Efficiency of genomic selection for breeding population design and phenotype prediction in tomato.

Genomic selection (GS), which uses estimated genetic potential based on genome-wide genotype data for a breeding selection, is now widely accepted as an efficient method to improve genetically complex traits. We assessed the potential of GS for increasing soluble solids content and total fruit weight of tomato. A collection of big-fruited F1 varieties was used to construct the GS models, and the progeny from crosses was used to validate the models. The present study includes two experiments: a prediction of a parental combination that generates superior progeny and the prediction of progeny phenotypes. The GS models successfully predicted a better parent even if the phenotypic value did not vary substantially between candidates. The GS models also predicted phenotypes of progeny, although their efficiency varied depending on the parental cross combinations and the selected traits. Although further analyses are required to apply GS in an actual breeding situation, our results indicated that GS is a promising strategy for future tomato breeding design.

Identification of two loci for resistance to clubroot (Plasmodiophora brassicae Woronin) in Brassica rapa L.

In an analysis of 114 F(2) individuals from a cross between clubroot-resistant and susceptible lines of Brassica rapa L., 'G004' and 'Hakusai Chukanbohon Nou 7' (A9709), respectively, we identified two loci, Crr1 and Crr2, for clubroot (caused by Plasmodiophora brassicae Woronin) resistance. Each locus segregated independently among the F(2) population, indicating that the loci reside on a different region of chromosomes or on different chromosomes. Genetic analysis showed that each locus had little effect on clubroot resistance by itself, indicating that these two loci are complementary for clubroot resistance. The resistance to clubroot was much stronger when both loci were homozygous for resistant alleles than when they were heterozygous. These results indicate that clubroot resistance in B. rapa is under oligogenic control and at least two loci are necessary for resistance.

Isolation and characterization of microsatellites in Brassica rapa L.

We report here the isolation and characterization of microsatellites, or simple sequence repeats (SSRs), in Brassica rapa. The size-fractionated genomic library was screened with (GA)(15) and (GT)(15) oligonucleotide probes. A total of 58 clones were identified as having the microsatellite repeats, and specific primer pairs were designed for 38 microsatellite loci. All primer pairs, except two, amplified fragments having the sizes expected from the sequences. Of the 36 primer pairs, 35 amplified polymorphic loci in 19 cultivars of B. rapa, while monomorphism was observed in only one primer pair. A total of 232 alleles was identified by the 36 primer pairs in 19 cultivars of B. rapa, and these primer pairs were examined also in nine Brassicaceae species. Most of the 36 primer pairs amplified the loci in the Brassicaceae species. Segregation of the microsatellites was studied in an F(2) population from a cross of doubled-haploid lines DH27 x G309. The microsatellites segregated in a co-dominant manner. These results indicate that the microsatellites isolated in this study were highly informative and could be useful tools for genetic analysis in B. rapa and other related species.

L-galactono-gamma-lactone dehydrogenase from sweet potato: purification and cDNA sequence analysis.

L-Galactono-gamma-lactone dehydrogenase (EC 1.3.2.3, GLDHase) was partially purified from mitochondria of sweet potato tuberous roots over 600-fold on a specific activity basis, followed by purification of the enzyme protein of 56 kDa by a preparative SDS-PAGE. The absorption spectrum of the hydroxylapatite column-purified GLDH-ase showed peaks at 448 and 373 nm, suggesting the presence of flavin as a prosthetic group. The activity of GLDH-ase was inhibited by lycorine, an alkaloid which inhibits ascorbic acid biosynthesis in vivo. N-terminal partial sequences of four internal polypeptides generated by partial digestion of GLDHase with V8 protease were determined. The deduced nucleotide sequences were used to amplify a cDNA fragment of the GLDHase gene. The clone encoded a polypeptide of 581 amino acid residues with a molecular mass of 66 kDa. The deduced amino acid sequence showed 77% identity with that of cauliflower GLDHase, and significant homology to those of L-gulono-gamma-lactone oxidase (22% identity) from rat and L-galactono-gamma-lactone oxidase from yeast (17% identity), which are enzymes involved in L-ascorbic acid biosynthesis in these organisms. The absorption spectrum and cDNA sequence suggested that the flavin group bound noncovalently. We conclude that GLDHase, L-gulono-gamma-lactone oxidase and L-galactono-gamma-lactone oxidase are homologous in spite of the difference in substrates and electron acceptors. Genomic Southern analysis suggested that GLDHase gene exists as a single copy in the genome of sweet potato.

Structure of an exocellular polysaccharide of Lactobacillus helveticus TN-4, a spontaneous mutant strain of Lactobacillus helveticus TY1-2.

Lactobacillus helveticus strain TN-4, a spontaneous mutant strain of Lactobacillus helveticus TY1-2, produced an exocellular polysaccharide from reconstituted skim milk. On the basis of the results of methylation analysis, enzymatic digestion, mild Smith degradation, mild acid hydrolysis, acetolysis, and 1D and 2D 1H-NMR spectroscopy, it was concluded that the polysaccharide has a D-galactofuranose containing hexasaccharide repeating unit with the following structure: [formula see text]