First report of tomato bacterial speck caused by Pseudomonas syringae pv. tomato in Tunisia.
In spring 2016, severe spots were observed on nearly all tomato (cultivars Amal, Kaouther and Malinche) plants grown in several greenhouses in the region of Teboulba, on the eastern coast of Tunisia. Affected plants presented 1 to 5 mm, angular, necrotic spots surrounded by a yellow halo on young and older leaves. When numerous lesions occurred on a single leaflet, they coalesced and a portion or the entire leaflet turned necrotic and died. Necrotic lesions were also observed on petioles, peduncles and stems of diseased plants. In some cases, a brown-black colouration was observed along the entire stem. Similar necrotic symptoms were observed during spring 2017 on tomato seedlings grown in nurseries in the Kairouan governorate, in the centre of Tunisia. Sixteen bacterial isolates were recovered from the diseased plants of the three tomato cultivars and seedlings described. Based on biochemical, physiological, molecular (PCR assay) and pathogenicity tests, the causal agent was identified as P. syringae pv. tomato. Infected seeds and/or transplants were the most likely source of introduction of this pathogen to Tunisia. This is thought to be the first report of the occurrence of bacterial speck of tomato in Tunisia.