With the scanner, into the terra incognita: How do you watch roots grow?

In the field: Benjamin Gruber prepares the scanner for detecting the root system underground.

The depths of the ocean are probably better explored than the finely branched roots of plants in the ground. It is the roots that decide how well corn, beets or other plants absorb water and nutrients from the soil. So, to some extent, they can help explain how much the farmer needs to irrigate or fertilize. Therefore, roots are an important factor in the breeding of drought-tolerant or nitrogen-efficient new plant species.

How well do plants cope with stress?

In the KWS research department, the Australian Benjamin Gruber and his colleagues explain how root growth can be observed, assessed and quantified. His goal is to test hundreds of plants in a short period of time, to see how well they cope with abiotic stress such as drought or lack of nutrients. This is one of the prerequisites when identifying new plant genes that can support stable yields and drought tolerance. Both are major breeding goals at KWS.

Observing roots and their growth in detail is not trivial: 10.76 square feet of grain field often contains 31 to 60 miles of roots (about 25 to 37 miles for corn, and 12.4 to 31 miles for sugarbeet). Sugarbeet roots protrude up to 16.4 feet deep into the earth. The finest root hairs are consistently thinner than a human hair. How can you achieve an accurate picture?

Dig, rinse and measure

A proven approach with corn follows the comparatively simple, and aptly named “shovelomics” approach: The plant with the root still on it is simply dug up during this “shovel research” and the soil is thoroughly rinsed off. Then, the root can be optically measured with cameras and software. From multiple images, specialists in image analysis and bioinformaticians calculate the number and thickness of the roots and their angle relative to the stem of the plant.

Into the deep: The scanner disappears into the soil.

Auch Angaben zur Verzweigung der Haupt- und Nebenwurzeln und viele weitere Merkmale werden erfasst. „Mit einer oder nur wenigen Pflanzen ließe sich das auch per Augenschein erledigen. Aber um ein wirksames Werkzeug für die Pflanzenzüchtung zu schaffen, müssen wir hunderte oder tausende Wurzeln erfassen. Das ist nur digital und automatisiert zu schaffen“, sagt Gruber. Beim Vermessen der Wurzelkrone arbeitet sein Team mit dem Forschungszentrum Jülich zusammen. Das ist nicht die einzige Kooperation: KWS kooperiert international mit vielen Partnern. Dazu gehören Universitäten, andere Institute oder auch Unternehmen.

Bilder aus der Tiefe

Nach dieser Art des Forschens mit der Schaufel in der Hand, ist die untersuchte Pflanze allerdings nicht mehr zu gebrauchen. Sehr viel besser wäre das fortlaufende Beobachten unter realen Bedingungen auf, respektive im Feld. Dafür lässt Gruber mit einem Spezialbohrer Löcher in den Grund von Rübenparzellen bohren. Anschließend steckt er durchsichtige Röhren in die Erde. Durch sie hindurch kann ein spezieller Scanner die wachsenden Wurzeln abfotografieren. Wer im Abstand von Tagen oder Wochen scannt, erhält ein fortlaufendes Bild aus der Tiefe.

Was einfach klingt, hat viele Versuche, Varianten und Veränderungen zur Grundlage. Die Mitarbeiter der KWS Werkstatt sind es gewöhnt, dass Gruber häufig mit Spezialaufträgen zu ihnen kommt. Und überhaupt, alleine käme er nicht weit, sagt der Biotechnologe. Feldarbeiter helfen beim Bohren der Löcher. Mehrere Züchter geben Hinweise auf gewünschte Merkmale und gesuchte Eigenschaften der Pflanzen. Die Bilderkennungsspezialisten von KWS tragen ihren Teil zum Erkennen des Wurzelsystems bei. Moderne Pflanzenzüchtung wird nur im Zusammenspiel vieler Experten möglich.

People at KWS

Exploring the roots opens up enormous potential for plant breeders.

Benjamin Gruber, Root researcher

“KWS is currently creating a new toolbox to capture root growth on a large scale. We test new processes and refine what has already been proven. Later, we need to understand which plant with which genetic makeup grows in which soil, and with which nutrient and water supply,” said Gruber. This costs time and money. Both are investments in the future of a company that has existed for more than 160 years and continues to offer growers high-yielding varieties. Family-oriented KWS spends about 17 percent of its revenue on research.

Breeding requires accurate observation.

Exact observation of plant traits, with the purpose of deriving impressions for breeding, is as old as agriculture itself. For example, the first farmers sowed from the thickest grains of the previous year for the next year. Gregor Mendel observed the color and shape of peas to establish his inheritance rules based on these results. With regard to the visible and measurable properties of plants, biologists talk about phenotypes.

Ben Gruber’s approach is similar to other phenotyping projects at KWS. KWS research experts collect data in the environment, either with drone-based cameras or underground scanners. The images are collected on a computer and automatically analyzed to give new clues to the breeders. “All of this has to work on an industrial scale, in wind and rain, in mud and in drought, not just in a lab or with 20 plants. Plant breeding is always a question of large numbers, and thousands of plants must be evaluated,” explained Gruber, before he returned to the statistical analysis of his data.

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