English
First Report of Internal Spongy Rot of Kiwifruit Caused by Albonectria rigidiuscula in Korea
Jaeyoung Jang1, Gyoung Hee Kim1,2*
1Department of Plant Medicine, Sunchon National University, Suncheon, Republic of Korea
2Department of Agricultural Life Science, Sunchon National University, Suncheon, Republic of Korea
*Email: ghkim@scnu.ac.kr
Kiwifruit (Actinidia deliciosa and A. chinensis) is an economically important fruit crop widely cultivated in major production regions of Korea, including Jeju, Jeollanam-do, and Gyeongsangnam-do. Boseong in Jeollanam-do is the largest kiwifruit-producing area in Korea and exports the ‘Hayward’ cultivar. In 2025, export consignments of ‘Hayward’ kiwifruit produced in Boseong were rejected during quarantine inspection due to the presence of internal red, spongy lesions. These symptoms gradually progressed to internal soft rot during storage, resulting in severe quality deterioration. A fungal pathogen was consistently isolated from symptomatic tissues and cultured on potato dextrose agar (PDA), where colonies exhibited orange to reddish-violet pigmentation. Microscopic observations revealed that microconidia were oval to obovoid, aseptate to 1-septate, measuring 6.3–15.0 × 3.3–6.0 μm. Macroconidia were elongated and relatively broad, with blunt to slightly curved apical cells and distinct foot-shaped basal cells, typically containing 5–9 septa and measuring 56.4–99.8 × 5.7–9.7 μm. Chlamydospores were not observed. For molecular identification, sequences of the internal transcribed spacer (ITS), translation elongation factor 1-α (TEF1-α), and RNA polymerase II second largest subunit (RPB2) genes were analyzed. Phylogenetic analyses identified the pathogen as Albonectria rigidiuscula. Pathogenicity tests using healthy kiwifruits reproduced the characteristic internal spongy rot symptoms, and the same fungus was re-isolated, thereby fulfilling Koch’s postulates. This study represents the first report of internal spongy rot of kiwifruit caused by A. rigidiuscula in Korea, indicating a newly emerging postharvest disease that may affect fruit quality and export stability.
