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We conducted a 3-year (2017-2020) field experiment in the wheat base of Jinzhong Agricultural Hi-tech Industries Demonstration Zone, aiming to determine the measures of nitrogen topdressing and the regulatory effect of cycocel in spring to increase wheat yield. Four nitrogen topdressing dates were set up under the condition of cycocel spraying and control (CK) during the rising period: 10 days (D10), 20 days (D20), 30 days (D30), and 40 days (D40) after regreening stage, to analyze the impact of different N topdressing dates on winter wheat yield and the regulation effect of cycocel on stem characteristics, lignin content and related synthetase activities. The results showed that compared to other nitrogen topdressing dates, D30 increased spike number by 1.4%-5.2%, grain number per spike by 0.4%-12.0%, 1000-grain weight by 1.7%-9.4% and yield 8.8%-22.1% respectively. Compared to D10 and D20, D30 significantly improved the activities of phenylalanine ammonia-lyase (PAL) at 0-21 days and 35-42 days after the formation of the second section and increased that of tyrosine ammonia-lyase (TAL) at 0-42 days after the formation of the second section, and increased the lignin content of stem, the internode quality, and the breaking resistance of stem, reduced plant height, and thereby improved the lodging resistance. However, D40 increased grain number per spike by 4.5%-10.1% and yield 0.04%-11.3%, but reduced the activities of PAL and TAL at 0-42 days after the formation of the second internode, reduced the lignin content, weakened the stem strength, and increased the risk of lodging. After spraying cycocel, plant height decreased significantly, the activities of PAL and TAL enhanced, the lignin content in internodes increased, the stem strength advanced, and reached a significant level under D30. Under the condition of nitrogen topdressing combined with cycocel spraying in spring, PAL and TAL activities were significantly positively correlated with lignin content. Lignin content was significantly positively correlated with stem breaking resistance. Stem breaking resistance was significantly positively correlated with lodging resistance index. Yield and its components were significantly posi-tively correlated with internode diameter, weight and breaking resistance, and significantly negatively correlated with plant height and internode length. Overall, nitrogen topdressing combined with spraying cycocel 30 days after regreening could promote the synthesis and accumulation of lignin, and improve stem plumpness, plant lodging resistance and yield.

To explore the effects of long-term tillage on bacterial community structure in different soil layers of dryland wheat fields and its relationship with soil physicochemical properties, a long-term field experiment was conducted from 2016 to 2021 in Wenxi Experimental Demonstration Base of Shanxi Agricultural University, Shanxi Province. We studied the effects of no-tillage (NT), subsoiling-tillage (ST), and deep plowing (DP) on soil physicochemical properties; α and β diversity of the bacterial community; and dominant and different species of phyla and genera in different soil layers. Additionally, PICRUSt2 was used to predict the metabolic function of soil bacterial community. The results revealed that subsoiling-tillage and deep plowing significantly increased the soil water content in the 20-40 cm soil layer and significantly decreased the soil organic carbon content in the 0-20 cm soil layer compared with that under no-tillage for five consecutive years. Compared with that under deep plowing, subsoiling-tillage significantly increased soil water content, soil organic carbon content, dissolved organic carbon content, and dissolved organic nitrogen content in the 0-20 cm soil layer. Compared with that under no-tillage, subsoiling-tillage and deep plowing increased the α diversity of the soil bacterial community in the 0-40 cm soil layer, and subsoiling-tillage was higher than deep plowing. Compared with that under no-tillage, subsoiling-tillage and deep plowing significantly increased the relative abundances of Acidobacteria and Nitrospirae in the 0-20 cm soil layer and Acidobacteria, Chloroflexi, Gemmatimonadetes, Rokubacteria, GAL15, and Nitrospirae in the 20-40 cm soil layer. Compared with that under no-tillage, subsoiling-tillage and deep plowing significantly increased the relative abundance of Nitrospira in the 0-20 cm soil layer and Rubrobacter and Streptomyces in the 20-40 cm soil layer. Compared with that under deep plowing, subsoiling-tillage significantly increased the relative abundance of Acidobacteria and Gemmatimonadetes in the 0-40 cm soil layer. Redundancy analysis demonstrated that the contents of soil organic carbon, dissolved organic carbon, and dissolved organic nitrogen in the 0-20 cm soil layer exerted positive effects on Actinobacteria and Blastococcus , and the soil water content in the 0-40 cm soil layer exerted positive effects on Acidobacteria, Chloroflexi, and Gemmatimonadetes under subsoiling-tillage. The results of PICRUSt2 prediction showed that subsoiling-tillage and deep plowing significantly increased the relative abundance of amino acid metabolism and the metabolism of cofactors and vitamins but decreased the relative abundance of lipid metabolism of bacterial communities in the 20-40 cm soil layer compared with that under no-tillage. Compared with that under deep plowing, subsoiling-tillage significantly increased the relative abundances of amino acid metabolism in the 0-40 cm soil layer and other amino acid metabolism in the 0-20 cm soil layer. In conclusion, subsoiling-tillage or deep plowing could increase the soil water content, α diversity of the soil bacterial community, and their metabolic capacity in the dryland wheat fields during the summer fallow period. The relative abundance of Acidobacteria and Gemmatimonadetes and the ability of amino acid metabolism of the bacterial community were increased by subsoiling-tillage, and thus the contents of soil dissolved organic carbon and dissolved nitrogen can be increased.

To examine the differences of three improved sowing methods in winter wheat yield and nitrogen efficiency and reveal the characteristics responsible for such differences, we conducted field experiments in the Jinnan area of the western Huang-Huai-Hai wheat region for three consecutive seasons from 2016 to 2019. The three improved sowing methods were wide space sowing (WSS), furrow sowing in moisture soil (FS), and three-dimensional uniform sowing (TDUS), with conventional drilling sowing (CDS) as the control. The results showed that meteorological factors such as accumulated temperature, solar radiation, and precipitation in the growing seasons from 2016 to 2019 showed great intra- and inter-annual variations. Compared with CDS, the improved sowing methods (WSS, FS, and TDUS) enhanced spike number per unit area and increased grain yield in three growing seasons by 18.3%-55.5%, 8.6%-22.2%, and 10.9%-39.5%, respectively. The three methods increased nitrogen uptake efficiency (NE up ) by 5.8%-57.1%, pre-flowering nitrogen transfer ratio ( N p / N t ) by 3.0%-15.3%, and nitrogen efficiency by 7.9%-35.7%, respectively. We developed a structural equation model (SEM) by integrating meteorological factors and experimental variables. The results showed that the three improved sowing methods could reduce the effects of extreme low temperature on wheat plant population, increase NE up and N p / N t , and provide sufficient nitrogen supply to the grains of high-spike number wheat population for high yield and high nitrogen efficiency. In summary, our results demonstrated that WSS, FS, and TDUS all improved NE up and N p / N t in the 2016-2017 season when meteorological conditions were favorable for wheat growth, and enhanced yield components with high SN, leading to high yield and high nitrogen efficiency. In contrast, in both 2017-2018 and 2018-2019 seasons with extremely low temperature and uneven distribution of meteorological conditions, WSS had a higher number of tillers at the jointing stage and enhanced pre-flowering nitrogen uptake and translocation, whereas TDUS had a relatively stable nitrogen uptake rate, leading to a stable grain yield.

Mechanisms underlying leaf photosynthetic acclimation in winter wheat under elevation of CO 2 concentration ([CO 2 ]) remain unclear. The aim of the study was to investigate the effects of source-sink variation on photosynthetic acclimation induced by drought under elevated [CO 2 ]. A winter wheat ( Triticum aestivum L. 'Zhengmai 9023') pot experiment was conducted in open top climate chambers with [CO 2 ] of 400μmol·mol -1 or 600 μmol·mol -1 and soil water content at 80%±5% or 55%±5% of field capacity. The parameters of chlorophyll fluorescence, electron transport rate, photosynthetic curve, leaf nitrogen content, and grain yield were measured at the elongation and heading stages. Under drought condition, leaf PSⅡ photochemical efficiency was not affected by elevated [CO 2 ], but the maximum electron transport rate and the ratio of electron partitioned to carboxylation reaction in Calvin cycle was increased at the elongation stage, and thus the Rubisco carboxylation rate and maximum photosynthetic rate were increased. Although the maximum electron transportation rate and partitioning ratio of electron to carboxylation reaction in Calvin cycle remained high at the heading stage, the PSⅡ photochemical efficiency, Rubisco carboxylation rate, and triose phosphate utilization rate were decreased by elevated [CO 2 ], which consequently reduced the maximum photosynthetic rate for plant under drought stress. Under drought condition, elevated [CO 2 ] increased wheat tiller biomass, kernel number, and kernel weight per ear, but decreased infertile kernel number, resulting in an overall increase in grain weight. In conclusion, the elevated [CO 2 ]-induced increase in wheat grain yield per tiller under drought condition was mainly caused by enhanced photosynthetic performance at the elongation stage. The photosynthetic acclimation in source leaves during the heading stage under elevated [CO 2 ] was mainly attributed to the reduction in PSⅡ photochemical efficiency and triose phosphate utilization rate, but not to the maximum electron transportation rate, ratio of electron partitioned to carboxylation in Calvin cycle or sink leaf strength.

In order to clarify the mechanisms underlying dryland wheat quality improvement through sowing technology, the effects of wide space sowing (WSS), furrow sowing (FS), and drill sowing (DS) on soil moisture dynamics and grain protein formation in dryland wheat field were studied in Wenxi, Shanxi Province in 2017-2018 (normal year) and 2018-2019 (dry year). The results showed that compared with the DS, FS significantly increased soil water storage in the 0-200 cm depth at anthesis stage (8.2%-18.7%), and increased the soil water storage in 0-60 cm layer during the two years, 60-120 cm layer in normal year, and 120-200 cm layer in dry year. WSS significantly increased soil water storage in 0-200 cm layer at anthesis stage in normal year (5.2%). Compared with DS, FS significantly increased water consumption of anthesis to mature stage, while WSS significantly increased water consumption from sowing to anthesis stage in dry year. Compared with DS, the glutamine synthetase (GS) activity of grains at 15-35 days after anthesis was significantly increased by FS and WSS, while the glutamate synthase (GOGAT) activity of flag leaves and grains at 5-35 days after anthesis was significantly increased by FS in the dry year. Compared with DS, FS significantly increased grain yield by 20.4%-44.8%, grain protein yield by 25%-49%, and increased grain albumin and globulin contents. WSS significantly increased grain yield by 9%-40%, and increased grain gliadin content. Under different sowing modes of dryland wheat, GS and GOGAT activities in flag leaves and grains after anthesis were significantly correlated with water consumption at anthesis to maturity stage. There were significant correlations between GS and GOGAT activities in flag leaves and grains and 0-120 cm soil layers in the normal water year, and between GS and GOGAT activities and 0-60 cm, 120-200 cm soil layers in the dry year. The contents of grain albumin, globulin and total protein were significantly correlated with soil water storage in 0-60 cm layer at anthesis stage, as well as soil water storage in 120-200 cm layer at anthesis stage in the dry year. In conclusion, FS was beneficial to increasing soil water storage at anthesis and water consumption after anthesis of dryland wheat, improving GS and GOGAT activities of flag leaf and grain, with positive consequences on yield and grain protein content. In addition, deep water storage was more conducive to quality improvement in the late growth period in the dry year.

To understand the effects of deep ploughing during the fallow period and soil moisture-based furrow sowing on the utilization of water and nitrogen in dryland wheat, a field experiment following split-plot design was carried out from 2016 to 2018 in Wenxi County of Shanxi Province, with deep ploughing during the fallow period and no-tillage as main plots and soil moisture-based furrow sowing and drilling sowing as sub-plots. The results showed that, compared with no-tillage treatment, deep ploughing during the fallow period significantly increased soil water storage efficiency (by 38.3%-42.2%), soil water consumption (by 9.2%-13.2%), and nitrogen accumulation in each growth period, which in turn increased the yield by 7.1%-12.0%, annual water use efficiency by 5.5%-14.0%, nitrogen fertilizer absorption efficiency by 4.4%-10.3%, and nitrogen fertilizer partial productivity by 7.1%-12.0%. Compared with the treatment of drilling sowing, the soil moisture-based furrow sowing increased the total water consumption during the growth period (by 2.0%-4.8%) and nitrogen accumulation in each growth period, increased the yield by 6.8%-12.4%, water use efficiency during the growth period by 4.5%-7.2%, nitrogen absorption efficiency by 4.4%-10.3%, nitrogen partial productivity by 6.9%-12.4%. In conclusion, deep ploughing during the fallow period and soil moisture-based furrow sowing in dryland wheat could promote the storage and utilization of natural precipitation, increase plant nitrogen accumulation, and facilitate high wheat yield.

To understand the growth responses of dryland wheat to different application rates of phosphorus fertilizer in different rainfall years, we examined root characteristics, spike number, yield and phosphate utilization. Results would help improve phosphate fertilizer use in dryland wheat production. We carried out a field experiment at the research station of Shanxi Agricultural University from 2012 to 2016. We examined the effects of four application rates of phosphorus (0, 75, 150 and 225 kg·hm -2 on root growth, phosphate utilization and yield formation of dryland wheat in different years with contrasting rainfall pattern. Compared with the treatment without phosphorus fertilization, phosphate application increased root surface area at all growth stages and root weight density in the 0-80 cm soil layer at jointing, anthesis, and maturity stages. Phosphate application significantly increased soil water consumption from jointing to anthesis, and total soil water consumption in the growing season. Phosphate application enhanced the amount of pre-anthesis phosphate translocation and phosphate accumulation of grain. Spike number, yield and water use efficiency were increased with 75, 150 and 225 kg P·hm -2 by 9.2% to 22.5%, 11.8% to 30.0%, and 2.1% to 12.1%, respectively. In the dry years, the application rates of 150 and 225 kg P·hm -2 in comparison to 75 kg P·hm -2 significantly increased root weight density and root surface area at all stages, soil water consumption from sowing to jointing and from jointing to anthesis, and total water consumption in the growing season. In comparison to the rate of 75 kg P·hm -2 , 150 and 225 kg P·hm -2 increased soil water consumption from sowing to jointing by 7.3-8.7 mm, soil water consumption from jointing to anthesis by 15.6-18.1 mm, and total water consumption by 15.6-18.1 mm. Significant increase in the pre-anthesis phosphate translocation and phosphate accumulation in grain was higher under 150 and 225 kg P·hm -2 than that under 75 kg P·hm -2 in dry years. Furthermore, the two rates (150 and 225 kg P·hm -2 ) in dry years increased spike number by 9.3%-10.7% and yield by 11.9%-14.6%. The application rate of 150 kg P·hm -2 significantly improved phosphorus use efficiency by 20%-82% in comparison to other rates. In normal years, the rates of 150 and 225 kg P·hm -2 increased root surface area, root weight density at both anthesis and maturity compared with 75 kg P·hm -2 . Soil water consumption from anthesis to maturity and total soil water consumption in the growing season were also increased by 1.2-15.0 and 3.8-23.1 mm, respectively. In addition, phosphorus accumulation in post-anthesis and phosphate accumulation in grain were increased in both 150 and 225 kg P·hm -2 , which increased spike number by 1.4%-9.6% and yield by 3.5%-10.4%. The effects of phosphate application at the rate of 150 kg P·hm -2 were significantly different from 75 and 225 kg P·hm -2 . In conclusion, phosphorus fertilizer application enhanced uptake of water and phosphate in dryland wheat at early and middle growth stages in dry years and at the late growth stage in normal years. Phosphorus application increased wheat yield mainly due to the increases of spike number. The application of 150 kg P·hm -2 is the best choice for high water and phosphorus fertilizer use efficiency and high yield in both dry and normal years.

To tackle the issue of rainfall delay during dryland wheat sowing season and further examine the effects of seeding rate on water use and yield formation, a field experiment was conducted at Wenxi Experimental Station, Shanxi Province between 2015 and 2017. We used two sowing dates, i.e. September 20 and October 10 as early (EB) and late (LB) sowing in main plots, and each with three seeding rates as 67.5 (LD), 90 (MD) and 112.5(HD) kg·hm -2 . The results showed that compared with LB, EB increased total soil water consumption by 11-22 mm over the entire growing season. With the increases of seeding density, total soil water consumption increased by 2-20 mm. Soil water consumption before anthesis tended to increase for LB, while there was a significant increase of soil water consumption after anthesis for EB. Compared with LB, the pre-anthesis nitrogen translocation and post-anthesis nitrogen accumulation amount in EB were increased under LD and MD, but decreased under HD. For EB, the pre-anthesis nitrogen translocation amount and post-anthesis nitrogen accumulation amount were highest at LD. Under LB, the pre-anthesis nitrogen translocation amount and post-anthesis nitrogen accumulation amount were greatest at high sowing density. EB significantly increased grain yield by 163-996 kg·hm -2 than LB. EB significantly increased grain yield and water use efficiency by 5%-26% and 2%-21% compared with LB, respectively. The nitrogen absorption efficiency and harvest index were 3%-36% and 11% higher under LB than that under EB. As for seeding rate, a low level tended to gain higher grain yield, water use efficiency, nitrogen uptake efficiency and nitrogen harvest index under EB, whereas a high level tended to gain higher values of grain yield, water use efficiency, nitrogen uptake efficiency and nitrogen harvest index under LB. In addition, the pre-anthesis nitrogen translocation was closely related with 100-200 cm soil water consumption before anthesis, especially for stem + sheath, glume + spike nitrogen translocation. The post-anthesis nitrogen accumulation was significantly correlated with 100-300 cm soil water consumption after anthesis. In conclusion, early sowing with a seeding rate of 67.5 kg·hm -2 and late sowing with a seeding rate of 112.5 kg·hm -2 could be promising options to boost dryland wheat production.

Crop yield improvement is necessary to keep pace with increasing demand for food. Due to climatic variability, the incidence of drought stress at crop growth stages is becoming a major hindering factor to yield improvement. New techniques are required to increase drought tolerance along with improved yield. Genetic modification for increasing drought tolerance is highly desirable, and genetic engineering for drought tolerance requires the expression of certain stress-related genes. Genes have been identified which confer drought tolerance and improve plant growth and survival in transgenic wheat. However, less research has been conducted for the development of transgenic wheat as compared to rice, maize, and other staple food. Furthermore, enhanced tolerance to drought without any yield penalty is a major task of genetic engineering. In this review, we have focused on the progress in the development of transgenic wheat cultivars for improving drought tolerance and discussed the physiological mechanisms and testing of their tolerance in response to inserted genes under control or field conditions.

Soil physical properties are a greatly important part of the soil and indicator of soil quality, which can directly affect soil nutrient turnover and crop yields in dryland. This study was carried out with three tillage practices during the summer fallow season since 2011, including no tillage (NT), plow tillage (PT), and subsoiling (ST) in dryland winter wheat fields of the Loess Plateau. Results showed that soil tillage during the summer fallow had a small effect on soil bulk density (ρ b ) in the 0-50-cm soil profile before sowing and after harvesting of winter wheat. Soil ρ b under NT at a depth of 20-30 cm was significantly greater than those under PT in both seasons. Both soil gravimetric water content (θ g ) and volumetric moisture content (θ v ) after harvesting increased by 28.8-78.6% and 37.5-87.3%, respectively, compared with those before sowing. Adoption of PT significantly increased soil θ g and θ v in the entire 0-50-cm profile before sowing compared with NT and ST (P < 0.05). In addition, there was a small effect on soil porosity (e.g., total porosity, air-filled porosity, and capillary porosity) in the profile of 0-50 cm both before sowing and after harvesting. Overall, short-term tillage during summer fallow mainly affected soil water content in the 0-50-cm soil profile, and it had a slight effect on other physical soil properties.

Field experiments were carried out to study the effects of different mulching times (30 or 60 d after previous wheat harvest) and mulching methods (whole-mulching, half-mulching and no- mulching) on wheat plant N absorption and assimilation after deep plowing in fallow period on dryland. The results showed that mulching improved water storage efficiency in fallow period and soil water storage of 0-300 cm at sowing stage significantly. Mulching in fallow period, especially the whole-mulching, increased the N accumulation amount of each growth stage, N translocation amount and rate before anthesis (NABA) , and N accumulation amount after anthesis (NAAA) and grain N. Yield, N uptake efficiency (NUPE), N partial factor productivity (NPFP) and N harvest index (NHI) were all significantly increased under mulching, and whole-mulching had better effects. Mulching at 30 d after previous wheat harvest significantly increased the soil water storage of 0-300 cm at sowing stage and the water storage efficiency in fallow period compared with mulching at 60 d after previous wheat harvest. Compared with mulching at 60 d after previous wheat harvest, mulching at 30 d increased the N accumulation amount of each growth stage, the N accumulation amount in leaf and shoot at maturity, the NABA of stem + sheath, leaf and shoot and the yield. The soil water at the depth of 0-300 cm at sowing stage was positively correlated to N mobilization amount before anthesis and N accumulation amount after anthesis. The N mobilization amount of stem + sheath had a remarkable direct effect on its yield with the direct path coefficient of 0.619. In summary, mulching in fallow period increased the soil moisture at sowing stage to promote N absorption and utilization, increase yield and improve quality, and whole-mulching in advance had better effects.

A field test was carried out in Qiujialing Village, Wenxi, Shanxi from 2009 to 2011 to study the soil water movement of 0-300 cm layer, yield formation and water use efficiency (WUE) of wheat with deep plowing and mulching the whole ground immediately (no mulch as control) 15 days and 45 days after harvest. The results indicated that deep plowing and mulch in fallow period could improve soil water storage of the 100-180 cm layer before sowing, the soil water storage efficiency in fallow period, and soil water storage from pre-wintering stage to booting stage. Compared with deep plowing 15 days after wheat harvest, deep plowing 45 days after wheat harvest did better in improving soil water storage and water use efficiency, as well as ear number and yield, which was more conducive in the year with more precipitation. Generally, deep plowing and mulching after raining during fallow period could benefit the soil water storage and conservation, thus would be helpful to improve wheat yield in dryland.

Field test was carried out to study the effect of tillage in fallow period on soil water before sowing and growth stages, and nitrogen (N) absorption, translocation by wheat plant. The current data showed that tillage in fallow period improved the soil water at the depth of 0-300 cm before sowing and growth stages, especially in dry years. Such tillage significantly improved N accumulation in leaf, stem and sheath (SS) at anthesis, grain N accumulation at maturity, N mobilization in SS and the contribution of mobilized N to grain N, amount of mobilized N in leaf, level of N accumulation before anthesis, N transportation from vegetative organs to grains after anthesis, and nitrogen accumulation after anthesis, which in turn enhanced the efficiency of N uptake. Deep tillage at 45 days after harvest had the best effect. Significant correlations were detected between soil water and N accumulation before anthesis as well as N translation from vegetative organs grains after anthesis, particularly in dry years, while the correlation between soil water from sowing to an thesis and nitrogen accumulation amount after anthesis was significant in wet years, but not in dry years. Tillage in fallow period especially deep tillage after raining could benefit soil water preservation, as well as N absorption and translocation by plant.