During a 23-year study at the University of Bonn, researchers found that organically grown barley genetically adapted to its environment, becoming genetically more diverse and healthy compared to conventionally grown barley. The study highlights the need to develop crop varieties specifically for organic farming to exploit these adaptive advantages. Credit: SciTechDaily.com
A research project conducted at the University of Bonn revealed the 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 cultivated barley in two adjacent fields, using conventional farming techniques on one and organic practices on the other.
For more than 20 years, organic barley has been enriched with specific genetic material that differs from the comparative crop. Among other things, the results show how important it is to cultivate 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 Leon began an experiment at the University of Bonn that he knew would last for a long time. His research group wanted to study the effects that growing conditions have on the genetic material in plants. To this end, they conducted a complex long-term study over a period of 23 years at the Institute of Crop Production and Resource Conservation (INRES). “We first crossed a high-yielding barley with a wild form to increase the genetic variation,” Leon says. “We then planted these populations in two adjacent fields so that the barley would grow in the same soil and under the same climatic conditions.”
The image above depicts the conventional population on the left and the organic barley on the right: Only experts can see the differences with the naked eye. However, vast differences can be identified using molecular genetics. By credit card: AG Prof. Leon/University of Bonn
The only difference was the method of cultivation. Conventional farming was used in one of the fields, where the researchers used pesticides to control pests, chemical agents to eliminate weeds and mineral fertilizers to ensure a good supply of nutrients. Researchers are taking a greener approach in the other area: no pesticides, weed control by mechanical methods, and fertilizing the soil with manure from stables
Some of the grain was saved each fall to seed the fields the following spring – using the organic grain in the organic field and conventionally grown barley in the comparison field. “However, we did not select the beans based on any specific characteristics, but simply selected a small portion of the crop at random,” emphasizes Leon’s colleague Dr. Michael Schneider.
Analyzing genome evolution over time
Researchers also analyze the genomes of conventionally and organically grown plants on an annual basis. Any single gene can exist in many different forms, called alleles. For example, the human gene responsible for eye color exists in the ‘brown’ and ‘blue’ alleles. The frequency with which certain alleles occur in a population can change over generations. Environmental conditions are one factor that plays a role in this process: The alleles that ensure that plants thrive in their current environment tend to become more common.
The researchers identified two interesting trends in their genetic tests: During the first twelve years, allele frequencies in barley changed in the same way in both fields. “Our interpretation of this finding is that the highly diverse populations caused by crossing with wild barley are adapting to local conditions,” says Dr. Agim Balvora, who was also involved in the study.
“After all, factors such as climate, soil and especially day length are identical for both populations.” However, the allele frequencies of the two crops diverged more and more over the following years. In particular, barley grown using organic farming methods has developed gene variants that are less sensitive to nutrient deficiencies or lack of water—i.e. alleles that affect root structure. “One of the reasons for this is probably the strong variation in nutrient availability in organic farming,” Leon says.
Genetic heterogeneity facilitates the process of adaptation
Conventionally grown barley also became more genetically uniform over time, meaning that the genetic material in individual plants grown in the field became more similar from year to year. However, organic barley remains more heterogeneous. Organic crop allele frequencies also varied more widely over time. This resulted in some years being extremely favorable or unfavorable for some alleles.
This may be because environmental conditions vary much more in organic farming than in conventional framing methods: if certain plant diseases prevail in one year, for example, plants will rely most heavily on those alleles that who will protect them. Variability in environmental forces acting on plants appears to result in greater genetic heterogeneity. “As a result, plants are better able to adapt to these kinds of changes,” Leon says.
Overall, the results demonstrate the importance of cultivating cultivars optimized for organic farming. Because their genetic makeup has adapted to these conditions, they will be healthier and produce higher yields. “Also, it seems to make sense when you cultivate plants to cross them with older or even wild varieties,” explains Leon. “Our data also show that it may even benefit conventional high-yielding 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 Balvora, and Jens Leon, 8 May 2024. Agronomy for sustainable development.
DOI: 10.1007/s13593-024-00962-8
The study was funded by the German Research Foundation (DFG).
