• Horticultural Science & Technology
• /
• v.28 no.4
• /
• pp.529-534
• /
• 2010

Occurrence of wilted symptom in watermelon plant ($Citrullus$ $lanatus$ L.) is known to be caused by physiological disorder. The symptom results in the loss of fruit production and thus the economical loss of watermelon growers. The incidence of symptom is often found from the middle of March to the end of May in the major watermelon crop production areas of Korea (i.e. Uiryeong, Gyeongnam (lat $37^{\circ}$56'64"N, long $126^{\circ}$99'97"E)). Despite of extensive information about the physiological disorder, little study has been conducted to understand a relationship between the wilted symptom and accompanying environment factors (e.g. temperature). This study aimed to investigate effects of environmental conditions amended by a forced-ventilation system on physiological characteristics of watermelon and incidence of the wilted symptom. Watermelon plants were grown from January to May, 2009 with either the forced-or natural-ventilation treatment in a greenhouse located in the Uiryeong. In the result, the forced-ventilation treatment decreased the air, leaf and root-zone temperature approximately $4.5^{\circ}C$, $5^{\circ}C$ and $3^{\circ}C$, respectively, compared to the natural-ventilation. The fruit growth rate was maximized twice during the entire growing period. The higher rate of fruit growth was observed under the natural-ventilation than the forced one. Maximization of the fruit growth rate (approximately 430 g per day) was first observed by 12 days after fruiting under the natural-ventilation treatment, while the second one (approximately 350 g per day) was observed by 24 days after fruiting. The wilted symptom started occurring by 22 days after fruiting under the natural-ventilation, whereas no incidence of the symptom was found under the forced-ventilation treatment. Interestingly, the forced-ventilation lowered the fruit growth rate (approximately 320 g per day) compared to the natural one. Maximization of the fruit growth rate under the forced-ventilation was found at 4 days later than that under the natural one. This result coincided with a slower plant growth under the forced-ventilation treatment. These results suggest that the forced-ventilation slows down extension growth of fruit and plant, which may be associated with lowering leaf temperature and saturation deficit. We suggest the hypothesis that the forced-ventilation may alleviate stress of the wilted symptom by avoiding extreme water evaporation from leaves due to high temperature and thus by reducing competition between leaves and fruits for water. More direct and detailed investigations are needed to confirm the effect of the forced ventilation.

• The Korean Journal of Mycology
• /
• v.47 no.4
• /
• pp.443-446
• /
• 2019

In 2017, wilting symptom was observed on seedlings of Anthurium andraeranum in Youngin, Korea. Brownish lesions with water soaking were developed on the stems and roots of the infected plants. The stems and leaves wilted and finally died. One fungal isolate was obtained in pure culture. Morphological features and nucleotide sequences of internal transcribed spacer rDNA and cytochrome oxidase subunit II mt DNA were analyzed. The results of this study indicated that the fungus is identified as Phytopythium vexans. Pathogenicity tests showed the isolate was pathogenic to the seedlings of A. andraeanum. To our knowledge, this is the first report of P. vexans causing stem rot on A. andraeanum in Korea.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.6
• /
• pp.978-980
• /
• 2010

This study was conducted to observe the cause of injury of fig plant. Nitrogen dioxide gas can be evolved at low pH or reduced in soil. Fig plant cultivated with nutrient solution was wilted or withered. Injury symptom for nutrient solution containing nitrous acid was worse as pH of soil decreased. However, increase in pH of nutrient solution treated with increasing $Ca(OH)_2$ solution prevented nutrient solution from producing nitrogen dioxide gas. Recovery of the fig plant by pH increase indicated that the cause of injury was nitrogen dioxide gas.

• The Plant Pathology Journal
• /
• v.23 no.1
• /
• pp.3-6
• /
• 2007

Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris(FOC) is the most destructive disease in India. It is seed-borne as well as soil-borne pathogen. The role of seed-borne FOC in introducing and establishing wilt in FOC free soils is unknown. Using seeds of FOC infected chickpea cultivar K 850, we provided an evidence of establishing wilt disease in the FOC free soils within three crop cycles or seasons. In the first cycle, typical wilt symptoms were observed in 24 pots in 41 days after sowing. These 24 pots were used for second and third cycles without changing the soil. These 24 pots were sown with seeds collected from healthy plants of a susceptible cultivar JG 62, one seed per pot and development of wilt symptom was recorded. Wilt symptoms appeared in all the pots 26 days after sowing in second cycle and in 16 days after sowing in third cycle. On selective medium, all of the wilted plants yielded FOC in all the three cycles indicating that the mortality was due to wilt. FOC propagules on selective medium were 172, 1197, and 2280 $g^{-1}$ soil at the end of the first, second, and third cycles, respectively. These studies indicated that Fusarium wilt of chickpea is seed-borne and seeds harvested from wilted plants when mixed with healthy seeds can carry the wilt fungus to new areas and can establish the disease in the soil to economic threshold levels within three seasons.

• Research in Plant Disease
• /
• v.21 no.1
• /
• pp.24-26
• /
• 2015

In April 2014, seedlings of Fallopia multiflora showing wilt symptom were first found at a greenhouse in Punggi-eup, Yeongju-si, Korea. A Fusarium-like fungus was isolated from the wilted plant and it was identified as Fusarium oxysporum based on morphological characteristics and nucleotide sequence data of translation elongation factor 1-${\alpha}$. The fungus isolated from the diseased plant was revealed to be pathogenic to the host plant through pathogenicity tests, and the reisolation of the pathogen confirmed Koch's postulates. This is the first report of Fusarium wilt occurring on Fallopia multiflora in the world.

• The Plant Pathology Journal
• /
• v.29 no.1
• /
• pp.67-76
• /
• 2013

A chitinolytic bacterial strain having strong antifungal activity was isolated and identified as Burkholderia cepacia MPC-7 based on 16S rRNA gene analysis. MPC-7 solubilized insoluble phosphorous in hydroxyapatite agar media. It produced gluconic acid and 2-keto-gluconic acid related to the decrease in pH of broth culture. The antagonist produced benzoic acid (BA) and phenylacetic acid (PA). The authentic compounds, BA and PA, showed a broad spectrum of antimicrobial activity against yeast, several bacterial and fungal pathogens in vitro. To demonstrate the biocontrol efficiency of MPC-7 on late blight disease caused by Phyto-phthora capsici, pepper plants in pot trials were treated with modified medium only (M), M plus zoospore inoculation (MP), MPC-7 cultured broth (B) and B plus zoospore inoculation (BP). With the sudden increase in root mortality, plants in MP wilted as early as five days after pathogen inoculation. However, plant in BP did not show any symptom of wilting until five days. Root mortality in BP was markedly reduced for as much as 50%. Plants in B had higher dry weight, P concentration in root, and larger leaf area compared to those in M and MP. These results suggested that B. cepacia MPC-7 should be considered as a candidate for the biological fertilizer as well as antimicrobial agent for pepper plants.

• The Korean Journal of Mycology
• /
• v.39 no.3
• /
• pp.254-255
• /
• 2011

Stem rot symptoms of Euphorbia marginata were occurred in the herb exhibition field at Gyeongsangnam-do Agricultural Research and Extension Services in Korea. The typical symptom was started with watersoaking lesion on the stem then gradually rotted, wilted, and blighted, the severely infected plants were eventually died. The sclerotia of the pathogen were globoid in shape, 1~3mm in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$. The hyphal width was 4~9 ${\mu}m$, and the typical clamp connection structures were observed in the hyphae of the fungus grown on PDA. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of stem rot on E. marginata caused by S. rolfsii in Korea.

• Korean journal of applied entomology
• /
• v.41 no.3
• /
• pp.217-223
• /
• 2002

The chestnut brown chafer, Adoretus tenuimaculatus Waterhouse, is serious insect pests in golf courses. Adults feed on the leaves of latifoliate trees but larvae feed on roots of turfgrases such as bentgrass, Agrostis spp. Damage of A. tenuimaculatus larvae was observed at the Jinju golf club which showed damage symptom on perennial ryegrass, Lolium perenne in tees and fairways in July, 2000. Damaged turf by A. tenuimaculatus larvae became yellowish and wilted. Symptom of laval damage of A. tenuimaculatus was similar to summer depression in warm season turfgrasses but not recovered by irrigation when Korean isolates of entomopathogenic nematodes were evaluated for the control of A. tenuimaculatus larvae in laboratory and field as a possible biological control agent. The nematodes used were Heterorhabditis bacteriophora Jeju strain, Hererorhabditis sp. Gyeongsan strain, Steinernema carpocapsae Pocheon strain, S.glaseri Dongrea strain, and S.longicaudum Nonsan strain. In the laboratory test H.bacreriophora Jeju strain and Heterorhabditis sp. Gyeongsan strain were highly effective for 3rd instars with 95% mortality. In the field test reduction rates of A.tenuimaculatus larvae were higher by ranging from 28 to 57% by H. bacteriophora Jeju strain, Heterorhabditis sp. Gyeongsan strain, and S.carpocapsae Pocheon strain compared to 7% by natural cause.

• Research in Plant Disease
• /
• v.13 no.3
• /
• pp.211-215
• /
• 2007

Since 2003, anthracnose symptoms on Eucalyptus globulus were observed in farmer's field at Jisepo, Ilwoon-myon, Geoje city, Gyeongnam province, Korea. Typical symptoms of dark brown to black spot appeared on the leaves, twigs, and stems. Infected young trees were wilted, blighted and died eventually. The pathogen isolated from the typical symptom formed gray to dark gray colony on potato dextrose agar and showed optimum growth at $30^{\circ}C$. Conidia were single celled, colorless, cylindrical with obtuse ends, and $9{\sim}22{\times}3{\sim}6{\mu}m$ in size. Appressoria were dark brown, ovate to obovate, and $6{\sim}18{\times}4{\sim}10{\mu}m$ in size. Perithecia were black and globose in shape and $76{\times}274{\mu}m$ in size. Asci were clavate to cylindrical in shape and $42{\sim}76{\times}8{\sim}12{\mu}m$ in size. Ascospores were cylindrical, fusiform, slightly curved at the center, and $10{\sim}23{\times}4{\sim}6{\mu}m$ in size. On the basis of mycological characteristics and pathogenicity test on E. globulus, the pathogen was identified as Glomerella cingulata. This is the first report of the anthracnose on E, globulus caused by G. cingulata in Korea.

• Korean Journal of Environmental Agriculture
• /
• v.24 no.1
• /
• pp.1-5
• /
• 2005

Continuous monocropping of Chinese cabbage in Gangwon highland increased gravel and sand contents due to surface soil erosion. Nutrient leaching and Chinese cabbage growth were investigated with different treatments of gravel contents and nitrogen application levels by using $0.5m^2$ Wagner pots. Gravel contents were 0, 10, 30, 50, 70, and 90%(w/w), nitrogen application levels were 60, 120, and 240 kg/ha, and manure compost application rate was 15 ton per hectare, respectively. Wagner pots were filled with loamy sand soil mixed with 5 cm-sized gravels. Fresh weight of Chinese cabbage was decreased as gravel contents in soil increased, and particularly severely decreased at 240 kg-N/ha. Yields of Chinese cabbage were remarkably decreased at the rate of 60 kg-N/ha with 30% gravel content and 120 kg-N/ha with 50% gravel content. Most of Chinese cabbages were severely wilted by heavy N application at the rate of 240 kg-N/ha in the middle of growth stages regardless of gravel contents, while about 50% of Chinese cabbage showed wilting symptom in the treatment of more than 50% of gravel contents and 120 kg-N/ha. N content in leachate increased as gravel content and N application increased. The relationship between gravel content and N contents showed linear regression: N in leachate = 0.014(gravel content) -0.039 (r = 0.961). Particularly, $NH_4-N$ contents in leachates with more than 30% gravel content and 240 kg-N/ha ranged from $139{\sim}339mg/L$. Chinese cabbage growth in loamy sand soil containing 30%, and 50% gravel contents could be adversely affected by N application at the rate of 240, and 120 kg-N/ha, respectively.