Efeito de extratos de Croton spp. sobre Scutellonema bradys e Pratylenchus sp. e caracterização fitoquímica de extratos de C. heliotropiifolius

Abstract

Among several diseases affecting yam (Dioscorea spp.), the dry rot, caused by Scutellonema bradys, Pratylenchus coffeae and P. brachyurus, stands out in the field. The objectives of this work were to evaluate the nematicidal effect of aqueous and ethanolic extracts from Croton spp. on the causal agents of the dry rot disease and to verify the phytochemical compounds found in extracts from C. heliotropiifolius leaves. Extracts from leaves, roots and seeds of C. campestris, and extracts from leaves and roots of C. heliotropiifolius at concentrations of 0, 2, 3, 4 and 5%, were tested in two experiments. In Kline slides, 200 μL of extract and 20 specimens of S. bradys were distributed into the wells. After 24 h of exposure the individuals who remained immobile were quantified and transferred to distilled water for 24 h, considering as dead those specimens which remained immobile after 24 hours of incubation. For the in vivo assay, naturally infected tubers were immersed for two hours in the aqueous extract obtained from C. heliotropiifolius leaves at concentrations of 0, 3, 4 and 5% and planted in pots containing sterilized soil. The initial population level of the nematodes was carried out in 1g of the tuber peel of each tuber seed. The experiment was performed in a completely randomized design with four treatments and eight replicates. Three months after the application of the treatments the percentage of sprouting of the seed tubers was evaluated. The final nematode population in the soil, roots and tuber peel were evaluated sixth month after seeding. The chemical analysis of extracts from leaves of C. heliotropiifolius was performed by Ultra-High Performance Liquid Chromatography (UHPLC). All extracts tested were able to inhibit motility and cause mortality to S. bradys. However, for C. campestris, the highest percentages of nematode mortality were observed in ethanolic extracts. The phytochemical analysis of the aqueous and ethanolic extracts from C. heliotropiifolius leaves showed the presence of flavonoids, such as ferulic acid, myricitrin and quercitrin.