• The Plant Pathology Journal
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• v.23 no.4
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• pp.308-313
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• 2007

A survey of the occurrence of abiotic diseases on kiwifruit (Actinidia deliciosa) trees was conducted at sixty-two kiwifruit orchards in twenty-one locations of Jeonnam and Jeju Provinces in Korea during the 2007 growing season. Various kinds of abiotic diseases were detected on the kiwifruit trees. Malformed fruits caused by incomplete pollination were commonly observed among the normally growing fruits on almost all of the kiwifruit trees examined. Fruits imbued with wire rust, fruits scratched or girdled by the wire and fruits injured by sunscald occurred in all of the examined orchards. Abnormal growth of girdled branches by the fence wire, dead trees killed by excessive soil moisture due to poor draining and leaf chlorosis by nutrient deficiencies were found in some orchards. Leaf spotting by herbicide and leaf scorch or blight by excessively high temperature were observed. Leaf blight on young shoots by late frost and bark split on trunks by freeze occurred in several open-field orchards. Flooding and strong wind damages by attack of typhoon 'Nari' were also found during the survey period. Cup-shaped leaves frequently occurred on young shoots in early spring and the incidence of the syndrome tends to increase annually in recent years, which are not etiologically defined until now.

• The Plant Pathology Journal
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• v.32 no.6
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• pp.545-551
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• 2016

A bacterial pathogen, Pseudomonas syringae pv. actinidiae (Psa), is a causal agent of kiwifruit bacterial canker worldwide. Psa biovar 3 (Psa3) was first detected in 2011 at an orchard in Dodeok-myeon, Goheung-gun, Jeonnam Province in Korea. In this study, we present the results of an epidemiological study regarding Psa3 occurrence on kiwifruit orchards in Korea for the period of 2013 to 2015. Since the first detection of Psa3 in 2011, there was no further case reported by 2013. However, Psa3 was rapidly spreading to 33 orchards in 2014; except for three orchards in Sacheon-si, Gyeongnam Province, most cases were reported in Jeju Island. Entering 2015, bacterial canker by Psa3 became a pandemic in Korea, spreading to 72 orchards in Jeju Island, Jeonnam, and Gyeongnam Provinces. Our epidemiological study indicated that the first Psa3 incidence in 2011 might result from an introduction of Psa3 through imported seedlings from China in 2006. Apart from this, it was estimated that most Psa3 outbreaks from 2014 to 2015 were caused by pollens imported from New Zealand and China for artificial pollination. Most kiwifruit cultivars growing in Korea were infected with Psa3; yellow-fleshed cultivars (Yellow-king, Hort16A, Enza-gold, Zecy-gold, and Haegeum), red-fleshed cultivars (Hongyang and Enza-Red), green-fleshed cultivars (Hayward and Daeheung), and even a kiwiberry (Skinny-green). However, susceptibility to canker differed among cultivars; yellow- and red-fleshed cultivars showed much more severe symptoms compared to the green-fleshed cultivars of kiwifruit and a kiwiberry.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.342-347
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• 1999

Kiwifruit pulp was separated into insoluble pulp and serum by centrifugation at 14,000 rpm for 10 min. The serum portion was concentrated at $30{\sim}50mmHg\;and\;50{\sim}55^{\circ}C$ with aroma recovery. Vapor generated at the early stage of vacuum evaporation was condensed and taken as aroma fractions: $E-I\;(0{\sim}10%),\;E-II,\;(10{\sim}20%)$. The volatile flavor compounds in kiwifruit pulp were collected by dynamic headspace technique and analyzed by GC and GC/MSD. The yield of serum separated from kiwifruit pulp was 70.1% and insoluble pulp fraction contained aroma compounds more than that of the serum. Twenty-six aroma compounds, including (E)-2-hexanal and ethyl butanoate were detected. The efficiency of the aroma recovery was reduced as the recovery time was extended, as indicated by the less peak numbers and kiwifruit areas of aroma fractions.

• Research in Plant Disease
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• v.24 no.3
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• pp.175-181
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• 2018

Incidence rates of bacterial canker, bacterial leaf spot and postharvest fruit rot on the Korean yellow-fleshed kiwifruit cv. Haegeum were compared with those on the most popular green-fleshed kiwifruit cv. Hayward grown in several naturally infected kiwifruit orchards in 2013 and 2014. The percentages of diseased leaves caused by bacterial canker were 18.5% and 17.3% on Hayward in 2013 and 2014, but those on Haegeum were 1.2% and 0%, respectively. The percentages of diseased leaves caused by bacterial leaf spot on Hayward were 63.5% and 16.2% in 2013 and 2014, respectively, but no bacterial leaf spots were observed on Haegeum in both years. The average percentages of diseased fruits caused by postharvest fruit rot were 24.2% and 20.5% on Hayward in 2013 and 2014, while 6.3% and 4.4% and Haegeum, respectively. Botryosphaeria dothidea was turned out to be the major pathogen of postharvest fruit rot on both cultivars.

• Korean Journal Plant Pathology
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• v.14 no.2
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• pp.109-114
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• 1998

To investigate Phomopsis species causing fruit decays of Japanese apricot, apple and kiwifruit, we collected diseased fruits from the fruit markets in 1995 and 1996 respectively. Phomopsis mali Roberts was identified based on cultural characteristics, morphological aspects and pathogenicity. There were no remarkable differences with respect to $\alpha$ and $\beta$ conidia, growth rates and colony characters among the isolates from Japanese apricot, apple and kiwifruit. The pathogens grew more than 70 mm on potato dextrose agar in 5 days at $25^{\circ}C$. The agar was slightly discolored by the production of a reddish purple pigment under the light at $25^{\circ}C$ and 3$0^{\circ}C$ respectively. Only $\alpha$ spores of the different isolates of P. mali were formed at 15$^{\circ}C$ and $\beta$ spores were mainly produced at 3$0^{\circ}C$, but and $\alpha$ and $\beta$ spores were produced in approximately equal numbers at 2$0^{\circ}C$ and $25^{\circ}C$. Pycnidia were a few under the dark condition but were abundant at wide range of 15~3$0^{\circ}C$ under near ultra violet illumination. Conidia were two types : $\alpha$ spores were unicellar, fusoid, hyaline and biguttulate, whereas $\beta$ sores were unicellar, acicular to filiform, straight or hooked and hyaline. An ascigerous stage was not formed in cultures or in nature. Isolates of Phomopsis mali from japanese apricot, apple and kiwifruit could infect fruits of apple, pear, apricot, Japanese apricot and kiwifruit. There were some differences in pathogenicity depending on stocks of fruit crops tested.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.355-364
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• 2022

BACKGROUND: Pre-harvest interval and decline pattern of thiamethoxam were determined in kiwifruit using liquid chromatography-tandem mass spectrometry (LCMS/MS). The study was carried out to propose import tolerance using OECD maximum residue limit (MRL) calculator for the export promotion of kiwifruit to Taiwan. METHODS AND RESULTS: The thiamethoxam residue in kiwifruit was determined by using the LC-TriQ-MS/MS with the analytical process to set up the import tolerance under greenhouse conditions for Taiwan. Excellent linearity was observed for all of the analytes with a determination coefficient (R²)≥0.99. The limit of quantification was determined to be 0.01 mg/kg for both thiamethoxam and clothianidin in kiwifruit. Linearity was determined from the co-efficient of determinants (R²) obtained from the seven-point calibration curve. The standard calibration curve showed as follows; 1) Site 1 (Gimje): y = 944,406X + 1,583 (R²=0.9995), 2) Site 2 (Goheung): y = 1,356,205X + 934 (R²=0.9983), and 3) Site 3 (Jangheung): y = 1,239,937X - 3,090 (R²=0.9908). The residue of thiamethoxam in the kiwifruit for three decline trials showed the range of 0.35 to 0.56 mg/kg in site 1 (Gimje), 0.24 to 0.55 mg/kg in site 2 (Goheung), and 0.28 to 0.42 mg/kg in site 3 (Jangheung), respectively. However, clothianidin was not detected in all of the treatments. The maximum residual amounts (decline) in the samples, sprayed according to the safe-use standard for thiamethoxam 10% WG in kiwifruit (30 days before harvest, 3 sprays every 7 days) were 0.56 mg/kg in site 1, 0.55 mg/kg in site 2, and 0.42 mg/kg in site 3, respectively. CONCLUSION(S): The import tolerance (IT) of thiamethoxam for kiwifruit may be proposed to be 0.9 mg/kg by using the OECD MRL calculator.

• Korean Journal of Environmental Agriculture
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• v.36 no.3
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• pp.169-174
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• 2017

BACKGROUND:Kiwifruit growers build their vineyards using many windbreaks to protect their kiwifruit vines from defoliation injury by strong winds such as typhoon. In this study, we have compared fruit quality, budbreak rate and floral bud as affected by windbreaks. And also we surveyed several microclimate indices of kiwifruit orchard depending on the covering materials of arch-type windbreaks. METHODS AND RESULTS: Five different windbreak materials including polyethylene film (PE), blue- and white-colored nets were tested in pipe-framed archtype kiwifruit vineyards as the covering materials. Photosynthetically active radiation (PAR), annual mean temperature (AMT) and chill unit (CU) as well as fruit quality were compared among the covering materials. In all treatments, annual PAR was more than $400{\mu}mol\;m^{-2}s^{-1}$, in which kiwifruit leaf could reach its maximum photosynthesis, since the leaves were emerged. Annual mean temperature was greater in 0.1 mm-PE covering as much as $1-2^{\circ}C$ than other windbreaks. In CU calculated by three different models, all windbreaks showed more than 1400 CU that is fully fulfilled CU for kiwifruit rest completion. There were no difference in budbreak rate among the covering materials. Fruit weight was heavier in 0.1 mm-PE and white-net (4 mm) than other windbreaks. CONCLUSION: Regardless of the windbreak materials, the PAR quantity was enough for kiwifruit photosynthesis. And CU for kiwifruit rest completion was fully achieved in all treatments. However, with respect to fruit weight, quantity of PAR, and AMT, etc., It is highly recommended for kiwifruit growers to choose 0.1 mm-PE and white-net (4 mm) as for their windbreaks materials.

• Horticultural Science & Technology
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• v.33 no.2
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• pp.259-267
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• 2015

This study was conducted to comparatively evaluate antioxidant capacity (AC) of seven cultivars of kiwifruit (Actinidia spp.) and their protective effects on neuronal PC-12 cells. The contents of total phenolics (TP) and total flavonoids (TF) of kiwifruits were also examined. Five cultivars of kiwifruit, Actinidia chinensis (cv. Haehyang and cv. Haegeum), A. eriantha (cv. Bidan), A. arguta ${\times}$ A. deliciosa (cv. Mansoo), and A. arguta (cv. Chiak), were bred in Korea, while two cultivars, A. deliciosa (cv. Hayward) and A. linguiensis (accession number 041AE), originated from New Zealand and China, respectively. Skin extracts of kiwifruit showed higher TP, TF, and AC than flesh extracts. The highest levels of TP and AC were found in cv. Bidan flesh extract among cultivars studied, but the TF content of cv. Bidan flesh extract was the lowest. The kiwifruit bred in Korea had higher AC than their counterparts. AC of kiwifruit had a highly positive linear correlation with TP and TF. The flesh extracts from cv. Hayward, cv. Haehyang, and cv. Haegeum significantly (p < 0.05) prevented PC-12 cells from oxidative stress induced using $H_2O_2$ compared to a control with $H_2O_2$ only. Overall, our results suggest that kiwifruit bred in Korea may offer a good source of antioxidants and serve as functional materials.

• Journal of Life Science
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• v.12 no.6
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• pp.752-758
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• 2002

This study was investigated on properties and thermostability of gelatin-degrading proteinases in the fruit of Actinidia chinensis (kiwifruit) for the industrial application. Three gelatin-degrading proteinases (PI, PII and PIII) were detected from the pulp of fruits. The molecular weights of these proteinases, PI, PII and PIII, were approximately 220 kD, 51 kD, and 26 kD respectively, on the basis of gelatin-containing SDS-PACE. The optimum pH of these proteinases ranged from 2.0 to 5.0 with a maximal activity at pH 4.0. These proteinases had a high sensitivity to E-64 and iodoacetate which are cysteine protease inhibitors, and required DTT, cysteine, and $\beta$-mercaptoethanol for their activities which are stimulators for cysteine proteases. These results indicate that these proteinases are cysteine proteinases and the proteinase PIII is actinidin (EC 3.4.22.14), based on the molecular weight and/or susceptibility against proteinase inhibitors. These proteinases were strongly activated by $Ca^{2+}$, $Mg^{2+}$ and $Mn^{2+}$, whereas strongly inhibited by Zn$^{2＋}$ and Hg$^{2＋}$. However, these proteinases have slightly different susceptibility against other cations ($Ca^{2+}$, $Cu^{2+}$, $Al^{3+}$, $Ca^{3+}$. The temperature stability of proteinase PIII was more stable than proteinases PI and PII. Moreover, proteinase PIII remained stable below $50^{\circ}C$ for 48hr, showing the residual activity above 75% of the enzyme activity.

• Research in Plant Disease
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• v.19 no.1
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• pp.1-6
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• 2013

Optimal spray time, interval and number of preventive fungicides against fruit rots of kiwifruit were investigated at the orchard which both green kiwifruit cultivar 'Hayward' and gold kiwifruit cultivar 'Hort16A' are cultivating side by side during 2009 and 2010 growing seasons in Jeju island, Korea. The highest control efficiency was obtained from benomyl WP and followed by thiophanate-methyl WP and carbendazim+diethofencarb WP. The control efficacies of the fungicides were much higher when applied onto the kiwifruit canopy after the flowering time than before the flowering time but thereafter their control efficiencies were decreased drastically according to delays of spray timing. With increasing spray numbers of the fungicides, the control efficacy increased. However, optimal spray time, interval and number of the preventive fungicides for the effective control of fruit rots of kiwifruit were determined as 4 time-spray schedule with 2-week-interval just after the flowering time on both 'Hayward' and 'Hort16A' cultivars.