Bacterial speck

Bacterial speck disease, which is caused by Pseudomonas syringae pv. tomato, is an economically important disease of tomato. P. syringae pv. tomato causes necrotic lesions on the leaves, stems, and fruit of tomato plants. Fruit lesions are slightly raised and vary in size from tiny flecks to visible lesions approximately 3 mm in diameter. Fruit infection can lead to infestation of tomato seed, and P. syringae pv. tomato can survive on seeds, especially inside cavities present on the seed surface. Seedlings from infested seeds either develop visible disease symptoms or remain symptomless; in the latter case, asymptomatic plants grown under high relative humidity contain massive populations of the pathogen, thus serving as a reservoir for future infections. Although several reports have suggested that P. syringae pv. tomato is seed-borne and can spread through tomato transplant fields, these aspects of disease etiology and pathogen biology are not well understood.