Effects of Histological Characteristics of the Leaves and the Microclimate on Disease Development Patterns in Chungjin, a Ginseng Cultivar Resistant to Leaf Blight Caused by Alternaria Panax

The occurrence of Alternaria leaf blight is known to reduce ginseng yields by 10-30%. To prevent the disease, agricultural pesticides are applied nine to twelve times a year. However, the repeated use of the same type of pesticides increases the incidence of pesticide resistant strains, disrupting the entire ecosystem. Addressing this issue requires the development of a new ginseng cultivar that is resistant to Alternaria leaf blight. To this end, Chungjin, a cultivar resistant to leaf blight, and Sunone, a cultivar susceptible to the disease, were examined using detached leaf methods. The examination covered a wide range of factors and topics, including the optimization of conditions for early diagnosis testing, the relationship between leaf cuticles and disease development, the correlation between microclimate conditions under the shade and disease development, and changes in the yield of ginseng resulting from reduced pesticide application. The optimal conditions for early diagnosis testing were determined as follows: adaxial leaf surfaces were inoculated with a conidial suspension containing a concentration of 1 x 105 spores/mL. Subsequently, the leaves were incubated at a temperature of 20 degrees C and relative humidity of 70% for eight days. The delayed development of Alternaria blight in Chungjin is attributed to the presence of well-developed leaf cuticles. Among the weather conditions considered here, rainfall exhibited the highest correlation with disease development, followed by temperature. High relative humidity was found to have little correlation. Despite the fact that pesticides were applied only twice in a period from July to late August, Chungjin also had 22% more yield. Chungjin reduces the required amount of pesticide application, thereby preventing the emergence of pesticide resistant strains and contributing to environmental protection. The major findings of this study are expected to serve as foundational data for further research on leaf blight resistance and agronomic control.