Etiology and Symptomatology of Crown Gall Disease Caused by Agrobacterium spp. on Rose in Ornamental Nurseries

Abstract

Crown gall disease caused by Agrobacterium spp. is a major constraint in rose cultivation, particularly in ornamental nurseries where plant quality and market value are critically important. The present study investigates the etiology and symptomatology of crown gall disease affecting rose plants in commercial nursery systems. Field surveys were conducted in affected nurseries, and plants exhibiting typical tumor-like swellings on stems, crowns, and roots were collected for pathogen isolation. Bacterial cultures obtained on selective media showed characteristic colony morphology consistent with Agrobacterium spp. Pathogen identification was confirmed through biochemical characterization and molecular analysis using 16S rRNA gene sequencing, which verified the presence of tumor-inducing Agrobacterium strains. Symptom development was observed as initial small swellings that progressively enlarged into irregular galls, leading to disruption of vascular tissues and reduced plant vigor. Severely infected plants exhibited stunted growth, chlorosis, wilting, and poor flower production. Wound sites caused by pruning and grafting were identified as primary infection entry points, facilitating bacterial penetration and tumor formation. Environmental conditions such as high soil moisture and nursery crowding were found to favor disease incidence and spread. Pathogenicity tests on healthy rose cuttings reproduced typical crown gall symptoms, fulfilling Koch’s postulates and confirming the causal role of the isolates. The study highlights the complex etiology of crown gall disease in rose nurseries and emphasizes the importance of sanitation practices and use of pathogen-free planting material. Overall, the findings provide detailed insights into symptom expression and bacterial identity, contributing to improved disease diagnosis and management strategies in ornamental horticulture systems.