Wheat Yield Loss Research Articles

Impact of the biofungicide tetramycin on the development ofFusarium head blight, grain yield and deoxynivalenol accumulation in wheat

Fusarium graminearum causesFusarium head blight (FHB), a devastating disease that leads to extensive yield and quality loss in wheat and barley production. Integrated pest management (IPM) is required to control this disease and biofungicides, such as tetramycin, could be a novel addition to IPM strategies. The current study investigatedin vitro tetramycin toxicity inFusarium graminearum and evaluated its effectiveness for the control ofFusarium head blight FHB. Tetramycin was shown to affect three key aspects ofFusarium pathogenicity: spore germination, mycelium growth and deoxynivalenol (DON) production. Thein vitro results indicated that tetramycin had strong inhibitory activity on the mycelial growth and spore germination. Field trials indicated that tetramycin treatment resulted in a significant reduction in both the FHB disease index and the level of DON accumulation. The reduced DON content in harvested grain was correlated with the amount ofTri5 mRNA determined by qRT-PCR. Synergistic effects between tetramycin and metconazole, in both thein vitro and field experiments were found. Tetramycin could provide an alternative option to control FHB.

Prediction of leaf rust severity and yield loss in wheat based on environmental factors

Six commercial bread wheat (Triticum aestivum L.) cultivars were evaluated against leaf rust (Puccinia triticina) at two different locations in Egypt during three successive growing seasons, i.e., 2016/2017, 2017/2018 and 2018/2019. Correlation between eight weekly environmental factors: solar radiation, total precipitation, average wind speed, maximum wind speed, minimum air temperature, maximum air temperature, minimum relative humidity and maximum relative humidity to leaf rust severity (%) and yield losses (%), was determined using stepwise regression analysis. Predictive models for each tested cultivar for final leaf rust severity (%) and yield losses using environmental data were determined. Generally, maximum relative humidity was positively correlated with final leaf rust severity (%). Significant correlation between yield losses (%) and the two factors, i.e., final leaf rust severity (%) and maximum relative humidity, was also found in this study. Meanwhile, negative correlation was found between final leaf rust severity (%) and yield losses (%) and the two environmental factors, i.e., solar radiation and minimum relative humidity. The effectiveness of tested models was estimated by using R2 values for all models, and these models were validated to predict leaf rust severity (%) and yield loss.

Detecting Frost Stress in Wheat: A Controlled Environment Hyperspectral Study on Wheat Plant Components and Implications for Multispectral Field Sensing

Radiant frost during the reproductive stage of plant growth can result in considerable wheat (Triticum aestivum L.) yield loss. Much effort has been spent to prevent and manage these losses, including post-frost remote sensing of damage. This study was done under controlled conditions to examine the effect of imposed frost stress on the spectral response of wheat plant components (heads and flag leaves). The approach used hyperspectral profiling to determine whether changes in wheat components were evident immediately after a frost (up to 5 days after frosting (DAF)). Significant differences were found between frost treatments, irrespective of DAF, in the Blue/Green (419–512 nanometers (nm)), Red (610–675 nm) and Near Infrared (NIR; 749–889 nm) regions of the electromagnetic spectrum (EMS) in head spectra, and in the Blue (415–494 nm), Red (670–687 nm) and NIR (727–889 nm) regions in the leaf spectra. Significant differences were found for an interaction between time and frost treatment in the Green (544–575 nm) and NIR (756–889 nm) in head spectra, and in the UV (394–396 nm) and Green/Red (564–641 nm) in leaf spectra. These findings were compared with spectral and temporal resolutions of commonly used field agricultural multispectral sensors to examine their potential suitability for frost damage studies at the canopy scale, based on the correspondence of their multispectral bands to the results from this laboratory-based hyperspectral study.

English

Ethiopia is the only country in Sub-Saharan Africa where smallholder wheat production meets more than 70% of the national consumption demand. Russian wheat aphid (RWA; Diuraphis noxia (Mordvilko) (Hemiptera: Aphididae) is one of the major insect pests of wheat throughout the world including in Ethiopia. Wheat yield loss due to RWA damage in Ethiopia was estimated to be 70%. Therefore, the present study was carried out to determine the effect of integrating the potentials of the plant extracts of Neem, Azadirachta indica L. (leaf and seed) and the Entomopathogenic fungi (EPF); Beauveria bassiana and Metarhizium anisopliae against the RWA. After 7 days of applications; the combined mixture of B. bassiana with M. anisopliae caused the maximum loss (73.4%) of aphids, while the combination of Neem leaf with seed extracts recorded the least (57.82%) abundance of aphids, which were negatively affected by single and combined treatments. The lowest abundance was recorded when the aphid was treated by the combination of both B. bassiana and M. anisopliae as well as the combined mixture of Neem leaf and seed extracts. The results indicated that bio-pesticides, based on entomopathogens and botanical extracts (Neem) can be the best replacements for synthetic chemicals and caused significant reduction in survival and abundance of RWA. Therefore, they could be used as promising natural alternatives to synthetic insecticides against RWA in Ethiopia. Key words: Russian wheat aphid, Diuraphis noxia, Beauveria bassiana, Metarhizium anisopliae, Neem, efficacy.

Remedial Application of Urea Eliminates Yield Losses in Wheat Waterlogged during Stem Elongation

Waterlogging remains a critical constraint to wheat production in areas with high rainfall. Exogenous application of nitrogen (N) can effectively diminish the adverse effects of waterlogging, but varies with specific events. To provide highly efficient remedial strategies, this pot study investigated the effects of urea application following 10 days of waterlogging initialing at the stem elongation stage (Zadoks growth stage, GS33). The remedial measures included foliar spray of urea solution at a single dose (0.108 g urea per pot) at the 0th day after finishing waterlogging (FU1) and twice at the 0th and 7th day (FU2), and soil surface spray of urea solution at single and double doses when soil water content was approximately 80% of field capacity (SU1 and SU2, respectively). Waterlogging significantly reduced grain yield, total N uptake, and N partial factor productivity (by 11%, 18%, and 11%, respectively), but subsequent remedial measures improved these to variable degrees. Reduction in grain yield owing to waterlogging could be effectively alleviated and even eliminated using these remediations. Grain yield and N partial factor productivity were higher under FU2 and SU2 than FU1 and SU1. Among all treatments, plants under SU2 exhibited the highest total N uptake and top-dressing N recovery. Diminished yield losses were attributed to (1) increased kernel number per spike resulting from increased spikelet fertility and kernel number per spikelet and (2) increased photosynthetic production by delaying senescence (improved chlorophyll content and maintained green leaf area) of the top leaves. This study suggests that urea application for a brief period of time following waterlogging during the stem elongation stage has remarkable remedial effects.

The Evaluation of Wheat Cultivar Resistance and Yield Loss Thresholds in Response to Barley Yellow Dwarf Virus-PAV Infection

The PAV strain of barley yellow dwarf virus (BYDV) is one of the causal agents of yellow dwarf disease in cereals. The use of germplasm resistant to BYDV is generally regarded as the most effective means of controlling damage caused by this pathogen. In field trials, response to infection with a barley yellow dwarf virus of selected wheat cultivars registered in the Czech Republic was compared with that of control cultivars. Although a good level of resistance to BYDV-PAV was found in cultivar Athlon and yield loss was low, symptoms were more severe than on the moderately resistant control cultivar Sparta. Several other cultivars, such as Nordika, Julie, and Replik, also had slightly less than a 30% reduction in grain weight per spike, even though symptoms were more severe on Sparta or Athlon. Our results showed that, in the case of approximately 60% of wheat plants with BYDV-PAV symptoms, the yield reductions under optimal agronomic conditions reached approximately 17% for moderately resistant cultivars and 30% for moderately susceptible cultivars. The application of N fertilizer significantly reduced yield losses in BYDV-PAV-infected wheat cultivars, particularly in the moderately resistant cultivars. Even when infected with BYDV-PAV, the yield of moderately resistant cultivars, including those of spring wheat, was still acceptable. However, the re-cultivation costs of spring wheat in replacing damaged winter wheat lead to a total economic loss per hectare that is much greater than that for BYDV-infected wheat cultivars (moderately resistant and/or moderately susceptible ones). Furthermore, the economic loss is much lower when a moderately resistant cultivar is used. Hence, even with a high level of disease symptoms in winter wheat, the re-cultivation of spring wheat is not economically feasible.

Understanding the Competitive Effects of Blessed Milkthistle Densities on Wheat

ABSTRACT: Weed-induced yield loss in wheat crop is a great threat to food security in Pakistan. A comprehensive understanding of weed-crop competition is very important to develop sustainable and cost-effective weed management. For this purpose, two-year field studies were conducted to determine the effect of different blessed milkthistle densities on the phenology and yield of wheat crop in a rice-wheat cropping scheme in Sargodha, Pakistan during 2013-2014 and 2014-2015. The experiment comprised seven treatments: control (weed free), weedy check (weedy without any control) and blessed milkthistle densities of 5, 10, 15, 20 and 25 plants m-2. In response to increasing weed density, a gradual reduction in yield and yield-related traits of wheat was noted. Compared to the weed-free control, a significant reduction in number of productive tillers m-2 (20% and 18%), plant height (15% and 18%), spike length (19% and 26%), number of grains spike-1 (23% and 26%), 1000 grain weight (28% and 28%), grain (29% and 30%) and biological (20% and 24%) yields of wheat occurred at and beyond blessed milkthistle density of 5 plants m-2 during 2013-2014 and 2014-2015 respectively. It can be concluded that blessed milkthistle weed must be controlled if its population density reaches 5 plants m-2 in order to avoid significant grain yield losses in wheat.

The costs of human-induced evolution in an agricultural system.

Pesticides have underpinned significant improvements in global food security, albeit with associated environmental costs. Currently, the yield benefits of pesticides are threatened as overuse has led to wide-scale evolution of resistance. Yet despite this threat, there are no large-scale estimates of crop yield losses or economic costs due to resistance. Here, we combine national-scale density and resistance data for the weed Alopecurus myosuroides (black-grass) with crop yield maps and a new economic model to estimate that the annual cost of resistance in England is £0.4bn in lost gross profit (2014 prices), and annual wheat yield loss due to resistance is 0.8 million tonnes. A total loss of herbicide control against black-grass would cost £1bn and 3.4 million tonnes of lost wheat yield annually. Worldwide, there are 253 herbicide-resistant weeds, so the global impact of resistance could be enormous. Our research provides an urgent case for national-scale planning to combat further evolution of resistance, and an incentive for policies focused on increasing yields through more sustainable food-production systems rather than relying so heavily on herbicides.

Endemic and panglobal genetic groups, and divergence of host-associated forms in worldwide collections of the wheat leaf rust fungus Puccinia triticina as determined by genotyping by sequencing.

The wheat leaf rust fungus, Puccinia triticina, is found in the major wheat growing regions of the world and is a leading cause of yield loss in wheat. Populations of P. triticina are highly variable for virulence to resistance genes in wheat and adapt quickly to resistance genes in wheat cultivars. The objectives of this study were to determine the genetic relatedness of worldwide collections of P. triticina using restriction site associated genotyping by sequencing. A total of 558 isolates of P. triticina from wheat producing regions in North America, South America, Europe, the Middle East, Ethiopia, Russia, Pakistan, Central Asia, China, New Zealand, and South Africa were characterized at 6745 single nucleotide loci. Isolates were also tested for virulence to 20 near-isogenic lines that differ for leaf rust resistance genes. Populations that were geographically proximal were also more closely related for genotypes. In addition, groups of isolates within regions that varied for genotype were similar to groups from other regions, which indicated past and recent migration across regions. Isolates from tetraploid durum wheat in five different regions were highly related with distinct genotypes compared to isolates from hexaploid common wheat. Based on a molecular clock, isolates from durum wheat found only in Ethiopia were the first to diverge from a common ancestor form of P. triticina that is found on the wild wheat relative Aegilops speltoides, followed by the divergence of isolates found worldwide that are virulent to durum wheat, and then by isolates found on common wheat.

Assessment of O3-induced yield and economic losses for wheat in the North China Plain from 2014 to 2017, China

Tropospheric ozone (O3) is a pollutant of widespread concern in the world and especially in China for its negative effects on agricultural crops. For the first time, yield and economic losses of wheat between 2014 and 2017 were estimated for the North China Plain (NCP) using observational hourly O3 data from 312 monitoring stations and exposure-response functions based on AOT40 index (accumulated hourly O3 concentration above 40 ppb) from a Chinese study. AOT40 values from 2014 to 2017 during the wheat growing seasons (75-days, 44 before and 30 after mid-anthesis) ranged from 3.1 to 14.9 ppm h, 4.9–17.5 ppm h, 7.3–17.6 ppm h, and 0.5–18.6 ppm h, respectively. The highest AOT40 values were observed in the Beijing-Tianjin-Hebei region. The values of relative yield losses from 2014 to 2017 were in the ranges of 6.4–30.5%, 10.0–35.8%, 14.9–34.1%, and 21.6–38.2%, respectively. The total wheat production losses in NCP for 2014–2017 accounted for 18.5%, 22.7%, 26.2% and 30.8% in the whole production, while the economic losses amounted to 6,292 million USD, 8,524 million USD, 10,068 million USD, and 12,404 million USD, respectively. The important impact of O3 in this area, which is of global importance, should be considered when assessing wheat yield production. Our results also show an increasing trend in AOT40, relative yield loss, total crop production loss and economic loss in the four consecutive years.

Mapping of QTL for partial resistance to powdery mildew in two Chinese common wheat cultivars

The increasing severity and prevalence of powdery mildew aided by extensive use of semi-dwarf cultivars and high levels of nitrogenous fertilizers are causing significant yield losses in wheat. Resistant cultivars are the most cost-effective and environmentally friendly approach to manage the disease. The objective of this study was to identify quantitative trait loci (QTL) for powdery mildew resistance in a doubled haploid (DH) population from a cross between leading Chinese cultivars, Yangmai 16 and Zhongmai 895. A high-density genetic map comprising of 14,480 non-redundant markers (equal to 148,179 SNPs) in 21 wheat chromosomes was constructed by genotyping the population with the Wheat 660 K SNP array. The DH population was phenotyped for powdery mildew resistance at the adult plant stage in multiple field trials, including four environments in the 2016–2017 cropping season and two environments in 2017–2018. Composite interval mapping detected six stable QTL explaining 3.8–23.6% of the phenotypic variance across environments. QPmyz.caas-5DS, QPmyz.caas-6BL and QPmyz.caas-7BS, are probably new QTL for powdery mildew resistance. One SNP marker closely linked to QPmyz.caas-6BL, the most stable QTL, was converted into a Kompetitive Allele-Specific PCR marker (K_AX-94973433) and validated on 103 commercial wheat cultivars. Significantly lower maximum disease severities of cultivars with the resistance-associated allele than those with the susceptibility-associated allele at QPmyz.caas-6BL in some environments indicated partial effectiveness of the marker. The novel QTL and their closely linked markers identified in the present study should facilitate development of cultivars with improved powdery mildew resistance.

Gamma Radiated Wheat for Combating Devastating Blast Disease (Magnaporthe Oryzae Triticum) In Bangladesh

Wheat is a global food security crop, providing 20 percent of protein and calories consumed worldwide and up to 50 percent in developing countries. It is the second most important cereal next to rice in Bangladesh and playing an important role in attaining food security. But wheat is very susceptible to diseases that often place major biological constraints on production. In 2016, a new wheat disease called “blast” was identified by wheat scientists for the first time in Bangladesh. Wheat blast disease caused by Magnaporthe oryzae triticum is causing enormous yield loss worldwide. At present, control of blast disease is a great challenge due to frequently introduction of new races of the pathogen. The present investigation focused on screening M2 population of gamma radiated wheat where four doses of radiations viz. 150 Gy, 200 Gy, 250 Gy, and 300 Gy were applied to the seeds of three wheat varieties viz. BARI Gom-25, BARI Gom-29 and BARI Gom-30 from a Cobalt 60 source (Gamma Chamber 5000). The irradiated seeds were sown in farmers’ fields of a wheat blast disease-prone area Chandbil, Meherpur Sadar. All the doses of irradiation showed a significant effect on incidence and severity of wheat blast disease in all three varieties. Among the treatments 200 Gy and 250 Gy reduced the disease effectively. Molecular detection of Magnaporthe oryzae triticum was also done using specific primer. The size of the band (350 bp) confirms the infection of M2 families by Magnaporthe oryzae triticum. Development of wheat blast resistant variety through irradiation could be a potential substitute to replace the available chemical control methods and it is described as eco-friendly, sustainable and nonhazardous strategy to reduce wheat yield loss due to blast disease.

Yield responses in spring wheat and barley cultivars, varying in stripe rust resistance in central Alberta

Yield losses in wheat and barley cultivars varying in stripe rust reactions were determined under natural infection conditions in fungicide treated and untreated plots at Lacombe and Olds, central Alberta, from 2012 to 2014. Stripe rust caused by Puccinia striiformis was the major disease observed during the 3-year test. Moderate stripe rust severity caused significant yield losses of over 20% in a highly susceptible wheat, ‘AC Crystal’, while no severe yield losses occurred for resistant and moderately resistant cultivars/lines. However, a moderate level of stripe rust and the leaf spot complex caused reductions in thousand kernel weight (TKW) ranging from 5.4% to 13.5% for all wheat and barley cultivars/lines tested except for ‘Lillian’ wheat and ‘Seebe’ barley. When stripe rust developed early in the growing season resulting in severe disease, there were significant yield losses ranging from 17.6% to 91% for five wheat and two barley genotypes. Severe TKW and test weight losses also occurred for susceptible wheat and barley. The magnitude of yield losses in resistant and intermediate cultivars was smaller than in susceptible cultivars in the same tests. The present study demonstrated that one foliar-applied fungicide application was generally capable of protecting susceptible wheat and barley cultivars from stripe rust, while the use of resistant and intermediate cultivars was necessary for yield protection when moderate levels of disease occurred. Fungicide application was needed to reduce yield losses for resistant and moderately resistant cultivars when leaf spot diseases were prevalent and an early onset of stripe rust was observed, which can lead to severe stripe rust development even in resistant varieties.

Large regional differences of soil water limitation effect on ozone induced yield loss for wheat and potato in Switzerland

The accumulated stomatal ozone (O3) uptake over a threshold (Phytotoxic Ozone Dose POD6), calculated by an ozone deposition model, has been shown to be the most appropriate metric to quantify negative effects of O3 on food crops. In this study we used data of 13 sites in different regions of Switzerland with multiple years of O3 measurements to quantify the stomatal O3 uptake and the related yield loss of wheat and potato. Flux patterns for different years were calculated with the DO3SE model to disentangle the influence of contrasting seasonal environmental conditions. Regional and inter-annual differences in meteorological conditions led to considerable variations in soil water conditions and the POD6 values for wheat. Potato stomatal uptake was much less influenced by soil water and showed a more even distribution of POD6 values across sites and years. The estimated nationally and temporally average yield loss was 3.2 ± 1.2% for wheat and 2.4 ± 0.8% for potato, calculated based on an area weighting.It was found that soil water deficit, observed frequently in the western part of Switzerland, had a large attenuation effect on stomatal O3 uptake by wheat and on corresponding yield losses. This highlights the importance of including soil moisture limitation in O3 uptake modelling even in moist climatic regions. The comparison of modelled evapotranspiration with water flux measurements over a wheat field showed a reasonable agreement concerning the temporal pattern and the magnitude. But it is also concluded that the DO3SE soil moisture module will need further testing and adaptation to improve accuracy of the model in dryer conditions.

Interference of Annual Sowthistle (Sonchus oleraceus) in Wheat

Abstract Annual sowthistle (Sonchus oleraceus L.) is a broadleaf weed that is increasing in prevalence in the northern cropping regions of Australia. Being a member of Asteraceae family, this weed possesses many biological attributes needed to thrive in varying environments and weed management pressure. Interference of this weed was examined in a wheat (Triticum aestivum L.) crop through field studies in 2016 and 2017. Different densities of S. oleraceus were evaluated for their potential to cause yield loss in wheat: 0.0 (weed free), low (9 to 15 plants m−2), medium (29 to 38 plants m−2), and high (62 to 63 plants m−2). Based on the exponential decay model, 43 and 52 plants m−2 caused a yield reduction of 50% in 2016 and 2017, respectively. Yield components such as panicles m−2 and grains per panicles were affected by weed density. At the high weed infestation level, S. oleraceus produced a maximum of 182,940 and 192,657 seeds m−2 in 2016 and 2017, respectively. Sonchus oleraceus exhibited poor seed retention at harvest as more than 95% of seeds were blown away by wind. Adverse effects on crop, high seed production and wind-blown dispersal may lead to an increased prevalence of this weed in the absence of an integrated weed management strategy utilizing both herbicides and non-chemical options.

Yield and nitrogen use efficiency of winter wheat with different soil fertility

Both the existing soil fertility and fertilizer application have important influences on crop yield and nitrogen (N) use efficiency, but knowledge about their interaction is still lacking. The interaction of N application and integrated soil fertility index on grain yield and N fertilizer use efficiency such as N recovery efficiency, soil N dependency rate, and N contribution rate of wheat was studied through 2-year in situ tests in Changshu County of the Taihu Lake region, China. The results indicated that there are desirable quantitative relationships among the assessment indices, N application level and integrated soil fertility index. The regression coefficients showed that the ratio of the relative contribution of soil fertility and N application level to wheat yield was 0.48:1, and their contribution ratios to fertilizer N utilization efficiencies were 1.10:1, 1.45:1 and 1.93:1, respectively. The effects of both soil fertility and N application level on yield and N recovery efficiency indicated that it is difficult to simultaneously improve yield and N recovery efficiency of wheat by improving soil fertility when attempting to maximize yield. Only by enhancing soil fertility, reducing the N application level and decreasing the maximum yield, can high levels of N recovery efficiency be achieved. For this study, a ratio of N application level decrement to integrated soil fertility increment greater than 0.89 was necessary to increase the N recovery efficiency to 55%. Under this optimal condition, the reduction in N application level was 16%, and the mean yield loss of wheat was only 8%.

In-silico prediction of novel genes responsive to drought and salinity stress tolerance in bread wheat (Triticum aestivum).

Common wheat (Triticum aestivum) is the most widely grown cereal crop and is cultivated extensively in dry regions. Water shortage, resulting from either drought or salinity, leads to slow growth and loss of wheat yield. In order to predict new genes responsive to the drought and salt stresses in wheat, 6,717 expressed sequence tags (ESTs), expressed in drought and salinity stress conditions were collected from the National Center for Biotechnology Information (NCBI). The downloaded ESTs were clustered and assembled into 354 contigs; 14 transcription factor families in 29 contigs were identified. In addition, 119 contigs were organized in five enzyme classes. Biological functions were obtained for only 324 of the 354 contigs using gene ontology. In addition, using Kyoto Encyclopedia of Genes and Genomes database, 191 metabolic pathways were identified. The remaining contigs were used for further analysis and the search for new genes responsive to drought and salt stresses. These contigs were mapped on the International Wheat Genome Sequencing Consortium RefSeq v1.0 assembly, the most complete version of the reference sequence of the bread wheat variety Chinese Spring. They were found to have from one to three locations on the subgenomes A, B, and D. Full-length gene sequences were designed for these contigs, which were further validated using promoter analysis. These predicted genes may have applications in molecular breeding programs and wheat drought and salinity research.

Differences in Aceria tosichella population responses to wheat resistance genes and wheat virus transmission

Severe winter wheat yield losses due to infestations of wheat curl mite, Aceria tosichella Keifer, and mite-transmitted viruses occur in wheat production areas of the United States and Canada. Mite infestation alone causes stunted, chlorotic plants in susceptible wheat varieties, and mites transmit Wheat Streak Mosaic (WSMV), High Plains Wheat Mosaic (HPWMoV), and Triticum Mosaic Virus (TriMV). Wheat curl mites were collected from 25 sites in Kansas, Missouri, Nebraska, Texas, North Dakota, and South Dakota in 2014 and 2015. At each site, mite virulence was determined to wheat plants harboring the Cmc2-, Cmc3-, or Cmc4 mite resistance gene; or Cmc4 plus the Wsm2 WSMV resistance gene. Mites collected from 92%, 36%, and 24% of sites were virulent to susceptible Jagger wheat plants (no Cmc), Cmc2, and Cmc3, respectively. The mega-population consisting of all 25 mite sub-populations was avirulent to 80% of plants containing Cmc4 + Wsm2 or Cmc4. WSMV, HPWMoV, or TriMV was present in mites at 76%, 16%, and 8% of the 25 sites, respectively. Our results will enable breeders to increase the efficiency of wheat production by releasing wheat varieties containing wheat curl mite resistance genes that reduce wheat yield losses.

Identification of Fusarium Head Blight in Winter Wheat Ears Based on Fisher’s Linear Discriminant Analysis and a Support Vector Machine

Fusarium head blight (FHB) is one of the diseases caused by fungal infection of winter wheat (Triticum aestivum), which is an important cause of wheat yield loss. It produces the deoxynivalenol (DON) toxin, which is harmful to human and animal health. In this paper, a total of 89 samples were collected from FHB endemic areas. The occurrence of FHB is completely natural in experimental fields. Non-imaging hyperspectral data were first processed by spectral standardization. Spectral features of the first-order derivatives, the spectral absorption features of the continuum removal, and vegetation indices were used to evaluate the ability to identify FHB. Then, the spectral feature sets, which were sensitive to FHB and have significant differences between classes, were extracted from the front, side, and erect angles of winter wheat ear, respectively. Finally, Fisher’s linear discriminant analysis (FLDA) for dimensionality reduction and a support vector machine (SVM) based on radical basis function (RBF) were used to construct an effective identification model for disease severity at front, side, and erect angles. Among selected features, the first-order derivative features of SDg/SDb and (SDg-SDb)/(SDg+SDb) were most dominant in the model produced for the three angles. The results show that: (1) the selected spectral features have great potential in detecting ears infected with FHB; (2) the accuracy of the FLDA model for the side, front, and erect angles was 77.1%, 85.7%, and 62.9%. The overall accuracy of the SVM (80.0%, 82.9%, 65.7%) was slightly better than FLDA, but the effect was not obvious; (3) LDA combined with SVM can effectively improve the overall accuracy, user’s accuracy, and producer’s accuracy of the model for the three angles. The over accuracy of the side (88.6%) was better than the front (85.7%), while the over accuracy of the erect angle was the lowest (68.6%).

Impacts of current ozone pollution on wheat yield in China as estimated with observed ozone, meteorology and day of flowering

Wheat yield loss due to ambient ozone (O3) and the associated economic losses in China were evaluated for years 2015 and 2016 using for the first time measured O3 concentration ([O3]) and meteorological data as well as phenological observations. Relative yield losses (RYL) were estimated using response functions based on both O3 exposure and flux metrics: AOT40 (the accumulated hourly [O3] over a threshold of 40 ppb) and POD12 (Phytotoxic Ozone Dose over a threshold of 12 nmol O3 m−2 s−1). Both metrics showed consistent spatial patterns being highest in the North China Plain, the largest wheat-producing area in China, followed by some provinces in Yangtze River region. The higher stomatal conductance in areas with high [O3] in year 2015 contributed to higher POD12 values than in 2016. The RYLs for the whole China estimated with AOT40 were 17.1% and 18.1% for years 2015 and 2016, respectively, whereas those with POD12 were lower, 10.6% and 10.2%, respectively. Wheat production losses as translated to annual economic losses were 10 304 and 10 745 million USD (AOT40) or 5912 and 5554 million USD (POD12), for 2015 and 2016, respectively. The O3 impact estimated with monitoring data suggests its overestimation by some of the previous studies based on model estimates of surface [O3]. The overestimation could be attributed to the uncertainties in estimating meteorological variables and [O3], particularly the omission of the correction for the vertical gradient of [O3] near crop canopy in some studies.