Colonization of Trichoderma and Bacillus in Seedlings of Agave tequilana Weber, var. Azul and the Effect on the Plant Physiology and Fusarium Density Colonización de Trichoderma y Bacillus en Plántulas de Agave tequilana Weber, var. Azul y el Efecto Sobre la Fisiología de la Planta y Densidad de Fusarium

One of the most important phytosanitary problems in two-year plantations of Agave tequilana var. Azul. is agave wilt, that is caused by several organisms, among those pathogens are reported several species of Fusarium and Thielaviopsis pradoxa. The main goal of this research was to introduce beneficial organisms in micropropagation plants as control measure. Inoculated treatments were T1 Trichoderma harzianum (Th), T2 T. virens (Tv), T3 T. aureoviride (Ta), T4 Bacillus subtilis (Bs) , T5 Tv + B, Ta + B T6, T7 absolute control (Tabs) and T8 regional control (Treg). Treatments were established in a randomized block design with two replications, the experimental unit (EU) consisted of 122 plants; the minimum sample size was 26 plants. Evaluated variables were colony forming units (CFU) of Trichoderma, Fusarium spp. and Bacillus from roots and substrate and plant height, chlorophyll from plants. Variables were evaluated every 30 days from October 2008 to May 2009. Area under curve (AUC) was calculated for each variable. Our results show that microorganism in the treatments T1, T3, T4 and T6 colonized agave roots and maintain high levels, creating a balance to Fusarium spp. in soil and roots. Under this conditions Fusarium density ranged from 2 to 2.5 -1 log (CFU/mL ). Analysis of variance did not detect any significant difference among treatments. However, Fusarium spp. density on soil (AUC) was higher in treatments T8 Treg (120) and T7 Tabs (75.75) compared with the rest of treatments (50 or less). Fusarium density on roots was higher on treatments T6 Ta + B (375) and T7 Treg (262.5) compared to T3 Ta (105), T5 Tv + B (187.5), and T1 T4 Th B (210). No significant differences were found on chlorophylls and plant heights.