THE PROCESS IN MOTION

Why did the Timor Hybrid matter?

Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.

▶ Play the process01At 33, a sterile hybrid02At 44, a fertile hybrid03Crossing back toward arabica04The defense and its neighborhood05Remaking it on demand

At 33, a sterile hybrid

From 1927, arabica and canephora were crossed by hand at Balehonnur, in India. The hybrids received 22 chromosomes from arabica and 11 from canephora: 33, and they were sterile. A hybrid that sets no seed is a dead end.

Read the stages without animation

1. At 33, a sterile hybridFrom 1927, arabica and canephora were crossed by hand at Balehonnur, in India. The hybrids received 22 chromosomes from arabica and 11 from canephora: 33, and they were sterile. A hybrid that sets no seed is a dead end.
2. At 44, a fertile hybridOn a plantation on Timor, an arabica and a canephora crossed on their own; the hybrid, identified in 1927, is tetraploid: four sets, 44 chromosomes, the count of an arabica. It is self-fertile, it sets its own seed.
3. Crossing back toward arabicaIt was therefore crossed back, generation after generation, with an arabica parent: this is backcrossing. What remains is introgression, the lasting entry of the genes of one species into another: 7 to 11% of the genome of the descendant varieties. The Catimor were born in 1959 from accession 832/1 crossed with Caturra.
4. The defense and its neighborhoodThree families of resistance genes are copied side by side on chromosome 4 of the canephora part: RPP8 in five copies, CPR1 in ten, LRK10L in three. But a cross transmits a whole segment, with all its neighborhood: backcrosses shrink it without detaching it, hence a quality penalty, “low to medium” for the hybrid according to World Coffee Research.
5. Remaking it on demandResearch stations wanted to remake the cross. The Ivorian Arabusta marries an arabica to a canephora made tetraploid with colchicine, a product that doubles the number of chromosomes and puts both parents at the same count; it remained little grown. And resistance is never a given: rust exists in races, and the Lempira lineage fell in 2017.

To remember: The chromosome count decided everything: 33, a dead end; 44, a lineage.

In history: The Rust Research Center, founded at Oeiras in 1955, drew from the hybrid almost everything that resists today.

Read the full article and its sources ↓

On a plantation in the Portuguese half of Timor, today Timor-Leste, an arabica and a canephora crossed spontaneously. Nobody had looked for it: the discovery is accidental. McCook places it in the 1920s, and the genomic analyses of 2024 retain 1927 for the identification.

Why did that cross matter, when others came to nothing? Because of the chromosome count. From 1927, arabica × canephora crosses were obtained by hand at Balehonnur, in India. They were diploid, 22 + 11 = 33 chromosomes, and sterile. A hybrid that sets no seed is a dead end: nothing can be built on it.

The Timor Hybrid, for its part, is tetraploid, that is, it carries four sets of chromosomes: 44 in all, the count of an arabica. And it is self-fertile like an arabica, so it sets seed on its own. This is what made systematic backcrossing possible, the repeated crossing with an arabica parent.

Salojärvi and his coauthors sequenced the hybrid itself and five of its backcrosses. Introgression, that is, the lasting entry of the genes of one species into another, covers 7 to 11% of the genome of the varieties descended from it.

They also located the defense. Three families of resistance genes are duplicated in tandem, that is, copied side by side on the chromosome: RPP8 in five copies, CPR1 in ten, LRK10L in three. Eight of these copies are retained as candidates. The three families lie on chromosome 4 of the canephora subgenome. The defense is stored in the part that canephora supplied.

McCook 2019, p. 134-135 (digest); Salojärvi et al., Nature Genetics, 2024, p. 726-727; Coste 1955, p. 349; LC ch. 14

The Rust Research Center, the CIFC, is founded at Oeiras in Portugal in 1955. Almost everything that resists today comes from there.

From the Timor Hybrid come the Catimor, born in 1959 from crossing accession 832/1 with Caturra. An accession is a specific material, collected at a given place and registered under a number. Another accession, 832/2, crossed with Villa Sarchí, gives the Sarchimor.

The principle does not change: the resistance of the hybrid is married to an already cultivated arabica, the Caturra here, the Villa Sarchí there. Through accession 1343, the CIFC also gave the Colombia and Castillo varieties of Cenicafé.

Except that this resistance has a price, and the World Coffee Research catalog makes no secret of it. It describes the Timor Hybrid as the source of almost all resistances, and rates its cup quality “low to medium.” Catimor and Sarchimor climb back to “good.” Bourbon, SL28 and Geisha are rated “exceptional.”

Yang's review, in 2026, gives a name to this cost: a quality penalty. And above all, it says where it comes from, which is far more interesting.

When two plants are crossed, what is transmitted is not an isolated gene but a whole segment of chromosome, with all its neighborhood. By taking the resistance gene, one also takes what lies next to it, and one does not always know what that is. Successive backcrosses, which consist of crossing the hybrid back with the quality parent generation after generation, reduce this baggage without ever detaching it completely. One cannot quite separate the front from the back.

Last point, and a discouraging one: this resistance is not permanent. Mayne had established it as early as 1932 in Nature: rust exists in races, that is, in different strains, and a resistance effective against one is not against another. The Big Rust of 2008-2013 reminded all of Central America of this, and the Lempira lineage fell in 2017.

WCR 2025, p. 11, 27, 53; Yang et al. 2026, p. 3; McCook 2019, p. 94 and 132-133; LC ch. 14 and 16

Deliberate routes followed the same path with less success. Timor had made the cross on its own; the stations wanted to remake it to order.

• ArabustaIvorian, from the 1960s and 70s. An arabica crossed with a canephora made tetraploid with colchicine, a product that doubles the number of chromosomes and puts both parents at the same count. The aim was a fine low-altitude coffee. It remained little grown.
• IcatuFrom the IAC, launched in 1950 on the same principle, then backcrossed with Mundo Novo to recover quality. It was released only in the 1990s, forty years later.
• CxR and Sln. 3RIn India. The CxR is a congensis × canephora. The Sln. 3R come from backcrosses to canephora.
• CongustaIn Java, at Bangelan: congensis × canephora, for 1,250 kg/ha around 1955.

Canephora finally serves as legs. The Nemaya (Promecafé-Cirad-CATIE) and Apoatã (IAC) rootstocks carry arabicas on nematode-infested soils, those microscopic worms that gnaw at the roots. The root holds, and the top of the tree remains an arabica. Liberica already carried the arabicas of Java in Coste's time.

In all, canephora has saved arabica three times. By the half of the genome it gave it at the origin. By what it produces where the other cannot hold. By the resistance transmitted in 1927.

The pack marked “100% arabica” contains in equal parts the heritage of the species it claims to exclude.

Coste 1955, p. 348-350; Arabusta, Icatu, Sln.6, Nemaya and Apoatã sheets of the atlas (WCR 2025); Kawuki et al. 2026, § 2.2; LC ch. 14