Competition of rapeseed (Brassica napus L.) cultivars with weeds
One of the agronomic methods in weeds management is to recognize cultivars possessing high competitive ability with weeds and to recognize the effective characters in order to breed competitive cultivars in weeds sustainable management. Cultivar identification and discrimination has become an important issue in rapeseed breeding programs. A field experiment was carried out at the research station of Islamic Azad University of Firoozabad, Iran in the 2009 to 2010 growing season. The experiment was conducted using split-plot arrangements in a randomized complete block design with three replications. The treatments included two levels of weed (W0: weed free, and W1: weedy) as main plots and eight rapeseed cultivars (Modena, Okapi, Sarigol, Licord, Hyola308, Zarfam, RGS003andSLM046) as sub-plots. Ten plant samples were chosen from the middle part of each row and days from emergence to flowering, days from emergence to physiological maturity, plant height, pod length, pods on main stem, pods per plant, seeds per pod, 1000-grain weight, harvest index and grain yield were determined. The ANOVA results show that weeds resulted in reduction of all traits except pod length. In this investigation, the highest and lowest grain yield in weed free condition was seen in Modena and Okapi, respectively while, the highest and lowest grain yield in weedy condition was seen in Sarigol and Hyola308, respectively. Based on the results of grain yield reduction, ability to withstand competition (AWC) index and cluster analysis, Sarigol cultivar, which had high grain yield in both weed free and weedy conditions, was the best cultivar that has competitive ability with weeds and Hyola308 cultivar was the worst. 1000-grain weight was also the best trait to evaluate cultivars that has competitive ability with weeds for grain yield improvement.
Key words: Competitive ability, weed, grain yield, cultivars.