No abstract

A winter-season warming trend has been observed in eastern Asian countries during the last century. Significant effects on dormancy and the subsequent bud-burst of deciduous fruit trees are expected. However, phenological observations are scant in comparison with long-time climate records in the region. Chill-day accumulation, estimated from daily maximum and minimum temperature, is a reasonable proxy for dormancy depth of temperate-zone fruit trees. A selected chill-day model was parameterized for the Campbell Early grapevine, which is the major cultivar (grown virtually everywhere) in South Korea. To derive model parameters (threshold temperature for chilling and the chilling requirement for breaking dormancy), a controlled-environment experiment using field-sampled twigs of Campbell Early was conducted. The chill-day model to estimate bud-burst dates was adjusted by derived parameters and was applied using 1994-2004 daily temperature data obtained from the automated weather station in the vineyard at the National Horticultural Research Institute. The model gave consistently good performance in predicting bud-burst of Campbell Early (RMSE of 2.5 days). To simulate dormancy depth of Campbell Early at eight locations in South Korea for the last century, the model was applied using data obtained for each location from 1921 to 2004. Calculations showed that the chilling requirement for breaking endodormancy of Campbell Early can be satisfied by mid-January to late February in South Korea, and the date was delayed going either northward or southward from the Daegu-Jeonju line that crosses the middle of South Korea in the east-west direction. Maximum length of the cold tolerant period (the number of days between endodormancy release and the forced dormancy release) showed the same spatial pattern. Dormancy release for 1981-2004 advanced by as much as 15 days relative to that for 1921-50 at all locations except Jeju (located in the southernmost island with a subtropical climate), where an average 15-day delay was predicted. The cold-tolerant period diminished somewhat at six out of eight locations. As a result, bud-burst of Campbell Early in spring was advanced by 6-10 days at most locations, and interannual variation in bud-burst dates increased at all locations. The earlier bud-burst after the 1970s was due to 1) warming in winter that results in earlier dormancy release (Incheon, Mokpo, Gangneung, and Jeonju), 2) warming in early spring that enhances regrowth after breaking dormancy (Busan and Jeju), and 3) a combination of both (Seoul and Daegu).

This study was carried out to improve the fruit color through ABA treatment and to determine the optimum harvest time for producing high quality fruits in 'Hongisul' grapes. Spraying of 1000 mg･L -1 exogenous ABA at early verasion (70 days after full bloom, DAFB) brought increase of endogenous ABA and soluble solid contents and enhanced fruit coloration. So, it was possible to harvest ABA treated fruits from 85 days after full bloom (15 days after treatment) by accelerated anthocyanin content which increased continuously until 110 DAFB. An increase of soluble solid and decrease of total acidity appeared steadily with the onset of berry ripening. After 100 DAFB, soluble solid content and total acidity did not change significantly, but the berry firmness was suddenly decreased. Consequently, it was suggested that ABA treated fruits need to be harvested at about 100 DAFB because of their short period of marketing by over ripening. On the contrary, harvesting of untreated fruit was totally impossible at 85 DAFB because of their poor berry coloration. But it was possible to harvest them at 100 DAFB based on the soluble solid/acidity ratio, whereas the berry coloration was progressed poorly. On the other hand, the fruits harvested at 110 DAFB showed acceptable berry coloration but their berry firmness was dropped significantly coincide with overripening. Therefore, it was needed to develop an altered production system for improving coloration at around 100 DAFB in 'Hongisul' grapes.

`Yumyeong' is one of the most popular peach varieties in Korea. This study was conducted to monitor the developments of cells and tissues, and the changes in sugar contents during the whole fruit growth stages. At bloom, there were two rows of vascular tissues, and the number and the position of internal vascular bundles were consistent during the fruit growth; however, the number of vascular tissues increased and the distribution was irregular in the flesh tissues. The tissues between the inner integument and the internal vascular bundles showed different development characteristics from other parenchyma cells, which consisted of small and dense cells containing tannins. Therefore, it was found that the nucleus of peach consisted of inner epidermis and cells in the internal vascular tissues. The outer epidermis consisted of single layer cells at bloom and was changed into one to two layers by horizontal cell division 14 days after full bloom. At 30 days after full bloom, the epidermis consisted of five to six layers by vertical cell division. The cell layers of the outer epidermis gradually decreased to one to two layers at maturity. The observations on the changes in the epidermis confirmed that some of the cells of the hypodermis of peach fruit originated from the cells of outer epidermis. Tylosis was observed from 35 days after full bloom, and the size and number of tylosis increased until full fruit maturity. The sucrose content sharply increased from 50 days to 120 days after full bloom, then decreased slightly. After stone hardening ended, other solids showed a gradual decrease from 80 days after full bloom.

Abstract. This experiment was conducted to find the effects of a GA 3 and thidiazuron (TDZ) on seedless rate, harvest time, fruit cracking and fruit quality in 'Kyoho' grapes over two years from 2008 to 2009. In 2008, fruit clusters were dip treated with GA 3 25.0 mg·L -1 twice at full bloom (FB) and 14 days after full bloom (DAFB) in a combination with TDZ 0 or 2.5 mg·L -1. Berry seedless rate and berry enlargement were slightly improved only when TDZ was added to the second GA 3 treatment at 14 DAFB, compared to GA 3 + TDZ treatments at both FB and 14 DAFB. However, berry cracking rate was significantly increased by any plant growth regulator (PGR) treatments compared to non treatment. In 2009, GA 3 at 12.5 mg·L -1 and 25.0 mg·L -1 was dip treated twice at FB and 14 DAFB while TDZ 2.5 mg·L -1 was treated only at 14 DAFB. Berry cracking rate was depended on the concentration of GA 3 applied. The higher concentration at 25.0 mg·L -1 significantly increased berry cracking rate while the lower concentration at 12.5 mg·L -1 had no effect. Also, the addition of TDZ to GA 3 25.0 mg·L -1 at 14 DAFB, substantially decreased the cracking rate to the level of untreated control. Although all PGR treatments advanced fruit maturity, the most significant advance occurred when TDZ was added to GA 3 12.5 mg·L -1 only at the second dip. Considering the overall aspects related to fruit maturity and quality, we concluded that the double applications of 12.5 mg·L -1 GA 3 at FB and 14 DAFB with addition of 2.5 mg·L -1 TDZ only at 14 DAFB was appropriate to produce about 400-500 g size of seedless 'Kyoho' grape cluster having 35-40 berries.