Some synthetic fungicides have been currently prohibited due to their adverse effects; thus, searching for alternatives to decrease their application is a priority worldwide. An alternative to the application of synthetic fungicides is chitosan -a natural biopolymer- because of its biocompatibility, biodegradability, and bioactivity. Chitosan has been used in different industries, such as cosmetology, pharmaceutics, food, among others. In agriculture, it has been used as a resistance inductor and bio-fungicide because of its antimicrobial activity and for plant development as growth promoter. Although many works have been published on chitosan for its characteristics and mode of action, the direct effects on agriculture -both in plant and fruit phytopathogens- have not been reported. Therefore, the objective of this review is to summarize recent advances and achievements of chitosan application in agriculture with special attention to its antimicrobial properties and plant defence induction mechanisms.

Synthetic fungicides have been the main control of phytopathogenic fungi. However, they cause harm to humans, animals, and the environment, as well as generating resistance in phytopathogenic fungi. In the last few decades, the use of microorganisms as biocontrol agents of phytopathogenic fungi has been an alternative to synthetic fungicide application. Actinomycetes isolated from terrestrial, marine, wetland, saline, and endophyte environments have been used for phytopathogenic fungus biocontrol. At present, there is a need for searching new secondary compounds and metabolites of different isolation sources of actinomycetes; however, little information is available on those isolated from other environments as biocontrol agents in agriculture. Therefore, the objective of this review is to compare the antifungal activity and the main mechanisms of action in actinomycetes isolated from different environments and to describe recent achievements of their application in agriculture. Although actinomycetes have potential as biocontrol agents of phytopathogenic fungi, few studies of actinomycetes are available of those from marine, saline, and wetland environments, which have equal or greater potential as biocontrol agents than isolates of actinomycetes from terrestrial environments.

Fusarium spp. damages the roots of crops, its control is with synthetic fungicides, however, marine actinomycetes can be an option to the use of agrochemicals. The objective of this work was the identification and morphological characterization of marine actinomycetes as antagonists to Fusarium solani (Mart.) Sacc. Fusarium spp. was isolated from diseased tomato plants and mangrove sediment actinomycetes, both identified through taxonomic keys and molecular techniques. Eight isolates of Fusarium spp. were obtained, H8 being the most virulent and it was identified as F. solani. Thirty actinomycetes were isolated, of which only four inhibited the phytopathogen, being A19 the one that inhibited the fungus by 70% and was identified as Streptomyces sp. Marine actinomycetes may be an option for disease management in plants of agricultural interest.

La producción orgánica de hortalizas es una alternativa promisoria ante los problemas de la agricultura convencional. En este trabajo tres variantes de abonos orgánicos se aplicaron al suelo con el propósito de evaluar su efecto en el cultivo de la berenjena. Los tratamientos utilizados fueron humus de lombriz, compost de jacinto de agua y la mezcla 50% humus de lombriz + 50% jacinto de agua así como, un testigo con fertilización química convencional. Se evaluó la alturas de las plantas a los 30, 45 y 60 días, número de frutos por cosecha, largo, diámetro y peso de los frutos en tres cosechas, además del rendimiento agrícola. Los resultados mostraron que las plantas que recibieron abonos orgánicos fueron más altas , tuvieron frutos más grandes y más pesados, así como mayor rendimiento agrícola que el testigo con fertilización convencional, siendo el mejor tratamiento de todos la mezcla 50% humus de lombriz + 50% jacinto de agua.

La aplicación de biofertilizantes y bioestimulantes a los cultivos constituye una estrategia priorizada para mejorar y preservar las condiciones físicas, químicas y biológicas de los suelos, elevar el potencial agroproductivo y sustituir importaciones. El objetivo del presente trabajo fue el de determinar la respuesta agronómica de dos variedades de maíz blanco (var. Chuco y Cariaco) a la aplicación de tres productos bioactivos. El experimento se desarrolló del 1 de abril al 26 de julio del 2016, utilizando un diseño experimental de bloque al azar con tres réplicas y cuatro tratamientos para cada variedad [T1: (semillas asperjadas con H2O), T2: (semillas embebidas en una solución de QuitoMax), T3: (Semillas tratadas con Azofert) y T4: (semillas peletizadas con una pasta formada por Ecomic y agua)]. Se realizó un análisis de varianza de clasificación doble. En los casos en que los indicadores mostraron diferencias estadísticas significativas, se utilizó la prueba de Comparación Múltiple de Medias por Duncan, para un nivel de significación del 5%. Los tres productos bioactivos superaron al tratamiento control en los indicadores del componente del rendimiento, alcanzando los máximos resultados mediante el tratamiento con Quito- Max, obteniéndose rendimientos de 2.84 y 3.2 (t.ha-1) en las variedades Chuco y Cariaco respectivamente.