Biotic aspects involved in the control of damping-off producing agents: The role of the thermotolerant microbiota isolated from composting of plant waste

Abstract

Along with the high temperatures generated during the composting process, the microbial community of a compost pile collaborates actively in the control of damping-off producing agents. Such collaboration could be justified on the basis of the ability of the microbiota to produce fungicide substances that are involved in the control of damping-off or other bioactive compounds that affect the growth promotion of plants. Thanks to ex situ experiments, a remarkable suppressive effect was corroborated against different agents producing damping-off. The microbial strains involved in this effect were detected mainly in the bio-oxidative and maturation phases of the composting process. However, only 3% of the total collection of strains proved to have a multipotential character with respect to its spectrum of action against the damping-off producing agents, as well as in relation to its capacity to produce substances of agronomic interest. It is worth mentioning the presence of two thermophilic isolates identified as Geobacillus thermodenitrificans and Bacillus aerius that showed the ability to inhibit the symptoms caused by Phytophthora capsici in vivo. Both strains were able to produce siderophores, salicylic acid and chitinase enzymes in vitro, but only G. thermodenitrificans was able to stimulate the development of the root in pepper seedlings. In this sense, it is suspected that the production of cyanide by this thermophilic bacteria could be related to this latter effect.