فصلنامه تحقیقات غلات
سال یازدهم شماره 4 (زمستان 1400)

To investigate the effect of foliar application of cytokinin on gas exchange, remobilization and allocation of photosynthetic materials of wheat cultivars, an experiment was carried out under field conditions. The experimental treatments included foliar application of 6-benzylaminopurine at two levels (0 as control and 50 μM), and six wheat cultivars (Azadi, Karaj 3, Roshan, Falat, Sardari and Yavarus) which as factorial experiment in a randomized complete block design with four replication were studied. The results showed that foliar application of cytokinin increased leaf area index (LAI) and Roshan had the highest leaf area index. Photosynthetic rate of the studied cultivars was also different and the use of cytokinin increased the photosynthetic rate. Foliar application of cytokinin increased the remobilization of Falat, Roshan and Sardari cultivars and decreased Azadi cultivar, but had no significant effect on Karaj 3 and Yavarus cultivars. The effect of cytokinin on the allocation of photosynthetic assimilates to stem, leaf and spike of the studied cultivars was very different, so that with the application of cytokinin, the allocation of photo-assimilates to leaf decreased in Falat and increased in the other cultivars, but in the case of spike, the allocation of photo-assimilates to spike decreased in Roshan cultivar and increased in Karaj 3 and Sardari cultivars, while it did not affect on the other cultivars. In contrast, the allocation of photo-assimilates to stem was reduced about 3.3% by foliar application of cytokinin and Sardari, Yavarus and Roshan cultivars had the highest percentage of the allocation of photo-assimilates to stem. Grain yield of Karaj 3, Yavarus and Sardari cultivars increased by foliar application of cytokinin and the highest and lowest grain yield was observed in the control treatment (no application of cytokinin) in Azadi (5700 kg/ha) and Roshan (3100 kg/ha) cultivars, respectively, while under cytokinin foliar application, Yavaros and Roshan cultivars with 6300 and 3300 kg/ha had the highest and lowest grain yield, respectively. The results of this experiment showed different effects of cytokinin on different traits and wheat cultivars, but to obtain more accurate and complete results, it is suggested to measure the internal cytokinin concentration of wheat cultivars.

Among the crop plants, maize has a quite special status for supplying human food. Researchers have found that drought has a direct relationship with the limitation of corn cultivation and production in the world. Drought stress cause about 17% decrease in the annual grain maize yield in the world. This study was carried out to evaluate the effect of drought stress on some gene expression and biochemical traits related to drought tolerance in maize under field conditions. The experiment was conducted in split plot based on randomized complete block design with three replications. The main factor was drought stress in three levels including 75±5 mm (normal conditions as control), 115±5 mm (mild stress) and 140±5 mm (severe stress) evaporation from the class A evaporation pan, and sub-factor included three maize hybrids, Karoon and SC704 (late maturity hybrids) and Mobin (mediun early maturity hybrid). The measured traits included the amount of abscisic acid (ABA) and indole acetic acid (IAA) and expression of MIPS, ZmFer1 and ZmPR10 genes. Sampling was done in three growth stages including four leaves, pollination and 10 days after pollination. The results showed Karoon hybrid had a significant difference with the other hybrids under under severe stress conditions and ten days after pollination for ABA and IAA content (345 and 468 ng/g fresh weight, respectively) and showed more tolerance to drought stress. The evaluation of MIPS, ZmFER1 and ZmPR10 genes also showed that among the studied hybrids, Karoon hybrid had more gene expression in different stress levels than the control and in almost all measured stages. The results of this research showed that the higher content of abscisic acid and indole acetic acid hormones as well as the higher expression of the studied genes are effective in inducing drought stress tolerance and among the studied hybrids, Karoon with the higher content of these hormones and the higher expression of genes compared to the other cultivars had higher tolerance to drought stress.

The production of hybrid cultivars is one of the most major maize breeding methods, which can be facilitated based on the heterotic grouping of cultivars. In this study, 93 maize inbred lines from different sources were grouped into two different heterotic groups based on SNP markers data. Then, six selected inbred lines from these two heterotic groups along with B73 MO17 as check inbred lines were crossed in a complete diallel crosses, and the grain yield of 64 produced hybrids were evaluated in a simple lattice design with three replications at the Urmia Tobacco Research Center, Urmia, West Azarbaijan province, Iran. Based on the grain yield of these F1 hybrids and the SNP markers data, grain yield of 1566 hybrids, which can be potentially produced from the cross of individuals of two heterotic groups, was predicted using a mixed linear model. The results showed that the hybrid H50 (1_4×18_2) had higher grain yield than the check hybrid SC704. Since this hybrid (H50) was early maturity compared to SC704 hybrid (as the dominant hybrid in the region), so if this result is confirmed in the other complementary experiments, it can be introduced as a new hybrid. To obtain the complementary results, 13 superior hybrids of the current study including H4, H9, H10, H11, H17, H18, H38, H41, H42, H45, H47, H49 and H50 along with three check hybrids, Simon, SC703 and SC704, were re-evaluated under environmental conditions of Karaj region, Alborz province, Iran. The results showed that although the check hybrids SC703, Simon and SC704 had high yields with an average of 12.63, 12.01 and 10.64 ton/ha, respectively, however, H50 hybrid with an average of 10.50 ton/ha not only had a desirable grain yield, but also showed fewer days to tasseling and silking compared to the check hybrids. Therefore, H50 as the superior hybrid of this experiment is suggested for evaluation in the regional trials to introduce as a new early maturity and high-yielding hybrid.

To overcome the increasing requirement of agricultural production in the future climate scenarios, the most effective and economic approach is to breed cultivars with high drought tolerance. To select drought tolerant lines in barley, 19 promising barley lines along with a check variety, Goharan, were evaluated under two environmental conditions, normal and terminal drought stress. The experiment was conducted in a randomized complete block design with three replications at the South Khorasan Agricultural and Natural Resources Research and Education Centre, during two cropping years, 2019-2021. Comparison of the environmental means showed that days to maturity, grain filling period, 1000-grain weight and grain yield of the studied lines in the first year were significantly reduced by drought stress. The results of the drought sensitivity and tolerane indices indicated that YI, HM, STI and GMP indices can be used to select barley cultivars and lines in the areas that are exposed to terminal drought stress, but in other areas, MP, STI, GMP and HM indices are suggested. Based on this result, lines number 20, 11 and 14 were respectively determined as the most tolerant lines to terminal drought stress in this experiment. Evaluation of stability indices and estimation of their correlation with grain yield of the studied lines also showed that grain yield had a positive and significant correlation with the variance of genotype and environment interaction (θ₍ᵢ₎) and regression coefficient (b) and a negative and significant correlation with the Kang (KR) and Thennarasu (NP(2,3)) statistics. In total, the results of most stability statistics investigated in this experiment showed that lines number 20, 14 and 8 were high-yielding and stable lines for cultivation under both normal and terminal drought stress conditions.

To evaluate the effect of planting management on forage production in hybrid and open-pollinated sorghum cultivars, a two-year experiment based on split plot factorial in randomized complete block design with three replications was conducted at the Seed and Plant Improvement Institute, Karaj, Iran. Planting date at four levels (July 1, 10 and 23, and August 1), was considered as the main factor and the factorial combination of planting method at three levels (without priming as control, seed hydropriming, and transplanting) and genotype at two levels (Pegah cultivar and Speedfeed hybrid) as the sub-factor. The results showed that delayed planting on July 10th and 23rd, and August 1st reduced forage yield by 15.1, 32.7, and 48.7%, respectively, compared to the July 1st planting date. The highest silage yield in the first and second harvests (106.21 and 62.78 ton.ha-1, respectively) were obtained by the transplanting Pegah and Speedfeed on the July 1st, respectively, whereas the seed hydropriming of Speedfeed produced the highest total forage yield (147.80 ton ha-1). The results of the economic evaluation showed that the highest net income (99.11 million Rials.ha-1) and the maximum benefit-to-cost ratio and sales return (2.52 and 60.35%, respectively) were obtained by planting the hydroprimed seeds of Speedfeed hybrid on the July 1st. The transplanting of Pegah cultivar was uneconomical in all the studied planting dates, whereas transplanting Speedfeed hybrid from July 1st to July 23rd was superior to the conventional sowing method. In total, the results of this study showed that to produce the maximum yield and economic profit, it is recommended to carry out the planting operation at the earliest possible time with hydroprimed seeds of Speedfeed hybrid.

To study the effect of biofertilizer and putrescine application on grain filling components and dry matter remobilization of triticale (Triticosecale Wittmack) in water limitation conditions, an experiment was conducted as factorial in randomized complete block design with three replications at the research farm of faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran, in 2020. The experimental treatments were included irrigation in three levels (full irrigation as control, irrigation withholding at 50% of heading and booting stages as moderate and severe water limitation, respectively), application of biofertilizers in four levels (no application as control, application of vermicompost, application of Mycorrhiza, both application vermicompost and Mycorrhiza), and application of putrescine (water sprying as control, and foliar application of 0.4 and 0.8 mM putrescine). The results showed that co-application of vermicompost and mycorrhiza along with foliar application of 0.8 mM putrescine under full irrigation conditions decreased dry matter remobilization from stem (34.59%) and shoot (28.76%) and their contribution in grain yield (94.14 and 85.74%, respectively) compared to no application of biofertilizers and putrescine under irrigation withholding conditions at booting stage. Furthermore, co-application of vermicompost and mycorrhiza along with foliar application of 0.8 mM putrescine under full irrigation conditions increased root weight (62.11%), root volume (63.17%), current photosynthesis (85.53%) as well as contribution of current photosynthesis in grain yield (28.65%), grain filling period (20.37%) and grain yield (39.6%) compared to no application of biofertilizers and putrescine under irrigation withholding conditions at booting stage. Based on the results of this experiment, it seems that the application of biofertilizers and foliar application of putrescine can increase the grain yield of triticale under water limitation conditions by improving current photosynthesis and grain filling components.