SummaryThis study was conducted to determine the biological effects of a 12C5+ ion beam on male-sterility in Solanum villosum, a leafy vegetable whose consumption and demand continues to escalate due to its high nutritional and medicinal value. S. villosum is still underutilised due to low vegetative yields that have hampered full domestication and commercialisation. Yields are limited mainly by prolific early flowering and excess fruit and seed set in competition with leaf expansion and productivity. Thus, there is a need to reduce this overbearing in order to circumvent the source-sink imbalances that occur after anthesis. Carbon-ion beam-induced male-sterility is proposed as a possible strategy. Based on overall plant development from germination rate, seedling survival frequency, the proportion of self-fertile M1 plants, and the frequency of diverse growth and development mutants in the M2 progeny, with an emphasis on male-sterility, 20–30 Gy of 12C5+ ions was determined to be optimum. Four male-sterile mutant types (T-1, T-2, T-3, T-4) similar to those reported from a previous -ray mutation study were isolated at higher frequencies. In addition, a novel abnormal floral organ mutant (T-5), whose flowers were sepalloid in mid-Spring, stamen-less in late-Spring, indeterminate in Summer and whose structure and fertility was partially restored, with berry and seed set in Autumn, was isolated. This restoration is potentially useful for seed propagation since the self-fertile seed progeny of the T-5 mutant were 100% male-sterile (sepalloid). Maintenance by seed has been made possible by conditional partial restoration of fertility that occurs in a regular and stable pattern.