Only three variants of nonrestoring alleles for sugar beet Rf1 were found from the US maintainer lines which were the selections from a broad range of genetic resources. Cytoplasmic male sterility is widely used for hybrid breeding of sugar beets. Specific genotypes with a nonsterility-inducing cytoplasm and a nonrestoring allele of restorer-of-fertility gene (rf) are called maintainers. The infrequent occurrence of the maintainer genotype evokes the need to diagnose rf alleles. Molecular analysis of Rf1, one of the sugar beet Rfs, revealed a high level of nucleotide sequence diversity, but three variants were tightly associated with maintainer selection in Japan. The question was raised whether this small number of variants would be seen in cases where a wider range of genetic resources was used for maintainer selection. Fifty-seven accessions registered as maintainers in the USDA germplasm collection were characterized in this study. Mitochondrial DNA types (mitotypes) of 551 plants were diagnosed based on minisatellite polymorphism. A mitotype associated with sterility-inducing (S) cytoplasm was identified in 58 plants, indicating S-cytoplasm contamination. The organization of rf1 was investigated by two PCR markers and DNA gel blot analysis. Eight haplotypes were found among the US maintainers, but subsequently two haplotypes were judged as restoring alleles after a test cross and another haplotype was not inherited by the progeny. Nucleotide sequences of rf1 regions in the remaining five haplotypes were compared, and despite the sequence diversity of the gene-flanking regions, the gene-coding regions were identified to be three types. Therefore, there are three rf1 variants in US maintainers, the same number as in the Japanese sugar beet germplasm collection. The implications of having a small repertoire of rf1 variants are discussed.

The wheat seed storage proteins gliadin and glutenin are encoded by multigenes.Gliadins are further classified into α-, γ-, δ-and ω-gliadins. Genes encoding α-gliadins belong to a large multigene family, whose members are located on the homoeologous group 6 chromosomes at the Gli-2 loci. Genes encoding other gliadins are located on the homoeologous group 1 chromosomes at the Gli-1 loci. Two-dimensional polyacrylamide gel electrophoresis (2-DE) was used to characterize and profile the gliadins. The gliadins in aneuploid Chinese Spring wheat lines were then compared in this study. Gliadin proteins separated into 70 spots after 2-DE and a total of 10, 10 and 16 spots were encoded on chromosomes 6A, 6B and 6D, respectively, which suggested that they were α-gliadins. Similarly, six, three and seven spots were encoded on chromosomes 1A, 1B and 1D, respectively, which indicated that they were γ-gliadins.Spots that could not be assigned to chromosomes were N-terminally sequenced and were all determined to be α-gliadins or γ-gliadins. The 2-DE profiles showed that specific α-gliadin spots assigned to chromosome 6D were lost in tetrasomic chromosome 2A lines. Furthermore, western blotting against the Glia-α9 peptide, an epitope for celiac disease (CD), suggested that α-gliadins harboring the CD epitope on chromosome 6D were absent in the tetrasomic chromosome 2A lines. Systematic 3 analysis of α-gliadins using 2-DE, quantitative RT-PCR and genomic PCR revealed that tetrasomic 2A lines carry deletion of a chromosome segment at the Gli-D2 locus. This structural alteration at the Gli-D2 locus may provide a genetic resource in breeding programs for the reduction of CD immunotoxicity.

No abstract