Creating drought to test drought resistance

Testing new varieties in a greenhouse didn’t translate to field conditions so researchers built their own on-field drought

Plant breeders working on disease resistant varieties use irrigation to replicate high moisture conditions.

But what about plant breeders working on drought tolerant varieties? How do they simulate a drought?

As climate change brings drought to more areas of the world, plant breeders increasingly turn their attentions to developing crops that make better use of available moisture.

Just as a breeder working on disease resistance depends on adding moisture to trial plots, a breeder working on drought resistance depends on depriving trial plots of moisture to get proper phenotyping data.

However, all it takes is one unexpected rain to mess up the results for possibly thousands of tests.

The solution is to use shelters to create man-made drought.

These open-ended greenhouse structures allow researchers to control the amount of rain hitting certain test plots. Long rows of plants can be sheltered at one end and open at the other.

Usually mounted on rails, the shelters can be rolled over a crop when rain threatens.

Rain-out shelters have been around for more than 50 years, but making them portable is new.

Moveable rain-out shelters were developed by Australian researchers who saw that greenhouse results seldom transferred to outdoor reality. As well, the cost and permanent locations of rain-sheltered structures often created barriers to research.

“There are always variations between field and greenhouse experiments. That is especially the case for drought tolerance research,” said Surya Kant, a scientist with the Victoria state government who led the project.

“Developing tools to enable precise testing under natural field conditions is key for breeding water stress-tolerant crops.”

Soil Science Society of America work describing Kant’s efforts points out that greenhouse trials often use premade soil mixes that do not mimic conditions outside the greenhouse. Nor do greenhouse comparison trials account for wind, insects, disease, crop density, weeds and other natural factors.

Kant said the compounding of these factors created problems that breeders didn’t need.

“All of these differences add up,” Kant said. “Results from greenhouse experiments can potentially be un-reproducible in the field.”

The Australian rain-out shelters use lightweight steel arches and polyethylene covering. They’re based in plastic road barriers filled with water to act as foundations. The barriers can be emptied when the shelters need to be moved to a different soil setting.

“This lightweight, robust design allows the structures to be portable,” Kant said.

“They can be relocated to another research station to allow for crop rotation and experimental site changes. It also means the shelters maintain durability in all weather conditions, especially high winds.”

Availability of electric power is a challenge for experimental sites in remote areas. Kant’s design uses six portable 200-watt solar panels, a controller and four six-volt, 400-amp batteries. The shelters have rain sensors and surveillance cameras so that researchers can monitor their experiments remotely.

The sensors also allow a 700-watt motor to move the 20 by 10 metre shelters autonomously over the plots when moisture in the air is detected. Motion-activated cameras record the two-minute moves.

Water that falls on the poly covers is diverted away from the plots.

These features allow breeders to move variety trials into remote regions of the globe where drought tolerance crops are most needed.

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