Ceratocystis fimbriata

Ceratocystis fimbriata is a fungus and a plant pathogen, attacking such diverse plants as the sweet potato (black rot) and the tapping panels of the Para rubber tree (moldy rot). It is a diverse species that attacks a wide variety of annual and perennial plants. There are several host-specialized strains, some of which, such as Ceratocystis platani that attacks plane trees, are now described as distinct species. Ceratocystis fimbriata, the type species of the genus Ceratocystis, was originally described on the sweet potato (Ipomoea batatus) in 1890. It has since been found on a wide variety of annual and perennial plants. It is a large, diverse complex of species that cause wilt-type diseases of many economically important plants. There are thought to be three broad geographic clades, the North American, the Latin American and the Asian clades. It is thought likely that Ceratocystis fimbriata contains many undescribed, hidden species. One form of the fungus that causes a wilt disease in cacao was in 2005 described as a new species Ceratocystis cacaofunesta. Another form that causes a disease on plane trees (Platanus), and which was previously known as Ceratocystis fimbriata f. platani, was in 2005 elevated to species Ceratocystis platani. Ceratocystis fimbriata is an ascomycete fungal pathogen. The species as a whole can infect a wide variety of hosts, but particular strains are host-specific. One example is the Ipomoea form of the fungus, which is specific to sweet potato (Ipomea batatas) and wild morning glory. Symptoms can be found on the fleshy root or visible in plants(). On sweet potato, Ceratocystis fimbriate causes a disease called 'black rot,' which displays firm and dry circular brown/black rots. Infected plants often show stunted growth, wilting, and yellowing. Wilting occurs because this pathogen can also travel through xylem and infect vascular system (). During disease, white, fuzzy mycelia with long black perithecia grow out from the lesions (). Additionally, research demonstrates that sweet potatoes infected with C. fimbriate demonstrate increased respiration which is partially due to the infection's influence on protein metabolism (). Higher respiration rates cause dry weight loss in the tubers which poses a problem for marketability. The Ipomoea form of the fungus that attacks the sweet potato (Ipomoea batatas), is thought likely to be native to Latin America, as is the sweet potato itself. It has spread to many locations probably on storage roots. The fungus may appear as a dry, black rot, usually with perithecia and ascospores. In some countries (such as China and Japan) it is an important constraint to sweet potato production. In other areas (such as southeastern USA) the damage is less severe due to the use of resistant varieties and sanitary measures. Fungicides can be used in sweet potato fields or as post-harvest dips of sweet potato roots. C. fimbriata produces ascospores, and these spores are found at the top of fruiting bodies known as perithecia (). There are also chlamydospores, which aid in survival as they overwinter in the soil and on roots (). Chlamydospores survive on infected roots/slips or in the soil and develop on the next season's plant material during spring. Then, mycelium produce long, black perithecia (fruiting structures) that have a sticky mass of ascospores at the top. These ascospores enter and infect new plants through wounds on any part of the plant/tuber/etc and are commonly dispersed by insects, wind, and equipment (). After infecting tubers, the disease can be spread up the xylem tissue of the stem causing wilt (). Ultimately, this pathogen will continue its lifecycle through vegetative propagation (transplants) of diseased tissue or chlamydospores that overwinter in roots or soil to spread the disease into the next season (). Environmental conditions such as temperature and nutrient levels are important for C. fimbriate's success. Specifically, temperatures ranging from 23-27 degrees Celsius encourage sporulation and disease growth (). Also, pre-sprouting roots at warm temperature favors disease and should be avoided when growing sweet potatoes. This is because roots infected with black rot produce sprouts that frequently rot at the attachment point of the root or the roots develop lesions on the stem that rot below ground. Boron deficiencies in the soil can also enhance the disease (). Since many sweet potatoes are grown from roots or slips, any diseased tissue present can lead to more widespread infection.