News Excerpt:

Based on a chromosome-level assembly, a study reveals the sources of genetic diversity of Arabica coffee; the genetic diversity may contribute to its unique flavour and resistance to pathogens.

Key highlights of the study:

• Researchers employed the latest sequencing technologies to generate a more complete genome assembly for Arabica coffee, allowing for a detailed analysis of the structure of its chromosomes.
• While analysing the genome, 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.
• They analysed the genomes of 174 samples collected from different species within the Coffea genus and noticed a very low level of genetic diversity within Arabica coffee.
• Diversity was found to increase in some Arabica coffee cultivars at specific genomic regions, due to two different sources of variation: chromosomal abnormalities and genetic segments donated by a Robusta-Arabica hybrid, known as the Timor Hybrid. 
• This hybrid has become the parental line of many modern cultivars that combine the disease resistance trait of Robusta coffee and the unique flavour of Arabica coffee.

About Coffee beans:

• Coffee beans come from the coffee plant, a bush-like plant which can get very tall.
• On average, it takes around one year for the coffee plant to begin to produce fragrant, white flowers, then up to four years later before it begins to bear fruit.
• It takes around 10 years for these plants to begin producing coffee beans on a commercial level.
• The general lifespan of the coffee plant occurs between 30 to 40 years.
• Once they’re ripe and ready for picking they turn red in colour.
• Most coffee plants are grown around the ‘the bean belt’, an area around the equator between the tropics of Capricorn and Cancer.
• Temperature from 15°C to 28°C, hot and humid climate, and rainfall from 150 to 250 cm provide ideal conditions for coffee cultivation.
• Presence of humus and minerals (iron, calcium), well-drained loamy soils are suitable for cultivation of coffee beans.
• The coffee capitals of the world such as Brazil, Vietnam, Colombia, Indonesia and Ethiopia, as these are the locations where coffee’s given the perfect growing conditions to thrive.
• The location of where coffee beans are grown can alter the taste. 
• Things such as climate, elevation and even soil type can impact the flavour of the coffee the beans produce.
• Snowfall, temperatures greater than 30°C, and strong sunlight are not suitable for coffee cultivation.

Varieties of Coffee Beans:

• There’s over 120 varieties of coffee plants and each produces a different type of coffee bean. 
  • However the majority of the coffee comes from just two variants, Robusta (also known as Coffea Robusta or Coffea Canephora) or Arabica (Coffea Arabica) or a blend of the two.
• Arabica Coffee:
  • About 60% of global coffee production is from the Arabica coffee species.
  • Arabica coffee is derived from the hybridisation between the ancestors of present-day Robusta coffee and another closely related coffee species, Coffea eugeniodes.
  • The beans are generally oval in shape, have a pronounced centre crease and are larger than Robusta beans.
  • Typically, Arabica coffee beans are grown at altitudes between 500m and 2500m and have low caffeine content. 
  • Latin America, specifically Brazil, is one of the largest producers of Arabica coffee.

• Robusta Coffee:

• Commonly grown in Africa, Vietnam and Indonesia, Robusta has lower acidity levels than Arabica coffee, meaning it generally tastes much less sweet. 
• Due to its simpler acidity and deeper and stronger flavour compounds, Robusta can produce tones of wood or burnt rubber.
• Robustas are grown in altitudes of no more than 1000m, and they produce fruit much more quickly than the Arabicas, which need several years to come to maturity, and they yield more crop per tree. 
• They are less vulnerable to pests and weather conditions and this is the main reason why they are on average cheaper than Arabicas. 
• Robusta coffee beans have a higher caffeine content.
• Coffee beans from the Robusta species are generally smaller and more circular than Arabica beans. 
• They are also usually paler, and the centre crease is less pronounced.

Conclusion:

Researchers suggest that the genetic diversity of Arabica coffee is essential for its commercial success, and the findings may help develop new coffee varieties with desirable traits, such as disease resistance or different flavour profiles.