Solanum viarum, commonly known as tropical soda apple (TSA), is native to Brazil and Argentina but has become a harmful weed in many countries with tropical climates. This study was conducted to reassess the seed biology of TSA found in South Africa. Cold stratification (14 d), acid scarification (20% H2SO4 for 5 min), and sandpaper scarification (30 s) significantly improved percentage germination when compared to the control. The highest germination (99.5%) was achieved when seeds were germinated in 50% Hoagland's nutrient solution (HS). The lowest germination (66%) was recorded in the absence of phosphorus (P) under alternating light conditions. HS without nitrogen (N) completely inhibited seed germination of TSA under constant light conditions. These findings are useful in controlling TSA by amending the levels of N and P in soils. Seed germination of TSA was significantly enhanced by different concentrations of smoke-water and butenolide solution. Smoke-water dilution of 1∶500 v/v and butenolide concentration of 10−8M showed the highest seedling vigor indices (6,688 and 6,666, respectively) in comparison to the control (1,251) and gibberellic acid (GA3) concentrations (< 5,327). These findings suggest that germination of seeds or seedbanks of TSA might be successfully stimulated using smoke solutions. Subsequently, patches of seedlings emerging after treatment can be mechanically uprooted to reduce the infestation of TSA. However, justifying this with field trials is essential.
Nomenclature: Tropical Soda Apple; Solanum viarum Dunal SOLVI.