Wang-Hyu Lee

The Effect of Blue-light-emitting Diodes on Antioxidant Properties and Resistance to Botrytis cinerea in Tomato

In higher plants, blue-light is mainly perceived by cryptochromes and phototropins, which subsequently orchestrates phototropism, chloroplast relocation, stomatal opening, rapid inhibition of hypocotyl elongation and leaf expansion. Blue-light signaling is also known to mediate the plant responses to biotic stresses, but relevant mechanisms are largely unknown. Here, we demonstrated that blue LED (Light Emitting Diode)-driven inhibition of gray mold disease was highly correlated with the increases in cellular protectants like proline, antioxidants and ROS (Reactive Oxygen Species) scavenger activities. After twenty one days of exposure to various wavelengths of LED lights, blue-LED treated tomato displayed significant increases in proline accumulation in the leaves and stems, whereas red- and green-LED treated tomato exhibited the lower proline contents. Similarly, the blue-LED treatment increased the amount of polyphenolic compounds in tomatoes, compared to other wavelength of LED lights. The activities of various ROS (Reactive Oxygen Species) scavenging enzymes were also slightly increased under the blue-LED lighted conditions. Finally, blue-LED significantly suppressed symptom development of tomato infected by gray mold. Combined results suggest that blue LED light inhibits the development of gray mold disease, which can be mechanistically explained by the enhanced proline accumulation and antioxidative processes at least in partial.

Isolation and Identification of Mushroom Pathogens from Agrocybe aegerita

Agrocybe aegerita is an important mushroom cultivated in Korea, with good feel and a peculiar fragrance. A. aegerita can be cultivated throughout the year using culture bottles but is more susceptible to contamination than other mushrooms. Twenty-two pathogens were isolated from the fruiting bodies and compost of A. aegerita, and seven isolates were isolated from Pleurotus ostreatus to compare with the A. aegerita isolates, collected from Gimje, Iksan, Gunsan of Chonbuk, and Chilgok of Gyeongbuk Province in 2009. These isolates were identified based on morphological and molecular characteristics. Of the 29 isolates, 26 were identified as Trichoderma spp. and the remaining three were Aspergillus spp., Mucor spp., and Penicillium spp. A phylogenetic analysis revealed that the 26 isolates of Trichoderma were divided into four taxa, namely T. harzianum, T. pleuroticola, T. longibrachiatum, and T. atroviride. Among the Trichoderma spp., 16 isolates (55.2%) were identified as T. harzianum, six as T. pleuroticola (20.7%), two as T. longibrachiatum, and the remaining two were T. atroviride.

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.

Occurrence of Gray Mold Caused by Botrytis cinerea on Common Fig in Korea

In 2010 and 2011, gray mold was found on common fig (Ficus carica) fruit grown at the research field of Jeollabuk-do Agricultural Research and Extension Services, Korea. Gray mold symptoms on common fig fruit mainly occurred after harvest season until December. The typical symptom included brown water-soaked rot and fruit decay. The diseased fruit was covered by gray to brown colored conidiophore and conidia. The conidiophores were tree shape and measured . Conidia on conidiophore were ellipsoidal or lemon shape, colorless, single cell, and measured . The nucleotide sequences of the rDNA ITS region obtained from the pure culture of the gray mold on common fig were 100% similar to the sequences of the GenBank accession number HQ171052, EU519210, HQ171053, FN812726, HM849615, and EU563120 of B. cinerea isolates. In phylogenetic tree, the representative isolate was placed within same clade of B. cinerea. Based on the morphological characteristics and analysis of rDNA ITS sequence data, the fungus was identified as B. cinerea.

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.

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.

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.

Characteristics of Brown Rot Caused by Monilinia fructicola on Stone Fruit in Korea

Hun-Tak Oh, In-Young Choi*, Ju Kim, Young-Eun Na, Wang-Hyu Lee, Kui-Jae Lee, and Hyeon-Dong Shin Jeollabuk-do Agricultural Research and Extension Services, Iksan 54591, Korea Department of Agricultural Biology, Chonbuk National University, Jeonju 54896, Korea Division of Biotechnology, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 54596, Korea Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Korea

The Development of Simple Methods for the Maintenance and Quantification of Polymyxa graminis

Polymyxa graminis, a root endoparasite of several cereal species, is considered to be non-pathogenic but serves as a vector of various plant viruses belonging to the genera Bymovirus, Furovirus, and Pecluvirus. Specifically, it reduces barley productivity by transmitting the Barley Yellow Mosaic Virus (BaYMV). To date, due to its obligate biotrophic property, no artificial culturing of P. graminis was reported and its quantification was also technically challenging. Here, we developed a novel and simple method to infect P. graminis within sterile barley roots in contamination free by preparing nearly pure zoospore inoculum. Such artificial maintenance of P. graminis was verified based on the presence of various developmental stages in infected barley roots under microscope. In addition, the population of resting spores in host tissue was determined by establishing standard curve between manually counted number of spores and Ct values of 18S rDNA amplification using quantitative real-time PCR. Furthermore, it was validated that standard curve generated was also applicable to estimate the abundance of P. graminis in soil environments. In conclusion, the present study would help to generate a system to investigate the etiological causes as well as management of plant diseases caused by P. graminis and BaYMV in tissue and soil.

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%.