WHEN THINGS RUST, IT IS ALWAYS METAL THINGS—IRON, ACTUALLY. PLANTS
CAN’T RUST AND COFFEE IS NO
DIFFERENT. COFFEE LEAVES, HOWEVER, CAN TURN RUST COLORED AND WHEN
THAT HAPPENS, IT’S NOT A GOOD SIGN.
WHEN COFFEE RUSTS, IT IS BECAUSE A
FUNGUS, HEMILEIA VASTATRIX, HAS ATTACKED IT AND THE
FUNGUS IS SPORULATING, OR PRODUCING SPORES THAT WILL MOVE TO OTHER
LEAVES AND INFECT THEM.
There are many diseases that infect coffee, but none are as prevalent and difficult
to control as this one. (Coffee Berry Disease is pretty horrible, but it is still
contained to the African continent.) Almost every coffee producing region in the
world has Coffee Leaf Rust ( roya, in Spanish), and they all struggle with
controlling it. The rust attacks the leaves and turns off any activity in a leaf where
it touches. Very light infections simply reduce the photosynthetic ability of a leaf.
As infections become more intense, leaves die.
If many leaves on a plant are heavily infected, then the plant can lose all its leaves
and any fruit that is maturing since there are no leaves to sustain the fruit. The
fungus doesn’t actively attack the coffee we drink, it just prevents us from ever having coffee to drink.
There are some fungicides that can be used to combat the fungus. However, they
are expensive and have to be applied multiple times throughout the season. For
small farmers (which make up the vast majority of coffee farmers worldwide), the
cost alone can be prohibitive. For farmers with larger tracts of land, the cost is not
inconsequential.
Moreover, many farms are planted on steep, mountain slopes that are difficult to
walk on.
Imagine the difficulty of walking on a steep slope and spraying a pesticide at the
same time!
With fungicides being a poor option, the best solution is to plant varieties that are
(at least somewhat) resistant to the fungus.
Unfortunately, there are no pure
arabica lines that are resistant. In the 1930s, by a highly unlikely fluke of nature, a
natural cross between C.
arabica and C. canephora occurred, producing the offspring known as the Timor
hybrid.
This plant, having genetic lineage of both species, was resistant to the rust. Once
it was discovered, it became the center of several breeding programs around the
world.
While the disease resistance was a nice inheritance from its canephora
parent, it also inherited some of the undesired taste attributes. So, the breeding
programs tried not only to improve its agronomic traits but its quality traits, as
well.
Over the years, other hybrids were discovered or made. These hybrids were,
over many generations, bred with pure arabica lines to further improve their
taste. Now the world is populated with many of these breeding program
offspring. The taste of these offspring has never managed to equal that of a pure arabica
line, no matter how many backcrosses have occurred. Still, these offspring are
rightly called arabica varieties because so much of their genetic material comes
from the arabica species. Currently, there are some recent releases that show a
great deal of promise in offering rust resistance and desirable quality.
Unfortunately, as with any disease, resistance is not a cure. The fungus is
constantly mutating and adapting. Many strains now exist that can attack not only
some of the hybrids but pure C. canephora lines, as well.
So long as coffee is a
crop, we will be in constant flux with this and other diseases. It isn’t particularly
fun or joyful, but it is the way of life.
It was a hybrid featuring the genetic lineage from both Arabica and Robusta
plants that became the savior for breeding more rust-resistant coffee plants.
Post a Comment