ABSTRACT
Isolation and characterization of diverse tumorigenic Rhizobiaceae strains associated with crown gall on flowering cherry (Prunus serrulata var. lannesiana) in Ningbo, China

Liang Liu1*, Zhilong Wang1, Qianshuang Guo2, Kai Feng1, Yueqiu He1, Qi Ye1, Fan Yang1, Wen Li1, Feng Liu1, and Tao Fu1
 
Crown gall disease threatens flowering cherry (Prunus serrulata Lindl. var. lannesiana (Carrière) Makino) cultivation in Ningbo, China. Six tumorigenic bacterial strains were isolated from gall tissues of diseased cherry roots. Based on biochemical phenotypic assays and partial 16S rRNA gene sequences, strain CA-6 was preliminarily assigned to the Agrobacterium tumefaciens species complex (syn. Rhizobium radiobacter), and isolates CA3-1 to CA3-5 shared high sequence similarity with Rhizobium calliandrae and are therefore referred to as R. calliandrae-like strains. The polymerase chain reaction (PCR) screening verified that all six isolates harbored three key virulence genes (virD2, tms2, and ipt) borne on the tumor-inducing (Ti) plasmids. Pathogenicity assays fulfilling Koch’s postulates demonstrated that all strains could induce crown galls on tomato, sunflower, and Prunus seedlings, and all six isolates were confirmed to be pathogenic on the three test hosts. This work offers preliminary data regarding the virulence traits of local cherry crown gall pathogens to support follow-up integrated disease management research.
Key words: Agrobacterium tumefaciens species complex, crown gall, pathogenicity, Rhizobium calliandrae-like strains, tumorigenic genes.
1Ningbo City Vocational Technology College, Zhejiang, Ningbo 315000, China.
2Ningbo Newcom Biotechnology Co., Ltd., Zhejiang, Ningbo 315000, China.
*Corresponding author (181310@nbcc.edu.cn).
Received: 4 May 2026; Accepted: 9 August 2026, Available online: 7 September 2026.