Karla L. Vega-Ramos’s research while affiliated with Sonora Institute of Technology and other places

México cuenta con una gran diversidad de especies de Agave, lo que ha permitido el aprovechamiento de sus azúcares fermentables para la elaboración de bebidas alcohólicas como el tequila y el mezcal. Ambos productos están protegidos con una denominación de origen, pero elaborados a partir de agaves distintos. Cuando el mezcal puede elaborarse a partir de más de 14 especies de Agave, el tequila sólo se produce a partir del Agave tequilana Weber cv azul. En años recientes, se han incorporado nuevos productores de mezcal que no cuentan con la habilidad en la identificación de material para propagar, siendo la caracterización morfológica de los hijuelos una alternativa, lo cual resulta una tarea demandante y en ocasiones poco precisa, debido a la falta de experiencia. Con la finalidad de contar con una herramienta rápida y confiable en la identificación de especies de Agave, se evaluaron marcadores ISSR (Inter Secuencias Simples Repetidas) para detectar polimorfismos entre especies de Agave tequilana, A. angustifolia, A. potatorum y A. karwinskii, estos tres últimos utilizados en la producción de mezcal. Empleando hijuelos de cada especie, se evaluaron seis iniciadores ISSR, presentando un patrón de amplificación diferencial y consistente. A partir de nueve parámetros morfológicos se determinó por medio de análisis de componentes principales (ACP) que los primeros tres componentes representan el 70 % de la variación, con lo que se logra identificar las especies de agaves evaluadas, lo que coincide en el agrupamiento de éstas con el obtenido a partir de los marcadores ISSR. Se considera que los seis iniciadores evaluados son una herramienta rápida y efectiva para la diferenciación genética entre las especies y que puede apoyar a las organizaciones regulatorias al cumplimiento de las normativas para asegurar la calidad del mezcal y el tequila, así mismo a las grandes destilerías o palenques que tienen la necesidad de comprar a terceros su materia prima.

One of the main strategies to control root diseases associated with Fusarium oxysporum, is the use of Trichoderma strains as biological control. However, most of the commercial products contain microorganisms isolated from others crops to those that are planned to protect and from environmental conditions that do not correspond to those where they will be used. Then, it is necessary to isolate strains associated to the root of the plants that have to be protected. This strategy was explored for the control of agave wilt, the main disease of blue agave (Agave tequilana Weber var. azul). The aim of this work was to isolate strains of Trichoderma associated with agave and to evaluate its protection against agave wilt. Samples of agave rhizosphere were taken on commercial crops of blue agave. Isolation of Trichoderma strains was made on selective media THSM. Subsequently, 20 isolates were selected to evaluate their protection capacity during infection of agave plantlets I with F. oxysporum. Plantlets were inoculated with a spore suspension (1X107 spores/ml) of each Trichoderma isolated. Subsequently, they were inoculated at the base of plant with a spore suspension of F. oxysporum (1X107 spores/ml). A scale of 1 to 5 for the disease index was performed, where 1 corresponds to a healthy plant and 5 a plant with severe symptoms of disease. For each Trichoderma strain, root colonization was evaluated by trypan blue staining. It was observed that several isolates of Trichoderma show a protective e¥ect against F. oxysporum, unlike commercial strains that did not show a better protection. In addition, better protection was observed in those isolates that had higher colonization of agave root. It was possible to obtain isolates of Trichoderma that colonize the root of the agave and protect it against infection by F. oxysporum.

In this study, 115 isolates of Fusarium oxysporum from roots of Agave tequilana Weber cv azul plants and soil in commercial plantations in western Mexico were characterized using morphological and molecular methods. Genetic analyses of monosporic isolates included restriction enzyme analysis of rDNA (ARDRA) using HaeIII and HinfI, and genetic diversity was determined using Box-PCR molecular markers. Box-PCR analysis generated 14 groups. The groups correlated highly with the geographic location of the isolate and sample type. These results demonstrate the usefulness of ARDRA and Box-PCR techniques in the molecular characterization of the Fusarium genus for the discrimination of pathogenic isolates.