Reduced Wheat Yield Research Articles

The end-use quality of wheat can be enhanced by optimal water management without incurring yield loss.

In China, water-saving irrigation is playing important roles in ensuring food security, and improving wheat quality. A barrel experiment was conducted with three winter wheat (Triticum aestivum L.) genotypes and two irrigation pattens to examine the effects of regulated deficit irrigation (RDI) on wheat grain yield, water-use efficiency (WUE), and grain quality. In order to accurately control the soil water content, wheat was planted in the iron barrels set under a rainproof shelter, and the soil water content in the iron barrel was controlled by gravity method. The mechanisms whereby water management influences the end-use functional properties of wheat grain were also investigated. The results revealed that RDI improved the end-use functional properties of wheat and WUE, without significant yield loss (less than 3%). Moderate water deficit (60% to 65% field capacity) before jointing and during the late grain-filling stage combined with a slight water deficit (65% to 70% field capacity) from jointing to booting increased grain quality and WUE. The observed non-significant reduction in wheat yield associated with RDI may be attributed to higher rate of photosynthesis during the early stage of grain development and higher rate of transfer of carbohydrates from vegetative organs to grains during the later stage. By triggering an earlier rapid transfer of nitrogen deposited in vegetative organs, RDI enhances grain nitrogen content, which in turn could enhance dough elasticity, given the positive correlation between grain nitrogen content and dough midline peak value. Our results also indicate that the effects of RDI on grain quality are genotype dependent. Therefore, the grain end-use quality of some specific wheat genotypes may be enhanced without incurring yield loss by an optimal water management.

Tracking the influence of drought events on winter wheat using long-term gross primary production and yield in the Wei River Basin, China

The Wei River Basin (WRB) is the main winter wheat-producing area in Northwest China and plays a pivotal role in national food security and economic development. Drought is the main agro-meteorological disaster affecting winter wheat yield in this region, and the accurate assessment of the drought impacts on crop growth and yield is an important part of maintaining food security. However, commonly used assessment methods, such as correlation analysis and crop model simulation, have some limitations. In this study, based on standardized precipitation evapotranspiration index (SPEI) at multiple time scales, gross primary production (GPP) and yield data from 1990 to 2018, sensitivity analysis, Pearson correlation, and superposed epoch analysis (SEA) were used to analyze the spatiotemporal characteristics of drought in the WRB and its influence on winter wheat growth and quantitatively assess the impact of drought at different levels on winter wheat yield. The results were as follows: 1) Overall, the WRB was in a dry state with a drying trend during 1990–2018, and the droughts in spring, summer, and winter were the main driving forces of annual drought that seriously threatened the growth and yield of winter wheat, especially in spring (March–May), which is the key growth period of winter wheat. 2) The average annual GPP of winter wheat in the WRB showed a significant upward trend of 0.465 · 10a−1, and the central part of the WRB was the region where winter wheat GPP had higher sensitivity to drought. In general, winter wheat GPP during the growing season was most sensitive to SPEI-3, indicating that seasonal water deficits had the greatest impact on winter wheat growth. 3) The yield reduction of winter wheat caused by drought presented a spatial distribution that is heavy in the north and light in the south, and as the drought grade increased, the winter wheat yield decreased more significantly, even in irrigated areas. Therefore, relevant government departments still need to strengthen the risk management of agricultural droughts in the WRB and formulate reasonable policies to maintain food security.

Response of Winter Wheat Production to Climate Change in Ziway Lake Basin

The crop production and limited freshwater resources in the Central Rift Valley (CRV) Lake Basin of Ethiopia have been facing pressure from warmer and drier climates. Thus, irrigation with the goal of increasing water use efficiency and the productivity of rainfed agriculture is vital to address climate effects, water scarcity, and food security. This study is aimed at assessing the sustainability of winter wheat production under climate change, and irrigation as an adaptation measure to improve yield, crop water productivity (CWP), and irrigation water productivity (IWP) in the CRV of Ethiopia. AquaCrop is applied to evaluate the effects of climate change and simulate irrigation as an adaptation measure. The analysis covers the baseline (1981–2020) and future (2026–2095) periods with each period categorized into three rainfall years (wet, normal, and dry). The future period is described using two representatives’ concentration pathways (RCP4.5 and PCP8.5) scenarios. The results under rainfed and future climate conditions show that the winter wheat yield and CWP are projected to be lowered as compared to the baseline period. Most importantly, a significant reduction in wheat yield and CWP is noticed during the dry years (−60% and −80%) compared to the wet years (−30% and −51%) and normal years (−18% and −30%), respectively. As compared to rainfed agriculture, irrigation significantly reduces the risk of wheat yield decline and improves the CWP. Irrigation is also able to improve the CWP of rainfed wheat production ranging from 0.98–1.4 kg/m3 to 1.48–1.56 kg/m3. A projected CWP improvement of 1.1–1.32 kg/m3 under irrigation is possible from 0.87–1.1 kg/m3 under rainfed conditions. The study concludes that optimizing irrigation as a climate-change-adapting strategy in the CRV has a more pronounced positive impact to the rainfed production system, especially for the dry and normal years.

Nitrification inhibitor application at stem elongation stage increases soil nitrogen availability and wheat nitrogen use efficiency under drought stress

ABSTRACT One of the practices which could mitigate the negative effects of drought stress is ammonium nutrition. Nitrification inhibitor (DMPP) can keep ammonium concentrations high in the soil for several weeks. Although there are contradictory reports regarding the priority of NH4 + uptake and its toxicity effects on wheat, it is necessary to understand better how to apply DMPP to increase drought tolerance without any negative effects. The field experiment was conducted using 15N trace technology. The fertilizers treatment included (15NH4)2SO4 and (15NH4)2SO4 with DMPP at four drought stress levels. Available soil mineral nitrogen was measured, as well as yield components and 15N recovery. The results showed that DMPP application at full irrigation and moderate drought stress caused an increase in grain yield of 13% and 10%, respectively. DMPP application at full irrigation, moderate and severe drought stress caused a significant increase in nitrogen use efficiency of 19%, 11%, and 17%, respectively. It seems DMPP application at the stem elongation stage, promoted NH4 + assimilation and transfer to the shoots, which has created relative resistance to drought stress conditions. In conclusion, it is recommended that farmers use DMPP at stem elongation to avoid wheat yield reduction and nitrogen recovery under drought stress.

Biochar Amendment Combined with Straw Mulching Increases Winter Wheat Yield by Optimizing Soil Water-Salt Condition under Saline Irrigation

The freshwater deficit is the major constraint to winter wheat production. Saline water irrigation could alleviate wheat water stress while increasing the risk of soil salinization, which would result in wheat yield reduction due to additional salt stress. The objective of the present study is to explore the effect of a straw-returning mode to promote winter wheat production under saline water irrigation. A field experiment was conducted during the winter wheat growing seasons of 2017–2018 and 2018–2019. Four returning modes were set, based on an equivalent carbon input: straw mulching (SM), biochar amendment (BA), straw mulching combined with biochar amendment (SM+BA), and the control without straw-returning (CK), along with three salinity levels of irrigation water: 0.47 dS m−1 (I0, freshwater), 3.25 dS m−1 (I1), and 6.75 dS m−1 (I2). Saline water irrigation alone triggered soil salt accumulation and reduced the wheat grain yield by 9.43––18.19%. Returning straw to fields increased soil organic carbon content by 16.41––52.21% and decreased soil bulk density by 0.69––1.46%. The highest increase in wheat grain yield (16.60––21.80%) was always obtained when using treatment SM+BA, due to the increased soil moisture content (3.15––12.31%) and lower salt levels (24.79––44.29%) compared to CK. The results of the present study established that SM+BA provided better soil water–salt conditions and nutrient environment for winter wheat growth than a single treatment. Thus, the combined application of SM and BA was shown to be a proper mitigating strategy to cope with the adverse effects of saline irrigation on winter wheat production and to promote the sustainable use of saline water irrigation.

Impact of recent climate change on corn, rice, and wheat in southeastern USA

Climate change and its impact on agriculture productivity vary among crops and regions. The southeastern United States (SE-US) is agro-ecologically diversified, economically dependent on agriculture, and mostly overlooked by agroclimatic researchers. The objective of this study was to compute the effect of climatic variables; daily maximum temperature (Tmax), daily minimum temperature (Tmin), and rainfall on the yield of major cereal crops i.e., corn (Zea mays L.), rice (Oryza sativa L.), and wheat (Triticum aestivum L.) in SE-US. A fixed-effect model (panel data approach) was used by applying the production function on panel data from 1980 to 2020 from 11 SE-US states. An asymmetrical warming pattern was observed, where nocturnal warming was 105.90%, 106.30%, and 32.14%, higher than the diurnal warming during corn, rice, and wheat growing seasons, respectively. Additionally, a shift in rainfall was noticed ranging from 19.2 to 37.2 mm over different growing seasons. Rainfall significantly reduced wheat yield, while, it had no effect on corn and rice yields. The Tmax and Tmin had no significant effect on wheat yield. A 1 °C rise in Tmax significantly decreased corn (− 34%) and rice (− 8.30%) yield which was offset by a 1 °C increase in Tmin increasing corn (47%) and rice (22.40%) yield. Conclusively, overall temperature change of 1 °C in the SE-US significantly improved corn yield by 13%, rice yield by 14.10%, and had no effect on wheat yield.

Automatic Tandem Dual BlendMask Networks for Severity Assessment of Wheat Fusarium Head Blight

Fusarium head blight (FHB) disease reduces wheat yield and quality. Breeding wheat varieties with resistance genes is an effective way to reduce the impact of this disease. This requires trained experts to assess the disease resistance of hundreds of wheat lines in the field. Manual evaluation methods are time-consuming and labor-intensive. The evaluation results are greatly affected by human factors. Traditional machine learning methods are only suitable for small-scale datasets. Intelligent and accurate assessment of FHB severity could significantly facilitate rapid screening of resistant lines. In this study, the automatic tandem dual BlendMask deep learning framework was used to simultaneously segment the wheat spikes and diseased areas to enable the rapid detection of the disease severity. The feature pyramid network (FPN), based on the ResNet-50 network, was used as the backbone of BlendMask for feature extraction. The model exhibited positive performance in the segmentation of wheat spikes with precision, recall, and MIoU (mean intersection over union) values of 85.36%, 75.58%, and 56.21%, respectively, and the segmentation of diseased areas with precision, recall, and MIoU values of 78.16%, 79.46%, and 55.34%, respectively. The final recognition accuracies of the model for wheat spikes and diseased areas were 85.56% and 99.32%, respectively. The disease severity was obtained from the ratio of the diseased area to the spike area. The average accuracy for FHB severity classification reached 91.80%, with the average F1-score of 92.22%. This study demonstrated the great advantage of a tandem dual BlendMask network in intelligent screening of resistant wheat lines.

Monitoring Wheat Lodging at Various Growth Stages.

Lodging is one of the primary factors that reduce wheat yield; therefore, rapid and accurate monitoring of wheat lodging helps to provide data support for crop loss and damage response and the subsequent settlement of agricultural insurance claims. In this study, we aimed to address two problems: (1) calculating the wheat lodging area. Through comparative experiments, the SegFormer-B1 model can achieve a better segmentation effect of wheat lodging plots with a higher prediction rate and a stronger generalization ability. This model has an accuracy of 96.56%, which realizes the accurate extraction of wheat lodging plots and the relatively precise calculation of the wheat lodging area. (2) Analyzing wheat lodging areas from various growth stages. The model established, based on the mixed-stage dataset, generally outperforms those set up based on the single-stage datasets in terms of the segmentation effect. The SegFormer-B1 model established based on the mixed-stage dataset, with its mIoU reaching 89.64%, was applicable to wheat lodging monitoring throughout the whole growth cycle of wheat.

Cytogenetic and Molecular Marker Analyses of a Novel Wheat-Psathyrostachys huashanica 7Ns Disomic Addition Line with Powdery Mildew Resistance.

Powdery mildew caused by Blumeria graminis f. sp. tritici is a devastating disease that reduces wheat yield and quality worldwide. The exploration and utilization of new resistance genes from wild wheat relatives is the most effective strategy against this disease. Psathyrostachys huashanica Keng f. ex P. C. Kuo (2n = 2x = 14, NsNs) is an important tertiary gene donor with multiple valuable traits for wheat genetic improvement, especially disease resistance. In this study, we developed and identified a new wheat—P. huashanica disomic addition line, 18-1-5—derived from a cross between P. huashanica and common wheat lines Chinese Spring and CSph2b. Sequential genomic and multicolor fluorescence in situ hybridization analyses revealed that 18-1-5 harbored 21 pairs of wheat chromosomes plus a pair of alien Ns chromosomes. Non-denaturing fluorescence in situ hybridization and molecular marker analyses further demonstrated that the alien chromosomes were derived from chromosome 7Ns of P. huashanica. The assessment of powdery mildew response revealed that line 18-1-5 was highly resistant at the adult stage to powdery mildew pathogens prevalent in China. The evaluation of agronomic traits indicated that 18-1-5 had a significantly reduced plant height and an increased kernel length compared with its wheat parents. Using genotyping-by-sequencing technology, we developed 118 PCR-based markers specifically for chromosome 7Ns of P. huashanica and found that 26 of these markers could be used to distinguish the genomes of P. huashanica and other wheat-related species. Line 18-1-5 can therefore serve as a promising bridging parent for wheat disease resistance breeding. These markers should be conducive for the rapid, precise detection of P. huashanica chromosomes and chromosomal segments carrying Pm resistance gene(s) during marker-assisted breeding and for the investigation of genetic differences and phylogenetic relationships among diverse Ns genomes and other closely related ones.

Graphene oxide modification enhances the activity of chitosan against Fusarium graminearum in vitro and in vivo

Fusarium graminearum (F. graminearum), a pathogen for Fusarium head blight (FHB) on wheat, significantly reduces wheat yield and poses potential threats to human food safety. In this study, graphene oxide (GO) modified chitosan (GO-CS composite) was synthesized and its antifungal activity against F. graminearum in vitro and in vivo was evaluated. The 1HNMR and FTIR results revealed the reaction between the carboxyl groups in GO and the amino groups in chitosan (CS). In vitro, the combination of GO and CS resulted in a significant synergistic inhibitory effect on the mycelial growth of F. graminearum relative to single GO or CS. The EC50 value of the GO-CS composite was 14.07 μg/mL, which was much lower than that of GO or CS alone. In vivo, the GO-CS composite significantly reduced the disease incidence and severity compared with single GO or CS, and the control efficacy could reach 60.01 %. Microbial cells might be ultimately damaged when interacting with GO-CS due to various mechanisms such as biological effects and physical barriers. Overall, the combination of GO and CS provides new opportunities for their application in the control of fungi.

Effect of Japanese foxtail (Alopecurus japonicus) at varying densities on the physiological characteristics of wheat

To evaluate the effect of Japanese foxtail (Alopecurus japonicus Steud.) at different densities on the photosynthetic physiology of wheat, “Yangmai 16” wheat was cultivated in a field using two sowing rates (150 kg ha−1, conventional seeding rate; 225 kg ha−1, high seeding rate) and with different densities of A. japonicus for two years. A. japonicus affected the physiological characteristics of wheat, such as its leaf photosynthetic rate, fluorescence parameters, Hill reaction activity, Rubisco activity, yield and yield components, to varying degrees. However, the physiological responses of wheat at different seeding rates varied; the effect of A. japonicus on wheat was more severe at the conventional seeding rate than at the high seeding rate. A. japonicus affected wheat leaf morphology and inhibited photosynthetic processes, leading to decreased PSII electron transport, energy metabolism and photosynthate accumulation, ultimately reducing wheat yield. An appropriate increase in the wheat seeding rate could improve specific leaf weight, maintain Rubisco activity, reduce photoinhibition, and alleviate the stress caused by A. japonicus.

Comparative transcriptome analysis of synthetic and common wheat in response to salt stress

Salt stress reduces wheat yield. Therefore, improvement for enhanced salt stress tolerance is necessary for stable production. To understand the molecular mechanism of salt tolerance in common wheat and synthetic hexaploid (SH) wheat, RNA sequencing was performed on the roots of three wheat lines salt-tolerant SH wheat, salt-tolerant common wheat, and salt-sensitive common wheat. Differentially expressed genes (DEGs) in response to salt stress were characterized using gene ontology enrichment analysis. Salt tolerance in common wheat has been suggested to be mainly regulated by the activation of transporters. In contrast, salt tolerance in SH wheat is enhanced through up-regulation of the reactive oxygen species signaling pathway, other unknown pathways, and different ERF transcription factors. These results indicate that salt tolerance is differentially controlled between common wheat and SH wheat. Furthermore, QTL analysis was performed using the F2 population derived from SH and salt-sensitive wheat. No statistically significant QTL was detected, suggesting that numerous QTLs with negligible contributions are involved in salt tolerance in SH wheat. We also identified DEGs specific to each line near one probable QTL. These findings show that SH wheat possesses salt tolerance mechanisms lacking in common wheat and may be potential breeding material for salt tolerance.

Soil warming and straw return impacts on winter wheat phenology, photosynthesis, root growth, and grain yield in the North China Plain

Soil temperature rise caused by global warming is one of the most serious threats to crop physiology and production. Straw return is considered as a potential strategy to improve soil health and agricultural productivity. However, little is known about their interactive effects on wheat growth and production, which limits the development of strategies and technological innovations for future food security. Therefore, in the two wheat seasons from 2018 to 2020, with or without straw return, the heating cable was laid at a depth of 20 cm to increase the soil temperature by 3.8 ℃, and the phenology, photosynthesis, root growth, and grain yield of winter wheat were studied. Soil warming advanced the anthesis date by one week and promoted pre-anthesis wheat growth and dry matter transportation. However, soil warming decreased post-anthesis duration, leaf area index, SPAD, net photosynthesis, and spectral vegetation indexes. Therefore, post-anthesis dry matter accumulation and grain filling were inhibited, lowering the 1000-grain weight and harvest index. Furthermore, the post-anthesis root weight, length, surface area densities and root to shoot ratio were also decreased under soil warming. Finally, soil warming reduced the grain yield by 35.2% in the dry 2018–2019 year. However, the wheat growth characteristics were considerably higher and no difference in grain yield was detected among treatments in the wet 2019–2020 season, indicating that increased precipitation may offset the adverse effect of soil warming on wheat yield. Straw return increased aboveground biomass, but had no effect on wheat yield, probably because the positive effects were limited in the short experimental duration. The findings suggested that soil warming would promote pre-anthesis wheat growth but accelerate post-anthesis wheat senescence, affect dry matter transportation and accumulation, eventually reducing wheat yield in the NCP, especially under dry condition.

Soybean Crops Penalize Subsequent Wheat Yield During Drought in the North China Plain.

Contemporary wisdom suggests that inclusion of legumes into crop rotations benefit subsequent cereal crop yields. To investigate whether this maxim was generically scalable, we contrast summer soybean–winter wheat (SW) with summer maize–winter wheat (MW) rotation systems in an extensive field campaign in the North China Plain (NCP). We identify heretofore unseen interactions between crop rotation, synthetic N fertilizer application, and stored soil water. In the year with typical rainfall, inclusion of soybean within rotation had no effect on wheat ear number and yield, while N fertilization penalized wheat yields by 6–8%, mainly due to lower dry matter accumulation after anthesis. In contrast, in dry years prior crops of soybean reduced the rate and number of effective ears in wheat by 5–27 and 14–17%, respectively, leading to 7–23% reduction in wheat yield. Although N fertilization increased the stem number before anthesis in dry years, there was no corresponding increase in ear number and yield of wheat in such years, indicating compensating reduction in yield components. We also showed that N fertilization increased wheat yield in MW rather than SW as the former better facilitated higher dry matter accumulation after flowering in dry years. Taken together, our results suggest that soybean inclusion reduced soil available water for subsequent wheat growth, causing yield penalty of subsequent wheat under drought conditions. We call for more research into factors influencing crop soil water, including initial state, crop water requirement, and seasonal climate forecasts, when considering legumes into rotation systems. Graphical Response of wheat population and yield to soybean inclusion under limited-irrigation.

Characterization of the WAK Gene Family Reveals Genes for FHB Resistance in Bread Wheat (Triticum aestivum L.).

Wall-associated kinases (WAKs) are important receptor-like proteins that play major roles in plant defense against pathogens. Fusarium head blight (FHB), one of the most widespread and devastating crop diseases, reduces wheat yield and leads to quality deterioration. Although WAK gene families have been studied in many plants, systematic research on bread wheat (Triticum aestivum) and its role in FHB resistance, in particular, is lacking. In this study, we identified and characterized 320 genes of the TaWAK family in wheat distributed across all chromosomes except 4B and divided them into three phylogenetic groups. Duplication and synteny analyses provided valuable information on the evolutionary characteristics of the TaWAK genes. The gene expression pattern analysis suggested that TaWAK genes play diverse roles in plant biological processes and that at least 30 genes may be involved in the response to Fusarium infection in wheat spikes, with most of the genes contributing to pectin- and chitin-induced defense pathways. Furthermore, 45 TaWAK genes were identified within 17 hcmQTLs that are related to wheat FHB resistance. Our findings provide potential candidate genes for improving FHB resistance and insights into the future functional analysis of TaWAK genes in wheat.

Salicylic Acid Reduces Wheat Yield Loss Caused by High Temperature Stress by Enhancing the Photosynthetic Performance of the Flag Leaves

High temperature stress during grain filling substantially decreases wheat productivity; thus, to ensure food security, heat tolerance in wheat must be developed. It remains unclear whether exogenous salicylic acid (SA) can induce tolerance to high temperatures in wheat at the grain-filling stage. In this study, a two-year pot culture experiment using the wheat cultivar ‘Yangmai 18’ was conducted from 2018 to 2020. The plants were pre-sprayed with SA from the heading stage (SAH), anthesis stage (SAA), 5 days after anthesis (DAA; SA5), and 10 DAA (SA10). After that, the wheat plants were subjected to high temperature stress (G) simulated using a passive warming method during the period between 15 and 19 DAA. The results showed that, compared with the normal temperature control group (NN), high temperature stress at the grain-filling stage significantly reduced the yield and photosynthetic capacity of wheat. The application of SA at different stages reduced the yield loss and the damage to the photosynthetic capacity caused by high temperature stress; the effectiveness of the treatments in descending order was SAAG > SA5G > SA10G > SAHG. Exogenous SA treatment increased the amount and proportion of dry matter distributed in the stem sheaths and leaves and grains, and decreased the amount and proportion of dry matter distributed in the rachises and glumes at the maturity stage, thereby reducing the yield loss under high temperature stress. The application of SA significantly increased the leaf area, stomatal density, chlorophyll content, soluble protein content, maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (ΦPSII), and activity of sucrose phosphate synthase (SPS) of the wheat flag leaves under high temperature stress at the grain-filling stage, thereby improving the photosynthetic performance of the flag leaves under stress. In summary, exogenous SA significantly restored the photosynthetic capacity of wheat flag leaves injured by post-anthesis high temperature stress, which effectively alleviated the inhibition of wheat growth caused by the stress and ultimately reduced the yield loss. Spraying SA at the anthesis stage had the greatest effect abating the loss of yield and reduced photosynthetic performance under high temperature stress.

Effects of warming and drought stress on winter wheat in Jiangsu Province, China

AbstractWe used the World Food Studies (WOFOST) model to analyze meteorological, soil, and winter wheat (Triticum aestivum L.) growth period data in Xuzhou, Huaian, and Changzhou, Jiangsu Province from 2008 to 2017. The data collected were used to study the effects of warming and drought on winter wheat yield and dry matter accumulation. The simulation results showed that single warming stress (1, 2, and 3 ℃), drought stress (mild, moderate, and severe), and combined drought and warming stress can reduce the yield of winter wheat. The highest yield reduction rate was 25.5% in Changzhou under the condition of single warming, and the yield reduction rate increased by 5% when the soil relative humidity decreased by 10% under the condition of single drought. The grain dry matter formation of winter wheat was also inhibited by warming and drought, and the lowest dry matter ratio was only 42.4% in Changzhou under drought. The influence of combined stress was greater than that of single stress under various contrasts. However, in the middle of Jiangsu Province, the yield of winter wheat was most affected by drought, and the distribution of dry matter accumulation decreased from south to north. The yield reduction of winter wheat under other stresses increased from south to north, and the dry matter distribution of grain was lower in the south than in the north and lower in the central part of Jiangsu Province.

Designing high-yielding wheat crops under late sowing: a case study in southern China

Cropping of rice and wheat (Triticum aestivum L.) in rotation contiguously in the same field is a fundamental pillar of double-cropping systems in southern China. Yields of such cropping systems are increasingly challenged as climate change (CC) drives increases in autumnal rainfall, delaying rice harvesting and subsequent sowing of wheat. Here, our purpose was to identify prospective traits of wheat crops enabling adaptation to later sowing and successively truncated growing seasons caused by CC. To identify traits that maintained or improved yields, we constructed 4,096 hypothetical genotypes underpinned by step-wise variations in parameters regulating phenology, growth and yield components. We then assimilated biophysical response surfaces through genotype (G) by environment (E) by management (M) analyses (G×E×M) using six locations spread across the breadth of southern China. We showed that later sowing reduced cumulative radiation interception, cumulative thermal time and crop capture of growing season rainfall. The culmination of these factors shortened crop duration and decreased biomass accumulation and retranslocation after anthesis, reducing grain number and penalising yields. Genotypes that had greater radiation use efficiency, longer juvenile phases and greater grain filling rates were more effective in alleviating yield losses with delayed sowing. However, not even the highest yielding genotype × management combination could entirely alleviate yield losses with delayed sowing. Our results suggest that CC and increasingly frequent extreme climatic events may reduce wheat yields in such cropping systems in the absence of other adaptation.

Wheat endophytes and their potential role in managing abiotic stress under changing climate.

Wheat (Triticum aestivum L.) cultivation differs considerably in respect of soil type, temperature, pH, organic matter, moisture regime, etc. Among these, rising atmospheric temperature due to global warming is most important as it affects grain yield drastically. Studies have shown that for every 1°C rise in temperature above wheat's optimal growing temperature range of 20-25°C, there is a decrease in 2.8days and 1.5mg in the grain filling period and kernel weight, respectively, resulting in wheat yield reduction by 4-6 quintal per hectare. Growing demand for food and multidimensional issues of global warming may further push wheat crop to heat stress environments that can substantially affect heading duration, percent grain setting, maturity duration, grain growth rate and ultimately total grain yield. Considerable genetic variation exists in wheat gene pool with respect to various attributes associated with high temperature and stress tolerance; however, only about 15% of the genetic variability could be incorporated into cultivated wheat so far. Thus, alternative strategies have to be explored and implemented for sustainable, more productive and environment friendly agriculture. One of the feasible and environment friendly option is to look at micro-organisms that reside inside the plant without adversely affecting its growth, known as 'endophytes', and these colonize virtually all plant organs such as roots, stems, leaves, flowers and grains. The relationship between plant and endophytes is vital to the plant health, productivity and overall survival under abiotic stress conditions. Thus, it becomes imperative to enlist the endophytes (bacterial and fungal) isolated till date from wheat cultivars, their mechanism of ingression and establishment inside plant organs, genes involved in ingression, the survival advantages they confer to the plant under abiotic stress conditions and the potential benefits of their use in sustainable wheat cultivation.

Study on the Nutrient Optimal Management Strategy of High and Stable Annual Yield in the Rice–Wheat System: A 10-Year Term Experiment

What strategy of nutrient management can maintain the high and stable annual yield in rice–wheat systems under climate change? A 10-year term experiment was conducted in the rice–wheat system to investigate the effect of optimal nutrient management on crop yield and meteorological drivers of year-to-year fluctuations in rice and wheat yield. Treatments were as follows: conventional fertilization (CF, as control), fertilizer postponing (FP, with the same amount fertilization as CF and increasing rate and times of panicle fertilizer) with/without straw incorporation (including only straw returned in rice (W) or wheat (R) season, and both straw incorporation (WS), RFP (reducing amount based on FP) with/without organic fertilizer. Results showed that FP with/without straw incorporation increased 10-year average yields of rice, wheat, and annual by 4.5~6.5%, 3.8~7.2%, and 4.8~6.8%, respectively, while RFP with/without organic fertilizer did not markedly reduce wheat yield, compared with CF. Effect of optimal treatments on wheat and rice yield stability was different; among the annual yield stability in FP + WRS was the greatest due to increasing and a stable number of spikelets and dry matter accumulation (DMA) after heading. Furthermore, the coefficient of variation (CV) of DMA during rice jointing-heading (21.6~30.0%) and heading-maturity stage (20.1~27.9%) was higher than before jointing (13.9~16.7%), which were affected by day photosynthetically active radiation (explain: 26%) and the number of rainy days (explain: 34%), respectively, using Stepwise regression; in contrast, in wheat season, the fluctuation of DMA before jointing was the highest (CV: 83.8~109.9% (before jointing) vs. 61.1~97.4% (heading-mature stage) vs. 33.7~46.3% (jointing-heading period), 55% of its variations was impacted by day-night temperature differences, the number of rainy days and photosynthetically active radiation accumulation. Our finding suggested that nutrient management to increase and stable the DMA after rice jointing and before wheat jointing could maintain the high and stable annual yield in rice–wheat systems.