By E&T editorial staff

An intelligent field robot and X-ray technology, using sensors developed by the Fraunhofer Development Centre for X-ray Technology, are helping plant breeders select heat-tolerant plant varieties to sustain crop levels during extremely dry periods.

Climate change is causing major challenges for plant breeders. Summers are getting hotter, year on year: this summer, Germany experienced a heatwave with temperatures of up to 40°C.

The resulting drought inevitably affected plants. Given an ample supply of water, these plants can cool themselves via evaporation. However, they cannot do this when under drought stress. This is why plant breeders hope to develop heat-tolerant, drought-resistant plants that can survive with less water whilst still producing a good yield, using the smallest possible amount of fertiliser and pesticides.

The breeders have been receiving support from researchers at Fraunhofer EZRT, where for many years research has been carried out into technologies for determining plant phenotypes. This refers to their external appearance, which includes a multitude of factors such as leaf size, leaf arrangement, root thickness and yield.

“People have been selecting crops based on external characteristics for thousands of years,” explained Dr Stefan Gerth, head of application-specific methods and systems (AMS) at the Fraunhofer Development Centre for X-ray Technology. “We’re developing technologies to objectively measure these phenotype characteristics and optimise breeding based on this data.”

Gerth's research team has developed DeBiFix, a field robot (pictured) for agricultural applications. As DeBiFix makes its way through densely packed ears of wheat, it continuously takes X-ray images of the plants. At the same time, it generates 3D images using an optical system. This is important information for the breeder who owns the field in which the robot is working: it allows them to essentially look inside the ears of wheat and determine whether the variety they are cultivating will produce a good yield.

The most important objective of the trans-regional Fraunhofer smart farming project is to support breeders. As part of this project, the Fraunhofer Centre for Plant Phenotyping Technologies is being launched in Triesdorf, Bavaria. At this location, Dr Gerth and his colleagues intend to develop their expertise and translate it into real-life application. Triesdorf, Germany’s smallest town with a university, is home to agricultural teaching institutes and the Weihenstephan-Triesdorf University of Applied Science, making it a trans-regional centre for agriculture. Fraunhofer IIS works closely with the Competence Centre for Digital Agriculture located there.

In the lab cubicle for phenotyping plants in climate-controlled environments at Fraunhofer EZRT in Fürth, Gerth has demonstrated how breeders may work in the future. On a narrow conveyor belt in front of the X-ray machine, pots of various crop plants are arranged in neat rows. The door of the X-ray machine opens and a pot rolls inside. Once the door has closed, the pot undergoes a computed tomography scan, among other tests. Five minutes later, it’s time for the next pot.

“Over ten years ago, we started X-raying potato plants to get information about the tubers’ growth,” said Gerth. “Based on the 3D X-ray scans, we can determine the weight of the tubers without having to dig them up.” This process is being used for tasks such as selecting particularly heat-tolerant varieties. To this end, the plants are placed under heat stress inside the lab cubicle. The scans then show which plants deal with the stress most effectively, forming strong tubers in spite of the heat.

Whereas only thick roots and tubers could be X-rayed with the first computer tomography scans, the new systems can also capture the delicate underground root structure of wheat. “Our new X-ray machine is the most modern, powerful system for X-raying parts of plants underground,” said Gerth.

Researchers at Fraunhofer EZRT are also conducting 3D digital imaging of the parts of the plants that are above ground, such as leaves and ears of wheat. This data can be used to determine more than just the area of the leaf surface; the 3D images also provide information on the plant’s heat tolerance, answering crucial questions such as whether the plant raises its leaves to protect itself from the sun, or if it curls up its leaves due to stress.

The efficiency of Fraunhofer EZRT’s optical plant recognition systems has been demonstrated in a test field at the seed company Strube D&S. In this case, a 'BlueBob' prototype field robot was used. This field robot navigates by itself and automatically removes weeds in sugar beet fields. As it moves between the rows, it records images of all living plants using multispectral cameras.

“By using artificial intelligence, the phenotype of each individual plant is analysed and classified as either a weed or a beet plant,” explained Christian Hügel, head of the Technical Centre of Seed Research at Strube. If BlueBob 2.0 identifies a weed, it removes it from the ground with its hoeing tools. It removes weeds both between the rows (using static tools) and within the rows (using moving tools). As a result, almost all of the weeds around the beet plants are removed. This means the use of chemical weed killers can be drastically reduced.

One major work package at the new centre in Triesdorf will involve processing the data obtained during phenotyping. “Our main goal is to use our technology to support small and medium-sized plant breeders,” Gerth emphasised.

The challenge of feeding the planet's burgeoning population is a vexing one, requiring new engineering and technology solutions to address the issues.

In June this year, a Stanford University-led study suggested that cutting air pollution would improve the yields of common crops, due to the inhibiting effects of nitrogen oxides on plant growth and development. The most common air pollutants present in many countries, primarily due to vehicle exhaust emissions, have been shown to lower crop yields.

Earlier this year, it was also suggested that relocating farmland worldwide could drastically reduce carbon emissions. Scientists produced a map showing where the world’s major food crops should be grown in order to maximise yield and minimise environmental impact. This could capture large amounts of carbon, increase biodiversity and cut agricultural use of freshwater to zero.

Meanwhile, in order to make the green fields even greener - wherever they may be - an international research collaboration is looking at new ways of monitoring crop growth using biodegradable sensors, which can be composted at the end of their lifespan and thus reduce agricultural e-waste.

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