Abstract

RODRIGUEZ, Margarita; MATEHUS, Juan; GERSTL, Armando  and  SANTANA, María A.. ISOLATION AND IDENTIFICATION OF A PHYTOPATHOGENIC BACTERIA FROM WATER YAM (Dioscorea alata L.). INCI [online]. 2008, vol.33, n.7, pp.537-541. ISSN 0378-1844.

Water yam (Dioscorea alata L.), a staple crop in Africa, Asia and the Caribbean, is a herbaceous twining vine plant generally reproduced by vegetative sections and highly affected by several phytopathogenic organisms including virus, fungi and bacteria. Diseased plants were collected from Guarataro, Bolívar State, Venezuela, in 2003. That year an unknown disease led to ~80% loss of water yam production. The leaves from diseased plants have watery or necrotic lesions on the leaf lamina. Pieces of necrotic tissue were surface sterilized, then transferred to saline solution and the bacteria allowed to diffuse into the solution from the edge of the dissected tissue. The bacteria were isolated on LB agar media. Yellow, shining, smooth colonies with regular margins were visible within 24-48h of incubation at 30^oC. Several isolates were inoculated on tobacco plants. Water and LB media were used as negative controls. Several degrees of hypersensitivity response resulted from the inoculation of tobacco. However, inoculation of in vitro water yam plants showed watering lesions on the leaf lamina inoculated with bacteria cultures and no lesions on water and media inoculated leaves. Bacterial cells observed by light microscopy showed Gram-negative regular rods. Several peritricous flagella were observed under EM. Data from biochemical and physiological tests indicated that the isolates belong to the Enterobacteriaceas family specifically to Pantoea agglomerans. Different methodologies for bacterial identification are discussed.

Keywords : Bacteriosis ; Dioscorea alata L. ; Fitopatógenos ; Ñame .