The Genesis of Modern Coffee
French missionaries introduced Bourbon from Yemen to Bourbon Island (now La Réunion)—giving it the name it has today—in the early 1700s. This pivotal moment in 1715 would fundamentally reshape the global coffee landscape. According to the World Coffee Research Variety Catalog, virtually all cultivated Arabica descends from just two ancestral varieties: Typica, which traveled from Yemen through India, Java, and the Caribbean in the 17th and early 18th centuries; and Bourbon, which developed on Réunion from a separate Yemeni introduction and was subsequently distributed to the Americas and Africa by the French . Coffea arabica has extremely low genetic diversity for a crop species — a consequence of its allotetraploid origin and narrow initial domestication from Ethiopian highland populations.
The isolation of Réunion Island proved crucial for Bourbon’s development. In the new environment with tropical island climate, fertile volcanic soil, and different ecological conditions, the coffee plants underwent natural mutation and selection processes over many generations. Gradually, a new coffee variety with distinct genetic characteristics formed – that is Bourbon as we know it today. This difference is clearly manifested through rounder bean shapes, yields about 20-30% higher than Typica, and characteristic sweet flavor.
Until the mid-19th century, Bourbon did not leave the island. Nowadays, there are many Bourbon-like varieties found in East Africa, but none exactly match the distinct Bourbon variety that can be found in Latin America.
The Great Migration and Multiplication
The variety spread from Réunion (as the island is now called, renamed after the 1789 revolution that abolished the Bourbon monarchy) to mainland Africa and Latin America through French colonial expansion, and it spawned natural mutations that became coffees with their own identities: Caturra, Catuai, SL28, and others.
In the mid-19th century, specifically in 1860, Bourbon was brought to Brazil – the country that would become the world’s largest Bourbon grower. In southern Brazil, Bourbon quickly developed strongly and spread to the North and Central America.
The French missionary network proved instrumental in Bourbon’s African expansion. French missionaries known as Spiritans established a mission in 1893 at Bura (Taita Hills, Kenya), in which Bourbon coffee seeds originating from La Réunion island were planted. The seedlings from Bura were brought to another French Mission in Saint Austin (near Nairobi) in 1899, and from there seeds were distributed to settlers willing to grow coffee.
Simultaneously, in the 19th century, French missionaries brought Bourbon to many African countries such as Rwanda, Burundi, Tanzania, and Kenya , establishing the genetic foundation for East Africa’s renowned coffee reputation.
The Compact Revolution: Caturra’s Impact
Caturra is a natural mutation of the Bourbon variety. It was discovered on a plantation in the state of Minas Gerais in Brazil sometime between 1915 and 1918. Caturra has a single-gene mutation that causes the plant to grow smaller (called Dwarf/Compactism).
The name “Caturra” comes from the Guarani word meaning “small” and refers to the plant’s dwarfism caused by a natural mutation of the Bourbon variety. This seemingly simple mutation revolutionized coffee agriculture.
Breeders were interested in Caturra’s small size, which allows plants to be placed closer together, and its closely spaced secondary branches, which enable it to produce more fruit in the same space.
By the 1950s and 60s, Caturra had become a cornerstone of coffee cultivation in Colombia, Costa Rica, and throughout Central America. The reason was simple economics: you could plant twice as many Caturra trees per hectare compared to traditional Bourbon, and they were easier to harvest thanks to their compact height. Its compact growth habit revolutionised coffee farming across Latin America by allowing significantly higher planting densities whilst maintaining Bourbon’s prized cup quality. The mutation that made modern specialty coffee farming possible.
However, Caturra inherited Bourbon’s vulnerabilities. Despite its agronomic advantages, Caturra shares Bourbon’s susceptibility to coffee leaf rust (Hemileia vastatrix), the fungal disease that has devastated coffee farms throughout history. When rust swept through Central America in 2012–13 in what became known as the “la roya” epidemic, Caturra plantations were hit particularly hard.
Brazilian Breeding Triumphs: Mundo Novo and Catuai
Brazil’s Instituto Agronomico (IAC) became a powerhouse of coffee breeding, creating two of Bourbon’s most successful descendants. Mundo Novo is the result of a natural cross between the Bourbon and Typica varieties found in Mineiros do Tiete, Sao Paulo, Brazil. Seeds of the original coffee plants were planted in the municipality of Novo Mundo, today called Urupês, where selection gave rise to the variety Mundo Novo. The variety was discovered in 1943.
After years of studying and breeding, Mundo Novo was released in 1952. Even today, it is still recognized for its high yields and good cup quality. Although not resistant to pests and diseases, this variety is still widely cultivated in Brazil due to its high production.
Building on this success, Brazilian researchers created Catuai. A cross between highly productive Mundo Novo and compact Caturra, made by the Instituto Agronomico (IAC) of Sao Paulo State in Campinas, Brazil. The plant is highly productive compared to Bourbon, in part because of its small size, which allows plants to be closely spaced; it can be planted at nearly double the density.
The Catuai group is a result of artificial breeding of Caturra, for its short qualities, and Mundo Novo, for its high yields. It benefits from a smaller size, meaning more plants can be sown in the same space, and high productivity. After years of research, the Red and Yellow Catuai group varieties were released in 1972.
African Excellence: The SL Selections
Kenya’s Scott Agricultural Laboratories, established in the 1920s, created some of Bourbon’s most celebrated descendants. SL28 was selected in 1935 from a single tree in a population called Tanganyika Drought Resistant. In 1931, the senior coffee officer of Scott Labs, A.D. Trench, conducted a tour of Tanganyika (now Tanzania). According to historical documents, he noticed a variety growing in the Moduli district that appeared to be tolerant to drought, diseases and pests. Seed was collected and brought back to Scott Laboratories, where its drought resistance was confirmed. It was widely distributed until superseded by its progeny, SL28.
SL28 was considered the prize selection of this period of intensive breeding.
SL34 was originally selected in Kenya the late 1930s at the Scott Agricultural Laboratories (for more on Scott Labs, see SL28). SL34 was selected from a single tree on the Loresho Estate in Kabete, Kenya since research at the Scott Laboratories was often conducted in cooperation with local, private estate owners.
SL28 was identified on a single tree in Tanzania and soon became ubiquitous thanks to its drought-resistance, high yield, and desirable cup profile. Since then, it has spread to other coffee-growing origins, including Uganda and Central America.
Both SL varieties became synonymous with Kenyan coffee excellence. Today, it is estimated that SL-series varieties comprise as much as 80% of all exported Kenyan coffee.
When describing the SL28, you’ll be using fruity descriptors for the most part, commonly finding blackcurrant, berries and citrusy notes used as descriptors.
The Modern Challenge: Disease and Climate
Today’s coffee industry faces unprecedented challenges that highlight both Bourbon’s legacy and limitations. The variety’s susceptibility to coffee leaf rust (Hemileia vastatrix), coffee berry disease, and nematodes is its significant liability. Bourbon lacks genetic resistance to the major diseases that devastate arabica plantations, which is why breeding programs have spent decades crossing it with disease-resistant varieties. The tradeoff is well-known in specialty coffee: disease-resistant hybrids are easier to grow but often produce cups that lack the complexity of heritage Bourbon.
This reality has driven continuous innovation in breeding programs. The Coffee Research Foundation of Kenya released Ruiru 11 in 1985. They bred it by combining several parent lines, including traditional varieties such as SL28 and SL34, and introduced disease-resistant genes from other coffee varieties. The goal was to create a compact, high-yield plant that could resist major diseases.
The farms that still grow old Bourbon trees — in Rwanda, Burundi, El Salvador, Brazil’s Minas Gerais — are producing something that cannot be replicated by the hybrids that replaced Bourbon in most of the world.
The perception tends to be that pure Bourbon, with its frequently lauded citric acidity, has a higher potential quality and cup score ceiling despite its lower disease resistance and productivity. The result is that many specialty coffee growers continue to cultivate Bourbon in droves, climate change and leaf rust be damned. The question facing the industry is whether Bourbon’s genetic legacy can adapt quickly enough to survive the challenges ahead, or whether its descendants will carry its essence into an uncertain future.