Coffea canephora varieties known as robusta were first brought to Guatemala in the 1930s. Robusta makes up a very small part of overall production in Guatemala. With the rise of leaf rust, however, that proportion has increased in recent decades, to 2.6% of trees planted.
Mature cherries on branches of a Robusta plant (Coffea canephora). Robusta is resistant to disease, and capable of producing high yields. Unlike Arabica, Robusta cherries tend to ripen around the same time.
Despite its limited presence, robusta plays an important role in coffee growing in Guatemala because of its natural resistance to nematodes. Nematodes, small worm-like parasites, attack plant roots, where they stunt growth or form cancer-like galls. Nematodes are particularly problematic in volcanic highland soils, such as those found in much of Guatemala (Villain et al 2008).
In 1966, the Guatemalan agronomist Efrain Humberto Reyna, working at the Chocolá experimental station, invented a technique for grafting arabica plants onto robusta root stocks. The robusta roots lend the plant resistance to nematodes and, in some cases, improve drought tolerance, while aboveground, the rest of the plant grows as a fully arabica variety. The technique is highly effective at protecting the plants and is now common in parts of Guatemala and El Salvador, where nematodes are endemic.
Nematodes M. Exigua, a type of root-knot nematode. Photo by Tim Williems; reproduced with the kind permission of World Coffee Research.