Evalution of Allelopathic Potential of Some Traditional and Improved Rice Cultivars of Guilan Province and their Comparison With Allelopatically IRRI Approved Rice Cultivars

To compare the allelopathic potential of some Guilan province rice cultivars with allelopathically approved IRRI rice cultivars, a factorial experiment was conducted in completely randomized block design with 3 replications on the Experimental Farm of Agricultural College of Guilan University in spring 2005. Two factors including a) seven rice cultivars (traditional cultivars of Hashemi, Ali Kazemi, and Tarom and 2 modern cultivars of Khazar, and Dorfak and two IRRI cultivars of Dollar and IR64), and b) two types of planting, (including monoculture and mixed culture of each cultivar with Barnyardgrass) were used. A monoculture of Barnyardgrass was also used as a control. Growth rate (GR) and leaf area index (LAI) of Barnyardgrass were determined after 2, 4, 6, and 8 weeks of transplantation (WT), in mixed and monoculture treatments. In addition, after 3, 6, and 9 WTs the type and number of weeds in 1 m2 of each plot was determined. Rice plant samples were taken in 2, 4, 6, and 8 WTs, and were extracted in the Lab to be tested for germination for barnyardgrass and redroot pigweed seeds in Petri dishes. The filed research results showed that GR, LAI, number of weeds and yield of barnyardgrass grown with Dollar cultivar were lower than the others, which indicates higher allelopathic properties of this cultivar. Rice cultivars water extract evaluation of Petri dish also showed that Dollar cultivar has higher allelopathic potential than the other cultivars. Increasing the concentration of the water extracts increased the suppression of treated seedlings. From starting to geramination stage of the rice cultivars, allelopathic effects of the water extracts decreased. Leaves had the highest level of allelopathic potential in comparison to other organs. In other words, the pure extract of Dollar cultivar taken form samples in 2 and 6 WTs had the highest allelopathy potential among the cultivars and samples.