Genetic improvement of agricultural crops has mostly focused on increasing the yield of each variety. But what if it were also possible to select plants by the effect they leave on the following crop? Researchers at the University of Queensland in Australia argue that this approach could open a new front in agricultural breeding and help reduce the need for fertilizers.
A investigation started from a simple idea: each crop leaves a kind of “legacy” in the soil, influencing nutrients, water availability, soil structure, and microbial communities. Therefore, the researchers wanted to understand whether these differences also have a genetic component that could be used in developing new varieties.
In a field trial conducted in southern Queensland, the team grew more than 300 genetically distinct types of mung bean and, subsequently, planted the same wheat variety in all plots. The results showed significant differences in wheat performance depending on the mung bean variety that had been grown previously.
“Some mung beans increased the yield of the following wheat by 45%, while others reduced it by half,” explains Millicent Smith, a researcher at the Queensland Alliance for Agriculture and Food Innovation.
Across the set of trials, the differences in wheat yield reached up to one tonne per hectare, showing that the choice of variety used in the first crop can have significant consequences for the next.
Genes Also Influence Rotation
The team identified specific regions of the mung bean genome associated with the performance of the following wheat crop. The results therefore suggest that the effects of crop rotations do not depend solely on the species chosen or the management practices, but also on the genetic characteristics of the varieties used.
“It is striking that some of these regions act against one another: the same genes that make a crop more productive may be the same ones that leave fewer resources in the soil for the next crop,” says Lee Hickey, a plant breeder and crop geneticist at the University of Queensland.
The researchers also simulated a scenario in which genetic selection would simultaneously take into account the yield of mung bean and the yield of the subsequently grown wheat. The model pointed to gains in both crops, suggesting that breeding could be directed toward the productivity of the entire agricultural system, not just the performance of a single crop.
According to Millicent Smith, the results show that the effect is real and heritable, but it is still necessary to understand the biological mechanisms that underlie it.
“We have shown that the effect is real and heritable, but we still do not know what is causing it. The next step is to understand the biology behind this phenomenon, and that will require an effort from the entire scientific community,” she says.
The team believes that the same approach could be applied to other rotations, including canola and wheat or chickpea and barley. The development of tools such as drones, genomics, crop models and greater computing power is enabling the study of these interactions at the scale required for genetic improvement.
“Each crop leaves a legacy, and we believe the time has come to start harnessing it,” concludes the researcher.
