Allelopathic effects of Averrhoa carambola L. leaf leachates on germination and growth of Hordeum vulgare L. and Eleucine coracana (L.) Gaertn.

This study investigated the allelopathic effects of phytochemical compounds in Averrhoa carambola L. [starfruit (family Oxalidaceae)] leaf leachates on seedling growth of Hordeum vulgare L. (Barley) and Eleucine coracana (L.) Gaertn. (Finger millet). The A. carambola leaf extract was bio-assayed to determine the bioactivities of compounds and their phytochemical nature. In GC-MS analysis, total 19 bioactive-chemical compounds were identified the major were: Triterpenes (21.31 %), Bis (2-ethylhexyl) phthalate (14.44 %), 3,7,11,15-Tetramethyl-2-hexadecen-1-ol (9.85 %), Gamma-Sitosterol (8.99 %) etc. Most of these suppressed the seedlings growth. In laboratory assay, effects of 3-concentrations (10 %, 20 % and 30 %) of leaf extract were determined on seed germination and seedling growth. To evaluate the allelopathic effects in nursery, 10 g, 20 g and 30 g leaf mulch was added per pot. Findings revealed dose-dependent dual allelopathic effects where low concentrations stimulated while higher concentrations acted as phytotoxic. It reduced seed germination, root length of Eleucine coracana and; shoot length and biomass of Hordeum vulgare. In pot culture, Eleucine coracana, compared to Hordeum vulgare showed more stimulation (hormesis) at lower concentrations and resistance at doses of mulch. This allelopathic tolerance in H. vulgare indicated its potential for inclusion of Averrhoa carambola in agroforestry systems. It is recommended to evaluate Averrhoa carambola for dose dependent allelopathic effects on the other important Himalayan crops under field conditions.