English
Disease Assessment of Apple leaf Blotch and Morphological Characterization of Its airborne conidia in Korea
Hobhin Lee1, Hyeon-Yeong Ju1, and Hyo-suk Kim1*
1Plant Disease Control Division, National Institute of Agricultural Sciences, Rural Development Administration, Wanju, 55365, Republic of Korea
*Email: monster1225@korea.kr
Apple leaf blotch (ALB) caused by Marssonina coronariae, has a significant impact on damage to apple orchards in South Korea. Ascospores have not yet been found in the field, conidia dispersed during the flowering season are regarded as the primary inoculum for ALB occurrence. This research focuses on analyzing temporal variations in ALB occurrence and the morphological characteristics of conidia to support crop growers in decision-making for disease management. Disease assessment was conducted at 7-day intervals at the apple orchard in Wanju during May 28th to Sep. 30th in 2025. Four branches of twenty apple tress with two varieties (Fuji and Hong-ro) were labeled to collect the disease incidence. Symptomatic leaves were surface-sterilized and incubated on 2% water agar (WA) to examine the morphological characterization of conidia under a light microscope at 400X. The first symptom was appeared on May 28th, with a disease incidence of 0.35%, increasing gradually to 38.85% over 54 days. A Temporal decrease of disease incidence was observed during July 31st to Aug. 5th due to early defoliation of apple leaves, whereas the disease intensity increase from 13.99% to 54.74% toward the late cropping season (Sep. 24th). Characterization of conidial morphology was carried out on the 30 samples of conidia were observed at 5 days after incubation. The shape of conidia were two-celled, obpyriform, hyaline and smooth-walled with the size of 20.78±2.37×8.92±0.89 ㎛. Further studies are required to provide supporting information for effective disease management based on the conidial morphology and disease variations with weather conditions.
