19 June 2024

Organic farming affects plant genetics

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A study by the University of Bonn shows how conventionally and organically grown barley plants develop differently. The latter experience adaptations in their genetic material

by Matteo Cavallito

 

The genetic material of plants can vary depending on the cultivation method used over the long term. This is the finding of a research conducted by the University of Bonn. The investigation, whose findings were published in the journal Agronomy for Sustainable Development, lasted more than 20 years.

“This long-term experiment highlights for the first time that allele frequency pattern difference between the conventional and organic populations grew with subsequent generations,” the study says. “Furthermore, the organic-adapted population showed a higher genetic heterogeneity.”

The experiment

The experiment started 23 years ago at the Institute of Crop Science and Resource Conservation (INRES) of the university. “We first crossed high-yield barley with a wild form to increase genetic variation,” explains Jens Léon, professor and lead author of the study in a statement released by the same university. “We then planted these populations on two neighboring fields so that the barley grew in the same soil and under the same climatic conditions.”

The two populations were grown using two different methods: conventional and organic farming. The impact of this choice on the genetic make-up was then assessed.

“A fraction of seeds harvested each year was sown the following year,” the study explains. “Various generations, up to the 23th were whole-genome pool-sequenced to identify adaptation patterns towards ecosystem and climate conditions in the allele frequency shifts.” Morevoer, “a meta-data analysis was conducted to link genomic regions’ increased fitness to agronomically related traits.”

Organic barley plants would be better adapted

The researchers focused on alleles, i.e. the different variants that occur within the same gene (to be clear, “For example, the human gene responsible for eye color exists in the alleles ‘brown’ and ‘blue’,” the researchers explain). The point, in short, is that the frequency with which certain alleles occur in a population can change over generations. Those associated with more favourable plant characteristics within a certain environment, in other words, tend to be more frequent. Genetic tests conducted in the course of the study found that in the first twelve years, the frequency of alleles in barley had changed equally in both fields.

In later years, however, organically grown barley developed root structure gene variants that made it less sensitive to nutrient or water deficit.

Conventionally grown barley has become genetically more uniform over time, whereas organically grown barley has remained more heterogeneous. The latter characteristic manifests itself in a wider availability of different alleles that can thus be thought of as distinct resources suited to multiple contexts. And, as such, it favours the plant’s ability to adapt to variable conditions.

The importance of adaptation

In summary, the authors conclude, “the results demonstrate the importance of cultivating varieties optimized for organic farming.” By adapting to these conditions, varieties will be more robust and produce higher yields. Especially, the authors emphasise, when it is possible to cross them with older or even wild varieties.

“In the context of climate change and agronomical transformations, wild forms contributed beneficial alleles to the population and, therefore, might be a valuable source for modern plant breeding,” the study concludes.