Allelopathic effects of the invasive plant Wedelia (Sphagneticola trilobata L.) aqueous extract on common beans (Phaseolus vulgaris L.)

Sphagneticola trilobata (L.) Pruski is an alien invasive weed with aggressive growth habits, environmental stress tolerance, and the ability to synthesize allelochemicals. However, in many parts of the world, this plant is still recommended for use in composting, phytoremediation, and as an ornamental ground cover in gardens. The present study investigated the allelopathic effect of S. trilobata on the seed germination, growth and yield of Phaseolus vulgaris L. To analyze the allelopathic effects of S. trilobata on P. vulgaris seed germination, hundred seeds of P. vulgaris were exposed to different concentrations of the aqueous extracts of fresh and dry S. trilobata (2.5×102, 5.0×102 and 7.5×102 g/L) in Petri dishes for five days. The impact of S. trilobata aqueous extract on the growth and yield of P. vulgaris was also studied with seedlings planted in a compost soil mixture. Results of the study suggested negative impacts of S. trilobata extracts on P. vulgaris seed germination, growth and yield. P. vulgaris seed germination was significantly lower in the treatments than in the control (p<0.05). Further, P. vulgaris plants treated with fresh plant extracts at 5.0×102 and 7.5×102 g/L concentrations had significantly lower shoot height, growth rate, leaf area, fresh shoot weight, dry shoot weight, root length, pod length and yield (p<0.05) than controls. From the results of the study, it can be concluded that S. trilobata aqueous extracts have a dose-dependent allelopathic effect on P. vulgaris seed germination, growth, and yield and among the dry and fresh plant extracts, fresh plant aqueous extracts have a more significant allelopathic impact. As S. trilobata contains water-soluble allelochemical, it should not be used in biofertilizer production, phytoremediation, or as live mulch.