Root Gall on Korean Zucchini (Cucurbita moschata) Caused by Agrobacterium tumefaciens in Korea

Crown gall and root gall diseases caused by Agrobacterium spp. are economically important bacterial diseases affecting a wide range of crops worldwide. In 2024, root gall symptoms were observed on greenhousegrown Korean zucchini (Cucurbita moschata) in Cheongju, Korea. Seven bacterial isolates were obtained from galled roots and subjected to cultural, morphological, pathogenicity, and molecular analyses. All isolates produced characteristic pink colonies on 1A selective medium and were rod-shaped with multiple flagella, as observed by transmission electron microscopy. Pathogenicity was confirmed through inoculation of zucchini seedlings and carrot disk assays, in which typical gall symptoms developed. Multilocus sequence analysis based on four housekeeping genes (atpD, dnaK, glnA, and rpoB) revealed that all isolates clustered within the A. tumefaciens clade. These results demonstrate that A. tumefaciens is the causal agent of root gall disease in Korean zucchini. To our knowledge, this is the first comprehensive report of root gall disease caused by A. tumefaciens on Korean zucchini in Korea.