Research shows that organic farming changes the genetic code of plants

Genetics of barley plants

During a 23-year study at the University of Bonn, researchers found that organically grown barley has genetically adapted to its environment and become genetically more diverse and robust compared to conventionally grown barley. The study highlights the need to develop crop varieties specifically for organic farming to leverage these adaptive benefits. Credit:

A research project conducted at the University of Bonn reveals differences in plant growth under organic and conventional farming methods.

A long-term study at the University of Bonn has shown that plants can genetically adapt to the specific conditions of organic farming. In the study, researchers grew barley in two adjacent fields, applying conventional farming techniques to one and organic practices to the other.

Over the course of more than twenty years, the organic barley was enriched with specific genetic material that differed from the comparative culture. The results show, among other things, how important it is to grow varieties, especially for organic farming. The results have now been published in the journal Agronomy for sustainable development.

In the late 1990s, Prof. Dr. Jens Léon started an experiment at the University of Bonn that he knew would last a long time. His research group wanted to investigate the effects of agricultural conditions on genetic material in plants. To this end, they conducted a complex long-term study at the Institute of Crop Science and Resource Conservation (INRES) over a period of 23 years. “We first crossed high-yielding barley with a wild form to increase genetic variation,” says Léon. “We then planted these populations in two adjacent fields, so that the barley grew on the same soil and under the same climatic conditions.”

Organic vs. conventional barley

In the image above, the conventional population is shown on the left and the organic barley on the right: only experts can see the differences with the naked eye. However, with the help of molecular genetics, enormous differences can be identified. Credit: AG Prof. Léon/University of Bonn

The only difference was the farming method. Conventional agriculture was practiced in one of the fields where the researchers used pesticides to control pests, chemicals to remove weeds and mineral fertilizers to ensure a good supply of nutrients. In the other area, the researchers opted for a more ecologically responsible approach: no pesticides, mechanical weed control and fertilizing the soil with farmyard manure.

Some of the grains were saved each fall to sow the fields the following spring – using the organic grains in the organic field and the barley grown under conventional conditions in the comparison field. “However, we did not choose the grains based on certain characteristics, but simply randomly selected a small part of the harvest,” emphasizes Léon’s colleague Dr. Michael Schneider.

Analyzing genome development in time-lapse

The researchers also analyzed the genomes of conventionally and organically grown plants every year. Each individual gene can exist in different forms, called alleles. For example, the human gene responsible for eye color consists of the alleles ‘brown’ and ‘blue’. The frequency with which certain alleles occur in a population can change from generation to generation. Environmental conditions are one factor that plays a role in this process: alleles that allow plants to thrive in their current environment tend to be found more and more often.

The researchers identified two interesting trends in their genetic tests: Over the first twelve years, the allele frequency in the barley changed in the same way in both fields. “Our interpretation of this finding is that the highly diverse populations caused by crossbreeding with wild barley adapted to local conditions,” says Dr Agim Ballvora, who also took part in the study.

“Factors such as the climate, the soil and especially the day length were identical for both populations.” However, the allele frequencies of the two cultures increasingly diverged in subsequent years. In particular, barley grown using organic farming methods developed gene variants that were less sensitive to nutrient deficiency or water deficiency – that is, alleles that affected the structure of the roots. “One reason for this is probably the strong differences in the availability of nutrients in organic agriculture,” says Léon.

Genetic heterogeneity facilitates the adaptation process

The conventionally grown barley also became more genetically uniform over time, meaning that the genetic material in the individual plants grown in the field became more and more similar from year to year. However, the organic barley remained more heterogeneous. Organic culture allele frequencies also varied more over time. This resulted in some years being extremely favorable or unfavorable for some alleles.

This could be because environmental conditions in organic farming fluctuate much more than in conventional framing methods: for example, if certain plant diseases manifest within a year, the plants will be most dependent on the alleles that will protect them. The variability of environmental forces acting on plants appears to lead to greater genetic heterogeneity. “This allows the plants to adapt better to these types of changes,” says Léon.

Overall, the results demonstrate the importance of growing varieties optimized for organic farming. As their genetic makeup adapts to these conditions, they will be more robust and produce higher yields. “Moreover, when growing plants, it seems useful to cross them with older or even wild varieties,” Léon explains. “Our data also indicates that this could even benefit high-yielding conventional varieties.”

Reference: “Deep genotyping reveals specific adaptive footprints of conventional and organic farming in barley populations – an evolutionary approach to plant breeding” by Michael Schneider, Agim Ballvora and Jens Léon, May 8, 2024, Agronomy for sustainable development.
DOI: 10.1007/s13593-024-00962-8

The research was funded by the German Research Foundation (DFG).

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