Potential Allelopathic Effects of Rice Hull Extracts on Barnyardgrass (Echinochloa crus-galli) Seedling Growth

Some rice cultivars have demonstrated allelopathic potential against most of the troublesome weed species in paddy fields. Hull extracts from 46 rice cultivars at various concentrations were used in bioassay tests to evaluate their effects on seedling growth of barnyardgrass. Hull extracts of cultivars Dashtisard and Dinorado showed higher inhibitory effects on root growth than the others while Alikazemi and Sepidrood had low inhibitory effects. Dinorado and Neda had high inhibitory effects on shoot growth, whereas hull extracts of Line-229 and USEN showed high stimulatory effects on shoot growth of barnyardgrass seedlings. The barnyardgrass roots were more sensitive to hull extracts than the shoot extracts. Hull extracts of five rice cultivars were identified with the highest inhibitory effect on barnyardgrass seedling growth, from which Dinorado, Neda, Dashtisard and IR-60 had inhibitory activities and Line- 229 had stimulatory potential. Inhibitory activity of rice hulls can be used to screen allelopathic rice cultivars. The cultivars with more hull allelopathic effects can lead us to cultivars with a natural source of herbicides. The genetic differences among rice cultivars exhibit variation in allelopathic effects on barnyardgrass growth. Breeding of Correspondence to: J. Asghari, Jafarasghari@yahoo.com J.Asghari et al 32 rice cultivars with greater allelopathic potential may provide natural herbicides for controlling weeds.