Pathogenesis and control of bacterial speck, Pseudomonas syringae pv. tomato, on tomato*

Abstract

Bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, was observed to cause severe symptoms, especially on protected tomato crops, during the winter season in the coastal area of Lebanon. This study was conducted to investigate the aetiology and pathogenesis of the bacterium involved and the efficacy of different chemicals for the control of the disease. Biochemical, physiological and pathological tests verified the identity of the bacterium involved as P. s. tomato. Periodic histological sectioning of inoculated tomato leaves showed that bacterial cells resided and multiplied in depressions and around trichome bases for 24 h before penetration through stomata and trichome basal cells. The bacteria invaded intercellular spaces and caused cell lignification, collapse and shrinkage, 48 h after inoculation. Necrotic lesions filled with bacterial masses and collapsed lignified cells were readily observable at and after 72 h. No detectable histological changes were observed in the yellow halo region surrounding the necrotic leaf specks. A thermostable toxin was produced by the pathogen and is involved in chlorotic symptom expression. An antibiotic mixture of streptomycin + oxytetracycline was most effective in controlling infections followed by copper oxychloride + mancozeb, tribasic copper sulphate + sulphur, copper oxychloride and copper oxychloride + zineb.

Isolation of Endophytic Actinomycetes From Leaves of Tomato Plants and Their Activities Against Bacterial Speck Disease

“…tomato. These results are agree with those reported by Saad and Hassan, 2000;and Schaad, 1988. Pathogenicity tests revealed that the Pst DC3000 was the most virulent isolate compared to Egyptian isolates. Tomato speck disease is worldwide that favored by low to moderate tem-peratures and high moisture conditions (Babelegoto et al, 1988;and Jones et al,1991).…”

Biocontrol activity of Bacillus against a GFP-marked Pseudomonas syringae pv. tomato on tomato phylloplane

“…Control of bacterial speck is usually accomplished by copper-based pesticides as well as mancozeb, zineb, and some antibiotics (Jardine and Stephens 1987;Saad and Hassan 2000). However, when environmental conditions favor disease development and inoculum levels are high, standard treatments are not always effective (Jardine and Stephens 1987).…”