Researchers from the Istituto di Genomica Applicata and elsewhere have released an improved genome assembly for Arabica coffee (Coffea arabica), a hybrid of Coffea eugenioides and Robusta coffee (Coffea canephora) that contributes to approximately 60% of world coffee production.
Coffea arabica is derived from the hybridization between the ancestors of present-day Coffea canephora and another closely related coffee species, Coffea eugenioides.
This hybridization resulted in Coffea arabica’s flavor and its large and complex genome, which poses challenges for breeding and genetic studies.
Several partial genome assemblies of Coffea arabica are currently available, but the mechanisms generating its genetic diversity are unclear.
Istituto di Genomica Applicata researchers Michele Morgante and Gabriele Di Gaspero and their colleagues employed the latest sequencing technologies to generate a more complete genome assembly for Coffea arabica, allowing for a detailed analysis of the structure of its chromosomes.
When analyzing the genome, including previously inaccessible regions, such as those around centromeres, they found differences in the structure, function and evolution of the genomes contributed by its two progenitor species, especially for genes involved in caffeine biosynthesis.
For the study, they also analyzed the genomes of 174 samples collected from different species within the Coffea genus and noticed a very low level of genetic diversity within Coffea arabica.
Diversity was found to increase in some Coffea arabica cultivars at specific genomic regions, due to two different sources of variation: chromosomal abnormalities and genetic segments donated by the so-called Timor hybrid, a Coffea arabica x Coffea canephora hybrid from East Timor.
This hybrid has become the parental line of many modern cultivars that combine the disease resistance trait of Coffea canephora and the unique flavor of Coffea arabica.
The authors suggest that the genetic diversity…
Read the full article here