Los Actinomicetos Como Agentes De Control Biológico De Hongos Fitopatógenos

Medio ambiente y desarrollo sustentable

Artículo arbitrado

Actinomycetes as biological control agents of phytopathogenic fungi
Los actinomicetos como agentes de control biológico de hongos fitopatógenos

Recibido: Febrero 23, 2009 Aceptado: Junio 3, 2009

Resumen
Los actinomicetos son un reservorio enorme de antibióticos y metabolitos bioactivos y muchos de ellos son excelentesagentes de biocontrol para proteger a las plantas contra fitopatógenos. Aunque miles de antibióticos y metabolitos bioactivos han sido descritos, se cree que estos representan solo una fracción de los compuestos bioactivos producidos por los actinomicetos. En esta revisión se abordan las características generales y propiedades de los actinomicetos como agentes de control biológico, sus mecanismos através de los cuales realizan el biocontrol y el impacto de la composición química de la pared celular de los hongos fitopatógenos en el proceso de control. Palabras clave: Streptomyces, competencia, parasitismo, antibiosis.

Abstract
Actinomycetes are an enormous reservoir for antibiotics and bioactive metabolites, and many are excellent biocontrol agents for use in protecting plants againstphytopathogens. Although thousands of antibiotics and bioactive metabolites have been described, these are thought to represent only a small fraction of the bioactive compounds produced by actinomycetes. In this review, we summarize the general characteristics and properties of actinomycetes as biocontrol agents, the mechanisms through which the biocontrol occurs, as well as the impact of thephytopathogenic fungal cell wall composition in the control process. Keywords: Streptomyces, competition, parasitism, antibiosis.

Introduction

A

ctinomycetes are among the most widely distributed group of microorganisms in nature. They are found abundantly in cultivated and uncultivated soils, in various regions throughout the world (Goodfellow and Simpson, 1987; Goodfellow and Williams, 1983).secondary metabolites of which some are antibiotics that are predominant in therapeutic and commercial importance (Alderson et al., 1993). Over one thousand secondary metabolites from actinomycetes were discovered during the years 1988-1992, and approximately 75% of these compounds were

Actinomycetes, especially streptomycetes, can degrade a wide diversity recalcitrant polymers occurring naturallyin plant litter and soil, including hemicelluloses, pectin, keratin, and chitin (Gooday, 1990; Warren, 1996). Actinomycetes also have the genetic capability to synthesize several biologically active

_________________________________ 1 Profesor de la Facultad de Ciencias Agrotecnológicas, Universidad Autónoma de Chihuahua, Ciudad Universitaria S/N Campus 1, Chihuahua, Chih., 31310, México. 2Dirección electrónica del autor de correspondencia: conzalez@uach.mx

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• Vol. III, No. 2 • Mayo-Agosto 2009 •

ANA CECILIA GONZÁLEZ-FRANCO Y LORETO ROBLES HERNÁNDEZ: Actinomycetes as biological control agents of phytopathogenic fungi

produced by strains of the genus Streptomyces (Sanglier et al., 1993). The compounds isolated during this period of time belong to 46 chemical classes,demonstrating the chemical diversity of the secondary metabolites biosynthesized by actinomycetes. Some examples of bioactive compounds include anti-viral and anti-cancer compounds, modulators of immune responses, various enzyme inhibitors, as well as herbicides, insecticides, anti-fungal, and anti-helmintic compounds (Sanglier et al., 1993; Vining, 1990).

Morphology and taxonomy of actinomycetesActinomycetes are Gram-positive bacteria with a high guanine plus cytosine content in

their DNA (> 55 mol%). The group encompasses genera covering a wide range of morphologies extending from the coccus (Micrococcus) and rod-coccus cycle bacteria (e.g. Arthrobacter), through fragmenting hyphal forms (e.g. Nocardia), to genera with a permanent and highly differentiated branched mycelium...