Morphological differences between Amaranthus cruentus, cv. BRS Alegria, and the weed species A. hybridus, A. retroflexus, A. viridis and A. spinosus

摘要

The pseudocereal grain amaranth, with the species Amaranthus caudatus, A. ruentus e A. hypochondriacus, domesticated by indigenous populations before America was discovered, has shown adaptability to production systems in the Brazilian savannah. The plants present apical panicles, divided into small branches which hold fruits (pixid type), containing one seed each. The seeds germinate quickly in the presence of moisture, after physiological maturity. At the early phase of development, grain amaranth can be confounded with the weed species A. hybridus, A. retroflexus, A. viridis, A. spinosus, which are associated with agricultural expansion in the savannah. Their morphological differences become more visible after flowering: branching, with axilary and terminal flowers in weed types contrasting with cultivated amaranth, in which panicles are apical; the light coloured seed testa contrasts with the black seed testas of the weed species. BRS Alegria (A. cruentus), the pioneer cultivar in Brazil, presents 180 cm plant height, of which the panicle occupies 48 cm; physiological maturity at 90 days; resistance to lodging; seed weight of 0.68 g per 1.000, with yields of 2.3 t ha-1 (seed) and 5.6 t ha-1 (total biomass). The seeds of weed types are smaller, germinate gradually and may remain in soil for many years, infesting cultivated areas. The morphological differences detected under experimentation show that the species are distinguishable; they contribute to guiding grain amaranth seed production and commercial cultivation, emphasizing adaptation characteristics, in contrast to t weed seeds from the same botanical genus.