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Titre : Efecto de Trichoderma y Bacillus en la dinámica poblacional de Fusarium spp. en agave tequilero (Agave tequilana Weber. var. Azul) en Jalisco.

Auteur : Tlapal Bolaños, Bertha

Université de soutenance : Colegio de Postgraduados (COLPOS)

Grade : Doctorado 2013

Résumé
The agave wilt is one of the most important plant pathology problems of the agave tequliero Agave tequilana Weber var. Azul, disease that has been associated with several plant pathogens such as Fusarium spp., and Thielaviopsis paradoxa, and this disease is present mainly on crops of 2 o more years old. In the present study agave tequilero plants that are used as propagative plant material were inoculated with beneficial organisms, and as a part of a preventive and integrated crop management strategy. Experiments were established in a greenhouse (Rancho el Indio, Tequila, Jalisco) condition and on two commercial agave crops, in the localities of Ahualulco and Tecalitlán, Jalisco, in order to study the possible establishment and later development of native isolate of Trichoderma harzianum, T. virens y T. aureoviride, and the commercial formulation of the bacteria Bacillus subtilis. These isolates were inoculated in the agave plants grown in the greenhouse. The possible effect of beneficial organisms on the population dynamics of Fusarium spp., present on agave plants growing on the greenhouse and the commercial agave plantations was also studied, where the microbial compositions was determined before the experiments were established. In both cases, at the greenhouse and the commercial agave plantation, the following variables were recorded : precursor units of colonies (PUC) of the beneficial organisms form the soil, content of chlorophyll, height and width of the agave plants were recorded. Treated agave plants had less PUC densities of Fusarium spp., and had a good establishment of T. harzianum, T. aureoviride and B. subtilis at the greenhouse, as well as with the mixture of the last ones. However, at the commercial plantation, the behavior and development of these beneficial organisms were affected by characteristic weather conditions of each ecological niche that is present at the rhizosphere, where the plant has an association with the native microbiological flora and the physical properties of the soil. At the commercial agave plantations B. subtilis may tolerate temperatures between 32 to 34ºC and wet extended conditions, with 40% relative humidity, while Trichoderma has been affected and reduced for such weather conditions. However, in regions with similar temperatures but with high relative humidity around 60%, Trichoderma could adapt very easily, regardless if native strains already existed, which may displace in some times the introduced ones ; this is because they had co-evolved with the weather and the host. Fusarium spp., were maintained at low levels compared to the introduced beneficial organisms at both experimental site

Mots clés : Marchitez del agave. Fusarium spp.. Antagonismo. Supresividad. Agave wilt. Antagonism. Suppressive. Fitopatología.

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