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The Coffee Plant

Green Coffee Glossary
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A

Accession

A single, unique sample, as when making selections for a gene bank or breeding program

B

Backcrossing

Creating a new generation of trees by breeding a hybrid with one of its parent plants. This is often done to reinforce a particular genetic trait like disease resistance or seed size. In a typical backcrossing scenario, Parent Plant A will have a characteristic that the breeder wants to introduce to the makeup of Parent Plant B. An F1 hybrid of the parents will be created, and that hybrid will then be backcrossed in with Parent B. The next offspring will be selected for the gene marker from Parent A, then backcrossed again, repeating the process, occasionally self-pollinating the generations, until the seedlings are a stable, uniform cultivar that expresses mostly Parent B’s characteristics, but with the new Parent A gene included.

C

Coffee Bean (Endosperm)

The seed of the coffee fruit. Two seeds are found inside most coffee cherries, and this is what we roast.

Cultivar

A variety of coffee that has been deliberately cultivated by selective breeding. These will not usually produce true to type offspring; rather, they are often hybrids or selected mutations and must be propagated with human intervention.

H

Heirloom

Broadly used to refer to any variety that has not crossed with another. More strictly, plant breeders and gardeners use “heirloom” to refer to non-commercial fruits and vegetables. In the 1940s and 50s, commercial breeds became increasingly important in global agriculture. Thus, an heirloom plant is often a private, home-garden reaction against this type of farming. In coffee, it is often (and somewhat controversially) applied to Ethiopian forest varieties, and more broadly to global legacy varieties like Typica and Bourbon.

Hybrid

Refers to a unique plant bred from two distinct genetic parents. Naturally occurring hybrids are not rare for coffee, since cross-pollination occurs readily with other nearby trees. Hybrids created in labs are commonly bred for disease resistance or improved yield, for example. Because hybrids contain unique genetic material contributed from two separate populations, they are said to have “hybrid vigor,” or increased genetic diversity. By selecting a particular accession for a unique genetic trait, a hybrid can be crafted to retain desirable characteristics of its parents and propagate new cultivars.

I

Intraspecific

Refers to hybrids bred from parents of the same species. Mundo Novo is a spontaneous intraspecific hybrid of two traditional arabica varieties, for example.  

Interspecific/Introgressed

Hybrids that are a cross of different species. The Timor Hybrid is an interspecific hybrid of Coffea arabica and robusta (C. canephora). Interspecific hybrids can also be referred to as introgressed, meaning new genetic material was introduced.

Jute

A type of plant fiber used to make the bags used to hold and transport coffee and many other products. Synthetic and natural alternatives exist, but jute remains the most common option. Sizes vary but the most common for coffee are 60, 69, and 70 kilos.

L

Landrace

A wild variety, like those found in coffee forests across Ethiopia. Landraces are generally considered domesticated, but locally adapted, and distinct from any formal breeding or selection. Thus both a wild forest coffee and a traditional home garden in Ethiopia could be growing a landrace variety.

M

Morphology

The study of the physical characteristics of plants, often for the purposes of identification. (See: Phenotypes)

Mucilage (Mesocarp) / Pulp

The flesh of the coffee cherry, directly beneath the skin. This layer surrounds the coffee seeds with a sticky, sugary substance.

Mutations

Genetic anomalies that change something significant about a plant’s nature.

P

Parchment (Endocarp)

The layer of cellulose beneath the mucilage that protects the coffee bean and resembles parchment paper when dried. Parchment may be hand-hulled for samples, but is removed commercially by machines at the dry mill.

Peaberry

A coffee cherry which underwent a genetic mutation to produce only one seed instead of two. Peaberries are smaller and rounder than coffee beans that develop in pairs. About 5% of an average harvest might be peaberry beans.

Phenotypes

Observed characteristics in a plant, like appearance and growth patterns (see: Morphology)

Polyembryony

A coffee cherry which underwent a mutation to produce multiple embryos instead of the usual two independent embryos, usually resulting in triangular seeds. “False” polyembryony results in that shell secondary defect.

S

Selection

Systematic and intentional botanical choices, which are reproduced for distribution. In other words, the process by which a landrace and/or natural variation in a field or offspring in a breeding program are chosen for further breeding, cloning, or wider dissemination. Ex: Gesha was selected from a limited number of seeds from a wild population in Western Ethiopia.

Silver Skin (Perisperm)

 A thin, semi-translucent peel that wraps the coffee seed. Usually grey-green in color (though it may take on reddish hues if ripened or dried in the fruit). During the roasting process this silver skin dries and falls off, becoming chaff.

Skin (Exocarp)

The outer skin of coffee cherry that covers the fruit.

V

Variety

A taxonomic rank of plants below species. Varieties are minor, naturally occurring phenotype variations evident across a population. Most varieties are “true to type,” meaning that the seedlings grown from a variety will resemble the phenotype of the parent plant.

Varietal

An adjective meaning “having the characteristics of a variety.” Strictly speaking, varietal can be used to refer to the coffee drink made from a specific plant variety, but not to the plant itself. People can drink a varietal that has the characteristics of the variety that was planted and harvested.