Constituent content and allelopathic potential of eighteen extracts for the control of Urochloa decumbens under laboratory conditions

Abstract

Invasive grasses, those of the genus Urochloa act aggressively, thereby inhibiting the germination and growth of native species. We investigated the allelopathic potential and constituent content of different plant species to determine their effect on the germination of Urochloa decumbens (Stapf) R.D. Webster. Eighteen (18) species from the families Anacardiaceae (1), Annonaceae (6), Euphorbiaceae (1), Fabaceae (2), Myrtaceae (1), Rubiaceae (4), Sapindaceae (2), and Tropaeolaceae (1) were selected to obtain methanolic extracts at 1% (m/v). The total phenols, flavonoids, condensed tannins, flavonols, and saponins were evaluated by colorimetric methods. To evaluate the allelopathic effect of methanolic extracts 25 seeds from U. decumbens were distributed in Petri dishes containing two sheets of germitest paper and 2 mL of extract, and they were maintained at 25 °C under white light. All methanolic extracts showed total phenols, flavonoids, flavonols, and condensed tannins; however, saponin was identified in A. coriacea, A. crassiflora, A. sylvatica, Psychotria carthagenensis, P. leiocarpa, and Tropaeolum majus. Annona dioica (Annonaceae), Stryphnodendron adstringens (Fabaceae), and Palicourea crocea (Rubiaceae) have allelopathic potential and showed decelerated U. decumbens seed germination and inhibited hypocotyl and radicle growth. These findings provide insights into alternative methods for controlling U. decumbens in areas of ecological restoration.