The amaranth (Amaranthus spp.) is becoming a socially and economically important crop due to the high level of quality proteins in its seeds and leaves. Among the factors that could limit the expansion of this crop are the smuts (Ustilaginales) that prevent normal development of the seeds. The objectives of the project were to: (i) characterize the pathogen which is responsible for smut on A. mantegazzianus, taking into account the cultural and morphobiometrical characters, and the germination of its teliospores; (ii) assess the incidence of smut in two amaranth cultivars; (iii) analyse fast techniques for the detection of the inoculum in seeds and plants cultivated in the field; and (iv) identify any possible reservoirs of the pathogen on wild amaranths. The results obtained allowed the authors to determine that: (i) Thecaphora amaranthicola is the causal agent of smut on A. mantegazzianus; (ii) the cultivar Don Manuel was affected most by the smut (36% incidence); (iii) the residue and plastic card techniques are fast and efficient for the detection of the pathogen inoculum; and (iv) the wild species A. hybridus and A. retroflexus are hosts of the pathogen. This is the first report in the world of Thecaphora amaranthicola as a pathogen of the A. mantegazzianus cultivated species.

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