Seed Dormancy and Germination Characteristics in Six Solanum Species Distributed on the Korean Peninsula

Crop wild relatives (CWRs) are critical resources for crop improvement and addressing food security. The genus Solanum includes many wild species genetically related to major crops. However, seed propagation methods for Solanum taxa distributed on the Korean Peninsula are not well-established. In this study, seed morphology and effects of incubation conditions on germination and dormancy were evaluated in 6 Solanum species classified as CWRs in Korea: Solanum lyratum, S. japonense, S. nigrum, S. sarrachoides, S. americanum, and S. viarum. The seeds possessed fully developed embryos at the time of dispersal and the seed coats readily absorbed water. We investigated germination characteristics under various temperatures, cold stratification periods, and gibberellic acid (GA3) concentrations. Germination percentage of S. lyratum and S. japonense was significantly higher under cold stratification (≥62.0% after 12 weeks at 5 °C) or GA3 treatment (≥77.0% at 1000 mg·L−1) than for temperature treatment alone (≤3.0% at 25/15 °C), indicating non-deep physiological dormancy (PD). Seeds of S. nigrum, S. americanum, and S. viarum exhibited non-deep PD with conditional dormancy and higher germination efficiencies through GA3 1000 mg·L−1 than under temperature treatment alone (25/15 °C). Seeds of S. sarrachoides were classified as non-dormant. These findings may contribute to the practical mass propagation of Solanum.