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Iwao Oiyama and Shozo Kobayashi

Seedlings from some small seeds of diploid × diploid crosses using `Miyauchi iyokan' (Citrus iyo Hort. ex Tanaka) as the seed parent were found to be pentaploid (2n = 5x = 45). The growth of pentaploid seedlings was extremely weak on their own roots, but was much more vigorous when micrografted on seedlings of tetraploid trifoliate orange [Poncirus trifoliata (L.) Raf.]. Diploid `Miyauchi iyokan' produced hexaploid seedlings from small seeds in addition to triploid and tetraploid seedlings from normal seeds when crossed with tetraploid `Funadoko' (C. funadoko Hort. ex Y. Tanaka) and `Trovita' sweet orange [C. sinensis (L.) Osbeck]. Based on this phenomenon, the origin of pentaploids is discussed.

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Yuri Nakamura and Shozo Kobayashi

Restriction fragment length analyses of mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) were carried out on 11 cultivars of Japanese persimmon (Diospyros kaki Thunb.) and five other Diospyros species. Total genomic DNA was digested with seven restriction endonucleases, Southern blotted, and hybridized with five mtDNA probes (PstI or SalI fragments of Brassica campestris L. mtDNA) and one cpDNA probe [pTBal, BamHI fragment of Nicotiana tabacum (L.) cpDNA]. All Japanese persimmon cultivars displayed identical mtDNA and cpDNA fragment patterns, while polymorphisms among species were observed using both mtDNA and cpDNA probes. A low degree of polymorphism was observed between D. kaki, D. oleifera Cheng., D. kuroiwai Nakai, D. virginiana L., and D. lotus L., suggesting that these species are closely related. A high degree of polymorphism was observed between D. rhombifolia Hemsl. and the other five species, indicating that this species is more distantly related to the other five.

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Iwao Oiyama, Shozo Kobayashi, Katsuichi Yoshinaga, Toshifumi Ohgawara and Shigetaka Ishii

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Satoru Kondo, Kentaro Hiraoka, Shozo Kobayashi, Chikako Honda and Norihiko Terahara

Cyanidin 3-galactoside was the primary anthocyanin in red `Tsugaru' apples [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. The concentration of cyanidin 3-galactoside in the skin decreased from 20 to 62 days after full bloom (DAFB), then increased rapidly after 104 DAFB. Small amounts of cyanidin 3-arabinoside and cyanidin 3-glucoside were detected at 122 and 133 DAFB (harvest). The expression of five anthocyanin biosynthetic genes of chalcone synthase (MdCHS), flavanone 3-hydroxylase (MdF3H), dihydroflavonol 4-reductase (pDFR), anthocyanidin synthase (MdANS), and UDP glucose-flavonoid 3-O-glucosyltransferase (pUFGluT) was examined in the skin of red and nonred apples. In general, the expression of anthocyanin biosynthetic genes in red apples was strong in juvenile and ripening stages. The expression of MdCHS, MdF3H, pDFR, and MdANS was observed before ripening stage when anthocyanin was not detected. In contrast, the expression of pUFGluT was detected in the development stage only when anthocyanin was detected. However, the expression of all five genes was observed at 20 DAFB in fruit bagged after fertilization, and anthocyanin was not detected. The expression of MdCHS, MdF3H, pDFR, and MdANS, excluding pUFGluT, was detected at 98 DAFB in fruit bagged after 30 DAFB, and anthocyanin was not detected. These results suggest that pUFGluT may be closely related to the anthocyanin expression in apple skin at the ripening stage.

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Nobuhito Mitani, Atsushi Kono, Masahiko Yamada, Akihiko Sato, Shozo Kobayashi, Yusuke Ban, Toshihito Ueno, Mikio Shiraishi, Shinya Kanzaki, Tomoyuki Tsujimoto and Keizo Yonemori

Persimmon (Diospyros kaki Thunb) is hexaploid, and the pollination-constant, non-astringent (PCNA)/non-PCNA trait of Japanese origin is qualitatively controlled by the AST/ast alleles at a single locus and the PCNA trait is recessive to the non-PCNA trait. To avoid inbreeding depression led by repeated crosses among PCNA genotypes, non-PCNA genotypes should be used as cross parents. The marker-assisted selection system has been developed for the selection of PCNA offspring in the progeny derived from the cross of non-PCNA ‘Taigetsu’ (non-PCNA ‘Kurokuma’ × PCNA ‘Taishu’) to PCNA ‘Kanshu’. The primer pairs E8.5/E9r and 7H9F/AST-R were used for detecting the molecular markers A1 and A3, respectively, which link AST alleles. Complete agreement was found between the sequence-characterized amplified region (SCAR) marker genotype and fruit astringency phenotype of the 48 offspring. The result confirmed that the marker-assisted selection using those markers was highly practical. In a larger offspring population (522 offspring) from the same cross, offspring segregated into 100 with both markers, 162 with only A1, 179 with A3, and 81 with neither, and this segregation ratio was significantly different from 2:3:3:2, which is the segregation ratio of random chromosome assortment in autohexaploid. The percentage of offspring expected to be PCNA was 15.5% (81 of 522), which was slightly lower than 20%.