Salicylic acid on the induction of resistance of tomato plants and control ofRhizoctonia solaniKuhnin vitro

Abstract

Among the diseases that affect the tomato culture, a special attention is given to the seedling damping off due to the damages it causes on the initial phase of the cultivation. We aimed in this study to assess the different concentrations of salicylic acid (SA) on the induction of resistance to the damping off of tomato seedlings and the control of Rhizoctonia solani Kuhn in vitro. The seed treatment of tomato plants was conducted with immersion in SA solutions for 5 minutes under the concentrations of 0.5; 1.0; 1.5 and 2.0 mMe and control (distilled water). Subsequently, we showed them in expanded polystyrene trays containing the substrate Plantmax Florestal®, previously sterilized and inoculated with R.solani, being the experimental unit constituted by 20 cells, in 4 replicates. The experiment was conducted over 14 days in cultivation chamber with control of temperature (23oC ±2), luminosity (photoperiod of 12 hours) and humidity (70% ±10); then we assessed the seed germination, incidence of damping off, seedling length and fresh matter mass. We also quantified in the tissues of the plants the levels of the enzymes phenylalanine ammonia-lyase (FAL), β-1,3-glucanase and chitinase. In the experiment in vitro, the experimental unit was constituted by a Petri dish, in four replicates, being the SA incorporated to the BDA (potato dextrose agar) and assessed the mycelial growth of R.solani. The AS application in the tomato plant seeds do not interfere on the incidence of seedling damping off, but it induces resistance, activating the enzyme β-1,3-glucanase. The SA did not present effect over the R.solani, in vitro.Keywords: Solanum lycopersicum Mill, elicitor, resistance inducer, PR protein. Ácido salicílico en la inducción de resistencia a Rhizoctonia solani Kuhn en tomate ResumenEntre las enfermedades que afectan a la cultura de tomate se tiene atención especial a "damping off" de plántula debido a los daños que causa en la fase inicial del cultivo. El objetivo de este estudio fue evaluar las diferentes concentraciones de ácido salicílico (AS) en la inducción de resistencia a la fusariosis de plántulas de tomate y el control de Rhizoctonia solani Kuhn in vitro. El tratamiento de las semillas de las plantas de tomate se llevó a cabo con la inmersión en soluciones durante 5 minutos bajo las concentraciones AS de 0,5; 1,0; 1,5 y 2,0 mMe y el control (agua destilada). Posteriormente, fueran sembrados en bandejas de poliestireno expandido con el sustrato Plantmax Florestal®, esterilizado y inoculado con R. solani, siendo la unidad experimental constituido por 20 celdas, en 4 repeticiones. El experimento se llevó a cabo durante 14 días en cámara de cultivo con control de la temperatura (23° C±2), luminosidad (fotoperíodo de 12 horas) y humedad (70 ± 10%); en seguida se evaluó de la germinación de las semillas, la incidencia de damping off, la 48 Print-ISSN 1983-6325 (On line) e-ISSN 1984-7548longitud de las plántulas y la masa de materia fresca. También se cuantificó en los tejidos de las plantas los niveles de...