High tech for maximum quality: checking seed in the computed tomography scanner

In the lab with Sylvia Letsch

Top-quality seed is the key to achieving the very best yields. One of the central requirements for seed to produce high-yielding plants is for it to contain a healthy embryo. But experts can’t tell that from the outside of a seed. An ideal solution would be if they were able to look directly inside the sugarbeet seeds, which are just a few millimeters in size. And KWS’ seed experts enable such an examination with a 3D computed tomography scanner.

That procedure is necessary because, of course, not all the seeds of a sugarbeet plant are exactly identical. A small percentage of the seeds is empty or contains two embryos, called twins. That’s a completely natural consequence of biological variation. It’s impossible to tell that from just looking at the grayish-brown, star-shaped grains ranging in size from about three to six millimeters. If the farmer were to sow such seed in the field, there would be either empty spaces or two plants growing in the same spot. Both situations would reduce yield. Of course, that isn’t the desired outcome – for the farmer or the breeder.

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A look at the sample: Every single seed is recorded in the analysis.
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60 samples with a total of 18,000 seeds at one stroke.
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The samples are placed in the scanner. The detector is on the left wall and the radiation source is on the right.

Each batch is examined individually

Instead the goal is, where possible, for a single, strong plant to emerge from each seed. That is why KWS expends great time and effort to screen out unwanted seeds. After the seeds have been processed into the familiar orange pellets, just less than 30 percent of the original total are usually left over following the rigorous selection process. To control the process as well as possible, each batch is examined individually. The computed tomography scanner helps the experts in the seed quality lab.

The KWS expert Olaf Brinkmann opens the door to an austerely equipped laboratory room. A device developed by the Fraunhofer Society and about two cubic meters in size is located there. Only a handful of these “Seed Inspectors” are in use worldwide. The interior houses a weak source for X-rays and, opposite it, an X-ray detector. Installed between them are a small electric turntable and a robotic arm

The sugarbeet seed in different 3D representations inside the container.

Details to achieve maximum quality: 300 seeds at a glance. That is one of the results of the interaction between machine and software.

You’ve probably never seen sugarbeet seed in this way: its interior is revealed by the light of the X-ray source.

Two images a second

A representative number of seeds from a sample is analyzed in a small container. There are 60 containers on each tray our colleague Sylvia Letsch inserts into the scanner. Switching it on initiates a fully automated process that takes around six hours. The robotic arm places a container on the turntable every six minutes.

Subsequent rotation of the container in the X-ray beam generates three-dimensional images. The sensor takes about two images a second. A computer then pieces together the individual images into a three-dimensional picture of the sample. Because of the high resolution, the seed quality control experts under the lab’s head Sebastian Förster can look deep inside each individual grain.

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Large vibrating screeners are used to help prepare the seed. Its quality is repeatedly examined using the computed tomography scanner.
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The upshot is the pellet: the finished seed.
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The seed then goes to the packaging line.
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That’s how things should end up looking: no sugarbeet twins or gaps in the field due to empty seeds.

Always objective

Moreover, the algorithm specially developed for KWS’ purposes automatically recognizes and measures the multi-layered sheath, the embryo and small cavities in each single grain. The three-dimensional volume images therefore not only enable empty seeds to be identified, but also those with shriveled embryos. The machine is tireless and the software’s algorithm is always objective. The quality control lab examines more than 3.9 million seeds a season in order to live up to one of KWS’ key principles: the very best seed for farmers.

“After the analysis we know whether the batch in question has to undergo processing again so as to further reduce the number of twins or empty seeds. Severely shriveled embryos are also an indicator of lower seed quality. That may impact germination capacity. We screen out those contingents so as to increase quality,” says Sebastian Förster.

Progress for breeders

Breeders of new varieties also benefit from the computed tomography scanner at KWS’ headquarters in Einbeck in the German state of Lower Saxony. “Our colleagues in breeding also want to know what the filling ratio of their new sugarbeet lines is like. That’s important information and a key criterion for examining new varieties,” adds Förster. Experience shows that there’s enormous variation among sugarbeets: Some varieties deliver a very low yield of high-quality seeds, while with others most of the seed can be processed further into the familiar orange KWS pellets.

The computer has pieced together an animation of the examined seed from numerous images

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