![]() The cells of Xam are motile and have polar, monotrichous flagellation. proposed a reclassification of Xanthomonas, renaming the CBB pathogen Xanthomonas axonopodis pv. Two decades ago, on the basis of genotypic investigations, Vauterin et al. It was first named Bacillus manihotis Arthaud-Berthet, then Phytomonas manihotis (Arthaud-Berthet and Bondar) Viegas, later Xanthomonas manihotis (Arthaud-Berthet) Starr, and then Xanthomonas campestris pv. The causal agent is a Gram-negative bacterium of the genus Xanthomonas. As CBB affects systemically cassava stems, this leads to shortages in the supply of healthy (bacteria-free) planting materials. This loss of leaves can affect the availability of leafy vegetables for humans and reduces cash income in communities where cassava leaves are sold. Under favorable ecological conditions, wilting of leaves and leaf fall due to CBB can be high. A low accumulation of starch in the roots due to CBB was observed. The poor yield of storage roots due to severe outbreaks of the disease can affect the population as well as the livestock in areas where cassava is a major staple food. ![]() Root yield reduction level may vary with the susceptibility of cassava cultivars, the climatic conditions and the inoculums pressure. The disease causes losses of fresh roots and also of planting material. It is the second most devastating disease after Cassava Mosaic Virus Disease Complex and may cause more damage to the crop than any other bacterial disease. A diagnostic survey in Africa (Ghana, Benin, Nigeria and Cameroon) revealed that CBB is present in all ecozones, but with variable incidence and severity. The detailed knowledge of the epidemiology, disease development, survival and dissemination, of the reaction of cassava varieties towards CBB such as physiological resistance mechanisms, identification of genetic resistance (QTL) and the background of observed field resistance as well as of the influence of planting time and cropping pattern allows to recommend integrated management measures such as sanitation, intercropping, removal of diseased leaves, management of planting dates according to ecozone, soil amendments, use of resistant genotypes.Ĭassava bacterial blight (CBB) was first reported in Brazil and later observed in several countries of the cassava production belt worldwide. Though, comparing the development of the disease and the damages caused in yield loss trials in two agro-eco-zones over 2 years, CBB was more pronounced and caused higher yield and biomass losses in the forest savannah transition zone than in the dry savannah where symptom development was positively correlated with the rainfall patterns. In regional disease surveys across ecozones in West Africa, no zone of preference has been found. ![]() Over seasons Xam also survives often latently, in cassava stems which are then used for establishing new plantations. Also, some insects in cassava field like the variegated grasshopper (Zonocerus variegatus) vehicles the pathogen for some time. Investigating the survival period over the seasons, a longer survival exceeding 5 months has been observed in non-decayed cassava debris. In fact, Xam survives epiphytically on some weeds occurring in and around cassava fields without developing blight symptoms. ![]() ![]() manihotis (Xam), possesses several means for survival and dissemination that may play an important role as inoculum sources for the infection when favorable conditions occur, and the subsequent damage of the plant causing severe yield losses. The epidemiological and ecological investigations undertaken on the disease showed that the causal agent, the bacterium Xanthomonas axonopodis pv. Cassava (Manihot esculenta Crantz) with its long life cycle is affected by several diseases of which cassava bacterial blight (CBB) is the major bacterial disease in the cassava belt worldwide. ![]()
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