Jong-Chul Nam

Transcript profiling of native Korean grapevine species Vitis flexuosa exposed to dehydration and rehydration treatment

Vitis flexuosa, a native Korean wild grapevine species, is more tolerant to abiotic stress than cultivated grapevines, but little is known about the mechanism underlying this tolerance. To better characterize the responses of V. flexuosa to drought stress and subsequent rehydration, we treated V. flexuosathe plants with four stress conditions: short- and long-term dehydration, rehydration immediately after long-term drought, and long-term rehydration after long-term drought. We examined gene expression profiles in response to these treatments using whole-genome microarray analysis at 12X coverage (using the NimbleGen protocol). We identified a 5,964 genes that were differentially expressed between the stress treatments and the well-watered control. Gene ontology analysis showed that most of the differentially expressed genes (DEGs), regardless of treatment, participate in the metabolism of proteins or phosphatecontaining compounds and function in the binding of metal ions, as kinases, or as phosphotransferases. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that genes involved in secondary metabolite biosynthesis were downregulated during dehydration but upregulated during rehydration. Among the DEGs encoding transcription factors, genes in the MYB family were the most common differentially genes in all treatment groups. The NAC family was the second most common group during dehydration, while the AP2/ERF family was the second most common during rehydration. These results will help elucidate the mechanisms underlying the response of V. flexuosa to drought stress and will be valuable for breeding drought-tolerant grapevines.

Influence of Elevated CO 2 and Air Temperature on Photosynthesis, Shoot Growth, and Fruit Quality of `Fuji`/M.9 Apple Tree

This study was conducted to find out the influence of elevated atmospheric CO2 concentrations and air temperature on photosynthesis and fruit quality of ‘Fuji’/M.9 apple trees and to investigate these to the effects of climate change during the last four years (2009-2012). The treatments employed were: ‘Ambient’ (ambient temperature + ambient CO2 concentration); ‘High CO2’ (ambient temperature + elevated CO2 concentration); ‘High Temp.’ (elevated temperature + ambient CO2 concentration); and ‘High CO2 + High Temp.’ (elevated temperature + elevated CO2 concentration). The elevated temperature plots were maintained at 4 o C higher than ambient air temperature, while the elevated CO2 plots were maintained at 700 µmol·mol �1 . Annual treatment period was applied from end of April to beginning of November for four years. Results showed that elevated CO2 decreased stomatal conductance and leaf SPAD value, but increased photosynthetic rate, intercellular CO2 concentration (Ci), and starch content of mesophyll tissue. In the vegetative growth, elevated temperature increased total number of shoot and total shoot growth per tree, but elevated CO2 decreased average shoot length. In the fruit quality, elevated CO2 increased soluble solid content, fruit red color, and ethylene production. In conclusion, elevated CO2 increased photosynthetic rate of apples during the early growth, but effect of increased photosynthetic rate due to elevated CO2 was decreased during latter growth stage. Elevated temperature, on the other hand, tended to decrease photosynthetic rate of apples during the early growth, but that tended to increase during latter growth stage. Both elevated CO2 and temperature tended to decrease the degree of decreased photosynthetic rate due to each factor.

Application of Color Index for Red Grapes (CIRG) for Assessment of Grape Quality

Hunter value (L*, a*, b*) is a rapid and convenience method for compare with different skin color, but not suitable to compare quality with various grape cultivars. Color Index for Red Grapes (CIRG) is one of a simply convert method for grape skin color as numeric data, and many previously result showed that high correlation between CIRG index and various quality factors of grape. In this experiment, we measured CIRG index, total soluble solids (TSS), titratable acidity (TA), and total anthocyanin content on the grapes (Campbell Early, Heukbosuk, Kyoho) from the varaison to harvest. As a result, CIRG index and anthocyanin contents have an exponential correlation; r-square is each 0.8595 in the ‘Campbell Early’ and 0.8500 in ‘Heukbosuk’. And TSS and CIRG index have a positive r-square, at the Campbell Early is 0.7758 and Heukbosuk is 0.7253. Also TA and CIRG index have a positive r-square, at the Campbell Early is 0.7279 and Heukbosuk is 0.6630. These results were shown that CIRG index is a reliable indicator for a none-destructive evaluation of the grape quality. Additional key words : color space, colorimeter, regression analysis

Effects of Microspraying of Water and Coating by White Materials on Fruit Sunburn Occurrence for `Fuji`/M.9 Apple Tree

This study was carried out to compare and analyze control methods of the sunburn occurrence that affected `Fuji`/M.9 planting systems in Korea from 2001 to 2003. It is very important to control temperature of the surface of fruits, because sunburn may occur when the temperature of fruit surfaces reaches due to high air temperature and sunlight during growing periods. As control methods of the sunburn occurrence, white coating materials such as or kaolin were applied four times at two-week intervals from late June, and microspraying of water was conducted when air temperature was over from late July to mid-August. Both methods were effective for preventing the sunburn occurrence and improving fruit quality by decreasing peel`s temperature of fruits and increasing photosynthesis.

Factors Involved in Rooting Response of M.9 (Malus domestica Borkh.) Dwarf Apple Rootstock to Stem Etiolation.

The main objective of this research was to improve rooting of M.9 apple rootstock through layering time, shading, layering material and water content of the layering part. Among the treatments, rooting was improved by mother plant shading or an earlier covering (layering in shoot length 2 cm) of shoots. Rooting and root growth of sawdust, chaff or vermiculite treatments were significantly higher than those of the control (soil). In the study of layering material water content, -40 kPa treatment increased rooting ratio, number of roots and root growth compared to -60 kPa treatment and control. These results suggest that early-covering, layering with sawdust, chaff, or vermiculite, and keeping the water content in the layering part at -40 kPa could improve rooting and root growth in M.9 rootstock propagation.