Wetenschap - 5 april 2001

Meter counts pathogens one by one - at lightning speed

Meter counts pathogens one by one - at lightning speed

Luiz Chitarra will soon be returning to Brazil with his doctorate. In the four years that he spent at Plant Research International he developed a method that seed companies can use to determine very quickly whether pathogens are present in their products. The method is based on medical technology.

One of the worst things that can happen to farmers is that seed is contaminated with a disease and as a result the harvest is already doomed to failure at the time of sowing. Seed companies are therefore very interested in techniques which can trace bacteria, such as those that cause black rot in cabbage or bacterial canker in tomato. Methods used by scientists up to now have either been inaccurate or time-consuming.

Narrow tube

The principle behind Chitarra's method is simple: a substance is added to an extract of the plant seed, which only attaches itself to the dangerous bacteria. This substance makes the pathogens light up. The seed extract is then passed through a flow cytometer. This is a narrow tube that lets all solid particles in the fluid through one by one and records them. The cytometer only counts the fluorescent particles: the pathogens. It is also in theory possible to treat the seed extract with other substances which light up the dead pathogens with a different colour than the living ones. This would enable the scientists to calculate the chance that a crop will become sick.

Chitarra received his PhD on 28 March for 'Fluorescence techniques to detect and to assess viability of plant pathogenic bacteria'. He was supervised by Professor Frans Rombouts of the Food Hygiene and Microbiology Group.

Willem Koert