Investigation of <i>Solanum carolinense</i> Dominance and Phytotoxic Effect in <i>Festuca arundinacea</i> with Special Reference to Allelochemical Identification, Analysis of Phytohormones and Antioxidant Mechanisms

Exposure to invasive weeds in pasturelands may result in significant losses and toxicity in forage crops. These species may also contain a compound that may be toxic as well as beneficial depending upon the effect induced. The Ministry of Environment of the Republic of Korea has now recognized <i>Solanum carolinense</i> (Horsenettle)—an invasive weed species—as a potential threat to forage crops in pasturelands and to the entire agro-ecosystem. As a forage crop, <i>Festuca arundinacea</i> (Tall fescue) is one of the major economical crops and diets of livestock; in this study, the competition patterns of <i>Solanum carolinense</i> and <i>Festuca arundinacea</i> were examined with respect to their seeding ratios and growth periods. In addition, an extract from the root of <i>Solanum carolinense</i> (SCE) was prepared and treated at 2500 ppm and 5000 ppm in a <i>Festuca arundinacea</i> plant to observe its effect. The experimental results showed that as the growth period of the Horsenettle and the SCE treatment increased, the germination rate, plant height, root length, fresh weight, and dry weight of the tall fescue were significantly decreased. Moreover, the SCE treatment significantly increased the quantities of reactive oxygen species (O₂⁻ and H₂O₂), antioxidants (Catalase and Peroxidase), and endogenous phytohormones (Abscisic acid and Salicylic acid), and simultaneously decreased the superoxide dismutase content in the tall fescue shoots. Furthermore, we identified several glycoalkaloids from the SCE extract, among which Solanidan-3-ol, (3β,5α)’ possessed a higher number (52%). Based on these results, we predicted that the Solanidan-3-ol, (3β,5α)’ present in horsenettle has a major role in imposing phytotoxicity on agricultural crops. The glycoalkaloids in the <i>Solanum</i> species have been reported to possess both phytotoxic and therapeutic uses. Based on this concept, we believe that the compound available in <i>Solanum carolinense</i> could be used in developing crop protection or medicinal products through broader research. Conversely, our findings also showed the probable risk of horsenettle to the agro-ecosystem, especially in terms of forage production.