ABSTRACT Fusarium wilt caused by Fusarium oxysporum f. sp. lactucae Race 1 was first detected in lettuce in the Region of Murcia (Spain) in 2017, in plantations in the northwestern area, where the crop is grown in the summer. In order to establish control strategies against the disease, studies have been carried out under controlled conditions with influence of temperature (25 °C and 28 °C), aggressiveness of isolates (four isolates from Race 1), and behavior of commercial cultivars (three susceptible cultivars and four not susceptible). In our study, all susceptible cultivars died at both temperatures for all the isolates, while the temperature of 25 °C was lethal for only one plant of a non-susceptible cultivar. The plants of non-susceptible cultivars that did not die presented index symptoms within a range from 1.7 to 3.7 according to cultivars and isolates; however, at 28 °C, all plants of the non-susceptible cultivars were infected, with 30 % to 100 % of plants dead. The results suggest that temperature affects the disease and that, in highly contaminated areas where the lettuce crop is grown in hot periods, management of the disease requires strategies complementary to using non-susceptible or resistant cultivars. f sp Spain (Spain 2017 area summer (2 C 2 , °C) 1, 1) three susceptible. . susceptible) study nonsusceptible non cultivar 17 7 1. 37 3 3. however infected 10 dead periods 201 ( 20

Abstract Introduction: Biosynthesis has emerged as an option for obtaining nanometric materials due to the need to use more environmentally-friendly synthesis methods. Objective: To synthesize silver nanoparticles (Ag NPs) with aqueous Crataegus gracilior Phipps (tejocote) bark extract as precursor. Methodology: Ag NPs were synthesized with AgNO3 and aqueous Crataegus gracilior bark extracts, and later characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, their size distribution and zeta potential were obtained. Results: The presence of Ag NPs reached maximum values at concentrations of 10 % (w/v). Mostly spherical nanoparticles were found in the range of 20 to 50 nm in size. FTIR confirmed the stabilization of the nanoparticles through their interactions with functional groups of carbohydrates and proteins. XRD and TEM results were explained by their face-centered cubic (FCC) structure with a size of 26 nm, a mean hydrodynamic diameter of 108 nm and polydispersity index of 0.24. The zeta potential values in the dispersions were -21.9 ± 5.11 mV, denoting colloidal stability. Limitations of the study: The characteristics of the nanoparticles obtained are only valid under the following synthesis conditions: 10 % (w/v) solids and pH 10. Originality: A non-reported plant material was used, capable of acting as a reducing and passivating agent of silver nanoparticles. Conclusions: Biosynthesis of Ag NPs with tejocote extract is an efficient, low-cost and environmentally-friendly method.

Resumen Introducción: La biosíntesis ha surgido como una opción para obtener materiales nanométricos debido a la necesidad de utilizar métodos de síntesis más amigables con el ambiente. Objetivo: Sintetizar nanopartículas de plata (NPs Ag) con extracto acuoso de corteza de Crataegus gracilior (tejocote) como precursor. Metodología: Se sintetizaron NPs Ag con AgNO3 y extractos acuosos de corteza de Crataegus gracilior, posteriormente se caracterizaron mediante espectroscopia ultravioleta-visible (UV-vis), espectroscopia infrarroja por transformada de Fourier (FTIR), microscopía electrónica de transmisión (MET) y difracción de rayos X (XRD), además se obtuvo su distribución de tamaño y potencial zeta. Resultados: La presencia de NPs Ag alcanzó los valores máximos a concentraciones de 10 % (m/v). Se encontraron nanopartículas mayormente esferoidales en el rango de 20 a 50 nm de tamaño. La FTIR confirmó la estabilidad de las nanopartículas mediante su interacción con grupos funcionales de carbohidratos y proteínas. Los resultados de XRD y MET se explicaron por su fase cúbica centrada en las caras (FCC) con tamaño de 26 nm, diámetro hidrodinámico medio de 108 nm e índice de polidispersidad de 0.24. Los valores del potencial zeta en las dispersiones fueron -21.9 ± 5.11 mV, denotando estabilidad coloidal. Limitaciones del estudio: Las características de las nanopartículas obtenidas solo son válidas bajo las siguientes condiciones de síntesis: 10 % (m/v) de sólidos y pH de 10. Originalidad: Se utilizó un material vegetal no reportado capaz de actuar como agente reductor y pasivante de nanopartículas de plata. Conclusiones: La biosíntesis de NPs Ag con extracto de tejocote es un método eficiente, de bajo costo y amigable con el ambiente.