The Competitive Response Investigation of Eighteen Wheat (Triticum aestivum L.) Cultivars with Wild Mustard (Sinapis arvensis L.)

The crop competitive ability is an important and profitable factor for increment impact on the weeds, and decreasing their yield loss. Characteristics such as height, leaf area, growth rate and tillering ability could be effective on competitive ability of cultivar ability. Primary growth rate is important on competitiveness, and any other factors that provides fast establishment of crops growth can be effective too. Thus, utilization of cultivars with height competitiveness ability is one of the considerable strategies for integrated weed managements. Many studies had shown that there are high correlation between crop height and its competitiveness ability. Asef et al (2) reported that tall cultivars reduced weed biomass more than dwarf cultivars due to light intercept and shading. Safahani- langrodi et al (32) in competition condition tall cultivars had high weed tolerance and cause to decrease weed biomass and set seed. There are an important relationship between LAI and weed competition. Hiffle et al. (13) showed cultivars with higher leaf area index had a greater yield stability. Dianat et al. (10) reported that in weed competitive conditions, there are significant difference in the number of tillers among wheat cultivars, while competitor and non-competitor cultivars have most and lowest tiller numbers respectively. Nadery and Ghadiri (25) showed that increasing wild mustard density decreased tiller number and more yield loss in weed competition have caused by decreased number of tillers.
Experiment was conducted in order to study morphological characteristics and yield of wheat (T. aestivum) cultivars in wild mustard (Sinapis arvensis L.) competition in greenhouse, University of Mohaghegh Ardabili, during 2013-2014. Treatments were 18 wheat cultivars [Karkheh, Alborz, Azadi, Shahpasand, Sepahan, Flat, Ghods, Roshan, Sorkh¬tokhm, Moghan3, Alvand, MS-81-14, Yarvarus, Shahriyar, Golestn, Bam, Niknajad, Karaj3] with and without competition. Treatments were arranged in a factorial experiment based on randomized complete block design with three replications. Each pot was filled with almost 5 kg soil mixture of sand and manure. In each pot 15 wheat seeds along or with wild mustard seeds had sown. In the spring after establishment of wheat seedlings, pots were thinned and 6 wheat seedling in each pots and only one established wild mustard was remained. At tillering stage, tillering numbers in 3 wheat plants were counted. Leaf area was calculated by Ross (28) and Pearcy et al. (27) method at heading stage then leaf area index was estimated by following equation.
Leaf area= K× (leaf length × maximum leaf width)
In which: K is constant coefficient (K = 0.75).
Light penetration within canopy and soil surface was measured by Lux meter version (LX-101). Wheat and wild mustard coverage were assessed visually (34, 23). All trails that involving yield such as (spike number, seeds number per spike and thousand seeds weight), at ripening stage of all wheat in the pots measured and weighted. Data were subjected to ANOVA, and means were separated using Fisher’s Protected LSD test at 0.05 probability (P ≤ 0.05).
Analysis showed that wheat cultivars had a significant effect on tillers number, but wild mustard competition had no significant effect (P ≤ 0.05). Means comparison showed that Alvand, Alborz, and Bam cultivars have 8 tillers and Flat only 2 tillers. Also, wheat cultivars at the stem elongation had significant difference on the leaf area but, wild mustard competition effects and interaction effects were did not a significant effects on the mentioned factor (P ≤ 0.05). Between wheat cultivars Alvand had maximum (1.09) and Alborz, Sepahan, Roshan and Flat had minimum leaf area. Wheat coverage at both tillering and stem elongation was different between wheat cultivars. At tillering stage, wheat coverage ranged 7.16 – 53.3, so Alvand and Bam had maximum and Flat and Ghods had lowest amount. Results revealed that, there was significant difference between cultivars light penetration percentage within canopy and soil surface. Wheat yield was influenced under wheat cultivars and wild mustard competition and interaction effects (P ≤ 0.05).
It has been hypothesized that increased crop density and spatial distribution and uniformity can increase weed suppression and thereby play an important role in weed management. This study results showed that, the means of light penetration percentage into soil surface on wild mustard competition were %9.82 in weed free and %13.69 in weedy treatments, also biological and economic yield reduced by %13.5 and %26, respectively. Although cultivars recommendation for each specific local area requires too long term studies (in time and site), but results of this study, well documented canopy architecture in view of more tillering potency for Alvand, Bam and Albors cultivars and %50 light penetration reached up to canopy middle for other cultivars such as Karkh, Alborz, Golestn and MS-81-14, which appear to be implemented in integrated weed managements design options.