Comparison of allelopathic potential of Sri Lankan traditional rice varieties (Oryza sativa L.) using radish (Raphanus sativus L.) as an indicator plant

Allelopathy is the direct influence of an organic substances released from one plant on the growth and development of other plants. To avoid the hazardous and indiscriminate use of chemicals for weed control in paddy fields much concerns were deposited on proper assessment and manipulation of allelopathic properties of rice plants. There is a huge variation in allelopathic potential among rice varieties. Therefore, in this experiment relay seeding technique without soil (experiment 1) and with soil as a medium (experiment 2) were conducted under laboratory condition to observe and screen the allelopathic potential of selected Sri Lankan traditional rice varieties on seed germination, shoot and root length and dry matter production of radish (Raphanus sativus) as a phototoxic sensitive test crop. Significant differences (p≤0.05) were observed among different rice varieties in terms of seed germination and growth inhibition of radish. The dry weight accumulation of rice cultivars ranged from 12.5-76.3% in experiment 1 and 15.9-79.9% in experiment 2. All tested varieties of rice performed inhibitions to studied characters of radish. In both experiments, the highest dry weight reductions were noticed with rice varieties Pachchaperumal and Herathbanda. Both the evaluation methods were positively correlated in determining percent reduction in all the measured parameters of radish. According to the results it can be concluded that the al-lelopathic potential of rice varieties varies in a very broad range and out of varieties tested Pachaperumal and Herathbanda showed highest allelopathic potential against radish growth.