Coffee leaf rust (CLR)

Coffee rust is a disease with the power to hinder, or even wipe out, a country’s national product.

Rust was first reported in 1879 by the English mycologist Michael Joseph Berkeley and his colleague Christopher Edmund Broome. Berkeley and Broome named the fungus Hemileia vastatrix, Hemileia referring to the half smooth characteristic of the spores and vastatrix for the devastating nature of the disease. They received their specimens from Sri Lanka where the disease was already causing enormous damage to productivity.

Many coffee estates in Sri Lanka were forced to collapse or convert their crops to alternatives, such as tea. By 1890 the coffee industry in Sri Lanka was nearly destroyed. Sri Lanka switched to tea production as a consequence of the disease, historians have since suggested this is one of the reason why Britons have come to prefer tea.

As of 1990, coffee rust had become endemic in all major coffee-producing countries, so what is the answer? Well in Timor in 1927 a naturally occurring hybrid of arabica and robusta was found. Its crucial feature: unlike normal robusta, is it can be bred again with arabica varieties, which means that it can transmit its rust resistance to them. To note, coffee rust attacks Arabica coffee, but not the Robusta.

By 1980, the first hybrid of Caturra – the dominant variety grown in the country was good enough to be accepted by growers and buyers – the Timor hybrid was called Colombia. However some years later the fungus as expected evolved, therefore Caturra maintains only a partial resistance, so the need for continued development.

Cenicafe of Columbia has developed other varieties. In 2005, they released a new seed, called Castillo after Jaime Castillo Zapata, the lead scientist behind the development of Colombia.

By increasing the gene pool, coffee scientists also aim at protecting the crops from other risks. By reducing genetic diversity, you have less resistance to climate, pests and diseases.

In some quarters it is believed Castillo is not a matter of luxury, it is a matter of necessity.