Ju-Hee Kim

Identification and Characteristics of Penicillium spp. Isolated from Postharvest Decay of Pear

This study was carried out to identify the causal pathogens and investigated the characteristics of Penicillium spp. isolated from postharvest decay of pear. One hundred and ninety eight Penicillium spp. were isolated from infected pear fruits. The lesions were formed when the isolated pathogen were inoculated into the wounds and unwounds of pear fruit. Total isolates were classified into 15 groups by the size, color, pigment of colony and shape of conidia. These isolates were identified to be P.expansum, P.solitum, and P.crustosum according to the types of morphological, cultural and physiological characteristics. The pathogenicity was higher in wound inoculation at low temperature than unwound one. This result confirmed that wound promoted the disease appearance. P.expansum was appeared to have the most strong virulence, whereas P.solitum and P.crustosum were classified as weak virulent species by pathogenicity test on pear fruits.

Stem Rot of Sweet Potato (Ipomoea batatas) Caused by Sclerotium rolfsii in Korea

During the early spring of 2007 to 2009, stem rot of sweet potato (Ipomoea batatas L.) caused by Sclerotium rolfsii occurred in seedling stage grown in plastic film house at Iksan. In seedling stage of sweet potato, symptoms were initially appeared in yellowing and then the seedlings were eventually wilted. The fungus produced abundant white silky mycelium on infected tissues and soil line. Seedlings were very susceptible and died quickly once they were infected. The whole area of a petridish was rapidly covered with white mycelium on agar medium. Sclerotia began to produce after 7 days of mycelial growth and white sclerotia quickly melanized to a dark brown coloration. The causal agent isolated from the diseased plants was identified as Sclerotium rolfsii Saccardo on the basis of the morphological and cultural characteristics. All isolates of S. rolfsii caused similar symptoms on the host petioles by artificial inoculation.

Yield Loss Assessment and Determination of Control Thresholds for Anthracnose on Red Pepper

This study was carried out to develop control thresholds for anthracnose on red pepper. To investigate relationship between anthracnose incidence and diseased fruits, experimental plots with six treatments were established. There existed close correlation between rate of diseased fruits and yields in field (Y = -16.83X + 327.57, R2 = 0.83), in rain shelter (Y = -4.92X + 361.02, R2 = 0.84), and in rain shelter with rain (Y = -5.91X + 359.71, R2 = 0.76). Control thresholds for anthracnose of pepper were 0.9% diseased fruits per plant in field and from 1.7 to 2.3% diseased fruits rate per plant in rain shelter.

Occurrence of Insect Pests in Rubus coreanus Miquel

In this study, 5 species (Tetranychus kanzawai Kishida, Endoclyta excrescens (Butler), leaf roller caterpillar (Adoxophyes orana Fisher), Anomis mesogona (Walker), and Aulacaspis rosae (Bouche)) were found in Rubus coreanus Miquel in Jeonbuk province, from 2006 to 2008. T. kanzawai appeared in mid-May and showed three peaks in late June, mid-July, and late August. Its density was over 10 adults per leaf. A. mesogona appeared in mid-June and showed two peaks in late July, and early October. Of the 28 insect pests in pre-harvesting, the 7 main species were T. kanzawai, T. urticae, A. orana, Lygocoris lucorum Meyer, Frankliniella intonsa (Trybom), Psylliodes punctifrons Baly and Motschulskyia serrata (Matsumura). Of the 19 insect pests in after-harvesting, the 6 main species were T. kanzawai, E. excrescens, A. mesogona, A. orana, P. punctifrons and A. rosae. Growth of R. coreanus decreased when insect pests were not managed and yields decreased approx. 7% a year. Management of insect pests in field using pesticide was not different.

Analysis of Genetic Relationship and Cultural Characteristics of Penicillium species Isolated from Postharvest Decay of Pear by Random Amplified Polymorphic DNA

Fifteen isolates from pear, and sixteen isolates from KCTC, KCCM, and Chungnam Univ. of Penicillium spp. were investigated for the analysis of their relationships of cultural characteristics and RAPD genetic variation by RAPD. The cultural characteristics of Penicillium spp. were shown different growth rate, morphology, and color. In addition, the cultural characteristics and RAPD analysis were conducted for the pear rot pathogens and related isolates. RAPD patterns were applied to compare the taxonomic and genetic diversity of the Penicillium species between 15 groups isolated from pear fruits and 16 standard species. The genomic DNA were amplified from by five URP primer and 744 bands were detected. The cluster analysis showed four genomic DNA RAPD groups and its similarity was 47.7%. Intraspecific relationships were 87.4, 97.5 and 95.2%, in P. expansum, P. solitum, and P. crustosum, respectively. These results appeared to be that there were high similarities between isolates, and consistent with the results of cultural morphological characteristics analysis.

Economic Threshold for the Diamondback Moth (Plutella xylostella L., Lepidoptera: Plutellidae) on Leaf Broccoli (Brassica oleracea var. botrytis italiana)

This study was conducted to estimate the economic injury level (EIL) to leaf broccoli (leaf vegetable) by the diamondback moth (Plutella xylostella L.) in 2007 and obtain basic data for pest management. To investigate the relationship between initial density of diamondback moth larvae and broccoli leaf yield, experimental plots with five treatments (0, 0.5, 1.0, 1.5 and 2.0 larvae per plant) as initial density were established. We inoculated larvae on cheesecloth covering to survey changes in larval density. When grown for consumption, leaves of broccoli are harvested in periods. High levels of larvae were associated with significant reductions in leaf yield. There were 0%, 15%, 35%, 42%, 44% yield reductions due to a density of 0, 0.5, 1.0, 1.5, 2.0 diamond back moth larvae per plant, respectively, 25 days after larva inoculation. The regression equation used to predict leaf yield based on the number of initial larvae per plant was y

Anthracnose of Black Raspberry Caused by Colletotrichum gloeosporioides, C. coccodes, and C. acutatum in Korea

Anthracnose was occurred on black raspberry (Rubus coreanus) grown at Gochang areas of Korea during the period of 2003-2009. Black raspberry was afflicted by anthracnose with initial lesion of dark brown circular spots on the naturally infected stems and petioles. The irregular spots was either fused or progressed into circular or elliptical shape. The causal fungi of anthracnose were isolated from the diseased plants and identified as Colltotrichum gloeosporioides, C. coccodes and C. acutatum based on the morphological and cultural characteristics. All isolates of C. gloeosporioides, C. coccodes and C. acutatum produced similar symptoms under pathogenic examination through artificial inoculation.

Analysis of the Cause of the Twig Blight on Mulberry Based on the Weather Conditions

The twig blight of mulberry caused by Fusarium lateritium occurs mainly in Buan area, which is the main area of mulberry. The initial symptom on twigs showed dark edge blight and dark orange tiny particles on the spot, and it was withered and died. In the case of mulberry twig blight, the difference in the degree of occurrence between the years is intense, and an average of 2.7% occurred in Buan in 2013, but in 2014, it was difficult to search for the generated fields. In order to find the cause of the difference in the incidence of mulberry twig blight, we investigated and analyzed the weather conditions during cultivation and as a result, the occurrence of the disease increased under the condition that the temperature of the spring was lower and the number of days passing below the winter freezing point increased. In addition, it was analyzed that the occurrence of the next year increases when the rainfall is high and the number of sunshine is low after removing the harvested branches. Therefore, in the event that weather conditions causing twig blight diseases have elapsed, it is necessary to prevent the disease by spraying the registered applied fungicide prophylactically.

Determination of Economic Control Thresholds for Bacterial Spot on Red Pepper Caused by Xanthomonas campestris pv. vesicatoria

This study was carried out to develop the economic thresholds for the control of bacterial spot of red pepper. The correlation between diseased leaf rate and yield in field was Y = -0.724X + 281.58, R2 = 0.78, r = -0.88. The correlation between diseased leaf rate and yield loss in field was Y = 0.813X + 15.95, R2 = 0.78, r = 0.88. We found that control thresholds was below 30.3% diseased leaves rate per plant in field. The economic control thresholds for bacterial spot of red pepper was below 16.3%.

First Report of Anthracnose on Bitter Gourd Caused by Colletotrichum gloeosporioides in Korea

Anthracnose occurred in bitter gourd grown in Jeongup areas of Korea in 2011. Anthracnose of bitter gourd appeared as dark brown circular spots on naturally infected leaves and fruits. The symptoms of infected leaves and fruits were small brown to dark brown spots and gradually enlarged to larger cylindrical dark brown lesions. The causal fungus of anthracnose isolated from the diseased plants was identified as Colletotrichum gloeosporioides based on the morphological and cultural characteristics and ITS rDNA sequence analysis. All isolates of C. gloeosporioides produced symptoms on the host leaves by artificial inoculation. This is the first report of anthracnose on bitter gourd caused by C. gloeosporioides in Korea.