Allelopathic interaction of pepper (Capsicum annuum) and pearl millet (Pennisetum glaucum) intercropped

Intercropping is common practice in many regions of Tunisia, particularly in Cap-Bon where different crops such as tomato, pepper, cucumber, peanut, corn, pearl millet and sorghum are grown together in the same field and at the same time for self-sufficiency. A number of these crops and vegetables are known for their allelopathic activities. The interaction between plants could be within the individuals of the same species (intraspecific interaction or autotoxicity) or between different species (interspecific interaction or teletotoxicity). Little is known about allelopathic interaction of some of these intercropped plants in mixed farming systems in our local conditions. Therefore, the objectives of the present investigation are to evaluate, under laboratory condition, the allelopathic effect of mixed crops, which interacted positively or negatively when cultivated together in the same field. Two plant species were used to study the effects of their aqueous extract on germination and growth of each other (pepper and pearl millet). The results suggested that aqueous extracts from shoots and roots significantly inhibited germination and seedling growth and the inhibitory effects were increased proportionally with the extract concentration. The shoot and root aqueous extract also exhibited intraspecific and interspecific allelopathy. Generally, it was observed that roots were more toxic than shoots. For root extract, the highest inhibition percentage was gained from the effect of pearl millet on pepper (40%) and highest autotoxicity was observed from pearl millet (36%). The effect of shoot extract on germination indicated that the highest reduction (55%) was obtained from pepper shoot extract on pearl millet and highest autotoxicity was observed from pepper which reached (45%). In most cases autotoxicity appeared to be more severe than teletotoxicity, on seed germination of the two intercropped plant species.