# Development and Validation of a Field-Based Colorimetric LAMP Assay for the Detection of Clavibacter michiganensis in Tomato Plants

## TL;DR

This study developed a portable, easy-to-use colorimetric LAMP test for detecting the tomato pathogen Clavibacter michiganensis in the field.

## Contribution

A novel field-ready colorimetric LAMP assay and device for rapid detection of Clavibacter michiganensis by untrained personnel.

## Key findings

- The cLAMP assay achieved high sensitivity (100 fg/reaction) and specificity for Clavibacter michiganensis.
- The assay performed reliably in plant extracts from different tomato varieties and experimentally inoculated seedlings.
- The developed method outperformed or matched traditional techniques like DAS-ELISA and PCR in detection limits.

## Abstract

Point-of-care diagnostics are revolutionizing the detection of plant pathogens by enabling rapid, on-site identification without the need for specialized laboratories. One of the tools used for this purpose is loop-mediated isothermal amplification (LAMP). LAMP is a powerful molecular technique increasingly used in pathogen control for its rapid, sensitive, and specific detection of plant pathogens. The aim of this study was the development of a novel, easy-to-use portable colorimetric LAMP (cLAMP) assay that could be used by inexperienced personnel for the detection of the pathogen Clavibacter michiganensis. The assay was combined with a newly constructed device in which LAMP can be performed in 30 min. Initially, a new set of LAMP primers targeting the micA gene was designed and evaluated the sensitivity (100 fg/reaction) and specificity of the assay. Next, the limit of detection (LoD) of two different commercial LAMP kits was compared with common laboratory detection techniques (DAS-ELISA, immunofluorescence, quantitative PCR, and PCR) using the same samples. Additionally, the LoD of the developed cLAMP assay was evaluated in bacterial suspensions and plant extracts spiked with C. michiganensis and validated the effect on the LoD of plant extracts from different tomato varieties. Lastly, its efficacy for C. michiganensis detection was assessed in experimentally inoculated tomato seedlings. The developed method for C. michiganensis detection can be used as a reliable tool for the early detection of the pathogen for field-based applications by untrained personnel.