Inheriting the Ability to Adapt

Diversity is nature's trump card. Grasslands, forests and fields in which diverse plant species grow and coexist are more productive and robust than monocultures, which consist of only one species. Such biodiversity results in plants being not only more productive and robust but also more resilient to environmental changes. These findings, among others, were impressively demonstrated by long-term research conducted at UZH by the now retired environmental scientist Bernhard Schmid.

Diversity also plays an important role in genetics: plant populations with a diverse gene pool can adapt relatively well to new surroundings and are more resilient to changes in their environment. This is not the case, however, for many of the crops that are currently cultivated around the globe. Rice, corn and wheat varieties have been bred to adapt to their local conditions to such an extent as to maximize their productivity. As a result, their genetic diversity has become increasingly lower. "Breeding has created a genetic bottleneck," says Ueli Grossniklaus, a plant geneticist and co-director of the University Research Priority Program Evolution in Action at UZH. He provides the following example: "The corn varieties that are currently planted in the United States, Italy and Switzerland are very different: they have been adapted to their local climate conditions and are thus relatively inflexible when it comes to large changes in climate." If environmental conditions change quickly, these plant varieties have limited capability to react. Furthermore, breeding new, adapted varieties is a complex process that requires a great deal of time.

This is why Grossniklaus is searching for new ways of developing crops for the future agricultural sector that are more flexible and more productive more quickly while at the same time taking advantage of the benefits of biodiversity. In other words, Grossniklaus is attempting to ease the genetic bottleneck and thus ensure more productive diversity in fields. This is desperately needed in view of climate change and the world's steadily increasing population.

Grossniklaus and his team are not the only ones conducting research in this area. Other research groups around the world such as Agroscope, Switzerland's federal center of excellence for agricultural research, are also investigating how farming productivity can benefit from the effects of diversity. Their approach involves planting a mixture of crop varieties, for example of wheat, in one field. Such mixed cultures, however, have their pitfalls. "A field should be as homogeneous as possible in order to cultivate it using modern farming practices," states Grossniklaus, "which means, for example, that plants need to flower at the same time and their seeds need to mature simultaneously." Achieving such timing with different varieties of plants so they can then be harvested at the same time is not easy. Despite this difficulty, researchers are beginning to experience success.

The environment influences these epigenetic processes. Research has shown that as identical (i.e. with the same genetic material) human twins age, their epigenomes become distinctly different - irrespective of their personal habits and circumstances. And in plants, certain epigenetic changes can have the exact same effect as genetic mutations, for example that they begin flowering later.

"Epigenetic changes, however, occur considerably faster and more often than genetic mutations," explains Grossniklaus. This has been demonstrated in experiments conducted with the model plant Arabidopsis thaliana (known as thale cress or mouse-ear cress). "While a mother and daughter plant differ from each other in only one single genetic mutation, there are thousands of epigenetic variations," states Grossniklaus. "These variations occur very quickly and very often." The question therefore arises as to whether researchers can use this fact when breeding plants in order to increase diversity within a plant variety and make the plants more adaptable.

In impressive laboratory experiments with thale cress, Grossniklaus and his team have demonstrated that this is fundamentally possible. They were able to prove that epigenetic traits - such as a plant variety's ability to adapt its flowering time - can be specifically selected and passed on over several generations. These findings unmistakably indicate that, essentially, epigenetics can be used in plant breeding.

Grossniklaus's team of plant researchers has also been able to demonstrate that epigenetic hybrids (i.e. plants descending from two parents with different epigenomes) are more productive (i.e. produce more seeds) than the parent plants. Known as heterosis, this phenomenon has already been observed in traditional plant breeding. The research conducted by UZH plant geneticists now demonstrates that it also occurs at the epigenetic level.