Abstract:
Tomato is one of the most economically important nutritious edible plants in the world that
belongs to the family of Solanaceae. In Ethiopia, tomato is a seasonal crop and an economically
important and widely grown vegetable crop for its fruits by small holder farmers, commercial
state and private farms including by Megech tomato production. Pathogenic bacteria are a
major constraint to tomato production in Ethiopia and many other countries leading to
significant crop losses. Characterization of the bacterial pathogens is crucial for disease
management and regulatory purposes. However, in Central Gondar Zone of Ethiopia, there is no
report on isolation, identification and characterization of pathogenic bacteria affecting tomato
plant. Thus, this study aimed to isolate and characterize pathogenic bacteria from infected
tomato plants grown in Megech irrigation farmland and their control using crude extracts from
Azadirachta indica and Calpurnia aurea leaf extracts. Out of ten isolates, seven yellowish and
three small rod shaped watery pigment bacterial colonies were observed on Yeast Dextrose
Calcium carbonate agar medium after streaking and incubation at 28 ºC for 72 h. All isolates
were Gram negative, rod shaped and displayed positive result for catalase, triple sugar iron,
citrate, acid production, gas production and carbohydrate fermentation tests. On the other hand,
all the isolates were oxidase negative and mixed results were obtained for motility and urease
tests. On the basis of cultural, morphological, and biochemical tests, seven isolates were
tentatively identified as genus Xanthomonas, the rest three were as genus Pseudomonas. The
isolates were tested for their pathogenicity, and the development of lesions on inoculated leaves
was observed after seven days post inoculation. Zone of inhibition ranging from 9.03±1.20 to
30.11±0.92mm from Azadirachtaindica leaf extracts against isolated pathogenic bacteria was
recorded, while zone of inhibition ranging from 8.72±0.24 to 31.12±1.03mm from Calpurnia
aurea leaf extracts against isolated pathogenic bacteria was recorded. Thus, the present study
has confirmed the existence of pathogenic bacteria causing disease in tomato plant in Megech
irrigation farmland and evaluate Azadirachta indica and Calpurnia aurea leaf extracts against
isolated pathogenic bacteria. The study further recommends using molecular tools for more
accurate characterization of pathogenic organisms like fungi and viruses from tomato plants for
better management.
