Abstract

Pseudomonas syringae pv. tomato (Pst) is one of the most harmful bacteria in the industrial and agricultural production of tomato. This phytopathogen causes bacterial speck disease and, therefore, significant economic losses. The control the pathogen, antibiotics and highly toxic chemical compounds are generally used. The objective of this study evaluates the effects of the use of the tomato rootstock on the physiology and antioxidant defense mechanisms in the Old Limachino Tomato (OLT) grafted plant challenged to Pst. Rootstocks have been widely used to produce tomatoes, contributing to clean handling, especially in sensitive crop to environmental conditions such as the Limachino tomato. This genotype is highly susceptible to environments of biotic and abiotic stress.The experiment involved self-grafted (L/L) and grafted plants on INIA rootstock (L/R) under a completely random design. Plants were evaluated at 3 and 14 days after inoculations with Pst. Growth parameters and damage produced were assessed in plants. Furthermore the plant physiology, gene expression, antioxidant metabolism in the defense mechanism were studied. The plant defense response through the antioxidant mechanism and H2S synthesis in the aerial part was determined. Rootstock increased gene expression of antioxidant metabolism (GR, APX, CAT, SOD) and salicylic acid content in Limachino plant. On the other hand, rootstockreduced the MDA increase and bacterial growth in Limachino tomato. At 3 days after infection, significant differences between grafted plant types were observed, where L/L plants showed higher incidence, severity and bacterial CFU than L/R plants.