Sensors are everywhere nowadays – and not just in horticulture. So why do we still need laboratories? That’s the question Ines van Marrewijk of Normec Groen Agro Control asked at the International Propagation Seminar of Grodan last week. “Most of the time, lab equipment is much more expensive than sensors, and data needs to be validated and credited, especially when legislation is involved.”
In short, laboratories have earned their place, and for Normec Groen Agro Control, it all started about thirty years ago, with researching water quality. “Back then, UV was one of the standards in water purification, and we did research into that – but we also do nutrition and residue analysis. Personally, I’m also responsible for monitoring systems for GlobalGAP.”
Ines then went on to talk about some of their research methods, for instance using gas tubes can be used to ‘simulate’ ethylene or fluoride in greenhouses, and researching their impact on the crop. “We also have our own trial greenhouses, where we look at the effects of substances on crops.”
Methods for testing plant diseases
Next, Ines discussed several methods of testing for plant diseases. “First there comes visual: when you have good eyes, you can get an idea of what’s going on with your plant. We also do that in the laboratory, for example by using a microscope, to narrow down the scope of analysis: is it a virus, an insect, or perhaps nutrition deficiency?”
Then there are quick tests, which can be used by the grower, but they’re also used by laboratory technicians. When the grower uses quick tests, it’s important to do it properly: “When you use too many leaves, or you add too much water, you can end up with false positives, even when the sample is negative in the viruses. That’s why we also develop better protocols, to get better results from those quick tests.”
‘Old-fashioned’ agar plates
At Normec Groen Agro Control, they also use a lot of agar plates. “That may seem a little bit old-fashioned, but we use them a lot, especially for water quality measurements. After all, plate count is the living thing. PCRs and Elisa tests detect DNA material or RNA material, but in the water, you want to know whether it’s dead or alive DNA or RNA.”
That’s where agar plates come in – although they can’t be used to detect plant viruses, they can be used for “germ counts on general fungi. And for Phytophthora and Pythium, we developed our own plate.”
Elisa
Another testing method is Elisa, which works with antibodies. “Those search for a protein of a specific virus. Every virus has its own specific protein, and this antibody reacts with it. Upon reaction, the test will colour yellow, and by the intensity of yellow, you can even identify specific pathogens.”
Elisa tests played a major role in discovering the global ToBRFV outbreak. “Elisa tests for the tomato mosaic virus, ELISA-TMV showed a lot of positive results at once, which put the world on alert.” Specific Elisa tests were even developed for ToBRFV, although those aren’t that good, Ines explains. “For ToBRFV, it’s better to use PCR tests, which are more sensitive.”
PCR to test for ToBRFV
As Ines already explained, PCR tests are better at detecting ToBRFV, which is why Normec Groen Agro Control developed their own PCR tests. That these are becoming the standard, is also emphasized by the International Seed Federation, which stipulates that PCR tests must be used when testing seeds for ToBRFV.
Those PCR tests can be carried out on plant material or on water, Ines goes on to explain. There is also the option to use Bio-PCR tests, where water is tested for purity by smearing some on plants and seeing what happens to them, but that method is a bit too complicated for growers to do themselves. “If you want to test your water for purity, be sure to check it for Fusarium and Pythium – all the living counts of pathogens. Are all the pathogens dead? Then you’ll know the viruses are probably also dead.”
For more information:
Normec Groen Agro Control
Distributieweg 1
2645 EG, Delfgauw
Tel.: +31 15 257 25 11
Mob.: +31 6 11347778
www.agrocontrol.nl
ines.van.marrewijk@normecgroup.com