Seed Yield and Bioactivity Against Ralstonia solanacearum of Yam Bean (Pachyrhizus spp.) Progenies

Yam bean is a leguminous crop that produces toxic seeds with potential for biopesticide development. This study evaluated seed yield of nine yam bean progenies and their activity against Ralstonia solanacearum (RS) phylotype II isolate FIO104B, which was collected from tomato in Iranduba, Amazonas, Brazil. A field experiment was conducted using a trellis system following a randomized complete block design with four replications and four plants per plot. Antibacterial activity was evaluated by exposing 30 µL of RS (1 × 10⁶ cells·mL⁻¹) to 20 mL of yam bean seed extracts at 0.5% and 5% (w/v) in sterile yeast-peptone-glucose medium for 6, 12, and 24 h. Seed yield ranged from 0.56 to 0.98 t·ha⁻¹. Antibacterial assays revealed biphasic, concentration-dependent activity: 0.5% (w/v) extracts stimulated bacterial growth at 6 and 12 h but suppressed multiplication at 24 h, whereas 5% extracts at 6, 12, and 24 h promoted bacterial growth. Progenies P14, P20, and P23 demonstrated both relatively high seed yields and strongest antibacterial efficacy (88-90% growth reduction at 24 h and 0.5% concentration). These findings establish baseline seed productivity for Amazonian yam bean and demonstrate that optimal biopesticide formulations require low concentrations (0.5%) with extended exposure periods (≥ 24 h).