One of the most important melon diseases is the bacterial blotch caused by Acidovorax avenae subsp. citrulli (Aac). Alternative hosts of this bacterium were determined in plants at the first true leaf stage of several species/cultivars, including cucurbits, solanaceous, gramineous, leguminous and caricaceous species. They were inoculated by spraying foliage with bacterial suspensions of strains Aac 1.49 and Aac 12.13, isolated from melon and watermelon, respectively. The susceptibility of plants was evaluated based on the incubation period (PI) and disease incidence (INC). Cowpea, bean, tobacco and maize did not show symptoms. The lowest PIs were observed in cucurbits (3.0 d), except sponge gourd (6.83 d). Disease incidences higher than 90% were observed in cucurbits, except sponge gourd, and in solanaceous species for both Aac strains. In another experiment, fruits of pumpkin, squash, eggplant, papaya, bur gourd, watermelon, melon, cucumber, bell pepper and tomato were analyzed for susceptibility to strains Aac 1.49 and Aac 12.13. Fruits were inoculated by sub-epidermal injection. PI and INC were determined and disease severity was evaluated by measuring external lesion diameter (DLE) and lesion depth (PL). Lowest PIs (2.0 d) were detected in fruits of papaya, watermelon, melon and bell pepper. One hundred percent incidence was observed in all inoculated fruits excepting squash (93.75%) and pumpkin (34.37%). Highest DLEs were seen in cucumber (1.47 cm) for strain Aac 1.49, and by watermelon (1.60 cm) and melon (1.70 cm) for Aac 12.13. Highest PLs were presented by watermelon (1.72 and 0.75 cm respectively for strains Aac 1.49 and Aac 12.13). Eggplant fruits did not show external symptoms but internal lesions were deep.
Cucumis melo; bacterial wilt blotch; bacterium
