Pseudomonas syringae pv. tomato and severity of bacterial speck disease on tomato plants in Egypt

Tomato is one of the most widespread vegetable crops in Egypt, which has a wide variation of cultivars. Tomato bacterial speck caused by Pseudomonas syringae pv. tomato is one of the most important tomato bacterial diseases. This study aimed to isolating and identifying P. syringe pv. tomato from infected tomato plants in Egypt, and investigate the tomato plants reaction towards the Egyptian bacterial strain, which the tomato cultivars or hybrids have low sensitivity to it.  Currently, the Egyptian tomato plants exhibited typical symptoms of tomato bacterial speck disease. The isolation and identification experiments resulted in the recovery of typical isolates of P. syringae pv. tomato. The pathogenicity of the bacterial isolate was confirmed by molecular identification through detection of coronatine production and 16S rDNA analysis. The obtained nucleotide sequence was deposited at GenBank with accession no. OQ117369.1 and designed as P. syringae pv. tomato strain Pst1-MAS. The tomato plants only produced the typical bacterial speck symptoms among the tested solanaceous and cruciferous plants. The tested tomato plants exhibited variation in disease severity against P. syringae pv. tomato strain Pst1-MAS using a lot of disease severity scales. The tomato cultivars VFN-8 and Peto 86 were sensitive to infection with severe symptoms, while the tomato cultivars Super Marmande and Edkawy expressed relatively low symptoms. According to the results of disease severity; depending on the mean of bacterial speck symptoms, the tested plants were divided into high; moderate, low sensitive, and resistant. The related defense enzyme activity was correlated inversely with the disease severity for some of the tested tomato plants.