Soil microorganisms and plant diseases associated to cocoa (Theobroma cacao L.) genotypes in the Ecuadorian Amazon

Abstract

Soil microorganisms and plant diseases associated to cocoa (Theobroma cacao L.) genotypes in the Ecuadorian AmazonMicroorganismos del suelo y enfermedades asociadas a genotipos de cacao (Theobroma cacao L.) en la Amazonía Ecuatoriana AbstractThe aim of this research was to analyze the relationship between soil microorganisms and the major diseases affecting promising clones of cocoa (Theobroma cacao L.) in the Ecuadorian Amazon. The EET-95, EET-96, EET-103 and CCN-51 cocoa clones were evaluated, respectively, the latter used as a control, for this, the amount of bacteria, fungi and total actinomycetes, expressed in colony forming units (CFU) per soil gram, was determined, present in the soil rhizosphere of the three cocoa clones, as well as the appearance of the major plant diseases which attacks the cocoa crop. Data were statistically analyzed by one-way ANOVA and Tukey HSD test p≤0.05. The bacteria were the microorganisms with the greatest association to the evaluated cocoa clones in this study, followed by actinomycetes and fungi. Clone CCN-51 had achieved the highest number of bacteria, clones EET-96 and EET-103, had achieved a higher incidence of actinomycetes and clone EET-103, the greater presence of parasitic fungi. The witch broom disease, whose causative agent is Cripinellis perniciosa Sthael Singer., affected to a lesser extent the EET-103 and CCN-51 clones, while frosty pod rot caused by the parasitic fungus Moniliophthora roreri (Cif & Par) Evans et al., showed the EET-103 clone with the highest incidence of this disease and conversely to the CCN-51 clone with the lowest incidence of this pathogen.Key words: Cocoa rhizosphere, cocoa yield, host-pathogen interaction, microbial ecology, parasitic fungus, soil biota. ResumenEl objetivo de la presente investigación fue analizar la relación de los microorganismos del suelo y las principales enfermedades que afectan los clones promisorios de cacao (Theobroma cacao L.) en la Amazonía Ecuatoriana. Se evaluaron los clones EET-95, EET-96, EET-103 y CCN-51, respectivamente, éste último utilizado como control, para ello, se determinó la cantidad de bacterias, hongos y actinomicetos totales, expresados en unidades formadoras de colonias (UFC) por gramo de suelo, presentes en la rizósfera de los tres clones de cacao, así como la aparición de las principales enfermedades que atacan al cultivo del cacao. Los datos fueron analizados estadísticamente mediante ANOVA de un factor y prueba HSD de Tukey p≤0,05. Las bacterias fueron los microorganismos de mayor asociación a los clones en este estudio, seguido de actinomicetos y hongos. El clon CCN-51 presentó la mayor cantidad de bacterias, los clones EET-96 y EET-103, presentaron mayor incidencia de actinomicetos y el clon EET-103, la mayor presencia de hongos. La enfermedad escoba de bruja, cuyo agente causal es Cripinellis perniciosa Sthael Singer., afectó en menor medida a los clones EET-103 y CCN-51, mientras que la moniliasis causada por el hongo Moniliophthora roreri (Cif & Par) Evans et al., puso en evidencia al ...