Coffee Varieties That Defeat Leaf Rust

There is a fungus that infests coffee plants and threatens the world’s supply of Arabica coffee. It is coffee leaf rust in English and La Roja to Colombian coffee growers. This fungus is also the reason that the English converted from coffee drinkers to tea drinkers in the 19th century. In that era the main coffee producing regions of the world were Sri Lanka, the Philippines and Indonesia. But the fungus wiped out those crops and planters switched to tea switching the British coffee drinker to a tea drinker at the same time. Arabica, the high quality coffee you get in a coffee house is also what you get in healthy organic coffee. It is also the coffee that is infested by leaf rust.

Robusta is the more sturdy variety, more rich in caffeine, a better producer and the main source of caffeine for soft drinks. Robusta is not bothered by leaf rust so one might think that coffee growers would cross breed Robusta and Arabica to produce a good tasting leaf rust resistant coffee. Unfortunately, Robusta and Arabica do not cross breed in controlled situations. And luckily back where leaf rust emerged in the East Indies there is a Robusta and Arabica cross bred strain that happened naturally on the island of Timor.

It took a century for coffee leaf rust to make its way from the East Indies to Africa and then finally to South America where it started in Brazil. That was in the 1960s. At that time Colombia which is a 100% Arabica producer saw a bleak future if they could not find a coffee variety that resisted leaf rust before the fungus reached their side of the continent. At the Cenecafe research facility high in the mountains of Colombia crop scientists set to work cross breeding the Timor strain with a standard Colombian coffee, Caturra. The first result was called Colombia followed by Castillo and Cenecafe 1. These coffee varieties that defeat leaf rust rely on several plant genes that confer resistance so that if the fungus mutates to counter one defense of the coffee plant there will be other plant traits that protect it.

Convincing the Coffee Farmer

When a coffee farmer plants new shoots of one of the leaf rust resistant Arabica coffee varieties it takes several years to get mature coffee plants and full production. Also a coffee farmer is used to the varieties that he has planted for years if not decades on his farm. Switching over is not always easy and can be costly. But several years ago a third of Colombia’s crop was infested with leaf rust and farmers were forced to make changes. The government offers subsidies for those who plant the new leaf rust resistant varieties and today a third of Colombian coffee is from new leaf rust resistant strains. As peace comes to Colombian coffee growing regions some growers will revert to old strains but for many who need to replant it will be an ideal time to go with coffee varieties that defeat leaf rust.

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