Allelopathic Potential of Sweet Basil Ocimum basilicum L.) and their allelopathic effect on Seed Germination and Seedling Growth of cereal crop, Pennisetum glaucum L.

Abstract

Ocimum basilicum (O. basilicum) L. (sweet basil) is a traditional medicinal plant, well known for its variety of therapeutic properties and its abundant bioactive secondary metabolites, while Pennisetum glaucum (P. glaucum) (pearl millet) is a drought-tolerant cereal of global economic importance. The present study investigated the allelopathic potential of O. basilicum leaves and seeds on the seed germination and early seedling growth of P. glaucum under laboratory and greenhouse conditions. The experiments were both completely randomized with 3 replications. The aqueous extracts were obtained and tested on the seeds of P. glaucum and morphological parameters of germination and growth of the germinated seedlings were determined after 3 days. It significantly (P < 0.05 to P < 0.001) inhibited germination and growth in a concentration-dependent manner. In the laboratory bioassay, dry-seed extract at 30 g reduced germination to 56 % (versus 100 % in the control), radicle length to 1.15 cm (versus 2.67 cm) and plumule length to 1.25 cm (versus 3.05 cm). Fresh-leaf extract produced milder but still significant reductions. In the greenhouse experiment, the powdered leaves and seeds were added to the soil at rates of 10, 20 and 30 g pot-1 and the growth responses of the plants were measured 30 days after sowing on the basis of plant height, root length, number of leaves and fresh and dry biomass. In the greenhouse, 30 g seed powder lowered germination to 74 %, plant height to 6.30 cm (versus 12.33 cm), leaf length to 2.87 cm and root length to 2.90 cm, with corresponding declines in fresh and dry biomass. The highest concentration (30 g) recorded the highest germination percentage reduction, plant height, root length and biomass reduction compared with the untreated control. O. basilicum has a high allelopathic potency to inhibit the germination and early growth of P. glaucum. The results suggest that O. basilicum possesses promising allelopathic properties.