Yong-Bum Kwack

Influence of cold stress on contents of soluble sugars, vitamin C and free amino acids including gamma-aminobutyric acid (GABA) in spinach (Spinacia oleracea).

The contents of soluble sugars (sucrose, fructose, glucose, maltose and raffinose), vitamin C and free amino acids (34 compounds, essential and non-essential) were quantified in open-field and greenhouse-grown spinaches in response to cold stress using liquid chromatography. In general, greenhouse cultivation produced nutritionally high value spinach in a shorter growing period, where the soluble sugars, vitamin C and total amino acids concentrations, including essential were in larger amounts compared to those grown in open-field scenarios. Further, low temperature exposure of spinach during a shorter growth period resulted in the production of spinach with high sucrose, ascorbate, proline, gamma-aminobutyric acid, valine and leucine content, and these constitute the most important energy/nutrient sources. In conclusion, cultivation of spinach in greenhouse at a low temperature (4-7°C) and exposure for a shorter period (7-21days) before harvest is recommended. This strategy will produce a high quality product that people can eat.

Carbohydrate reserves of non-fruiting young kiwifruit vines as affected by early artificial defoliation

Accumulated nutrient reserves provide an important energy source for deciduous fruit trees in their initial growth and development the following spring. This study investigated the effect of mid-season defoliation on the growth and accumulation of carbohydrate reserves of kiwifruit vines in Korea. The ‘Goldrush’ (Actinidia chinensis) vine was used for this experiment, following de-blossoming in spring. The vines were artificially defoliated to varying degrees at 1 month intervals from Jul. 15 to Oct. 14. The degree of defoliation was 0 (control), 25, 50, 75, and 100%. From Jul. 15 to Sep. 15, the dry weight of kiwifruit vines with 50% or more defoliation was reduced as compared to the control. In particular, 75 and 100% defoliation on Aug. 16 resulted in decrease of 79.2 and 83.1 g from the control vines (145.6 g), respectively. Defoliation on Aug. 16 decreased both the aboveground and underground dry weight of the vines. Most carbohydrate reserve of the young vines (which did not have fruit) accumulated in the roots. Defoliation on Aug. 16 and Sep. 15 reduced the accumulation of carbohydrate reserves, which was correlated with a decline in vine dry weight. For vines with 75% or more defoliation on Aug. 16 and Sep. 15, about less than half amount of starch accumulated in the roots as compared to the control (4.3 g per vine). In contrast, the accumulation of soluble sugars was not significantly influenced by defoliation, except for vines with 75% or more defoliation on Aug. 16. In conclusion, 75% or more defoliation on Aug. 16 and Sep. 15 has a negative impact on the growth and carbohydrate reserve of a new cultivar, ‘Goldrush’.

KiwiPME1 encoding pectin methylesterase is specifically expressed in the pollen of a dioecious plant species, kiwifruit (Actinidia chinensis)

Pectin methylesterases (PMEs) mediate demethylesterification of pectic polysaccharides such as homogalacturonan, a major component of the primary plant cell wall, in the apoplasm. The PMEs are implicated in a number of developmental processes, including pollen development and pollen tube growth, through the fine tuning of the methylesterification status of pectin. In this study, we isolated a full-length cDNA (KiwiPME1) encoding PME from kiwifruit and characterized its molecular features. Analyses of the primary protein structure and gene structure revealed that KiwiPME1 encodes a pre-pro-PME protein that is predicted to localize to the outside of the cell and belongs to group 2 (formerly type 1). The KiwiPME1 expression was highly detected in pollen grains of kiwifruit but not in vegetative tissues investigated. Expression pattern analysis of KiwiPME1 among different floral tissues of male and female plants revealed that KiwiPME1 was expressed specifically in the stamens of flower buds in male and female plants, whereas its expression was detected only in the stamens of male plants when the flowers opened. Expression analysis of KiwiPME1 promoter fused to the GUS reporter gene in Arabidopsis displayed a very similar pattern to that in kiwifruit. Our study suggests that the cell wall-localized KiwiPME1 is likely implicated in the pollen development and pollen tube growth of a dioecious species kiwifruit.

Effect of Different Soil Water Potentials on Growth Properties of Northern-Highbush Blueberry

The soil moisture has an important effect on growth and development of highbush blueberry (HB), mainly because the root system, devoid of root hairs, is superficial. Moreover, the texture and organic matter content of Korean soil is different from the main producing counties, such as USA and Canada. To facilitate the growth and development of HB and long-term maintenance of productivity, the research related to soil moisture condition in Korea should be the priority. This study was performed to investigate the growth properties of the HB in various soil moisture conditions in order to determine the irrigation trigger point and optimum soil water potential. The texture of soil used in this experiment was loam. For the experiments, the soil was mixed with peatmoss at a rates 30% (v/v). Irrigation was scheduled at -3, -4, -5, -8, -15 and -22 kPa soil water potential then investigated leaf macronutrient, bush growth, and fruit properties. The leaf K content of HB showed the same trend in the soil water potential, but Leaf P and Mg content was highest in -5 and -22 kPa, respectively. The productivity and growth amount of HB showed the peak at the range of -4~-8 kPa as normal distribution pattern, and greatly decreased at above -15 kPa. Total dry weight and Cane diameter were highest at -4 kPa, plant width, fruit weight and yield were highest at -5 kPa, and plant height, cane number and shoot tension were highest at -8 kPa. Soluble solids content showed same trend in the soil water potential, but titratable acidity, anthocyanins and total polyphenols were not significantly different. Therefore, the optimal soil water potential for the development and a maximum production of HB were a range of -4~-8 kPa, and the recommended ideal irrigation trigger point was within -15 kPa.

‘Redvita’: A Yellow-fleshed Kiwifruit with Red ColorAround the Core

Namhae Branch, National Institute of Horticultural and Herbal Science, Rural Development Administration, Namhae 55365, Korea Protected Horticulture Research Institute, National Institute of Horticultural and Herbal Science, Rural Development Administration, Haman 52054, Korea Apple Research Institute, National Institute of Horticultural and Herbal Science, Rural Development Administration, Gunwi 39000, Korea Department of Vegetable, National Institute of Horticultural and Herbal Science, Rural Development Administration, Wanju 55365, Korea

Effect of Nitrogen Fertigation on The Growth and Nutrition Uptake of ‘Brightwell’ Rabbiteye Blueberry

블루베리의 주요 품종군은 북부형(Vaccinium corymbosum L.), 남부형(Vaccinium corymbosum hybrid)하이부쉬 블루베리와 래빗아이 블루베리(Vaccinium ashei Reade)로 나뉜다. 이들 품종군은 공통 적으로 배수성이 좋은 산성토양과 뿌리털이 없는 천근성 뿌리구조로, 보비력과 양분이용이 매우 취약한 환경을 가지고 있다. 따라서 본 연구는 시비효율성 증대를 위하여 래빗아이 블루베리의 생육특성에 미 치는 관비효과를 구명하고자 수행하였다. 시험장소는 경남 남해에 소재한 국립원예특작 과학원 남해출 장소 시설포장에서, 2013년 4년생 ‘Brightwell’(V.ashei Reade)레빗아이 블루베리 품종을 완숙유기물(피 트모스) 30%(v/v)혼합된 토양에 재식하여 수행하였다. 시비는 오레곤 주립대학에서 제공하는 표준시비 량 14g plant -1 의 관행시비와 4수준의 관비를 처리하여 양분흡수량과 수체생육 그리고 과실특성을 조사 하였다. 시비방법에 따른 수체생육과 과실생산량은 관비시비가 효과적이었으며, 관비수준별 시비효과는 표준시비량의 50%처리가 가장 효과적이었다. 처리별 엽중 질소함량은 표준시비량의 50% 관비처리가 14.4g kg -1 으로 가장 높았으나, 200% 관비구는 11.5 g kg -1 으로 가장 낮았다. 처리별 엽중 인산함량은 유의차가 나타나지 않았으나, 칼리와 칼슘 그리고 마그네슘함량은 표준시비량의 50%관비처리에서 가장 높았으며, 시비량의 증가는 엽중 무기성분 함량을 낮추는 경향을 나타냈다. 처리별 수관면적은 관행시 비가 4.86 m 3 으로 가장 낮은 수준을 보였으며, 50% 관비처리가 9.61 m 3 로 가장 높았다. 이와같이 50% 관비처리의 높은 시비효과는 각각 3,650 g plant과 12,849 g plant을 나타낸 건물중과 과실생산량에서 도 유사한 경향이었다. 한편 시비방법과 관비수준에 따른 과실의 안토시아닌과 당 그리고 산함량 등 과 실품질은 일정한 경향을 나타내지 않았다.

The Effect of Soil Texture on Fruits and Growth Properties in Rabbiteye Blueberries

This study was conducted to compare the plant growth and fruit quality of blueberries grown in different soil textures of Korea, in order to utilize the results for stable production and soil improvement. Rabbiteye blueberry cultivars ‘Tifblue’ and ‘Baldwin’ were planted and grown for three years from 2013 in wagner pot(1 2000 a -1 ) in a greenhouse of Namhae Sub-station, Institute of Horticultural and Herbal Science. The plants were grown in four soil textures, sand, sandy loam, loam and silt loam, and nutrient uptake and growth characteristics of plants were investigated. Leaf nitrogen and phosphorus contents of two cultivars grown in different soil textures ranged between 8.6 to 10.5 g kg -1 , which was lower than appropriate level for rabbiteye blueberry. However, the contents of potassium, calcium and magnesium in leaves were appropriate levels as 2.29~3.62 g kg -1 , 4.46~5.46 g kg -1 and 1.45~2.12 g kg -1 , respectively. Nitrogen and phosphate contents in leaves were higher in the two cultivars grown in silt loam soil. There was no significant difference in plant volume and root dry weight among four soil textures in two cultivars. However, dry weight of leaves and branches were highest in loam soil. Fruit production was highest in loam and silt loam soil in two cultivars, showing negative correlation with the amount of sand in soil. However, sugar and acidity showed no correlation with sand content in soil. These results show the limit to the blueberry growth in soil that has no nutrient holding capacity; however, most of Korean soils that have good nutrient holding capacity can produce competitive fruits if the drainage is improved.

Optimum Double-Row Spacing in the Autumn Cultivation of Radish (Raphanus sativus L.)

Optimum Double-Row Spacing in the Autumn Cultivation of Radish (Raphanus sativus L.) Eun Seon Kang, Sun Mi Ha, Seoung Ryong Cheong, Myeong Whoon Seo, Su hyoung Park, Yong-Bum Kwack, Keun Jin Choi and Won Byoung Chae (Department of Vegetable, National Institute of Horticultural & Herbal Science, Rural Development Administration, Wanju 55365, Korea, Namhae Sub-Station, National Institute of Horticultural & Herbal Science, Rural Development Administration, Namhae 52430, Korea)

Floral Bud Cold Hardiness and Cultural Safety Zone in Rabbiteye Blueberry Cultivars

Floral Bud Cold Hardiness and Cultural Safety Zone in Rabbiteye Blueberry Cultivars Hong-Lim Kim, Yong-Bum Kwack, Jeom-Hwa Han, Pill-Kyung Oh, Won-Byoung Chae, Seong-Cheol Kim, Mok-Jong Kim and Jin-Gook Kim, (Namhae Sub‐Station, NIHHS, RDA, Namhae 668‐812, Korea, Fruit Research Division, NIHHS, RDA, Suwon 440-706, Korea, Vegetable Research Division, NIHHS, RDA, Suwon 440‐706, Korea, Department of Horticulture, Gyeongsang National University, Jinju 660‐701, Korea)