The present paper has aimed to characterize the bioactivity being exerted on S. rolfsii in vitro by seed aqueous extracts from 64 yam bean (Pachyrhizus spp.) genotypes as well as their maceration times (0, 48 and 72 h). Three experiments were carried out following a completely randomized design with 64 treatments (potato-dextrose-agar PDA+extracts) with two controls (PDA with no extract and PDA+Cabrio® Top in the dose of 4 g/L) with four replicates with one Petri dish per experimental unit. The 64 treatments were adjusted in the dose of 0.1%. The mycelial growth diameter was assessed on the fifth day. Findings showed the diameters of macerating extracts to be 34.3 - 67.0, 23.5 - 57.8, and 37.5 - 63.8 mm at 0, 48, and 72 h, respectively. PDA+Cabrio® Top and PDA with no extract controls ranged from 0.05 to 0.50 mm and 73.2 to 80.7 mm, respectively. P14, P1, P15, and P46 genotypes extracts achieved the lowest mean diameters (47 - 48% shorter). P61 was the genotype bearing the largest mean diameter tantamount to a reduction of 21%. Therefore, every aqueous extract has shown to be active against S. rolfsii, which indicates that genotypes exerting higher toxicity should either be tested against other pathogens or used in the field macerating them for 48 h.

Keywords: Jacatupé, yam beam, secondary metabolites, toxicity, natural fungicides