Prune trees (Prunus domestica L.) are optimally suited to dry climates, and a major production area for prune trees is California, which has little rainfall. The East Asian temperate monsoon zone, where summer is hot and rainfall is relatively abundant, is not well suited for cultivating prune trees. The purpose of this study was to investigate prune cultivars that are ideal for this temperate monsoon zone to expand the possibility of production. We evaluated the performance of 8 prune cultivars, 'Puchull', 'Purple Ais', 'Blue Tan', 'Edwards', 'Stanley', 'Valor', 'President', and 'Marjorie's Seedling', by harvesting fruits from August to October to identify optimal cultivars in Izumo, western Japan, as a model area in the temperate climate monsoon zone. Results showed that the flowering period of prune trees was from late March to mid-April, and average temperature in March influenced whether flowering time would occur early or late. The flowering period varied by year. Therefore, companion planting with other cultivars that have overlapping flowering periods is necessary for self-incompatible cultivars. To avoid spring frost damage during the flowering period, protection from frost was necessary. Additionally, to avoid fruit cracking, cultivating prune trees under rain shelter conditions was also necessary. With these management approaches, two mid-ripening types, 'Stanley' and 'Valor', and two late-ripening types, 'President' and 'Marjorie's Seedling', yielded over 1000 kg/10 a/ canopy area and produced high-quality fruit with over 20 soluble solids content (SSC)/titratable acid (TA). However, three early-ripening types, 'Puchull', 'Purple Ais', and 'Blue Tan', and the mid-ripening 'Edwards', showed relatively low yields and produced fruit with low SSC/TA. Moreover, flesh darkening before harvest was observed as a result of high-temperature injury in these cultivars, and skin color and fruit taste were not good enough before flesh darkening; thus, these four cultivars were not suitable for table use. In summary, we consider mid-to late-ripening cultivars suitable for table use in Izumo. Our findings also indicate the possibility that these prune fruit cultivation methods could be used in other parts of the East Asian temperate monsoon and humid temperate climate zone.

The effects of high-temperature treatment for enhancing budbreak in 'Delaware' grapes grown under forced conditions in Shimane Prefecture were investigated. Cuttings (10 cm) with one bud each were treated with high temperature at 35°C and 40°C in November, December, and January. Treatments for 48 h at 35°C and 24-48 h at 40°C led to a significantly higher budbreak rate than in controls (23°C 12 h-L/18°C 12 hD). Additionally, the number of days required for budbreak (NDRB) increased when treated at 25°C in November and December compared to treatments at 30°C in November and 35°C in December. On the other hand, NDRB for 24 and 48-h treatments in December and January were lower than for 8-h treatments. Treatment at 40°C also resulted in a lower NDRB than that at 35°C, where the NDRB with intermittent treatment (heating for 4 h/d) was higher than that with continuous treatment. The NDRB on treatment at 25°C in November and December was higher than on treatment at 30°C in November or 35°C in December. NDRB with 24-h treatment was also higher than that with 48 and 64-h treatments in November. Lastly, the NDRB was lower if the high-temperature treatment was performed for longer. These results suggest that high-temperature treatments may promote budbreak and may also be dependent on the exposure period and temperature.

The large berry mutant (LBM) of the 'Delaware' (V. vinifera × (V. labrusca × V. aestivalis)) is known to produce larger berries than 'Delaware' when subjected to traditional double gibberellic acid-3 (GA 3 ) treatment. In this study, we first compared 'Delaware' and the LBM in terms of their berry and cluster quality to reevaluate previous findings on LBM. Next, we compared berry size without GA 3 , histological characteristics of the early developmental berry, and then GA-related gene expression to reveal the characteristics of the LBM. The previous finding that LBM yielded larger berry sizes than 'Delaware' with double GA 3 treatment was verified, but without GA 3 treatment, LBM did not produce larger berries than 'Delaware'. This highlights the prerequisite of exogenous GA for larger berry size in LBM. Histological analysis revealed an increase in cell numbers of the inner and outer mesocarp walls in the early developmental stage of LBM berries. Gene expression analysis of the flower buds and berries indicated an increased expression of VvGID1A, encoding the GA receptor, in LBM than in 'Delaware' 3 h after the first GA 3 treatment. Additionally, the expression of VvGID1A and VvGID1B was higher in LBM than that in 'Delaware' before and after the second GA 3 treatment. The expression of VvGID2A, which interacts with the GA receptor and promotes GA signaling, was also higher in LBM than in 'Delaware' before the first GA 3 treatment. However, the expression of VvSLR1, VvGAI1, and VvGAI2 that encode DELLA proteins, essential negative regulators for GA reactions, mostly showed no significant changes. These results suggest that LBM berries had higher GA sensitivity than the 'Delaware'. Based on these results, we believe that the larger berry size in LBM may be due to increased cell numbers resulting from high GA sensitivity.

The annual fluctuation and difference among fields or among trees during on-tree fruit softening (OTFS) of the Japanese persimmon 'Saijo' were investigated. The mineral concentrations, especially the Mn concentration, were compared between OTFS trees and healthy trees in order to obtain basic information about OTFS. The annual fluctuation and difference among fields of OTFS were found over a four-year period (1995 to 1998). Comparing the concentrations of the main minerals in the flesh, the Mn concentration in fruit from the OTFS tree was about 1/3 of that from healthy trees, except in 1998 when the OTFS rate was markedly higher and there were significant differences at a 5% level in 1996 and 1997 as well. Negative correlation between Mn concentration in each organ; fruit, calyx and leaf, of tree and the OTFS rate was found at a 1% significance level. There was a tendency for the OTFS rate to increase as the Mn concentration in each organ decreased. The Mn concentrations in the flesh, calyx and leaf of trees with a high OTFS rate were less than 20, 180 and 300 ppm, respectively.