Allelopathic effect of aquatic hull extract of rice (Oryza sativa L.) on growth of Silybum marianum and Echinochloa crus-galli

In this research, the allelopathy effect of rice hull extracts (Oryza sativa L.) onSilybum marianum and Echinochloa crus-galli was investigated. The water extracts were gotten from 13 cultivated rice cultivars (Oryza sativa L.) and then used to show their phytotoxicity potential on germination and seedling growth of Silybum marianum and Echinochloa crus-galli. The water hull extracts of Kadus and Chapar sar 3 had the highest inhibitory effect on dry weight and root length of Silybum marianum, respectively. It seemed that not only did the hull extracts have inhibitory effect on germination of Silybum marianum, but also had stimulatory effects on stem length. On the other hand, there was no significant effect on root and stem length and germination of Echinochloa crus-galli. Meanwhile, the extract of Shafagh induced the highest increase in the dry weight of Echinochloa crus-galli. Therefore, it was shown that the various rice cultivars had different effects on the plants, and it may be possible to breed rice cultivars to gain greater allelopathic potential.   Key words: Allelopathy, Echinochloa crus-galli, Oryza sativa L., Silybum marianum.