Junichi Soejima

Anthocyanin biosynthetic genes are coordinately expressed during red coloration in apple skin

Five genes of anthocyanin biosynthetic enzymes, chalcone synthase (CHS; EC 2.3.1.74), flavanone 3-hydroxylase (F3H; EC 1.14.11.9), dihydroflavonol 4-reductase (DFR; EC 1.1.1.219), anthocyanidin synthase (ANS; EC 1.14.11.X), and UDP glucose:flavonoid 3-O-glucosyltransferase (UFGluT; EC 2.4.1.X), were isolated, and their expression was investigated to elucidate the molecular mechanism for red coloration in apple 〚Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.〛 skin. In ‘Orin,’ a yellow apple cultivar, no significant levels of anthocyanin were detectable, whereas in ‘Jonathan’ and ‘Fuji,’ both red apple cultivars, anthocyanin concentrations increased during fruit development. At the ripe stage, the level of anthocyanin concentration was about three times higher in ‘Jonathan’ than in ‘Fuji.’ The accumulation of transcripts for the five genes was induced at the later developmental stages in all three cultivars. The levels for the expression of the five genes basically corresponded to the anthocyanin concentrations; that is, the induction of the genes in ‘Orin’ was less pronounced, and that in ‘Fuji’ and ‘Jonathan’ was notable, with much higher expression levels in ‘Jonathan’ than in ‘Fuji’. These results indicate that the five genes are coordinately expressed during fruit development and that their levels of expression are positively related to the degree of anthocyanin concentration. This is the first report that characterizes the relationship between the expression of anthocyanin biosynthetic genes and apple fruit coloration.

Apple has two orthologues of FLORICAULA/LEAFY involved in flowering

Two orthologues of FLORICAULA/LEAFY, AFL1 and AFL2 (apple FLO/LFY), were isolated from the floral buds of apple trees. Their expression was detected in various tissues and during differentiation of the floral buds. Furthermore, the flowering effectiveness of each gene was assessed with transgenic Arabidopsis. Both AFL1 and AFL2 showed high homology to each other (90%) and a high degree of similarity to PTLF and PEAFLO (70%), which are homologues of FLO/LFY from poplar and pea, respectively. RNA blot analysis showed that AFL1 was expressed only in the floral bud during the transition from vegetative to reproductive growth, whereas AFL2 was expressed in vegetative shoot apex, floral buds, floral organs and root. Genomic Southern analysis showed that apple had other homologues in addition to AFL1 and AFL2. The transgenic Arabidopsis with over-expressed AFL2 showed accelerated flowering and gave rise to several solitary flowers from rosette axils directly. AFL1 had similar effects, but the phenotypes of the transgenic Arabidopsis with AFL1 were weaker than those with AFL2. These results suggest that both genes are involved in flower differentiation in apple.

Genetic studies on resistance to Valsa canker in apple: genetic variance and breeding values estimated from intra- and inter-specific hybrid progeny populations

Malus sieboldii Rehd. exhibits high levels of resistance to Valsa canker caused by Valsa ceratosperma (Tode ex Fr.) Maire while cultivated apples (Malus domestica Borkh.) are susceptible to the disease. In this study, progenies from 23 full-sib families derived from both inter- and intra-specific hybridization among 16 Malus genotypes as parents were assessed for resistance to V. ceratosperma (Vc) for two seasons using an excised shoot assay to determine the pattern of inheritance of the resistance and to also estimate the variance components, narrow-sense heritability, and breeding values of parental genotypes. Generally, M. sieboldii × M. domestica and its reciprocal crosses had more resistant progenies to Vc than intra-specific crosses of M. domestica. Resistance to Vc expressed as the relative lesion length among progenies showed continuous variation irrespective of cross, suggesting the quantitative nature of the resistance to the three virulent isolates of Vc that were tested. Resistance to Vc using the progeny population was analyzed using a mixed linear model based on restricted maximum likelihood. The parental effect (general combining ability (GCA)) was significant while the interaction effect between parents (specific combining ability (SCA)) was relatively small and non-significant. The ratio of SCA/GCA variance was about 32%, suggesting that additive genetic variance had a major contribution to the total genetic variance for resistance to Vc. There was a positive correlation (r = 0.49, p < 0.01) between mid-parental GCA and SCA predictions among 23 full-sib families for the resistance. Narrow-sense heritability estimated by sib analysis was moderate

S-allele genotypes of apple pollenizers, cultivars and lineages including those resistant to scab

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Genomic DNA sequences encoding Malus x domestica Borkh. "Akane", "Delicious"and Malus transitoria S-RNases

. The predicted breeding values (BV) of the 16 parents indicated that M. sieboldii “Sanashi 63” and “Hayanarisanashi 1” would be useful for breeding for high levels of resistance to Vc.

Expression pattern of homologues of floral meristem identity genes LFY and AP1 during flower development in apple.

Summary S3-, S5-, S9- (=Sc-), Sf-, Sg- and Sh (=S24)-alleles in the wild apple were deduced by using S-allele-specific-polymerase-chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analyses. Within the alleles, the deduced amino acid sequence of Sg 9-RNase in Sg-allele of Malus transitoria differed by one amino acid from that of Sg-RNase in Sg-allele of M. × domestica ‘Indo’. From the cross pollination analysis of M. transitoria and M. × domestica ‘Indo’, and S-allele-specific-PCR-RFLP analyses of their progenies, it was indicated that the pistil Sg 9 RNase in M. transitoria rejected the pollen of Sg-allele from ‘Indo’. A difference of one amino acid within the RHV region produced by natural mutation was not enough to generate a new S-allele. This is the first report in the literature concerning S-allele diversification in the apple.

Identification of Quince Varieties Using SSR Markers Developed from Pear and Apple

Summary We examined S-allele genotypes of ten apple cultivars and species to determine their possible usefulness as pollenizers for all apple cultivars. ‘Dolgo’ did not contain any known S-RNases encoded at the S-locus, suggesting its possible usefulness as a pollenizer for almost all apple cultivars. We also identified and confirmed the S-allele genotypes of 18 apple cultivars by polymerase chain reaction (PCR)-digestion analysis. The S-genotype of ‘Kiou’ (S1S7), ‘Korei’ (S3S28), ‘Korin’ (S1S9), ‘Kotoku’ (S1S28), ‘Kyokkou (S7S25), ‘Lobo’ (S1S7), ’Mahe 7’ (S2S7), ‘Mellow’ (S2S3), ‘Takahara’ (S3S9) and ‘Warabi’ (S9S28) were confirmed by pollination results. These cultivars seemed not to have originated from the expected seed or pollen parents or, in the case of ‘Lobo’, might have been mislabelled. Finally, we identified the S-allele genotypes of ‘Prima’ (S2S10), ‘Querina’ (S3S9) and ‘Yoko’ × ‘Prima’ (S3S10), which are resistant to scab.

A New S-allele in Apple, `Sg', and Its Similarity to the `Sf' Allele from `Fuji'

Environmental variance components associated with year, tree, and harvest date were estimated for fruit softening after harvest in apple (Malus × domestica Borkh.) to determine their relative importance and design optimum sampling strategies to discriminate genotypes in apple breeding. Fruit were stored after harvest under 20± 2 ∘C and 80± 5%RH. Softening was evaluated by adapting the change in firmness during storage to a linear regression and defining the regression coefficient as the softening rate. Environmental variances associated with genotype × year interaction, among trees, year × tree interaction, and among harvest dates were all very small, namely, 2.7, 0.1, 5.2, and 5.7%, respectively, to the total variance obtained from the analysis of variance for the softening rate. The variance associated with genotype, at 57.3%, was very large. On the basis of the number of fruit necessary for firmness measurements, two times harvest is an efficient strategy to determine a genotype mean for the softening.