A LAMP Assay for the On‐Site Identification of the Pathogens Xanthomonas campestris pv. campestris and 

ABSTRACT

Xanthomonas campestris , the causative agent of black rot and leaf spot disease in Brassicaceae , is a bacterial pathogen of international importance. It is seed‐borne and can cause a disease outbreak at low infection percentages of seed batches. Effective measures for controlling this pathogen rely mainly on early detection. In this study, we developed a loop‐mediated isothermal amplification (LAMP) identification assay for Xanthomonas campestris pv. campestris and pv. raphani in plant leaf material. We show that the assay is highly specific for these two pathovars and can detect approximately 10 ⁴⁻ 10 ⁵ cells/mL in Brassica plant material extract. In addition, an amplification control for the plant cytochrome c oxidase gene was added in a multiplex assay, effectively preventing false negative results. Finally, the multiplex assay was evaluated at a seed‐producing company using freeze‐dried primers, enzyme mixes and a portable detection device. In all cases, the pathogen could be identified in symptomatic plant material. Thus, the developed assay was confirmed as a quick and on‐site identification tool for X. campestris for use in seed production systems.