Interception of Xanthomonas campestris pv. dieffenbachiae on Anthurium Plants from the Netherlands

Xanthomonas campestris pv. dieffenbachiae, the causal agent of anthurium bacterial blight, is a major concern of the anthurium industry worldwide. This pathogen has many hosts in the family Araceae (e.g., Anthurium, Dieffenbachia, Syngonium, Aglaonema, Philodendron, Xanthosoma, Caladium, and Colocasia). Most anthurium cultivars are susceptible to bacterial blight, making it very difficult to manage the disease once introduced to a production area. Therefore, sanitation and exclusion of the pathogen through pathogen-free propagative stock are vital aspects of anthurium cultivation. The anthurium industry is expanding in India, and as many new cultivars are being imported, the plant material is subject to thorough quarantine inspection at the port of arrival. During routine inspections on three separate occasions, Anthurium andreanum plants imported from The Netherlands had watersoaked spots at leaf margins bordered by chlorotic or necrotic zones. Xanthomonas-like colonies were isolated from four different cultivars with semiselective media (2). Bacteriological tests confirmed that the cultures were X. campestris. Pathogenicity tests, performed by rubbing leaves with a cotton swab dipped into a suspension of the bacteria (approx. 10⁷ CFU/ml), resulted in production of leafspots in 6 days and early blight symptoms in 10 to 12 days. The bacterium was further identified as X. campestris by carbon source utilization (similarity coefficient = 0.582; Biolog, Hayward, CA). Enzyme-linked immunosorbent assay reaction patterns with a panel of monoclonal antibodies for X. campestris pv. dieffenbachiae designated as Xcd1 (clone 72E-E3-B9-C5, isotype IgG2a), Xcd2 (clone 97-2-1-01, isotype IgM), Xcd3 (clone 72B-F9-B6-E9, isotype IgM), Xcd7 (clone72D-E10-C2-D9, isotype IgM), T1 (clone 92-16, isotype IgM), and T2 (clone 92-59-1-1, isotype IgG) showed that the intercepted strain belong to the serogroup 5 of X. campestris pv. dieffenbachiae (1). This pathogen is not known to occur in India, and there is high probability of risk of introduction through large-scale import of anthurium plants with either visible or latent infections. References: (1) R. L. Lipp et al. Phytopathology 82:677, 1992. (2) D. J. Norman and A. Alvarez. Plant Dis. 73:654, 1989.