Comparing the Competitive Ability of Old and New Wheat Cultivars Against Rocket {Eruca Sativa) in Iran

During the 2003-2004 growing season, an experiment was conducted at the plant protection research institute in karaj, iran, to compare the competitive ability (ca) of eight wheat cultivars released during the last 50 years. each cultivar (tabasi, roshan, karaj2, azadi, niknejad, mahdavi, shiraz and pishtaz) was grown in weed-free conditions or infested with rocket (eruca sativa). the results indicated that grain yield competitive indices differed significantly between the cultivars. an old cultivar, karaj2, showed a high ability to withstand competition (awc), high competitive indices (ci) and low grain yield in the weed-free plots (3865 kg ha'1). cultivar tabasi, a less competitive cultivar, had the lowest awc and ci amongst the cultivars. there was a significant negative correlation between awc and grain yield in the weed-free plots. also, no significant correlation was observed between ci and awc. the number of spikes m'2, number of fertile tillers plant1, number of plants m'2, and number of kernels spike1 were the most influenced components of yield in weedy conditions. this study showed that local adaptation is important for the karaj2 cultivar to prevent yield loss (tolerance) in weed-infested conditions, and more suppression ability in the presence of rocket.