotes FS was estimated. The hybrids of mutant homozygotes outperformed the hybrids of normal homozygotes in all parameters examined (germinating capacity of seeds, length and weight of 1-week shoots, chlorophyll content in leaves, and root weight). The hybrids of heterozygotes had intermediate values of the parameters. The results obtained are discussed with regard to the mechanisms underlying the recovery of viability of mutant homozygotes and the formation of a compensating gene complex (CGC).