Wheat Flowering Research Articles

A Realistic Approach to Calculating the Nitrogen Use Efficiency Index in Cereals with Winter Wheat (Triticum aestivum L.) as an Example

Nitrogen use efficiency (NUE) is a reliable index of nitrogen (N) management, given that it expresses the real relationships that exist between crop yield, its components, and the content of available N (Nmin) in the soil in the critical stages of yield formation. This article proposes a method for calculating NUE which is based on N input (Nin) into the soil/crop system in the critical phases of yield formation in winter wheat. For the validation of this hypothesis, a field experiment with WW in three subsequent growing seasons (2012/2013, 2013/2014, 2014/2015) was used. Treatments were arranged in a factorial distribution of two factors: (1) three rates of soil-applied magnesium (Mgs, 0, 25, 50 kg Mg ha−1); (2) foliar application of Mg to winter wheat (no application—control; double-stage Mg application in BBCH 30 and in 49/50). The dose of N fertilizer (Nf) was 190 kg ha−1. Two groups of N pools (soil Nmin and N mass in the wheat biomass) were determined in BBCH 30, 58, and 89. These core datasets were used to calculate total N input (Nin) to the soil/crop system during the two main periods of WW growth: (1) before (vegetative mega-phase, V) and (2) after wheat flowering (reproductive mega-phase, R, or grain filling period, GFP). The number of grains per ear (GE) and the number of grains per unit area (grain density: GD) depended significantly on Nin at the onset of flowering. A Nin58 of 517 kg N ha−1 resulted in a GD of 28.3 × 1000 grains m−2, producing 9.47 t grain ha−1. The NUE indices calculated in the V phase were the best predictors of GE and GY. The apparently low NUE index in this phase clearly indicates (i) the high potential of winter wheat for grain set per ear, (ii) consequently resulting in a strong depletion of N soil resources during the GFP. Therefore, the reduced NUE before winter wheat flowering is essential for the achievement of a high GD. The NUE feedback phenomenon as found in this study is a crucial condition for the effective depletion of the inorganic N pool during the grain filling period of winter wheat. It can be concluded that the NUE indices obtained in the V mega-phase actually describe the N economy in winter wheat production very well.

Cytoplasm of the Wild Species Aegilops mutica Reduces VRN1 Gene Expression in Early Growth of Cultivated Wheat: Prospects for Using Alloplasmic Lines to Breed Varieties Adapted to Global Warming.

In a warm winter due to climate warming, it is necessary to suppress early flowering of autumn-sown wheat plants. Here, we propose the use of cytoplasmic genome effects for this purpose. Alloplasmic lines, or cytoplasmic substitution lines, of bread wheat (Triticum aestivum) have cytoplasm from a related wild Aegilops species through recurrent backcrossing and exhibit altered characteristics compared with the euplasmic lines from which they are derived. Thus, alloplasmic lines with Aegilops mutica cytoplasm show delayed flowering compared with lines carrying normal cytoplasm. In the wheat flowering pathway, VERNALIZATION 1 (VRN1) encodes an APETALA1/FRUITFULL-like MADS box transcription factor that plays a central role in the activation of florigen genes, which induce floral meristems in the shoot apex. Here, we compared expression of VRN1 alleles in alloplasmic and euplasmic lines after vernalization. We found that alloplasmic wheat showed a lower level of VRN1 expression after vernalization compared with euplasmic wheat. Thus, nuclear-cytoplasm interactions affect the expression levels of the nuclear VRN1 gene; these interactions might occur through the pathway termed retrograde signaling. In warm winters, autumn-sown wheat cultivars with spring habit can pass through the reproductive growth phase in very early spring, resulting in a decreased tiller/ear number and reduced yield performance. Here, we present data showing that an alloplasmic line of 'Fukusayaka' can avoid the decrease in tiller/ear numbers during warm winters, suggesting that this alloplasmic line may be useful for development of varieties adapted to global warming.

Modeling Risk in Fusarium Head Blight and Yield Analysis in Five Winter Wheat Production Regions of Hungary

The five-year mean yield of five Hungarian wheat production counties was 5.59 t ha−1 with a 7.02% average coefficient of variation. There was a regional effect on yield when progressing from south to north with a 1–2 °C higher mean winter air temperature, meaning that the Ta in southern counties increased the five-season mean yield by 15.9% (p = 0.002) compared to the yield of northern counties. Logistic regression models developed to assess the FHB risk driven by a few meteorological variables (Ta; RH) provided proper predictive performance. The results in the regression model were validated against the measured infection rates (P%) provided by the NÉBIH 30 days before and after heading. The FHB pressure was comparatively higher in Zala County, probably due to its special topological and growing conditions, irrespective of the season. Across all areas studied, two of the five identified counties (Pest and Somogy) provided the best classification for FHB infection. In the remaining three counties, the seasonal mean prediction accuracy (differences) exceeded 10% in only 6 out of 30 model outputs. The modeled five-season P% values averaged 70.4% and 93.2% of the measured infection rates for models 1 and 2, respectively. The coincidence of wet and warm weather around the time of wheat flowering enhanced the risk of FHB.

Over-expression of a plant-type phosphoenolpyruvate carboxylase derails Arabidopsis stamen formation

We examined whether plant-type phosphoenolpyruvate carboxylase (PEPC) is involved in flower organ formation or not by over-expression in Arabidopsis. A wheat PEPC isogene Tappc3A, belonging to the ppc3 group, was targeted due to its preferential expression pattern in pistils and stamens. Transgenic Arabidopsis over-expressing Tappc3A exhibited irregular stamen formation, i.e., a lesser number of stamens per flower and shorter filaments in T2 and T3 generations. Irregular stamens were frequently observed in homozygous T4 lines, but no morphological change was observed in other floral organs. High-degree gene co-expression of Tappc3 isogenes with wheat SEEDSTICKs but not with other homeotic transcription factor genes for flower formation implicates that Tappc3 is under control by the class D genes of the ABCDE model to flower development. In addition, the conservation of CArG box sequences on the Tappc3 promoters supported the developmentally programmed gene expression of ppc3 in wheat flowering organs. Thus, this study provides the first experimental evidence for the critical regulation of plant-type PEPC for flower formation.

Genome-wide evolutionary analysis of TKL_CTR1-DRK-2 gene family and functional characterization reveals that TaCTR1 positively regulates flowering time in wheat

BackgroundFlowering time has an important effect on regional adaptation and yields for crops. The tyrosine kinase-like (TKL) gene family is widely existed and participates in many biological processes in plants. Furthermore, only few TKLs have been characterized functions in controlling flowering time in wheat.ResultsHere, we report that TaCTR1, a tyrosine kinase-like (TKL) gene, regulates flowering time in wheat. Based on identification and evolutionary analysis of TKL_CTR1-DRK-2 subfamily in 15 plants, we proposed an evolutionary model for TaCTR1, suggesting that occurrence of some exon fusion events during evolution. The overexpression of TaCTR1 caused early flowering time in transgenic lines. Transcriptomics analysis enabled identification of mass differential expression genes including plant hormone (ET, ABA, IAA, BR) signaling, flavonoid biosynthesis, phenolamides and antioxidant, and flowering-related genes in TaCTR1 overexpression transgenic lines compared with WT plants. qRT–PCR results showed that the expression levels of ethylene (ET) signal-related genes (ETR, EIN, ERF) and flowering-related genes (FT, PPD1, CO, PRR, PHY) were altered in TaCTR1-overexpressing wheat compared with WT plants. Metabonomics analysis showed that flavonoid contents were altered.ConclusionsThus, the results show that TaCTR1 plays a positive role in controlling flowering time by activating various signaling pathways and regulating flowering-related genes, and will provide new insights on the mechanisms of wheat flowering regulation.

Trade-Off Strategy for Usage of Phosphorus Fertilizer in Calcareous Soil-Grown Winter Wheat: Yield, Phosphorus Use Efficiency, and Zinc Nutrition Response

Although phosphorus (P) fertilizer application is widely used to improve production, irrational P application has a negative impact on the zinc (Zn) nutrition of cereal crops. Previous researchers observed and confirmed that P application decreases grain Zn concentrations and bioavailability in cereal crops. However, it remains unclear whether different P fertilizer types can alleviate the antagonism of P and Zn in the soil and grain and, thus, enhance the Zn nutritional level of cereal crops while maintaining production. Thus, a completely randomized pot experiment was conducted on winter wheat grown in two calcareous soils (lime concretion black soil and fluvo-aquic soil). Five P fertilizer types (single superphosphate, diammonium phosphate, fused calcium–magnesium phosphate, triple superphosphate, and ammonium polyphosphate, abbreviated, respectively, as SSP, DAP, FMP, TSP, and APP) were applied to each soil compared to no P fertilizer (CK). Plant and topsoil samples were collected during the flowering and maturity stages of winter wheat, and biomass, Zn concentrations in each organ, and grain phytic acid concentrations were analyzed. Grain yield was not affected by the application of different P fertilizer types to lime concretion black soil, while it was significantly increased by the application of TSP and APP to fluvo-aquic soil. The application of DAP and APP effectively promoted soil available Zn concentrations in both calcareous soils. In lime concretion black soil, the application of FMP significantly increased Zn remobilization to grains, while the application of DAP increased post-anthesis Zn uptake, thereby increasing grain Zn concentrations and its bioavailability. In fluvo-aquic soil, post-anthesis Zn remobilization and uptake were significantly increased by the application of TSP and APP, finally achieving higher grain Zn concentrations and Zn harvest index and effectively promoting grain Zn bioavailability. In conclusion, the rational application of DAP to wheat grown in lime concretion black soil and of TSP or APP to fluvo-aquic soil can achieve superior grain Zn nutrition quality while concurrently retaining high production and high P use efficiency, reducing micronutrient deficiency and further contributing to green agricultural development and human health.

Historic winter wheat yield, production, and economic value trends in Kansas, the “Wheat State”

AbstractYear‐to‐year weather variability and technologies (fertilizer, irrigation, herbicides, conservation tillage, varieties, mechanization, and others) are among factors that affect winter wheat (Triticum aestivum L.) yields in water‐limited cropping systems. The objective of these analyses was to quantify winter wheat yield trends, variability, relationship with weather, yield gap, and value in the “Wheat State,” Kansas. Two data sources were used for this study, that is, annual winter wheat yield reported for selected counties from the United States Department of Agriculture and the Kansas State University wheat variety performance trial near Colby, Garden City, Hays, and Tribune, Kansas. Results of the study showed a decline in harvest area and inflation‐adjusted market value per area of winter wheat beginning in the 1930s. However, both the survey and research data showed continuous increase in winter wheat yield at rates of 3–180 kg ha−1 year−1 that varied by irrigation, location, data source, or time range considered, except for a few years where yield stagnated or declined. Despite increased productivity, results indicated an increase in annual winter wheat yield variation over time. A positive correlation was observed between nonirrigated wheat yield and all months of precipitation except for January, February, and June. October through December precipitation provided the best positive correlation with nonirrigated wheat yield. Wheat yields were negatively correlated with high temperature in months that coincided with wheat flowering and maturity. The yield gap between actual and potential wheat yield was estimated at 15%–55%. The decreasing revenue per land area may be one of the reasons for decreasing wheat planted acreage over time. We concluded producers need to increase adoption of latest technology (varieties with drought and heat tolerance) and management to obtain yield potential. Research should investigate methods to increase the stability of state‐wide wheat production and financial return.

Can agronomic options alleviate the risk of compound drought-heat events during the wheat flowering period in southeastern Australia?

The impacts of compound drought-heat (DH) events on crops are more devastating than a single extreme event of drought or heat. Previous studies mainly assessed the change of individual extreme climate events. However, studies quantifying the characteristics of DH events during crop growth periods are still lacking. To the best of our knowledge, there is no study that has quantified the potential of adjusting sowing time and changing cultivars to reduce the risk of DH events for wheat in Australia. We aimed to (1) develop a combined index to capture the DH events occurring during the wheat flowering period at six study sites in southeastern Australia’s wheat belt; (2) quantify the changes in the frequency (DHF), duration (DHD), and intensity (DHI) of DH events under future climate; and (3) identify feasible agronomic options to reduce the risk of DH events. We used the APSIM model driven by climate projections from 27 GCMs for the period of 1981–2100 to simulate the wheat flowering time and daily plant available water (PAW) at 0–100 cm soil layer. The wheat sensitive period (WSP) was defined as the period from 2 weeks before flowering to 2 weeks after flowering time. A DH event occurs when the daily maximum temperature is higher than 28 ℃ and daily PAW is less than 40% of plant available water capacity for three consecutive days or more. Then, we assessed the DHF, DHD, and DHI under projected climate change. Finally, we investigated the potential of changing sowing time and cultivars to alleviate DHF, DHD, and DHI under different climate scenarios. According to the average values across six sites, the DHF, DHD, and DHI during the WSP increased by 15%, 12%, and 0.9% in 2040 s, and 49%, 44%, and 5% in 2080 s, respectively, compared to 2000 s. Such increases in DH events were mainly due to enhanced heat events. Early sowing and planting better-performing wheat cultivars with early flowering had great potential to lower the risk of future DH events. They could reduce the DHF, DHD, and DHI by 15%− 100%, 18%− 100%, and 16%− 100%, respectively, compared to without adaptation options. However, the strategy may introduce an increased frost risk across six sites, especially in regions with climates that are less dry and hot, such as Mudgee and Wagga Wagga. We expect our modelling work can provide useful information for developing effective agronomic management practices to help Australian wheat growers better prepare for DH events under climate change. The newly proposed DH framework can be applied to other dryland wheat growing regions globally.

The TaSOC1-TaVRN1 module integrates photoperiod and vernalization signals to regulate wheat flowering.

Wheat needs different durations of vernalization, which accelerates flowering by exposure to cold temperature, to ensure reproductive development at the optimum time, as that is critical for adaptability and high yield. TaVRN1 is the central flowering regulator in the vernalization pathway and encodes a MADS-box transcription factor (TF) that usually works by forming hetero- or homo-dimers. We previously identified that TaVRN1 bound to an MADS-box TF TaSOC1 whose orthologues are flowering activators in other plants. The specific function of TaSOC1 and the biological implication of its interaction with TaVRN1 remained unknown. Here, we demonstrated that TaSOC1 was a flowering repressor in the vernalization and photoperiod pathways by overexpression and knockout assays. We confirmed the physical interaction between TaSOC1 and TaVRN1 in wheat protoplasts and in planta, and further validated their genetic interplay. A Flowering Promoting Factor 1-like gene TaFPF1-2B was identified as a common downstream target of TaSOC1 and TaVRN1 through transcriptome and chromatin immunoprecipitation analyses. TaSOC1 competed with TaVRT2, another MADS-box flowering regulator, to bind to TaVRN1; their coding genes synergistically control TaFPF1-2B expression and flowering initiation in response to photoperiod and low temperature. We identified major haplotypes of TaSOC1 and found that TaSOC1-Hap1 conferred earlier flowering than TaSOC1-Hap2 and had been subjected to positive selection in wheat breeding. We also revealed that wheat SOC1 family members were important domestication loci and expanded by tandem and segmental duplication events. These findings offer new insights into the regulatory mechanism underlying flowering control along with useful genetic resources for wheat improvement.

Identification of candidate genes responsible for chasmogamy in wheat

BackgroundThe flowering biology of wheat plants favours self-pollination which causes obstacles in wheat hybrid breeding. Wheat flowers can be divided into two groups, the first one is characterized by flowering and pollination within closed flowers (cleistogamy), while the second one possesses the ability to open flowers during processes mentioned above (chasmogamy). The swelling of lodicules is involved in the flowering of cereals and among others their morphology, calcium and potassium content differentiate between cleistogamic and non-cleistogamous flowers. A better understanding of the chasmogamy mechanism can lead to the development of tools for selection of plants with the desired outcrossing rate. To learn more, the sequencing of transcriptomes (RNA-Seq) and Representational Difference Analysis products (RDA-Seq) were performed to investigate the global transcriptomes of wheat lodicules in two highly chasmogamous (HCH, Piko and Poezja) and two low chasmogamous (LCH, Euforia and KWS Dacanto) varieties at two developmental stages—pre-flowering and early flowering.ResultsThe differentially expressed genes were enriched in five, main pathways: “metabolism”, “organismal systems”, “genetic information processing”, “cellular processes” and “environmental information processing”, respectively. Important genes with opposite patterns of regulation between the HCH and LCH lines have been associated with the lodicule development i.e. expression levels of MADS16 and MADS58 genes may be responsible for quantitative differences in chasmogamy level in wheat.ConclusionsWe conclude that the results provide a new insight into lodicules involvement in the wheat flowering process. This study generated important genomic information to support the exploitation of the chasmogamy in wheat hybrid breeding programs.

Increasing interannual climate variability during crop flowering in Europe

Climate change has increasingly adverse effects on global crop yields through the occurrence of heat waves, water stress, and other weather-related extremes. Besides losses of average yields, a decrease in yield stability—i.e. an increase in variability of yields from year to year—poses economic risks and threatens food security. Here we investigate a number of climate indices related to adverse weather events during the flowering of wheat, maize and rapeseed, in the current cultivation areas as well as the main European producer countries. In 52 projections from regional climate models, we identify robust increases in the interannual variability of temperature, precipitation and soil moisture by ∼+20% in standard deviation in the model median. We find that winter wheat is most exposed to variability increases, whereas rapeseed flowering escapes the largest increases due to the early flowering time and the northern locations of cultivation areas, while the opposite (escape due to southern locations and late flowering) is true for maize to some extent. Considering the timing of crop development stages, we also find a robust increase in the variability of the temporal occurrence of flowering, which suggests a decreased reliability in the timing of crop stages, hampering management steps like fertilization, irrigation or harvesting. Our study raises concerns for European crop yield stability in a warmer climate and highlights the need for risk diversification strategies in agricultural adaptation.

Estimation of Fv/Fm in Spring Wheat Using UAV-Based Multispectral and RGB Imagery with Multiple Machine Learning Methods

The maximum quantum efficiency of photosystem II (Fv/Fm) is a widely used indicator of photosynthetic health in plants. Remote sensing of Fv/Fm using MS (multispectral) and RGB imagery has the potential to enable high-throughput screening of plant health in agricultural and ecological applications. This study aimed to estimate Fv/Fm in spring wheat at an experimental base in Hanghou County, Inner Mongolia, from 2020 to 2021. RGB and MS images were obtained at the wheat flowering stage using a Da-Jiang Phantom 4 multispectral drone. A total of 51 vegetation indices were constructed, and the measured Fv/Fm of wheat on the ground was obtained simultaneously using a Handy PEA plant efficiency analyzer. The performance of 26 machine learning algorithms for estimating Fv/Fm using RGB and multispectral imagery was compared. The findings revealed that a majority of the multispectral vegetation indices and approximately half of the RGB vegetation indices demonstrated a strong correlation with Fv/Fm, as evidenced by an absolute correlation coefficient greater than 0.75. The Gradient Boosting Regressor (GBR) was the optimal estimation model for RGB, with the important features being RGBVI and ExR. The Huber model was the optimal estimation model for MS, with the important feature being MSAVI2. The Automatic Relevance Determination (ARD) was the optimal estimation model for the combination (RGB + MS), with the important features being SIPI, ExR, and VEG. The highest accuracy was achieved using the ARD model for estimating Fv/Fm with RGB + MS vegetation indices on the test sets (Test set MAE = 0.019, MSE = 0.001, RMSE = 0.024, R2 = 0.925, RMSLE = 0.014, MAPE = 0.026). The combined analysis suggests that extracting vegetation indices (SIPI, ExR, and VEG) from RGB and MS remote images by UAV as input variables of the model and using the ARD model can significantly improve the accuracy of Fv/Fm estimation at flowering stage. This approach provides new technical support for rapid and accurate monitoring of Fv/Fm in spring wheat in the Hetao Irrigation District.

Effects of nitrogen application rate on the accumulation of 13C assimilates after flowering and water-nitrogen use efficiency of wheat under supplemental irrigation based on soil moisture.

This study aimed to explore nitrogen fertilizer management measures to synergistically improve wheat yields and water and nitrogen use efficiency under supplemental irrigation based on soil moisture in the Huang Huai winter wheat area. Wheat variety "Yannong 1212" was used as the test material. There were three nitrogen application levels, 150 kg·hm-2 (N1), 210 kg·hm-2 (N2), and 270 kg·hm-2 (the conventional nitrogen application rate in the Huang Huai winter wheat area, N3), with the relative soil water content of 0-40 cm of each treatment was supplemented to 70% at the jointing and flowering stages. We investigated the effects of nitrogen rates on photosynthetic characteristics of flag leaves after flowering, 13C assimilate accumulation and transport, and water and nitrogen use efficiency after flowering of wheat. The results showed that photosynthetic capacity of flag leaves in the N2 and N3 was significantly higher than that in N1 14-35 days after flowering, and that there was no significant diffe-rence between N2 and N3 treatments. The 13C isotope tracing results showed that the translocation amount of 13C assimilates in vegetative organs in N2 was 12.1% and 7.1% higher than that in N1 and N3, respectively. The distribution amount of 13C assimilates in grains at maturity was 10.1% and 5.3% higher than that of N1 and N3, respectively. The amount of nitrogen fertilizer affected water consumption, water consumption proportion, and total water consumption in different growth stages of wheat. Water consumption during the whole growth period showed no difference between N2 and N3 treatments, but both were significantly higher than that for N1. Water consumption and water consumption proportion of N2 were higher from the jointing to maturity stages, water use efficiency of N2 was 7.5% and 4.8%, and grain yield was 4.7% and 10.9% higher than that of N3 and N1 treatments, respectively. The partial productivity of nitrogen fertilizer was 34.6% higher in the N2 than that of N3. Considering wheat grain yield and water and nitrogen use efficiency, 210 kg·hm-2 nitrogen application was the best rate under water-saving condition of supplementary irrigation after soil moisture measurement in the study area.

Estimation of the net photosynthetic rate for waterlogged winter wheat based on digital image technology

AbstractThe net photosynthetic rate (Pn) is one of the important indicators to measure photosynthetic capacity of crops. Therefore, it is critically important to find real‐time methods for accurately estimating Pn of winter wheat (Triticum aestivum L.). This information could provide guidance on the management of waterlogging stress. To explore the optimal monitoring method for Pn of winter wheat under waterlogging stress, the correlations between Pn and 16 characteristic image indices were analyzed in irrigated and drained microplot experiments. Then, based on the indices values, Pn was estimated using the multiple linear regression (MLR), support vector machine (SVM), backpropagation neural network (BP), and random forest (RF) models, which were constructed based on the optimal monitoring image indices. Water logging when compared to no waterlogged wheat had similar Pn values <6 days. After 12 days, waterlogged wheat plants had a lower Pn value than in no waterlogged plants. All indices were correlated with the Pn (p < 0.05), and Pn estimation accuracy was lower at the winter wheat flowering and complete ripeness periods than at the milky and waxy ripe maturity periods. Based on the results of the models tested, the RF model had higher R2 (0.904) values than the other models. These findings suggest that machine learning models could be used to accurately predict Pn, and the random forest algorithm was the best.

Genome-wide evolutionary analysis of AUX/IAA gene family in wheat identifies a novel gene TaIAA15-1A regulating flowering time by interacting with ARF

Flowering time is a critical agronomic trait that has strong effects on crop yields. Auxin signaling pathway plays an important role in various development processes, such as flowering, grain development. However, no Aux/IAA gene had been reported to have functions involving in wheat flowering time. Here, we systematically performed genome-wide identification, classification, domain distribution, exon-intron structure, chromosome locations and global expression pattern of Aux/IAA gene family in 14 plant genomes (including Triticum aestivum). A phylogenetic model was proposed to infer the Aux/IAA evolutionary history involving in a central exon-intron structure “2121” during evolution. Overexpression of TaIAA15-1A caused an early flowering time in Brachypodium. RNA-seq analysis showed that TaIAA15-1A overexpression alters various pathways including phytohormone signaling pathway, flowering-related pathway, and polyamine biosynthesis pathway. Screening of auxin response factor (ARF) genes identified BdARF16 that interacted with TaIAA15-1A. Exogenous polyamine (spermidine and spermine) treatments promoted early flowering and (putrescine and DCHA) delayed flowering time of WT plants. Our finding will provide insights on mechanisms of Aux/IAAs gene family and TaIAA15-1A, illustrating the potential during crop improvement programs.

Comparison of Droplet Distribution and Control Effect of Wheat Aphids under Different Operation Parameters of the Crop Protection UAV in the Wheat Flowering Stage

Aphid is one of the main insect pests of wheat in the flowering stage, so timely and effective control of wheat aphids plays an important role in ensuring wheat yield. The crop protection Unmanned Aerial Vehicle (UAV) is widely used in the control of wheat pests and diseases nowadays. In order to screen out the suitable operation parameters of the crop protection UAV to control the wheat aphids, this study conducted wheat aphid distribution investigation tests and droplet distribution tests. With the P20 electric four-rotor crop protection UAV (Guangzhou Jifei Technology Co., Ltd., Guangzhou, China) as the test equipment, four levels of flight speed (FS: 3, 4, 5, 6 m/s) and three levels of flight height (FH: 1.5, 2, 2.5 m) were combined as operation parameters, tests were carried out to compare the density and uniformity of droplet coverage, and the wheat aphid control tests were carried out by using the optimized operation parameters. The results of the wheat aphid distribution investigation test showed that aphids mainly distributed in the lower layer of the wheat plant canopy, accounting for more than 90.61%. The results of the droplet distribution test showed that with the increase in FS and FH, the coverage density and the droplet distribution uniformity in the upper and lower layers of wheat showed a downward trend under the condition of considering the boundary overlap of spraying width (SW) in multi-routes. Through the comparison of operation efficiency and droplet distribution quality, two combinations of parameters A1 (FS: 3 m/s, FH: 1.5 m) and B1 (FS: 4 m/s, FH: 1.5 m) were selected for the aphid control effect test. The results of the control test showed that the average control effect of A1 (92.05%) on aphids was 10.3% higher than that of B1 (81.75%) 7 days after pesticide application, which indicated that improving the droplet distribution uniformity in the lower layer of wheat could significantly improve the control effect of aphids. This study result could provide reference for the same type of crop protection UAV to control the same type of wheat diseases and insect pests in the same growing stage.

Genetic Mapping and Candidate Gene Prediction of a QTL Related to Early Heading on Wild Emmer Chromosome 7BS in the Genetic Background of Common Wheat

Heading date (HD) is an essential agronomic objective in wheat conventional breeding. Field experiments from several years and locations indicated that the chromosome arm substitution line (CASL) of wild emmer chromosome 7BS in the genetic background of common wheat var. Chinese Spring (CS) always showed a substantially earlier HD than CS planted in different seasons; usually about 8 d earlier than CS grown under a normal autumn sowing season. CASL7BS consistently showed a much earlier HD than CS when treated for vernalization under a long or short photoperiod and then grown under a short or long photoperiod in the growth room. CASL7BS showed faster spike development than CS at the stages before the glume stage when grown under long days, and depicted relatively rapid growth at all stages when grown under short days. To map the early gene in CASL7BS, F2 plants from the cross of CASL7BS and CS were planted in the field and growth room, forming two mapping populations (P1 and P2, respectively). According to the HD distribution of P1, the HD was most likely regulated by a dominant gene. A QTL was detected consistently in the distal region of about 8.94 cM flanked by C268 and C309 with LOD scores of 5–8, explaining 9.14 and 12.35% of the phenotypic variation in the two mapping populations. The QTL was further narrowed down to an interval between ZAFU058724 and ZAFU061354 of 58–61 Mb based on the HD and genotype of F3 and F4 families. A total of 41 genes were located in this region, and eleven of them were thought to be the candidate genes based on the gene functions. According to the HD and mapping location, the QTL identified in this study was a new gene associated with flowering, which will be helpful in understanding the mechanism of wheat flowering and for breeding an early wheat variety.

MiR172-APETALA2-like genes integrate vernalization and plant age to control flowering time in wheat.

Plants possess regulatory mechanisms that allow them to flower under conditions that maximize reproductive success. Selection of natural variants affecting those mechanisms has been critical in agriculture to modulate the flowering response of crops to specific environments and to increase yield. In the temperate cereals, wheat and barley, the photoperiod and vernalization pathways explain most of the natural variation in flowering time. However, other pathways also participate in fine-tuning the flowering response. In this work, we integrate the conserved microRNA miR172 and its targets APETALA2-like (AP2L) genes into the temperate grass flowering network involving VERNALIZATION 1 (VRN1), VRN2 and FLOWERING LOCUS T 1 (FT1 = VRN3) genes. Using mutants, transgenics and different growing conditions, we show that miR172 promotes flowering in wheat, while its target genes AP2L1 (TaTOE1) and AP2L5 (Q) act as flowering repressors. Moreover, we reveal that the miR172-AP2L pathway regulates FT1 expression in the leaves, and that this regulation is independent of VRN2 and VRN1. In addition, we show that the miR172-AP2L module and flowering are both controlled by plant age through miR156 in spring cultivars. However, in winter cultivars, flowering and the regulation of AP2L1 expression are decoupled from miR156 downregulation with age, and induction of VRN1 by vernalization is required to repress AP2L1 in the leaves and promote flowering. Interestingly, the levels of miR172 and both AP2L genes modulate the flowering response to different vernalization treatments in winter cultivars. In summary, our results show that conserved and grass specific gene networks interact to modulate the flowering response, and that natural or induced mutations in AP2L genes are useful tools for fine-tuning wheat flowering time in a changing environment.

Influence of Structure of Detrital Food Webs on Fusarium Head Blight of Winter Wheat

Conventional methods for Fusarium head blight (FHB) control are ineffective. A better understanding of the mechanisms linking the abundance of Fusarium species in soil before winter wheat flowering and mycotoxin content in mature grain may help to improve the effectiveness of methods for FHB control. In this study, we established a field experiment aimed to trace the impact of three types of organic mulch with different C:N ratios on the structure of detrital food webs and the manifestation of winter wheat FHB. T2-toxin content in grain was significantly higher in N-poor treatment (52.1 ± 0.2 µg g−1) compared to N-rich treatment (40.4 ± 1.6 µg g−1). The structure of detrital food webs in the studied treatments changed significantly after mulch addition; the abundance of soil saprophages and mycophages increased up to 50%. Based on the results of mixed-effects modeling, the abundance of herpetobionts and soil mesofauna were positively associated with an increase in Fusarium biomass in grain. The increase in the content of T2-toxin in the grain was associated with an increase in the abundance of earthworms and phytophagous macrofauna in the soil. Results suggest the existence of a previously undescribed mechanism for FHB infection by transfer of pathogenic spores by soil invertebrates, while the content of mycotoxins in grain can be triggered by the grazing activity of soil phytophagous invertebrates.

First report of Head blight of wheat caused by Fusarium vorosii in Serbia.

The cosmopolitan species Fusarium graminearum Schwabe directly reduces yield, as well as grain quality of cereals, due to its ability to synthesize mycotoxins. Previously it was considered to be one species occurring on all continents. However, phylogenetic analysis employing the GCPSR method (Genealogical Concordance Phylogenetic Species Recognition) revealed the existence of 15 phylogenetic species within what is now recognised as the Fusarium graminearum Species Complex (FGSC) (Sarver et al. 2011). During 1996-2008, a MRIZP collection of FGSC isolates was established and isolates originating from wheat (5), maize (3) and barely (2) were selected for further study. Morphological features including the appearance of colonies and macroconidia (average size 38.5-53.1 × 4.6-5.4 µm, No 50) of all 10 isolates on PDA were consistent with descriptions of F. graminearum (O'Donnell et al. 2004, Leslie and Summerell 2006). Total DNA was isolated from mycelium removed from 7-day old colonies of single-spore isolates grown on PDA using the DNeasy Plant Mini Kit (Qiagen, Hilden). Further identification was based on amplification and sequencing of elongation factor TEF-1α, histone H3 and β-tubulin in both directions, with primers ef1/ef2, H3-1a/H3-1b and T1/T22, respectively (Jacobs et al. 2010). The sequences were deposited in NCBI under accession numbers MF974399 - MF974408 (TEF-1α), MG063783 - MG063792 (β-tubulin) and MF999139 - MF999148 (histone H3). Sequence analysis was performed using BLAST while genetic similarity was calculated using MEGA 6.0 software. Isolate 1339 originating from wheat (collected at the locality of Kikinda in 2006), shared 100% nucleotide identity with TEF-1α (DQ459745), histone H3 (DQ459728) and β-tubulin (DQ459643) of F. vorosii isolate NRRL37605 (Starkey et al. 2007). The remaining nine isolates were identified as F. graminearum as they shared 99% to 100% nucleotide similarity with F. graminearum NRRL 28439 (O'Donnell et al. 2004). Pathogenicity was tested using artificial inoculations of spikes during wheat flowering (Mesterhazy et al. 1999). Thirty classes were inoculated with each isolate, in three replicates. Inoculum was prepared from 7-day colonies on PDA, and 30 ml of a conidia suspension (1x105 conidia/ml) was used. Control plants were inoculated with sterile water. Three weeks after inoculation, typical Fusarium head blight symptoms were visible on inoculated plants, from which all 10 isolates were successfully reisolated. Control spikes remained symptomless. Disease severity was estimated on the 1-7 scale (Blandino et al. 2012). Average pathogenicity of the F. vorosii isolate 1339 was 1.9, and 2.4 -5.1 of F. graminearum isolates. Toxin production was determined using gas chromatography-tandem mass spectrometry. Kernels inoculated with the 10 isolates were ground and tested for the presence of deoxynivalenol (DON) and its acetyl derivatives 3ADON, 15ADON and NIV. F. vorosii isolate 1339 possessed the 15ADON chemotype, as well as eight F. graminearum isolates, while only one F. graminearum isolate was 3ADON chemotype. To date, F. vorosii has only been detected in Hungary on wheat (Toth et al. 2005) and Korea on barley, corn and rice (Lee et al. 2016). This is the first report of F. vorosii in Serbia, which is of great importance, because it indicates the spread of this toxigenic species. Further studies should be focused on determining the distribution, aggressiveness and toxicological profile of F. vorosii.