investigation of casual relationships between effective morphophysiological traits of spring bread wheat cultivars tolerance to wild oat

introduction integrated weed management is based on combination of several management methods, while reducing the rate of the use of herbicides, will result in efficient management and sustainable weed control. ability of crop tolerance and prevent weed growth are two important traits in weed competition. an appropriate and suitable cultivar, has high yield potential in the presence of weed and under weed free conditions. such cultivar is weed tolerated and prevent the growth of weed. therefore this study was conducted to determine the relationships between some morphophysiological traits that affecting on tolerance index of bread wheat cultivars with wild oat in tropical regions condition such as the province of khouzestan. materials and methods in order to investigate the casual relationships between effective morphophysiological traits of tolerant spring bread wheat cultivars to wild oat, an experiment was conducted as strip block includes 4 densities of wild oat (0, 40, 80 and 120 plant per m2) in linear plots and 10 spring bread wheat cultivars (chamran, baz, atrak, arvand, maroon, shoeleh, chenab, virinak, dez and falat) in horizontal plots based on randomized completely blocks design with three replications in research farm of khozestan ramin agricultural and natural resources university during 2011-2012 and 2012-2013 growing season. each plot consists of 10 lines of wheat planting in distance of 20 cm. distance between the plots was 50 cm and the distances between the blocks was two meters and the plots were prepared with hand. the rate of wheat seed for cultivars of chamran, baz, atrak, maroon, chenab, virinak, falat and dez was 400, arvand 300 and shoeleh 250 plants per square meter and wild oat seed were planted at regular intervals between the wheat lines (for densities of 40 wild oat plant: 12.5 cm; 80 plant: 6.25 cm and 120 plant: 4.16 cm). results and discussion the results showed that with increasing weed density, tolerance index of wheat decreased. so with presence of wild oat, the average of grain yield of cultivars decreased by 0.31 percent. between wheat cultivars, maroon cultivar with 86.8 percent, had the highest index of tolerance. this cultivar had the highest grain yield and well prevent dry matter accumulation of wild oat. while virinak cultivar with 69.3 percent had the least tolerance index. this cultivar had the highest accumulation of dry matter of weed and also had the lowest grain yield. therefore these cultivars based on tolerance index were classified at three groups: 1) tolerant group (maroon), 2), medium group (some new cultivars such as baz, atrak, dez and chamran and old cultivars such as arvand, chenab and shoeleh) and 3) weak group (such as virinak and falat). modeling of wheat cultivars tolerance ability index with wild oat showed that different traits such as fertile spike number, harvest index, thousand grains weight, grain number in spikelet and spikelet number in spike cause to increase of wheat cultivars tolerance index ability against wild oat. but none-fertile spike trait, spike upper and under internode length could not strengthen tolerance index. yield and harvest index of wild oat decreased wheat cultivars tolerance ability index. conclusions therefore in wheat cultivated areas rich with wild oat, the cultivars are more favorable that to weed infestation, its yield does not decrease too much. such cultivars, well tolerated to weeds, prevented of its growth and seed production. so these cultivars such as maroon that is weed tolerant with preventing of its seed production, have ability to control the weed population in subsequent years with actions weed ecological control can be used in integrated control programs.