Abstract: In this paper, allelopathic rice PI312777 (PI) and non-allelopahtic rice Lemont(Le) were grown in the nutrient solution with two levels of phosphorus (P) supply, and their allelopathic effects on Echinochloa crus-galli L. were studied. The results showed that under phosphorous deficiency stress, the inhibitory effect of PI on E. crus-galli root growth had an obvious increase. After growing in the nutrient solution with low P supply (0.5 mg·L^-1) for 5, 10 and 15 days, the inhibitory rate of PI on E. crus-galli root dry matter increased by 5.64%, 3.89% and 12.13%, respectively, while that of Le did not show the same trend, compared with normal P supply. With low P supply for 5, 10 and 15 days, PI allelopathic effect on the leaf POD activity of E. crus-galli increased by20.19%, 15.47and 6.68%, IAAoase activity increased by 18.08%, 17.71% and 12.50%, while NR activity increased by 13.89%, 18.60% and 2.10%, respectively, suggesting that under P deficiency, PI enhanced its allelopathic potential through two pathways, i . e ., to increase the weed POD and IAAoase activities to slow down its growth rate, and to decrease the weed NR activity to affect its N uptake.

Key words: Fusarium 9568D, Abiotic Dracaena cochinchinensis, Blood resin