Determination of the Resistance Reactions of Some Tomato Cultivars against Bacterial Speck Disease

Abstract

Pseudomonas syringae pv. tomato is the causative agent of the bacterial speck disease of tomato (Lycopersicon lycopersicum), a disease that occurs worldwide and causes severe reduction in fruit yield and quality. Disease resistance conferred by the pto gene, encodes a serine–threonine protein kinase, is one of the first R-genes to be cloned and sequenced. In this research, the resistance reactions of 50 different tomato cultivars which are grown commonly in Central Anatolia against P. s. pv. tomato causal agent of bacterial speck disease were determined. Six-week-old plants were inoculated by spraying of P. s. pv. tomato strains, YA-1 and YA-2 (10⁸ CFU ml^-1), until leaf surfaces were uniformly wet. After inoculation, the plants were incubated at 25±1 °C in 65-75 % relative humidity with a 12 h photoperiod and the disease progress occurred on the seedling leaves by P. s. pv. tomato was followed by counting the dark brown-black leaf necroses in 21^st days after inoculation of the seedlings. Each experiment was performed at least three times and control plants were sprayed with sterile distilled water. The results of resistance reactions on plants were evaluated according to Chambers and Merriman scale. The resistance levels of the cultivars were statistically determined by using ANOVA variance analyze and Duncan multiple range tests. Presence of pto gene in the tomato cultivars was verified by using the primers SSP17 and JCP32 (a 963 bp DNA fragment) by PCR and the gene was determined in 15 different tomato cultivars. The determination of the pto gene in some tomato cultivars may help to develop new resistant cultivars and to reduce of disease severity.