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José Luis Araus, professor at the University of Barcelona's Faculty of Biology and member of Agrotecnio—CERCA center in agrotechnology—participated in a study showing that wheat varieties that perform best under ideal conditions (water, nutrients, temperature) also yield more in challenging environmental and agronomic situations, such as excessive heat or drought.

As a result of this discovery, researchers have considered how to breed more productive varieties, and point out that the most economical and efficient strategy to genetically improve crops is a two-step process: the first step is to select varieties with the highest yield potential, and the second step is to select varieties that are best adapted to the environment in which they will grow. This approach could lower costs, since it would reduce the number of sites needed to select advanced breeding lines.

The , a review of the scientific literature, published in Trends in Plant Science, involved researchers Alejandro del Pozo, from the University of Talca (Chile), and Victor Sadras, from the University of Adelaide (Australia).

A possible solution to a scientific debate

Increasing the yield potential of wheat and its resilience to factors such as drought or high temperatures—increasingly frequent due to climate change—is essential to feed a world population estimated to reach 9.5 billion people by 2050.

Genetic selection is essential in this challenge, but it is an iterative and slow process: it consists of crossing individuals with the best agronomic and physiological traits and selecting the most promising offspring over multiple generations.

The scientific debate about what is best is raging: some argue that selection is best based on the yield potential of the grain under optimal conditions, while others believe that it should be based on the grain's ability to adapt to stressful situations.

Araus considers that the results of the study show that selecting varieties in very severe environmental conditions "is not the best breeding strategy, as it can limit their performance. Taking into account physiological efficiency in the use of water (understood as the photosynthesis-transpiration ratio) would be negative in terms of productivity.

"On the other hand, what is good under optimal conditions is also good under less optimal conditions: a high-yielding candidate selected in the best environment will normally outperform varieties that have not been selected for their yield potential, and this will occur under a wide range of conditions, such as moderate drought."

The only exceptions would be in extremely stressful environments. But here too, Araus defends this strategy: "Even in a climate change environment such as the current one, in which we will encounter more and more extreme situations, it is necessary to go for this strategy, as the productivity of varieties developed under extreme conditions would not be profitable for European farmers."

A more cost-effective and efficient strategy

The study has allowed the researchers to establish the most appropriate strategy to carry out this genetic selection process. According to the results, the first phases—the first six or seven generations—should be focused on an optimal agronomic environment (with the best possible conditions) and the varieties would be selected considering the highest possible yield.

In the next phases, advanced lines with good agronomic traits would be sent for final selection to the specific area where they should be grown—for a couple of additional generations—to identify the most locally adapted varieties.

This approach would have two major advantages. The first would be economic, since "reducing the number of places to select advanced lines, prioritizing the development of well-managed crops in favorable environments, would also reduce the overall cost of varietal improvement worldwide," says Araus. The second advantage would be efficiency: selecting in optimal environments is more efficient, as it minimizes factors that can confound the breeder.

"If conditions are optimal, the genetic potential of the plant is better expressed. On the other hand, in suboptimal conditions (lack of water, unfertile soils or variable temperatures) there is more environmental noise, which makes it difficult to identify the best individuals," notes the UB professor.

Key agronomic and physiological traits

The study has also identified agronomic and physiological traits associated with better performance. "Some of the traits that make plants perform better, especially considering that water is the factor that most limits productivity, are those that increase the ability to capture water: it's not so much that they are very efficient at using water, but that they can use more than other varieties," explains Araus.

This can be achieved, for example, "with roots capable of exploring the soil in depth when there is no water or taking advantage of surface water when it rains or if the crop is irrigated," he points out.

The architecture of the crop is also key: the light must be distributed as evenly as possible between the upper and lower layers of the plants. "In order for all the leaves to contribute to the use of light, the upper leaves should be as vertical as possible to allow radiation to pass through and reach the most basal parts," the researcher explains.

Other determining factors would be the production of more ears per unit area, an increase in the number of grains, and a higher photosynthesis rate of the canopy per unit of solar radiation. "All this is achieved with the right architecture and good water uptake conditions that keep the stomata open," he stresses.

According to Araus, there is no "panacea or single feature," but rather a set of features to improve the efficiency of radiation and water use.

Finally, the study has also analyzed transgenic pathways to increase yield, but "so far, they have not yielded significant results." Moreover, "the results of adaptation to specific stress conditions such as drought are rather modest," concludes the researcher.