Cassava (Manihot esculenta) is the staple food of nearly 600 million people in the world’s tropical regions. Xanthomonas axonopodis pv. manihotis (Xam) is the causal agent of CBB, a major disease, endemic in tropical
and subtropical areas. This foliar and vascular disease severely affects cassava production worldwide. Losses of between 12% and 100% affect both yield and planting material. Over recent years, a significant recurrence of the disease has been reported in different regions in Africa and Asia. Xam induces a wide combination of symptoms, including angular leaf lesions, blight, wilt, stem exudates and stem canker. Host resistance is still the most effective way to control this disease. However, no breeding strategy is being developed for the control of CBB disease. Only two cassava CBB resistance genes have been identified so far (C. Lopez, personal communication, Universidad Nacional, Bogota, Colombia). Plant defence responses to Xam have been well characterized. Genomic tools for cassava, such as a large expressed sequence tag (EST) database and a cassava microarray, have been developed
and used for Xam–plant expression studies.