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  • Author or Editor: Sadao Komori x
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S-allele genotypes of nine apple (Malus ×domestica Borkh.) cultivars were identified using S-allele–specific polymerase chain reaction (PCR)–restriction fragmentlength polymorphism (RFLP) analysis. A new S-allele, Sg, was proposed to be present in `American Summer Pearmain', `Indo', `Kitanosachi', and `Meku 10'. This allele is very similar to Sf at the nucleotide sequence (92%) and deduced amino acid sequence (94%) levels.

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Cross-incompatible combinations among the main cultivars in apple are rarely reported in Japan. Recently, however, most new Japanese cultivars are progenies of `Ralls Janet', `Delicious', `Golden Delicious', `Jonathan', and `Indo'. Cross incompatibility in apple, therefore, will become a serious problem in the near future. Since the analysis of the S-allele genotypes were not performed, especially in Japanese apple cultivars, the fruit set percentage were examined in several combinations of `Hatsuaki' (`Jonathan' × `Golden Delicious') and `Iwakami' (`Fuji' × `Jonathan') progenies using back crossings. As a result, we found that `Golden Delicious' and `Jonathan' had no common S-allele, while `Fuji' and `Jonathan' had one common S-allele. These facts were used as basics for the S-allele genotype analysis, and fruit set percentage and seed number per fruit were investigated on a large scale. The cross seedlings between `Delicious' and `Jonathan', `Ralls Janet' and `Jonathan', `Iwakami' and `Golden Delicious', `Golden Delicious' and `Delicious', `Hatsuaki' and `Fuji', `Hatsuaki' and `Delicious', `Hatsuaki' and `Jonathan', and `Hatsuaki' and `Golden Delicious' were analyzed. In addition, incompatibility between `Redgold' and `Kinesei' (`Golden Delicious' × `Ralls Janet'), `Senshu' (`Toukou' × `Fuji') and `Iwakami', and progenies of `Northern Spy' also were analyzed. As a result, we have found the existence of six alleles and 15 genotypes, and we have established S-allele standard cultivars and strains as follows: (Sa, Sb) = `Golden Delicious'; (Sa, Sc) (4)-354, (4)-425; (Sa, Sd) = `Toukou'; (Sa, Se) = `Redgold', `Kinsei'; (Sa, Sf) = `Narihokou', (4)-4195; (Sb, Sc) = `Hatsuaki', `Kuifua', `Sekaiichi'; (Sb, Sd) = `Tsugaru', (4)-300; (Sb, Se) = (4)-150, (4)-743; (Sb, Sf) = `Northern Spy', M.9, `Umezawa'; (Sc, Sd) = `Jonathan', `Himekami'; (Sc, Sf) = `Fuji', `Shinkou'; (Sd, Se) =; (Sd, Sf) = `Senshu', `Iwakami'; (Se, Sf) = `Ralls Janet'.

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The development of new high-quality apple (Malus ×domestica) cultivars that are resistant to flesh browning is needed to expand the use of apples in the food service and catering industry. However, conventional methods for evaluating apple flesh browning can be both time-consuming and costly, thereby rendering such methods unsuitable for breeding programs that must characterize a large number of product samples. Therefore, it is necessary to develop new, simple, and inexpensive methods. The aim was to develop a method for simultaneously measuring the color values of 42 apple samples using a digital camera. The processing time per sample was reduced to less than one-tenth of that of the conventional method. The measurement dispersion [sd of the color difference between two colors ( Δ E ab * ) ] of this system was less than 0.08, equivalent to the nominal value of a general colorimeter. Time-series analysis of six apple cultivars using this method showed that the calculated browning index values correlated well with the degree of browning judged by human perception. Further, the measurement data showed that the CIE L* a* b* value trends associated with browning in reddish- and watercored-flesh samples, was different from the corresponding trends in yellowish-flesh samples. This work reports the development of a high-throughput analytical system of apple browning and provides cautionary notes for evaluating reddish- and watercored-flesh browning, which should be measured on a different basis from that used for normal-flesh browning.

Open Access

Doubled haploids can improve the efficiency of breeding and genetic study in apple (Malus ×domestica Borkh.). Seventeen homozygous genotypes were obtained by in vitro anther culture from ‘Senshu’ apple. Flow cytometry analysis revealed that the ploidy level of the anther-derived plantlets was diploid. Simple sequence repeat (SSR) analysis determined the origin and homozygous status of the anther-derived plantlets. The results of S-RNase polymerase chain reaction (PCR)-digestion analysis reinforced the homozygous state. The morphological characteristics and reproductive potential of the doubled haploids were investigated. It is especially interesting that one of the doubled haploids derived from anther culture had fertile pollen grains (rate of in vitro germination was 20.6%–33.0%), and several progenies were obtained from the cross between ‘Prima’ apple and the doubled haploid. The hybridism of these seedlings was confirmed by SSR analysis. Furthermore, the female gametes of the doubled haploid showed slight fertility. Thus, this doubled haploid will be valuable for breeding and genetic studies.

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Two apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] homologous fragments of FLO/LFY and SQUA/AP1 (AFL and MdAP1, respectively) were analyzed to determine the relationship between floral bud formation and floral gene expression in `Jonathan' apple. The AFL gene was expressed in reproductive and vegetative organs. By contrast, the MdAP1 gene, identified as MdMADS5, which is classified into the AP1 group, was expressed specifically in sepals concurrent with sepal formation. Based on these results, AFL may be involved in floral induction to a greater degree than MdAP1 since AFL transcription increased ≈2 months earlier than MdAP1. Characterization of AFL and MdAP1 should advance the understanding of the processes of floral initiation and flower development in woody plants, especially in fruit trees like apple.

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