Establishment of a Rapid Propagation System for Waltheria indica L. and Acquisition of Nematode-Repellent Active Compounds

This study aimed to establish an efficient tissue culture and rapid propagation system for Waltheria indica L., to evaluate the potential of its tissue-cultured materials producing active compounds with repellent activity against Meloidogyne incognita . The proliferation of sterile seedlings was investigated using seeds as explants. Adventitious buds and root induction from hypocotyls and leaves, adventitious root suspension culture system was also established. The results showed that the optimal sterilization method was 75% ethanol for 30 s followed by 15% NaClO for 15 min, achieving non-contamination and 49.17% germination rate. The best medium for seedling proliferation was MS + 0.05 mg/L 6-BA with a proliferation coefficient of 9.17, while the optimal rooting medium was MS + 0.1 mg/L IAA, yielding a rooting rate of 96.67%. Adventitious buds and seedings were induced from hypocotyls on MS + 0.1 mg/L 6-BA. Callus induction from leaves reached 100%, and adventitious roots were induced from callus on MS + 1.0 mg/L 6-BA + 0.2 mg/L NAA + 1.0 mg/L 2,4-D. The optimal suspension culture medium for adventitious roots was MS + 30 g/L sucrose + 1.0 mg/L NAA, with a relative proliferation multiple of 5.03, and the best subculture time was 30 days after inoculation. Among the 12 compounds isolated from W. indica , antidesmone and trans-tiliroside exhibited repellent effects on second-stage juveniles of M. incognita , with chemotaxis index of 0.41 and 0.22, respectively at 10 mg/L. Analysis of compound content revealed that suspension-cultured adventitious roots significantly enhanced the relative content of antidesmone. Although tissue culture conditions suppressed trans-tiliroside synthesis in stems and leaves, exogenous application of 0.05 mg/L 6-BA effectively reversed this inhibition and promoted its accumulation. This study establishes a rapid propagation system for W. indica , providing a theoretical foundation for its large-scale production, accelerates breeding, and enhances its secondary metabolite content.