A New Bacterial Disease of Cassava in Venezuela Caused by Enterobacter cloacae.

In this article we report a new cassava (Manihot esculenta Crantz) bacterial disease in Venezuela. The disease has been observed in different Venezuelan regions since 2001. Leaves of the collected samples showed angular water-soaked lesions on the leaf lamina, which became later necrotic with a chlorotic halo. Advanced disease stages induce an early senescence of leaves leaving the stem bare. Bacteria isolated formed small beige, glistening, smooth colonies with regular margins within 24 h incubation at 30°C on LB agar or semi-selective threhalose agar. All isolates were Gram negative, facultative anaerobic with several peritrichious flagella observed under the Electron Microscope. The bacterium was identified as Enterobacter cloacae by biochemical assays, but 16S rRNA gene sequence analysis did not allow discrimination between E. cloacae and Pantoea agglomerans. Other PCR based identification methods such as ERIC and GIRRN-LIRRN ribotyping, and hsp60 sequence identified the strains as E. cloacae. Pathogenicity test on cassava plants reproduced the disease symptoms and allowed the reisolation of E. cloacae from the infected tissues. This is the first report of a disease caused by E. cloacae on cassava and it may have an impact on cassava seed production. [ABSTRACT FROM AUTHOR]