• Horticultural Science & Technology
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• v.33 no.2
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• pp.202-209
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• 2015

In this study, we investigated the cumulative effect of low temperature on bud dormancy release and bud break characteristics in 'Campbell Early' grapevine (Vitis labruscana B.) cuttings grown in water culture. Additionally, we observed the development of buds while exposed to low temperatures in an attempt to improve our understanding of dormancy and bud break. The shoots were collected 120 days after full bloom (DAFB; leaf abscission period), and the accumulated chill unit (CU) value was calculated by reducing the temperature to $7.2^{\circ}C$ at 125 DAFB. The rate of bud break was 100% in shoots collected at 150 DAFB, The period until the first bud break was two times longer than in the shoots collected 165 DAFB, and bud break speed was significantly reduced. These results indicate that buds are released from endodormancy after 165 DAFB, because at this point the bud break was complete (bud break rate 100%) and it occurred in a very short time period. During this period, when the low-temperature accumulated value was 321h and 442CU according to the CH and Utah models, respectively. Furthermore, the survival rate of main buds decreased rapidly after 165 DAFB, and survival rate of accessory buds was maintained at more than 90% without seasonal differences. The rate of flower bud formation of main buds was much higher than in accessory buds (1:0.23) before the release from endodormancy at 150 DAFB. The final ratio of accessory buds to main buds was high, 1:1.54, at 255 DAFB. Correlation analysis of each investigated factor revealed that bud survival rate and bud formation rate were related only for the main buds, and there was a close relationship between the survival rate of main bud and time. In addition, the survival rate of main buds was positively correlated to the rate of flower bud formation.

• Horticultural Science & Technology
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• v.31 no.2
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• pp.135-140
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• 2013

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 $GA_3$ $25.0mg{\cdot}L^{-1}$ twice at full bloom (FB) and 14 days after full bloom (DAFB) in a combination with TDZ 0 or $2.5mg{\cdot}L^{-1}$. 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 $12.5mg{\cdot}L^{-1}$ and $25.0mg{\cdot}L^{-1}$ was dip treated twice at FB and 14 DAFB while TDZ $2.5mg{\cdot}L^{-1}$ was treated only at 14 DAFB. Berry cracking rate was depended on the concentration of $GA_3$ applied. The higher concentration at $25.0mg{\cdot}L^{-1}$ significantly increased berry cracking rate while the lower concentration at $12.5mg{\cdot}L^{-1}$ had no effect. Also, the addition of TDZ to $GA_3$ $25.0mg{\cdot}L^{-1}$ 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 $GA_3$ $12.5mg{\cdot}L^{-1}$ only at the second dip. Considering the overall aspects related to fruit maturity and quality, we concluded that the double applications of $12.5mg{\cdot}L^{-1}$ $GA_3$ at FB and 14 DAFB with addition of $2.5mg{\cdot}L^{-1}$ TDZ only at 14 DAFB was appropriate to produce about 400-500 g size of seedless 'Kyoho' grape cluster having 35-40 berries.

• Horticultural Science & Technology
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• v.35 no.2
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• pp.170-177
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• 2017

This study was conducted to estimate the light pollution damage caused by night-break lighting in 'Kyoho' grapes. Night irradiation was performed every night for four hours (10 p.m. to 2 a.m.) from the full bloom to the harvest stage using red, blue, and white lamps as artificial light. Fruit yield, soluble solid content, anthocyanin content, and chlorophyll a content were affected by night irradiation. The soluble solid content of the control was $17.5^{\circ}Brix$, approximately $1^{\circ}Brix$ higher than the red ($16.4^{\circ}Brix$), blue ($16.2^{\circ}Brix$), and white light treated grapes ($16.3^{\circ}Brix$). The anthocyanin content of the skin was also higher in the control at $4.08{\mu}g{\cdot}cm^{-2}$ compared to the red ($3.14{\mu}g{\cdot}cm^{-2}$), blue ($2.47{\mu}g{\cdot}cm^{-2}$), and white ($2.82{\mu}g{\cdot}cm^{-2}$) light treated samples. On the other hand, the chlorophyll a content of the control was the lowest at $0.268{\mu}g{\cdot}cm^{-2}$ as compared with the red ($0.339{\mu}g{\cdot}cm^{-2}$), blue ($0.345{\mu}g{\cdot}cm^{-2}$), and white ($0.372{\mu}g{\cdot}cm^{-2}$) light treated samples. Considering that higher soluble solid contents, higher accumulation of anthocyanin, and lower chlorophyll a contents are factors involved in fruit maturation, night irradiation may delay fruit maturation and red light treatment may result in decreased yield. Our results confirmed that night-break lighting regardless of the wavelength provoked light pollution in 'Kyoho' grapes. Therefore, fruit maturation may be poor in the presence of artificial light, including streetlamps, in neighboring vineyards.