Ranking the Wheat Cultivars Based on Competitive Ability with Weeds

Weeds are an important challenge to crop production, particularly in sustainable agriculture. Today, identification of highly competitive cultivars is an easy and inexpensive method for weed management in sustainable agriculture systems. Watson et al. in their study of 29 barley varieties found that yield loss due to weed competition varied from 6 to 79 percent, which is related to their ability to compete. In the case of wheat, for more than four decades, the difference of the weed competitive ability between wheat cultivars has been investigated. Two aspects of cultivar competitiveness can be defined, competitive index (CI) and weed interference tolerance index (WITI). CI is the ability of a cultivar to reduce weed growth and WITI is the ability of a cultivar to achieve high yield despite weed competition. These traits differ based on genetical and agronomical aspects. CI is often associated with traits including vigorous growth, allelopathic potential, crop cover, and height and leaf area. Although for environmental stresses high tolerance indexes are important, the competitive index is more important in the long-term management of weed management. Trusting the tolerance index alone can lead to a sharp increase in the weed seed bank, which may not tolerate high-tolerance cultivars. So, the present study was carried out to classify Iranian wheat cultivars based on traits related to competition and tolerance indices and to determine the correlation between indices with yield and yield components.
Material and This experiment was conducted to classify Iranian wheat cultivars based on traits related to competition and tolerance indices and to determine the correlation between indices with yield and yield components in the agricultural research farm of the faculty of agriculture and natural resources, University of Mohaghegh Ardabili at 2015-2016 growing season. For this purpose, 25 wheat cultivars were tilled in November 2015 under with or without weed competition. In each plot, 10 wheat lines were cultivated at a distance of 20 cm and a length of 5 m. The experiment was conducted in a randomized complete block design with three replications. At the beginning of spring, from each plot, a sample of wheat plants was harvested at a surface area of 0.25 m2, dried at 75 ° C for 48 hours in order to measure the initial dry weight of the cultivars. Sampling from weeds was conducted before the end of growing season. Wheat plants harvested at maturity stage from 1 m2 and seed yield was reordered. To determine the yield loss, CI and WITI was used appropriate formulas.
The results showed that there was no significant correlation between weed density with growth traits of wheat cultivars, while there was a significant negative correlation between weed dry weight and these traits. The highest correlation was found between the primary cover with dry weeds weight (R2= -0.70; P