MECHANICAL TREATMENT INDUCES A BASAL TOLERANCE AGAINST NECROTROPHIC PATHOGENS IN TOMATO PLANTS

RAMALLO, ANA; CHAN , RAQUEL L; SALAZAR, SERGIO; WELCHEN, ELINA; CASTRO, JENIFFER; CABELLO, JULIETA

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research; 2022

Tomato (Solanum lycopersicum L.) is one of the most important horticultural crops due to its high consumption, nutritional value, and extensive production area worldwide. Strategies to increase its production through the modification of growth parameters or by increasing disease resistance are objectives pursued by many research and breeder groups. Fusarium oxysporum f. sp. Lycopersici (Fol) is a necrotrophic fungus responsible for the tomato vascular wilt disease by colonizing the xylem vessels of roots and stems. Previous results of our group showed that a mechanical treatment on Arabidopsis stems increased the xylem area and enhanced seed yield. A commercial tomato variety also showed an increment in the stem diameter after 48 h of treatment. We then analyzed the impact of mechanical treatment on different cultivars, which allowed us to study the mechanisms deployed at the physiological and molecular levels using available mutants. We observed that the Money Maker (MM), M82, and Ailsa Craig (AC) varieties responded to the mechanical treatment, each requiring a different weight and application time. AC-tomato seedlings of 4-5 cm in length responded after 48 h of treatment with a 3 g-mechanical dispositive. We observed an increment of 35 % in the stem diameter and 60 % in the aerial biomass in the mechanical-induced plants. In addition, we quantified 1,6 more lateral roots compared to the control and an increment of 20 % in the root area in treated AC tomatoes, which could indicate the induction of an adaptive advantage for growing better under different soil conditions. We performed a detailed analysis of the morpho-anatomical and molecular changes at the vascular level at 3 h, 6 h, 12 h, and 24 h post-mechanical challenge. The histological analyses of the stem cross-sections of treated AC-tomato plants showed an increment in the number of vascular bundles and high stele area 6 h and 12 h post-treatment, respectively. In addition, cross-sections near the root collar showed an increment in the number of vascular bundles 6 h post-treatment. Furthermore, AC-tomato plants induced by mechanical treatment were more tolerant to Fol-infection than non-treated tomatoes since they were less affected, remained greener, and showed fewer signs of wilting after the Fol infection. Concerning the physiological and molecular mechanisms elicited by the mechanical treatment, no differences in ROS levels were observed in the challenged plants between 3 to 24 h post-treatment. A global transcriptional analysis is underway. We focus on the expression profile of genes differentially expressed in Fol-resistant varieties in connection with those increased after mechanical treatment. Gene expression patterns, modifications in the regulation of hormonal pathways, and biochemical and metabolic processes must be analyzed to evaluate the global impact of mechanical treatment in conferring the ability to overcome Fol infection to tomato plants.