ASHS 2025 Conference

The plant root system is vital for nutrient uptake and plays a significant role in abiotic stress adaptation and defense. In sweetpotato, optimum root system architecture (RSA) development determines storage root (SR) yield potential. Root architectural responses to simulated natural lead levels (Pb) during the establishment and SR formation phases were characterized in two sweetpotato cultivars with known contrasting storage root yield potentials. Cultivars ‘Bayou Belle’ (BB) and ‘Beauregard’ (BX) grown on sand substrate were provided with 0.5X Hoagland’s nutrient solution with varying levels of Pb: 0, 10, 20, and 30 mg⋅L-1. The first experiment sampled entire root systems at 5, 10, and 15 days, corresponding to key adventitious and SR development stages. The cultivars varied in RSA attributes in response to Pb levels. In contrast to the cultivar BB, BX provided with 10 mg⋅L-1 Pb showed 83%, 21%, and 15% increases in main root length relative to the untreated controls at 5, 10, and 15 days, respectively. The cultivar BB consistently showed increased lateral root number and length relative to BX across all treatment levels. A second experiment was performed to produce SR samples at 50 days. The cultivar BX accumulated a 200- and 300-fold increase in Pb in SR at 20 and 30 mg⋅L-1 Pb, respectively, relative to BB storage roots at similar Pb levels. There were no differences in Pb accumulation across treatment levels in the cultivar BB. These findings are consistent with the hypothesis that increased root mass was associated with low accumulation of Pb and provide a basis for incorporating RSA traits in selecting Pb-tolerant cultivars.