Study of the Response of Rainfed Wheat (Triticum aestivum L.) Cultivars in Semi-arid and Semi-humid Regions of Golestan Province

Introduction: Wheat (Triticum aestivum L.) is one of the world's largest cultivated plants and one of the most important aspects in wheat breeding is the stability of cultivars under various environmental conditions. The stability of a product is, in fact, its ability to survive in a particular environment. In other words, a plant must be able to tolerate cold, heat, shortage or excess water, changes in the length of the day, the intensity of light, and a wide range of chemical and physical conditions of the soil. Materials and Methods: In order to study the response of rainfed wheat cultivars in semi-arid and semi-humid regions of Golestan province, an experiment was conducted at the research farm of Gonbad Kavous University (semi-arid area) and a field in Gorgan (semi-humid area) based on the randomized complete block design with four replications and with seven wheat cultivars (Aftab, Azar 2, Sardari, Qaboos, Karim, Koohdasht and Line 17) in 2015-2016. In this experiment, the phenological traits (days from planting to anthesis, physiological maturity), morphological traits (grain filling period, grain filling rate, maximum leaf area index), yield and yield components (number of tillers per square meter, grain per spike, spikelet per spike, grain per square meter, mean grain weight, grain yield, biological yield and harvest index) of cultivars were evaluated in two regions. To compare the means, LSD test was used at the 5% probability level. All analytical steps were performed in SAS software version 9.4. Results and Discussion: The results of analysis of variance showed that the effect of cultivar in Gonbad and Gorgan regions on all traits except grain filling rate in Gorgan and number of tillers per m2 in Gonbad-Kavous was significant at 1% and 5% levels. The average period of examination in Gonbad-Kavous was 178 days and in Gorgan 195 days after planting. In Gonbad-Kavous, Sardari cultivar (33 days) had the highest and Line 17 (27 days) had the least grain filling period. But in Gorgan, the Qaboos cultivar (41 days) was the highest and the Koohdasht cultivar (38 days) had the least grain filling period. The results also showed that there was a significant difference between the cultivars in both locations in terms of grain filling rate. In Gonbad-Kavous, Azar 2 had the lowest grain filling rate (5.8 g.day.m-2), and Line 17 had the highest grain filling rate (14.2 g.day.m-2). But in Gorgan, Sardari cultivar had the lowest (5.5 g.day.m-2) and Koohdasht cultivar had the highest (14.37 g.day.m-2) grain filling rate. Correlation coefficient between grain filling period and grain yield (r= 0.359**) and grain yield and grain filling rate (r= 0.847**) were positive and significant. Grain yield and harvest index were higher in Gorgan than Gonbad-Kavous. In Gonbad-Kavous, there was no significant difference between grain yield per unit area, biological yield per unit area and harvest index in most of the cultivars. In Gorgan, there was a significant difference between cultivars for grain yield, but there was no significant difference between biological yield and harvest index among more cultivars. In Gorgan, Koohdasht and Sardari cultivars had the highest and lowest grain yield per unit area (564.2 and 218.3 g.m-2) and harvest index (50.32 and 32.2%) respectively. There was a significant correlation between grain yield and harvest index (r= 0.907**) and biological yield (r= 0.665**) in the level of 1%.Conclusions: In general, due to the fact that other than cultivars Sardari and Azar 2, which are special for cold regions, other cultivars are compatible with tropical and semi-arid conditions. According to the climatic conditions (rainfall and temperature), two regions of Gorgan and Gonbad-Kavous were observed during the experimental period which were more in line with the tropical conditions. In most traits, there was a slight difference between the cultivars. Different cultivars achieved high grain yield in Gonbad and Gorgan. In Gorgan region, Koohdasht cultivar had a shorter time from planting to maturity and this cultivar had higher grain yield. In Gonbad Kavoos region, although the Qaboos cultivar had no superiority in most traits than other cultivars, it had the highest yield and shorter time from planting to maturity and harvest.