M. RAJABIAN - Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Guilan, I. R. Iran
J. ASGHARI - Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Guilan, I. R. Iran
S. M. R. EHTESHAMI - Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Guilan, I. R. Iran
M. RABIEE - Division of Seed Breeding, Rice Research Institute, Rasht, I. R. Iran

In order to determine the responses of morphological characteristics, yield and yield components of rapeseed (Brassica napus L.) to plant density and weed interference duration, a factorial experiment was conducted using a randomized complete block design with ۳ replications at the Rice Research Institute of Iran (RRII) in Rasht, in the ۲۰۰۸ growing season. The factors comprised plant density at ۲ levels (۸۰ and ۵۷ plants m۲) and weed interference duration at ۷ levels (including weed competition with canola until the end of crop emergence, ۲, ۴, ۸ leaf stages, and formation of flower buds). After the above mentioned growth stages, weeds of each treatment were removed manually until harvest. Two check treatments including weedy and weed free were also selected as control. The traits evaluated in this research were plant height, number of secondary branches plant۱, height of the lowest pod bearing branch, pod length, pod number plant۱, grain number pod۱, ۱۰۰۰ grain weight and grain yield. The results indicated that plant density, weed interference duration and their interaction had significant effects on all traits except pod length. In addition, the ۱۰۰۰ seed weight showed significant response to separate effect of each factor, but was not influenced by their interaction. The highest value of grain yield was related to a density of ۸۰ plants m۲ on total weed free check (full season weed free) and the lowest value of this trait was obtained from a density of ۵۷ plants m۲ on weedy check (fullseason weed infested) treatment.

canola, Full Season Weed Free, Grain yield, Plant Density, Weed Interference