In this study, we investigated the traits associated with fruit and seed maturation during fruit development of Japanese apricot (Prunus mume Sieb. et Zucc.) fruit in Taiwanese cultivars (‘Ellching’, ‘ST’ and ‘Taiwan’; TCs) and then compared them with the Japanese cultivar ‘Nanko’. In on-tree fruits, ethylene production either remained below the detection limit or at 1 μL kg^–1 h^–1 until mid-June, and there were no differences among cultivars. In collected fruits, an increase in ethylene production or the response to propylene (analog of ethylene) was observed between May 14 and 29, suggesting a shift to system-2 ethylene synthesis at the same time between TCs and ‘Nanko’. The h* value, which decreases with fruit yellowing, showed a similar change in on-tree ‘Ellching’ and ‘Nanko’, but remained high in ‘ST’ and ‘Taiwan’ until the end of June or early July. Fruit firmness showed similar changes in TCs and ‘Nanko’ for both on-tree and collected fruits. The color chart index for the stone surface, seed germination rate and normal seedling rate did not differ significantly from year to year, and the seed maturity date was not significantly different between TCs and ‘Nanko’. The date when the color chart index went over 3 (except for ‘ST’), that when the seed germination rate exceeded 80%, and that of an ethylene production increase in collected fruits were the same for all cultivars. These results suggest that seed maturation and transition to system-2 occurs at the same time in TCs and ‘Nanko’, but that there are differences in the speed of fruit maturation after that time, which may be the cause of the different fruit maturity date of these cultivars.

Crossbreeding of tetraploid grapes including ‘Pione’ and ‘Aurora Black’ using primary flowers is inefficient due to the poor fruit set, low seed germination rate, and short period for effective pollination. In this study, we investigated the usefulness of lateral flower clusters (secondary flowers arising from lateral shoots) compared with primary flower clusters. In spur-pruned cultivation, the flowering season of lateral flower clusters lasts for approximately one month after the full bloom of primary flower clusters. The number of seeds per lateral flower cluster obtained by natural crossing increased, and the germination rate was higher than that of primary flower clusters on moderately growing shoots. Furthermore, when compared with primary flower clusters on weakly growing shoots, the number of seeds per lateral flower cluster and the germination rate were either comparable or superior, depending on the node position. In addition, we compared the pollen germination rate between the primary and lateral flower clusters. As a result, pollen from primary flower clusters stored in a refrigerator after collection showed higher germination rates than that from lateral flower clusters. When the lateral flower clusters of ‘Pione’ and ‘Aurora Black’ were used for crossbreeding, the number of full seeds per fruit cluster and seed germination rate were higher compared with those from weak primary shoots. These results indicate that lateral flower clusters are valuable for crossbreeding of tetraploid grapes.

The SSR marker G2SSR1566, which is closely linked to the PavCNR12 gene that controls fruit weight and cell number in sweet cherry (Franceschi et al., 2013), was used to determine SSR genotypes in 149 sweet cherry (Prunus avium L.) cultivars and lines. As a result, previously unreported SSR genotypes were identified, and the PavCNR12 genotypes could not be determined in some cultivars and lines. Consequently, primers were designed to detect SNPs specific to PavCNR12-1, 2, and 3 alleles, as reported by Franceschi et al. (2013). Subsequently, PavCNR12 genotypes were determined in 149 cultivars and lines. The results were consistent with G2SSR1566 alleles 228 and 232 being linked to PavCNR12-1, 262 and 264 to PavCNR12-2, and 234, 236, 238, 240, 248, 252, and 254 to PavCNR12-3. This facilitates low-cost detection of PavCNR12 allele-specific SNPs by agarose gel electrophoresis and efficient PavCNR12 genotyping by sequencing for G2SSR1566 genotype detection. Furthermore, the influence of the PavCNR12 genotype was examined in a population segregated by PavCNR12 genotypes. The test for the effect of the PavCNR12 genotype revealed that the fruit weight of genotypes 1/1, 1/2, and 1/3 was significantly greater than that of the genotype lacking PavCNR12-1, being consistent with the observations reported by Franceschi et al. (2013). This suggests that selecting individuals with PavCNR12-1, using either G2SSR1566 or SNP markers in this study, would be an effective approach for the efficient development of large-fruited sweet cherry varieties.

High temperatures during the ‘Kyoho’ grape ripening period result in poor coloring. In recent years, high temperatures associated with global warming and expansion of seedless cultivation areas highlight the urgent need to prioritize this issue. This study was aimed to determine an effective method of applying a novel S-ABA pesticide on ‘Kyoho’ grapes. The results showed that hand-spraying a 100-fold solution (S-ABA at 1000 ppm) on clusters at the onset of coloring improved color development, reduced sugar and acid contents, and increased the sugar-acid ratio. Similar color development was observed for dilution ratios of 100 (S-ABA at 1000 ppm) and 200 (S-ABA at 500 ppm), with treatment applied from berry softening to two weeks after the onset of coloring. Neither treatment caused practical issues. Furthermore, fruit surface staining caused by spraying S-ABA-containing liquid can be reduced using equipment with a small average particle size, such as a fine nozzle or compressor spray gun. However, to obtain a consistent color-improvement effect, measures to prevent uneven spraying, such as increasing the amount of liquid sprayed, are necessary.

We invented multiple rootstock seedlings by grafting multiple rootstocks onto a single scion. The possibility of increasing yield using multiple rootstock seedlings in the production of ‘Mizunasu’ eggplant, a specialty of Osaka Prefecture, was examined. Using seedlings with multiple ‘Daitaro’ rootstocks, seedlings grafted with two or three rootstocks were planted in 1/5000 a Wagner pots and experimentally cultivated in a single-layered vinyl greenhouse from autumn to winter, up to the fruit-bearing stage of the first flower. Results revealed that compared with conventionally grafted seedlings (one rootstock grafted to one scion), multiple rootstock seedlings showed an increase in the number of expanded leaves and maximum leaf area from early after planting, and the growth of both above-ground parts and roots was vigorous, resulting in earlier flowering dates after the second flower. The nitrogen and carbon contents of these plants were higher in the multiple rootstock than conventionally grafted seedlings, suggesting that nitrogen absorption and substance production were enhanced with the multiple rootstock. These results suggest that the use of multiple rootstock seedlings in institutional cultivation during the cold season may accelerate the growth of ‘Mizunasu’ eggplant and increase the initial yield compared with conventional grafted seedlings.

This study was aimed to investigate the growth characteristics of neutron-irradiated small-flowered chrysanthemums, including the types and frequencies of induced mutations, as well as survival rates after irradiation, in order to clarify the effectiveness of mutation breeding through neutron irradiation. The germination rates of axillary buds in three tested varieties after neutron irradiation revealed that the median lethal dose (LD₅₀) for germination rates was 11.10–16.65 Gy for ‘17c02’, and 5.55–11.10 Gy for both ‘18c22’ and ‘Hitachi Summer Light’. Additionally, weak individuals with significantly inhibited growth were observed after irradiation. For ‘17c02’ and ‘18c22’, all germinated individuals were weak at doses of 11.10 Gy or higher, while for ‘Hitachi Summer Light’, all germinated individuals were weak at doses of 16.65 Gy or above. The irradiated individuals exhibited different tendencies in the types of mutations depending on the tested varieties and strains. From the red-flowered ‘17c02’, a large number of color mutants (138 individuals) were generated. However, no color mutants were obtained from the white-flowered ‘18c22’. From the yellow-flowered ‘Hitachi Summer Light’, seven individuals with lighter-colored flowers were obtained, indicating a broader spectrum of flower color mutations in red varieties. Additionally, from ‘Hitachi Summer Light,’ unique leaf and plant form mutants were obtained, such as those with white-colored lateral buds and individuals with variegated leaves. These mutations were characteristic and not observed in the other two varieties. As for flower shape mutations, malformed and miniaturized flowers were observed in all three tested varieties, suggesting minimal differences among them. Moreover, even under low-dose conditions, where the germination rate of axillary buds after irradiation was high at over 92%, the mutation rate remained high at 5.0–16.0%. This suggests that compared with low LET mutagens such as gamma rays, neutron irradiation can effectively produce useful mutants with less radiation damage.

‘Koiminori’ is a new June-bearing strawberry (Fragaria × ananassa Duch.) cultivar that originated from a cross between 03042-08 and ‘Kumaken-i-548’ in 2008. This cultivar exhibits upright and vigorous growth. Although the first flowering date is the same as that of ‘Sachinoka’, the harvest date is earlier owing to the fewer days required for fruit maturation under forcing cultivation. The morphology of the inflorescence is closely related to the uniformity of the fruit size in strawberries. The inflorescence shape of ‘Koiminori’ is intermediate between the distal-branching and basal-branched types, and the fruits are large and uniform. The short cone-shaped fruit has orange-red skin and white flesh, and Brix and acidity are similar to those of ‘Sagahonoka’. Fruit firmness is greater than that in ‘Sagahonoka’, and it can be adapted to mechanical operations using an automatic fruit-sorting and packaging robot. ‘Koiminori’ is a high-yielding cultivar, and requires less labor per area and yield, making labor-saving cultivation possible. The compatibility of the high-yield and labor-saving characteristics derived from the intermediate type of inflorescence shape is novel in strawberries for forcing cultivation. Plant vigor, axillary bud vigor, early flowering, and characteristics of faster fruit maturation may have contributed to this compatibility.