فصلنامه علوم زراعی ایران
سال نوزدهم شماره 2 (پیاپی 74، تابستان 1396)

In this study, all information about management practices in wheat crop were recorded and measured (including 250 variables) from 684 irrigated and rainfed wheat fields during two growing seasons of 2013-2014 and 2014-2015 in Golestan province, Iran. Wheat production in Golestan province can be divided into three production systems including low- yielding rainfed, high- yielding rainfed and irrigated wheat. This study covered 216 fields in low-yielding rainfed, 119 fields in high- yielding rainfed and 349 fields in irrigated wheat and evaluated using comparative performance analysis (CPA). In each system one production model was identified and according to this model, potential yields of wheat were estimated. The results showed that while the average yield of farmers were 1966, 3985 and 3936 kg kg.ha-1, they could harvest up to 5025, 7954 and 8029 kg.ha-1 in low-yield rainfed, high- yielding rainfed and irrigated farms, respectively, hence there were yield gaps of 60, 50 and 51%, respectively. The most important factors found for these yield gaps in low- yielding rainfed system included: use of no-till planter (32%), seedbed prepartation (17%), foliar fertilization (15%), chisel (15%), herbicide (13%) and nitrogen fertilizer (9%). The most important factors for yield gaps in high- yielding rainfed system included: legume rotation (26%), field size (21%), nitrogen fertilizer (15%), potassium fertilizer (12%), manure fertilizer (11%), subsoiler (10%) and fungicide (5%). However, the most important factors for yield gaps in irrigated wheat system included: irrigation (27%), nitrogen fertilizer (25%), sowing date (20%), use of N8720 cultivar (10%), subsoiler (9%) and using of furrower (8%). It was concluded that with proper management of field and considering the listed yield gaps factors in each system, it would possible to obtain higher yield levels comparing with current yield levels that farners harvest. The amount of yield increased will be about 3000 kg.ha-1 in low- yielding rainfed wheat system and about 4000 kg.ha-1 in high- yielding rainfed wheat and irrigated wheat systems in comparison with current yield levels.

Bread wheat is known as the staple food crop and its quality properties are variable because of diffrences among cultivars, climatic conditions and farming systems. Due to the lack of adequate information about the quality of different bread wheat cultivars in the farmers’ fields, in this research quality and bakery properties (thousand grain weight, protein content, wet gluten and SDS) of grain samples of four different cultivars of bread wheat (irrigated and rainfed), collected from the farmers’ fields during two growing seasons 2013-14 and 2014-15, which grown on large areas in the country were evaluated. The results showed cv. Azar 2 had better quality than cv. Sardari cultivar by 11.46% protein, 26.3 wet gluten and 55.2 ml SDS in two growing seasons. On the other hand, the quality characteristics of Chamran and Pishgam irrigated bread wheat cultivars were notsignificantly different in different provinces. Also the lowest quality of wheat was observed in Kurdistan, Hamadan and Kohgiluyeh and Boyerahmad. This may be due to nutrient shortage in the soil of those provinces that are largely under rainfed production of wheat.

To evaluate germination and grain yield of three spring bread wheat cultivars affected by seed hydropriming and sowing date, three experiments were conducted. In the first experiment, effect of 7 hydropriming durations (0, 6, 8, 10, 12, 14 and 16 h) was examined on germination and seedling growth of Star, Chamran and Fong cultivars. In the second experiment, some biochemical traits and enzyme activities were measured in the primed seeds for 6, 8 and 10 h hydropriming durations. Effect of three sowing dates (12 Nov., 10 Dec. and 7 Jan.). hydropriming and control treatments on grain yield of wheat cultivars was researched in third experiment which was carried out as factorial arrangement in randomized complete block design with three replications in the research field of Faculty of Agriculture, Shahid Chamran University of Ahvaz, during 2014-2015 growing season. Results of the first experiment showed that hydropriming with 8 h imbibition had the most positive effect on seed vigor of bread wheat cultivars. Results of the second experiment showed that with increasing hydropriming duration to 10 h, α amylase enzyme activity and of soluble carbohydrates and proteins contents in seeds increased, also higher malondialdehyde content and insufficient antioxidant enzyme activities (enzyme activity was not increased or reduced by following imbibition to 10h) in 10 h when compared with 8 h hydropriming duration was observed. In this research, Relationship between antioxidant enzyme activities with germination and seedling growth were positive and significant. Results of the field experiment showed that hydropriming treatments significantly improved seedling emergence, by 2.3%, and reduced average emerging time by 1.4 days as compared with control. The sowing date× cultivar interaction effect indicated that delayed sowing had the highest and lowest effect on star and fong cultivars, respectively. Average grain yield significantly increased, by 7%. in hydropriming treatment in comparison to control. Also application of seed hydropriming with suitable soaking duration improved seed emergence in delayed sowing dates.

Plant growth regulators (PGRs) have been used to reduce losses of wheat grain yield under limited moisture conditions. The effect of three PGRs including cycocel, salicylic acid and brassinoestroeid on growth and grain yield of four bread wheat cultivars Chamran, Shiroudi, Pishtaz and Sirvan under normal and withholding irrigation after flowering was examined. The experiment was carried out as factorial split plot arrangement in randomized complete block design with three replications in 2014-15 and 2015-16 growing seasons. The results showed that water stress significantly reduced number of grains per spike, grain weight per spike, thousand grain weight, harvest index, biological yield and grain yield. However, water stress had the least effect on thousand grain weight (11.2%) and the highest effect (25.2 %) was observed on biological yield. Furthermore, application of PGRs, especially cycocel, increased spikes.m2, grains per spike, harvest index, thousand grain weight and grain yield. Cycocel, salicylic acid and brassinoestroeid, had positive non-significant effect on grain yield components. The highest grain yield was achieved from application of cycocel in both growing seasons (3696 and 4439 kg.ha-1, respectively). Also, the highest grain yield was obtainted from Sirvan cultivar in both growing season (3608 and 4448 kg.ha-1, respectively). According to these results, although water stress reduced yield and its components, the alleviating effect of PGRs could compensate some proportions of water stress effect. The compensatory effect of PGRs was 31.3, 23.5 and 23.2 percent for cycocel, salicylic acid and brassinoestroeid, respectively. Therefore, application of PGRs can be considered as an alternative way to alleviate the effect of terminal drought stress on grain yield of bread wheat cultivars.

The present study was conducted in two separate experiments under drought stress and normal irrigated conditions using randomized complete block design with three replications at Rice Research Institute of Iran in Rasht, Guilan, Iran, during 2014-2015 growing season. Plant materials included 14 mutant lines (7 lines from Hashemi, 6 lines from Tarom and one line from Khazar) and four commercial rice cultivars (Hashemi, Tarom, Khazar and Gilaneh). Factor analysis resulted in five and four main factors for normal irrigated and drought stress conditions, which explained 81.5% and 79.3% of the total variation, respectively. The results indicated that under drought stress and normal irrigated conditions, selection of plants with high grain fertility (%) and panicle length and shorter plant height and internode length leads to increased grain yield. Cluster analysis classified the genotypes into five groups under both conditions. Discriminant function analysis indicated very high accuracy (100%) of grouping based on cluster analysis. The results of different analyses identified rice lines; TM6-230-VE-8-4-1, TM6-250-10-7-1, TM6-B-2-1-E and HM5-250-E-1-1 as superior genotypes with higher grain yield (2227.6 kg.ha-1) and the other desirable traits including high grain fertility (80.9%) and low panicle exsertion (6.3 cm) under drought stress condition. The average grain yield of these genotypes was 4739.9 kg.ha-1 in normal irrigated condition. Reduction of grain yield due to drought stress was 53% for these genotypes, and 60% for all of genotypes. Therefore, these selected genotypes can be considered in rice breeding programs to improve drought tolerance germplasm.

To evaluate response of two rice cultivars to different rate of nitrogen fertilizer, an field experiment was carried-out with three factors including cultivar at two levels (Gilaneh and Abjiboji), nitrogen fertilizer application at two levels (split and non-split) and rate of nitrogen fertilizern at five levels (0, 60, 75, 90 and 105 kg.ha-1 nitrogen from urea source). These factors were arranged as factorial in randomized complete block design with three replications at the experimental field of rice research institute (Rasht) and rice research station of Chaparsar (Tonkabon) in two growing years 2014 and 2015. Grain yield, plant height, harvest index and agronomic nitrogen use efficiency were measured. The results revealed that the difference between Gilaneh and Abjiboji (A local cultivar) for grain yield and plant height was the same in two growing seasons. However, the grain yield of Gilaneh was significantly higher than Abjiboji, and its plant height was significantly shorter than this local rice cultivar at all levels of fertilizer in two growing seasons. Also, the response of graing yield of these two rice cultivars to nitrogen fertilizer was different in two locations (Rasht and Chaparsar). Therefore, management of nitrogen fertilizer application should be different in Rasht and Chaparsar. The superiority of nitrogen use efficiency of Gilaneh in split application of nitrogen fertilizer (Max. 18.5 kg.kg-1) compare to Abjiboji (12 kg.kg-1), revealed the superiority of Gilaneh and split application of nitrogen fertilizer. For Abjiboji split application of 75 kg.ha-1 nitrogen fertilizer (with grain yield of 3830 kg.ha-1) can be recommended in Chaparsar, and 90 kg.ha-1 nitrogen fertilizer as nonsplit in Rasht (with grain yield of 4050 kg.ha-1) were suitable. However, for Gilaneh, new improved rice cultivar, split application of 90 and 90-105 kg.ha-1 nitrogen fertilizer can be recommended in Chaparsar and Rasht (with grain yield of 5050 and 4650 kg.ha-1), respectively were more suitable.