Allelopathic Effect of Three Wild Plants ( Azadirachta indica, Tithonia diversifolia and Thevetia peruviana) on Tomato ( Lycopersicum esculentum Mill.) Growth and Stimulation of Metabolites Involved in Plant Resistance

Abstract

The aim of this study was to determine the allelopathic effects of Azadirachta indica oil and aqueous extracts of Tithonia diversifolia and Thevetia peruviana on the growth and stimulation of metabolites involved in tomato plant resistance. Randomized in blocks within a shaded area, the different treatments prepared at 10% and 15% (v/v and w/v) in water were subsequently applied on tomatoes seeds to monitor the effect on germination, and on tomatoes leaves to monitor the effect on growth and resilience of the plants. The result showed that in stressful conditions all the treatments significantly inhibit (p < 0.05) the germination capacity of the seeds from 21.22% to 92.61%, the germination rate from 39.82% to 92.76% and the germination viability of the seedlings from 64.67% to 100%. However, the negative allelopathic effect of the treatment was significantly reduced (p < 0.05) when used for germination initiation by botanical priming. In addition, while T. diversifolia at 10% promotes a better aerial and root growth in tomato plants, T. peruviana at 15% induces the activation of resistance mechanisms in tomato plants by increasing protein levels to 104.5%, phenol levels to 183.33% and peroxidase enzyme activity to 586.15%. Therefore, allelopathic compound of wild plants would be a good alternative for growth promotion and resistance of tomato crops.