• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.252-269
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• 2017

This study was carried out to examine the base temperature to flowering and the average days to flowering by accumulated hours of low temperature ($5.0^{\circ}C$) or changing temperature after bud breaking. Over-all, the prediction of flowering time in the commercial apple cultivars ('Fuji' and 'Tsugaru') and apple cultivars ('Chukwang', 'Gamhong', 'Hongan', 'Honggeum', 'Hongro', 'Hongso', 'Hwahong', 'Summer dream', 'Sunhong') bred in Korea at the Gunwi region for 4 years (from 2009 to 2012) was investigated. Also, this study estimated the flowering time when the air temperature of Gunwi region rises at $5.0^{\circ}C$ was investigated using the same data. The range of accumulated hours of low temperature (chilling requirement) was from 0 hour to 1,671 hours, and the range of high temperature (heat requirements) to flowering after low temperature treatment was from $5.0^{\circ}C$ to $29.0^{\circ}C$. The treatments of changing temperature after bud breaking were classified as constant temperature treatment (control) and $5.0{\sim}10.0^{\circ}C$ elevation or descent treatments. The results show that the average days to flowering was longer with shorter accumulated hours of low temperature, and the average days from bud breaking to flowering of 0 hour treatment was longer about 2~4 weeks than that of 1,335~1,503 hours treatments. In comparing to apple cultivars, the all cultivars were not flowered under $10.0^{\circ}C$ after bud breaking, and the cultivars with low chilling requirements needed low heat requirements for flowering. The average days to flowering of treatments that the air temperature after bud breaking was controlled about $15.0^{\circ}C$ was shorter about 1~3 weeks than that of treatments was controlled about $10.0^{\circ}C$. In the treatment of changing temperature after bud breaking, the average days from bud breaking to flowering of temperature elevation treatment was shorter than that of constant temperature treatment. By use of these results, the base temperature to flowering of main apple cultivars in Korea was seemed to $10.0^{\circ}C$, and if the air temperature of Gunwi region rises about $5.0^{\circ}C$ than that of current, the flowering time was estimated to be delayed by 1 week.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.535-541
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• 2015

'Taichung No. 2' is a new Asian pear cultivar developed in Taiwan with low chilling requirement; however, is likely to develop internal browning disorder under low temperature storage conditions. We investigated the impact of storage time on flesh browning disorder in pears harvested from 22 orchards in 2010 and 2011, and analyzed the levels of nutrients in different fruit parts such as the peel, flesh, and core. Calcium and potassium contents were higher in the flesh and peel, respectively, of more severely browned fruits, whereas a lower magnesium content was recorded in the peel and core of these fruits. Nitrogen and potassium contents in the peel, and calcium content in the flesh were positively correlated with browning disorder severity. By contrast, the magnesium content in the core was negatively correlated with browning disorder severity. However, the nutrient contents in fruits varied between the two sampling years considered. Only the K/Mg ratio was an effective predictor of the browning disorder severity and showed a positive linear correlation in the two years. We recommend that the K/Mg ratio should be lower than 10 to avoid severe browning disorder in pears.

• Korean Journal of Agricultural and Forest Meteorology
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• v.10 no.2
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• pp.58-64
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• 2008

This study was carried out to determine the availability of development rate(DVR) model for predicting bud break time of 'Niitaka' pear. In addition, the study also assessed the effect of an increase in temperature on predicting bud dormancy breaking time in winter season. The DVR model, which was developed for 'Kosui' pear, illustrated that the bud break time(e.g., Dec. 12-Dec. 19) of 'Niitaka' pear observed in the field corresponded to the predicted bud break time by DVR model. This result indicates that the bud break time of 'Niitaka' pear can be predicted by DVR model tuned for 'Kosui' pear. As the temperature increased during the winter season, the bud break time was delayed. Chilling requirement deficiency for the bud break time is expected in Jeju Province when the temperature increased above $4^{\circ}C$ in winter season.

• Horticultural Science & Technology
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• v.33 no.1
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• pp.18-23
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• 2015

Time-specific responses of flower bud differentiation were investigated in 'Shinko' (Pyrus pyrifolia Nakai) pear grown at different altitudes from July through December 2013 to determine their suitability as scions in a top-grafting system. Flower bud initiation and bud necrosis were monitored on each of three sections of one-year-old shoots: terminal, middle, and basal. Flower bud differentiation s tarted in September in the highlands of the Lishan area, and in J uly in the lowlands of the Zhoulan area. In Lishan, flower bud differentiation was higher in the middle and basal segments; during leaf fall, however, flower bud differentiation occurred rapidly in the terminal segment. In Zhoulan, flower buds began to differentiate from the terminal section of the shoot, and severe flower bud necrosis was noted. In July, flower buds developed normally; however, in early August, some of the buds at the basal segment showed browning. During leaf fall, some flower buds showed symptoms of necrosis with rapid and complete browning. Flower bud necrosis began at the basal segment and progressed rapidly towards middle and terminal sections. Before leaf fall, flower buds fell off when scales swelled. The terminal and middle parts of the current-year shoots, with some flower buds, collected in October or later from the Lishan area could be used as scions for top-grafting of 'Shinko' pear. Each grafting scion was a 3-5 cm shoot with one flower bud. These results suggest that scions from the terminal and middle segments of stems of 'Shinko' pear from the Lishan area can be used as scions whereas those from Zhoulan area show necrosis and might not be suitable as scions.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.1
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• pp.50-58
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• 2013

This study was carried out to evaluate the geospatial characteristics of blooming date migration in three major spring flowers across North and South Korea as influenced by climate change. A thermal time-based phenology model driven by daily maximum and minimum temperature was adjusted for the key parameters (i.e., reference temperature, chilling requirement, heating requirement) used for predicting blooming of forsythia, azaleas, and Japanese cherry. The model was run by the RCP 8.5 projected temperature outlook over the Korean Peninsula and produced the mean booming dates for the three climatological normal years in the future (2011-2040, 2041-2070, and 2071-2100) at a 12.5 km grid spacing. Comparison against the observed blooming date patterns in the baseline climate (1971-2000) showed that there will be a substantial acceleration in blooming dates of the three species, resulting in cherry booming in February and flowers of azaleas and forsythia found at the top of mountain Baikdu by the 2071-2100 period. Flowering dates of the three species in the near future (2011-2040) may be accelerated by 3-5 days at minimum and 10-11 days at maximum compared with that in the baseline period (1971-2000). Those values corresponding to the middle future (2041-2070) can be from a minimum of 9-11 days to a maximum of 23-24 days. Blooming date of Japanese cherry can be accelerated by 26 days on average for the far future (2071-2100). The acceleration seems more prominent at islands and coastal plain areas than over inland mountainous areas.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.1
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• pp.40-49
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• 2013

Current service system of the Korea Meteorological Administration (KMA) for blooming date forecasting in spring depends on regression equations derived from long term observations in both temperature and phenology at a given station. This regression based system does not allow a timely correction or update of forecasts that are highly sensitive to fluctuating weather conditions. Furthermore, the system cannot afford plant responses to climate extremes which were not observed before. Most of all, this method may not be applicable to locations other than that which the regression equations were derived from. This note suggests a way to replace the location restricted regression equations with a thermal time based phenology model to complement the KMA blooming forecast system. Necessary parameters such as reference temperature, chilling requirement and heating requirement were derived from phenology data for forsythia, azaleas and Japanese cherry at 29 KMA stations for the 1951-1980 period to optimize spring phenology prediction model for each species. Best fit models for each species were used to predict blooming dates and the results were compared with the observed dates to produce a correction grid across the whole nation. The models were driven by the KMA's daily temperature data at a 5km grid spacing and subsequently adjusted by the correction grid to produce the blooming date maps. Validation with the 1971-2012 period data showed the RMSE of 2-3 days for Japanese cherry, showing a feasibility of operational service; whereas higher RMSE values were observed with forsythia and azaleas.

• Journal of Plant Biotechnology
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• v.42 no.4
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• pp.336-341
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• 2015

Blueberry (Vaccinium spp.) is a bush that grows well at special cultural environments such as acid soil, high organic matter content, and a good drainage and aeration compared to other general crops. Blueberries are well known to contain high amounts of anthocyanins and phenolic compounds, resulting in high antioxidant activity that provides health benefits, and expanding the cultivation areas and consumer's demand in the worldwide. However, the full genome of blueberry has not been announced until now. Furthermore, the genomic analysis and transcriptome approaches are not so popular compare to major crops such as orange, apple, and grape. The aim of the review about blueberry genomic research is to establish the platform for setting blueberry breeding target, increasing proficiency of blueberry research, and making the practical cultivation techniques in Korea. The main topics in the blueberry genomic research including transcriptome, genetic mapping, and various markers are related with cold hardiness, chilling requirement, hot tolerance, anthocyanin content, and flavonoid synthesis pathway on various tissues like flower bud, leaf bud, shoot, root, and berry fruit. The review of the current status of blueberry genomic research will provide basic information to the breeders and researchers and will contribute to development of blueberry industry with sustainable productions and increase of blueberry consumption as new profitable crops in Korea.

• Korean Journal of Plant Resources
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• v.31 no.1
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• pp.90-94
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• 2018

The 'Hongsil' strawberry ($Fragaria{\times}ananassa$ Duch.) is a new cultivar released by Gyeongsangnam-do Agricultural Research & Extension Services in 2015. This cultivar originated from a 2011 cross between '802a312' and 'Okmae' and exhibited suitable fruit characteristics for export due to the high soluble solids content and firmness of the fruit. The breeding line '1116-74-15' was selected as an elite line after examining its characteristics and productivity from 2013 to 2014. A field trial of this line was conducted on a farm in 2015, and it was registered as 'Hongsil' thereafter. The 'Hongsil' strawberry demonstrates intermediate plant type and moderate vigor in growth. It is suitable for forcing culture due to its early flower bud differentiation and low chilling requirement. The soluble solids content of 'Hongsil' is $10.0^{\circ}Brix$, which is approximately $0.4^{\circ}Brix$ higher than that of 'Seolhyang' The Fruit firmness of 'Hongsil' is $13.1g{\cdot}mm^{-2}$, similar to that of 'Maehyang'. Fruits of 'Hongsil' are long conical having a red skin color and marketable yield is $4,269kg{\cdot}10a^{-1}$ which is 16% higher than that of 'Maehyang'. The 'Hongsil' cultivar is sensitive to powdery mildew, and it therefore warrants further investigation regarding disease control.

• Korean Journal of Agricultural and Forest Meteorology
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• v.11 no.4
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• pp.213-220
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• 2009

In order to predict the risk of freeze injury for 'Changhowon Hwangdo' peach trees, we used the dormancy depth (i.e., the daily chill unit accumulation during the overwintering period) as a proxy for the short-term, physiological tolerance to freezing temperatures. A Chill-days model was employed and its parameters such as base temperature and chilling requirement were optimized for peach trees based on the 12 observational experiments during the 2008-2009 winter. The model predicted the flowering dates much closer to the observations than other models without considering dormancy depth, showing the strength of employing dormancy depth into consideration. To derive empirical equations for calculating the probabilistic freeze risk, the dormancy depth was then combined with the browning ratio and the budburst ratio of frozen peach fruit branches. Given the exact date and the predicted minimum temperature, the equations calculate the probability of freeze damages such as a failure in budburst or tissue browning. This method of employing dormancy depth in addition to freezing temperature would be useful in locating in advance the risky areas of freezing injury for peach trees production under the projected climate change.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.4
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• pp.250-257
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• 2020

It is difficult for farmers to select new crops for cultivation to increase income. So we conducted land suitability assessment of grapes with soil and climate information related to crop growth. At first, land suitabilities for grapes were classified into three categories (most suitable, suitable, low productive & not suitable areas) according to soil and climate conditions, respectively. In details, land suitability with respect to soil was assessed by soil morphological and physical properties including soil texture, drainage class, available soil depth, slope and gravel content, whereas one in accordance with climate was evaluated by average annual temperature, temperature during the growing season, temperature during maturation, the lowest temperature, chilling requirement and precipitation during the growing season. Secondly, we combined both soil and climate classification results using a most-limiting characteristic method. Maps showing the suitable land for grapes cultivation were drawn. The results indicate that the most suitable area of cultivation for grapes in south Korea was 3.43% and suitable (possible) area was 10.61%. This study may help to preserve land and increase the productivity through providing valuable information regarding where more suitable areas for grapes are located.