Mycosphaerella coffeicola
| Mycosphaerella coffeicola | |
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| Arabica coffee infected with Cercospora berry blotch | |
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Dothideomycetes |
| Order: | Capnodiales |
| Family: | Mycosphaerellaceae |
| Genus: | Mycosphaerella |
| Species: | M. coffeicola |
| Binomial name | |
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Mycosphaerella coffeicola (Cooke) J.A.Stev. & Wellman (1944) |
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| Synonyms | |
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Mycosphaerella coffeicola is a sexually reproducing fungal plant pathogen. It is most commonly referred to as the asexual organism Cercospora coffeicola.
There are 40 species in the genus Coffea (family Rubiaceae) that are susceptible to the disease caused by M. coffeicola, but only a few that are commercially relevant. Arabica coffee (Coffea arabica L.) is the most significant of the susceptible species, affecting 70% of the world's coffee production.Coffea arabica ranges in growth habit from a shrub to a small tree and has ovate, shiny, pointed leaves, with clustered white flowers. The fruits begin as green berries which ripen to a deep red color. These are often called the coffee "cherries". Each fruit contains 2 seeds (i.e. coffee beans) in a drupe.
Symptoms of M. coffeicola vary depending on the plant organ affected. These differing symptoms help explain the various common names for the disease: Cercospora "Leaf Spot" and Cercospora "Berry Blotch" (Cercospora is reference to the deuteromycete stage). On leaves, lesions begin as chlorotic (yellow) spots that expand to become deep brown and necrotic on the upper leaf surface. These spots often have a discolored, light center where sporulation can occur, and many have a yellow "halo" around the margins. This halo is caused by the toxin cercosporin, produced by Cercospora species. Not all lesions have distinct edges or a halo, however, and some occur in concentric rings. In general, lesions of this species are able to fuse, and can form large irregular areas of necrotic tissue. Leaves may drop in extreme cases. Fruit symptoms typically appear 90 days after flowering. On green berries, this includes irregularly shaped brown, sunken lesions that are surrounded by a purple halo. Infected red cherries also have large, dark areas of sunken flesh. At this stage, fruit is susceptible to attack by opportunistic bacteria and fungi (such as Colletotrichum gloeosporioides), though symptoms from these organisms should not be falsely attributed to M. coffeicola.
Disease is often affected by the environment and the changing conditions. M. coffeicola is a tropically adapted pathogen due to its host narrow geographical range around the equator. Favorable environmental conditions around the equator are warm and humid wet seasons followed by a warm and dry season. The highest disease pressure occurs when the temperature is 20–28 °C (68–82 °F) and continuous environmental wetness for 36–72 hours. Mornings where temperatures reach the dew point (>98% humidity) are perfect conditions for conidia to disperse. A nitrogen-deficient plant as well as a plant with excess nitrogen favors disease prevalence, making well-timed fertilizer applications important. Other factors that can increase disease incidence are insufficient shade, herbicide injury, plant stress, and other diseases caused by nematodes. The reason for increased disease is that stressed plants are more susceptible.
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Wikipedia