Document Type : Original Articles
Gaduate in Weed Science, Tehran University
Professor, Department of Agronomy and Plant Breeding, Faculty of Agricultural Science and Engineering, Tehran University.
Associate Professor, Weed Science Research,Iranian Research Institute of Plant Protection.
Instructor, Gilan Rice Research Institute. 5-Expert, Weed Science Research, Iranian Research Institute of Plant Protection.
Instructor, Gilan Rice Research Institute. 5-Expert, Weed Science Research, Iranian Research Institute of Plant Protection
The probability of Barnyardgrass resistance to some common rice herbicides used in the rice fields of Gilan, Mazandaran and Fars Provinces was investigated by conducting a series of greenhouse and Petri dish bioassay tests on 37 biotypes collected in 2005-2006. Greenhouse experiments involved screening tests with Petri dish tests implementing dose response assays to determine doses of herbicides inhibiting root and stem length growth by 50% (ID50) as well as to determine the sensitivity of the biotype to herbicides. Screening tests were carried out for each province separately for a given herbicide using a randomized complete blocks design with four replications. Minimum recommended doses of Butachlor, Molinate, and Thiobencarb were added to pots of 8cm water height before 2-leaf growth stage of Barnyard grass. Propanil was sprayed at the 3-4 leaf stage. Measurement of dry weight, number of surviving plants and visual rating (based on the EWRC rating scale) were conducted 4 weeks after treatments. A completely randomized design with four replications was also used in the Petri dish tests. This sensitive biotype was subjected to a range of herbicide doses resulting in 50% inhibition of root and stem growth and the response of biotypes to the ID50 of the sensitive biotype was further studied. Root (for Propanil) and stem length (for Butachlor, Molinate, and Thiobencarb) were measured 7 days after treatments. According to results obtained from greenhouse and Petri dish assays, it was revealed that Barnyardgrass biotypes collected from Gilan, Mazandaran and Fars Provinces were not resistant to the tested herbicides (Propanil, Butachlor, Molinate, and Thiobencarb). The results from Petri dish tests were correlated to those of greenhouse experiments.