A portable field pathogen detection system for disease-free planting material
When it comes to preventing disease damage to crops, time is of the essence – but so is accuracy. This is why growers and crop experts need better means to accurately diagnose diseases and identify causal agents in the field without having to wait several days for laboratory results.
In a pioneering effort to meet this need, CIAT cassava scientist Elizabeth Alvarez has developed with her team a portable pathogen detection system. About the size of a small toolbox, it offers an immediate “yes” or “no” answer concerning the presence of particular pathogens in cassava fields.
“Contaminated planting materials are the main reason for rapid disease outbreak, particularly in vegetatively propagated crops like cassava,” said Alvarez. This is why we developed a kit that is sensitive enough for testing of seed and other planting materials to make sure they are disease free.”
To use this portable system requires only minimal training, in contrast with the more laborious methods used by skilled personnel to detect pathogens in sophisticated laboratories. The system works on the basis of loop mediated isothermal amplification (LAMP), an established technique that detects plant pathogens by amplifying the target nucleic acid sequence rapidly at a constant temperature without the use of a thermal cycling machine. This enables the system to test pathogens that cannot be cultured under lab conditions, as is the case with phytoplasmas.
The kit consists of a small metallic box with a small solar panel on top, which is connected to a 12V battery inside, where there is also a voltmeter with an on-off switch, a miniature heated water bath, and a test kit. The test kit includes lyophilized primers designed for the specific disease, one micro pipette to drain the samples, 0.2-ml micro centrifuge tubes, and mini envelope-sized pouches to evaluate 40 samples.
To determine the presence of a particular pathogen, you take a small sample from any part of the test plant, create a suspension with the buffer, add it to the reaction tube with a specific primer, and insert this into the water bath. After an hour, you can determine the result based on changes in color that indicate the pathogen’s presence or absence.
“It has taken a long time to design a pathogen detection system like this; it’s really a dream come true,” said Alvarez. “We want to make this system more useful for farmers in developing countries, especially women, so they have their own means to ensure that planting materials are disease free.”
Alvarez and her team initially designed the system to detect cassava frog skin disease associated pathogen, but they expect to adapt it for detecting other diseases of root and tuber crops as well.