Pathology

The presence of diseases, changes in severity, and the performance of cassava clones in 5 different ecosystems were studied. A wide-type resistance to existing biotic problems and its durability in these ecosystems were investigated. The relationship between plant reaction to CBB (Xanthomonas campestris pv. manihotis) in the greenhouse and in the field, and its stability through several continuous cycles was investigated. The differences in the severity of CBB, superelongation [Sphaceloma manihoticola (Elsinoe sp.)], and anthracnose (Glomerella manihotis) in monoclonal and multiclonal plots at high and low inoculum levels were also examined. Root and stem rot caused by Diplodia manihotis, which could be synonymous with Botryodiplodia manihoticola, was identified. Confirmation of this synonymy awaits further taxonomic study. Studies on the characterization of the causal agent of the frog skin disease continued with emphasis on detection, transmission, and isolation. Furthermore, the variation encountered in the field within and among cv. regarding their susceptibility to deterioration was studied and the biochemical processes which leadto physiological deterioration were analyzed. (CIAT)

Se estudiaron la presencia de enfermedades, los cambios en la severidad de las mismas y el comportamiento de clones de yuca en 5 ecosistemas diferentes, y se investigo la resistencia de tipo amplio a problemas bioticos existentes, y su durabilidad en estos ecosistemas. Por otra parte, se investigo la reaccion de la planta al CBB (Xanthomonas campestris pv. manihotis) en el invernadero y en el campo, y su estabilidad durante varios ciclos continuos; tambien se examinaron las diferencias en la severidad del CBB, del superalargamiento (Sphaceloma manihoticola (Elsinoe sp.) y de la antracnosis (Glomerella manihotis) en parcelas monoclonales y multiclonales, a niveles alto y bajo de inoculo. Se identifico la pudricion de la raiz y del tallo cusada por Diplodia manihotis, probablemente sinonimo de Botryodiplodia manihoticola, la cual sera objeto de estudios taxonomicos mas detallados. Se continuaron los estudios sobre caracterizacion del agente causal del cuero de sapo con enfasis en aspectos de deteccion, transmision y aislamineto. Ademas, se estudio la variacion encontrada en el campo dentro y entre cv. en relacion con su susceptibilidad al deterioro y el analisis de los procesos bioquimicos que llevan al deterioro fisiologico. (CIAT)