چكيده لاتين :
Background and objectives: Approximately 10% of the world's land is affected by flooding. Almost all crops, including wheat, are not tolerable to flooding stress. The occurrence of flooding stress in wheat has limited root growth, decreased dry matter accumulation, aging of the leaves before puberty, decreased tillering, production of insect florets, decreased hight, number of spikes and number of grain per spike, decreased biologicall yield, reduced 1000 grain weight and ultimately reduced grain yield. Accordingly, this study was carried out to evaluate the effects of flooding on grain yield and its components during tillering and stemming of wheat in two Morvarid and Koohdasht cultivars.
Materials and methods: To conduct this research, a pot experiment was conducted in a completely randomized block design with factorial arrangement in Gorgan University of Agricultural Sciences and Natural Resources in 2016. The experimental treatments consisted of the duration of stress period at five levels (0, 7, 14, 21, 28 days) as the first factor, the time of flooding based on developmental stages (tillering and stemming) as the second factor, and the cultivars (Morvarid and Koohdasht) were considered as the third factor. In order to apply flood stress, the pots for each treatment were placed inside a pond filled by water, so that up to 2 cm from the stems were underwater. After applying stress treatments, traits such as leaf area, number of spikes per plant, number of seeds per spike, 1000 grain weight, biological yield, grain yield and harvest index were measured. Also, linear and nonlinear functions were used to describe the relationships between measured traits and flood duration.
Results: The results of this study showed that the damages of flood stress in wheat depend on the time of plant placement under stress, the developmental stage where the stress coincides with it, and the type of cultivar used. In this study, characteristics such as leaf area, number of spikes per plant, number of grain per spike, 1000 grain weight, grain yield, biological yield and harvest index were significantly decreased by increasing the duration of flooding. The changes in some of the traits such as leaf area in Koohdasht cultivar, number of grain per spike in both cultivars, 1000 grain weight in Morvarid cultivar, and biological yield in both cultivars, followed by a segmented curve. So that in the first stages, Despite the increasing duration of flooding, each of these traits was fixed and unchanged, but, its value was linearly decreased by increasing duration of flooding to more than a certain limit for each trait. In other cases, the traits were reduced linearly from the beginning by increasing the duration of flooding. On the other hand, the number of grain per spike, grain yield, biological yield and harvest index in Kohdasht cultivar were always higher than Morvarid cultivars in different flooding treatments. Also, the highest flooding damage to leaf area, number of grain per spike, 1000 grain weight, grain yield and biological yield occurred when stress was applied at the stemming stage.
Conclusion: In general, flooding stress played a very important role in reducing wheat grain yield. In this regard, the length of stress period was the most important factor affecting the yield. The developmental stage and cultivar were ranked second and third in terms of importance, respectively. Therefore, due to the susceptibility of Golestan Province to flooding stress during tillering and stemming of wheat, it is very necessary to take the contraption to prevent of flooding in the fields and thereby prevent of yield losses.
