Potential allelopathic effects of allelochemicals in aqueous extracts of leaves and root exudates of Capsicum annuum on vegetable crops

Phytotoxic effects of aqueous extracts of leaf (control (CK), 0.5, 1, 2, 4 and 8 %, w/v) and root exudates (CK, 10d, 20d, 30d, 40d, 50d) of Capsicum annuum were studied under laboratory condition on seed germination and seedling growth of 6 test vegetable crops [Hot pepper (Capsicum annuum L.),- tomato (Lycopersicon esculentum Mill.), cucumber (Cucumis sativus L.), radish (Raphanus sativus L.), pumpkin (Cucurbita moschata Duch.) and lettuce (Lactuca saliva L.)]. Both aqueous extracts and root exudates inhibited the seed germination and seedling growth of lettuce, and their inhibitory effects increased with increasing concentration and increase in the duration of cultivation time. In aqueous extracts of leaves and root exudates of C. annum, 28-compounds (alkanes, phthalate ester, phenols anilines and carboxylic acid) were isolated and identified by GC and GC-MS. The bioactivity of 15-suspected allelochemicals were studied on seed germination and seedling growth of Lactuca sativa. Two main inhibitory substances, N-phenyl-2-naphthylamine, phthalic acid, were found as potential allelochemicals of Capsicum annuum, with inhibitory effects on seed germination and seedling growth of lettuce. Both N-phenyl-2-naphthylamine, phthalic acid, showed separate and synergetic potential allelopathic effects.