Chromosome mutations in coffee: the potential for the industry
When you consume Arabica coffee from different parts of the world and taste the difference between them, you may think that this difference is due to the genes present in the beans.
This, according to a recent study published in the journal Nature Communications, is a misconception. Although different gene frequencies control taste, it is chromosomal mutations that lead to these frequency differences.
Steaming cup of chromosomes
Arabica, unlike Robusta, has more than two copies of each chromosome, a phenomenon known as polyploidy. This makes it difficult to cross Arabica with other species (where most genetic variation comes from), meaning that the main source of variation between varieties of these coffee beans is mutation. These mutations occur at a constant rate.
Over the past 50,000 years, Arabica was created by the fusion of Coffea canephora (robusta) and a strain called Coffea eugenioides. The variations explain the mutations of the chromosomes since this event.
Arabica and Robusta
There are two main types of beans used to brew coffee: Arabica, which is generally considered the more high-quality of the two and accounts for 60% of coffee sold, and Robusta, which makes up the remainder.
However, due to climate change, Arabica, which must be grown at higher altitudes, is now more difficult to cultivate. Arabica must grow below a certain temperature threshold, which rising global temperatures are making rarer. Thus, the more resistant Robusta is taking an increasing share of the market.
By examining a number of different Arabica varieties, researchers discovered not only variations in taste, but also variations in functions such as disease resistance. They also found in some cases, such as in the Bourbon arabica variety, chromosomal rearrangements, extra copies of chromosomes, missing chromosome fragments (deletions), and in some cases entire chromosomes missing.
“We identified chromosomal aberrations of different types as a major source of genetic variation in Coffea arabica. These mutations occur randomly during meiosis, the process that leads to the production of gametes (reproductive cells) probably with a higher frequency in Coffea arabica due to its tetraploid nature (having four sets of chromosomes),” plant geneticist Michele Morgante, one of the researchers on the study, told FoodNavigator.
It’s difficult, Morgante admits, to determine how these mutations affect taste between varieties. “Chromosomal differences result in copy number differences between eugenioides and canephora-derived genes. If the properties of genes derived from Canephora and Eugenioides in terms of expression or protein product are different, then this could result in qualitative differences translating into differences in taste.
“Since eugenioides and canephora genes often have different properties in terms of expression or protein product, with all four genes originating from one or the other, whether these genes are involved in the traits quality of the bean, like many genes involved in secondary metabolism, they could determine qualitative differences which translate into differences in taste.
Can the industry benefit from it?
These discoveries could have considerable consequences for the industry. According to Kassahun Tesfaye, one of the researchers, understanding the genome could offer all sorts of benefits to producers, such as allowing coffee breeders to select for low caffeine levels or resistance to fungi such as coffee rust.
“There are treatments known to increase the frequency of chromosomal aberrations of different kinds, such as in vitro culture of plant cells followed by regeneration of whole plants,” Morgante added.
Is too much caffeine risky?
Research into the mutations opens up the possibility for growers to select low-caffeine varieties. This could be an important development, because according to a new study from the US Food and Drug Administration (FDA), excessive caffeine consumption can be dangerous for your health, although much depends on the individual in question.
For healthy adults, 400 milligrams per day is a roughly safe amount, according to the FDA. That’s about four or five cups of coffee.
“The industry could analyze Arabica germplasm for varieties/genotypes with chromosomal aberrations that could form the starting material for improved varieties, but could also, as explained above, engage in programs inducing novel chromosomal aberrations to increase the genetic variation of the species and improve either quality or sustainability characteristics. Germplasm is the term used to describe plants, plant parts, or seeds used in plant breeding research and cultivation efforts.
However, according to the industry itself, it is too early to tell. Nestlé said it had not yet determined whether the study would have a practical impact.
“The correlations between chromosome rearrangement and differences in flavor notes are not yet known enough to impact how we grow Arabica beans. Although the findings in this paper are very informative at an academic level, the direct implication on Arabica cultivation cannot yet be estimated,” a Nestlé spokesperson told FoodNavigator.
Still, a better understanding of how the genome is organized could prove useful, Nestlé said. “Since our abilities to identify genes and molecular markers associated with traits are linked to the quality of the genome assembly we use, this study is useful but will require additional research to select low-density coffee varieties. caffeine and/or disease resistant. »
Sourced from: Nature Communications
“A chromosome-scale assembly reveals chromosomal aberrations and exchanges generating genetic diversity in the genetic material of Coffea arabica”
Published on: January 23, 2024
I am: https://doi.org/10.1038/s41467-023-44449-8
Authors: S. Scalabrin, G. Magris, M. Liva, N. Vitulo, M. Vidotto, D. Scaglione, L. Del Terra, MR Ruosi, L. Navarini, G. Pellegrino, JC Berny Mier y Teran, L. Toniutti, RS Liverani, M. Cerutti, R. Di Gaspero and M. Morgante
Sourced from: natural foods
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I am: https://doi.org/10.1038/s43016-022-00614-8
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