Bourbon, Caturra, SL28 and Typica

The story of Arabica coffee begins with two primary matriarchs: Typica and Bourbon. Genetic research confirms that the majority of the world's Arabica coffee descends from these two ancient cultivars, which were originally transported from Ethiopia to Yemen and subsequently spread globally. Typica is the original variety from which many others evolved, while Bourbon emerged as a natural mutation after Typica plants were introduced to Réunion Island, then known as Bourbon Island. These two lineages form the genetic backbone of the global coffee industry, particularly in Latin America, where they account for the vast majority of production.

Caturra is a significant descendant of this lineage, discovered in Brazil between 1915 and 1918 as a natural dwarf mutation of the Bourbon variety. This single-gene mutation results in a compact plant stature, which allows for higher planting density and easier harvesting. Because it retains much of the Bourbon cup profile—characterized by bright acidity and sweetness—it became a staple for smallholder farmers in Central America. However, like its parent, Caturra is highly susceptible to coffee leaf rust, a major challenge for producers managing these traditional varieties.

In East Africa, the story took a different turn with the development of the SL series in Kenya during the 1930s. Researchers at the Scott Agricultural Laboratories (SL) selected specific trees for their resilience and cup quality, resulting in the iconic SL28. While SL28 is noted for its drought tolerance, it is most celebrated for its distinct, high-quality flavor profile, often described as having intense blackcurrant and grapefruit notes. It remains one of the most well-regarded varieties in the world, serving as a primary reference point for quality in African coffee production.

In the field, these varieties behave quite differently. Typica is known for lower yields compared to its descendants, while Bourbon generally offers higher productivity and higher sugar concentrations. Caturra’s compact size makes it ideal for intensive farming, yet its vulnerability to disease requires significant management. SL28, while prized for its performance in high-altitude Kenyan climates, also faces the common struggle of traditional Arabica varieties against pests and pathogens, particularly coffee leaf rust.

For the roaster and the drinker, these varieties represent the spectrum of classic coffee flavor. Typica and Bourbon are often associated with balanced, sweet, and clean profiles. Caturra provides a reliable, bright, and citrus-forward cup that is widely recognized in specialty markets. SL28 offers a more complex, vibrant acidity that has become synonymous with the identity of Kenyan specialty coffee. These profiles are not merely historical artifacts; they are the standard by which the industry evaluates the success of new hybrids and cultivars.

Producers choose these varieties based on a complex balance of cup quality, yield potential, and environmental adaptation. Because World Coffee Research uses Caturra and SL28 as standard references in their variety catalog, farmers can compare the performance of newer, more disease-resistant varieties against these established benchmarks. This allows for informed decision-making regarding which plants will thrive in specific microclimates, soil types, and management systems.

Today, these four varieties stand as the pillars of the coffee world. While modern breeding programs continue to introduce F1 hybrids and rust-resistant cultivars to combat climate change and disease, the genetic influence of Bourbon, Caturra, SL28, and Typica remains omnipresent. They are the rhythm section of the coffee industry, providing the foundational quality that sustains the specialty market and continues to shape the expectations of coffee drinkers globally.