Flag Leaf Stage Research Articles

Fungicide application at anthesis of wheat provides effective control of leaf spotting diseases in western Canada

Leaf spotting diseases commonly occur on spring wheat crops grown in Saskatchewan, causing yield losses of up to 15%, although greater losses have been documented during severe epidemics. In the past decade, Fusarium head blight (FHB) has become a major concern for growers resulting in extensive use of fungicide to mitigate the disease. The optimal fungicide timing for leaf spot control is generally at the flag-leaf stage, while the optimal timing for FHB is during anthesis. The objective of this study was to determine whether applying fungicide at anthesis timing can provide adequate control of leaf spots when compared to application at flag-leaf stage. Fungicide treatments applied at flag-leaf, anthesis, and both growth stages were evaluated on the cv. Carberry. Prothioconazole + tebuconazole and tebuconazole (only) applied at anthesis provided adequate control of leaf spots, although the severity of leaf diseases was slightly higher in this treatment than application at flag-leaf stage but yields were similar. Test weight and thousand kernel weight were improved with the application at anthesis relative to that at flag-leaf stage. Two applications of fungicide provided only a small incremental benefit to the anthesis application, and would not be economically justified in western Canada at this time. Anthesis fungicide application provided adequate leaf spot disease control and is the optimum timing for the control of FHB.

Identification of jumonjiC domain containing gene family among the Oryza species and their expression analysis in FL478, a salt tolerant rice genotype

The jumonji (JMJ)-C domain containing proteins belong to histone demethylases family with the ability to demethylate the tri-methylated histone residues. They act as chromatin regulators to regulate many physiological functions in plants. The present study deals with the characterization of JMJ-C gene family members in wild as well as cultivated rice species and their expression analysis in salt tolerant rice genotype, FL478. The genome wide study identified 151 members belonging to JMJ-C gene family in 11 different Oryza species. We also studied their structure, genomic location, gene duplication events, phylogenetic relationship, in silico expression analysis and identified cis elements in their promoters. We also found a few JMJ-C gene family members in rice which underwent duplication before the whole genome duplication event of the rice. The qRT-PCR based expression profiling revealed that out of the total 15 rice JMJ-C members, two were highly expressed in the flag leaf stage of FL478 under salt treatment. These two candidate JMJ-C members were also found to render salinity tolerance when over-expressed in yeast cells. Thus, the present study helps in further structural as well as functional characterization of JMJ-C genes under salinity stress in Oryza species.

15N Natural Abundance Evidences a Better Use of N Sources by Late Nitrogen Application in Bread Wheat.

This work explores whether the natural abundance of N isotopes technique could be used to understand the movement of N within the plant during vegetative and grain filling phases in wheat crop (Triticum aestivum L.) under different fertilizer management strategies. We focus on the effect of splitting the same N dose through a third late amendment at flag leaf stage (GS37) under humid Mediterranean conditions, where high spring precipitations can guarantee the incorporation of the lately applied N to the soil-plant system in an efficient way. The results are discussed in the context of agronomic parameters as N content, grain yield and quality, and show that further splitting the same N dose improves the wheat quality and induces a better nitrogen use efficiency. The nitrogen isotopic natural abundance technique shows that N remobilization is a discriminating process that leads to an impoverishment in 15N of senescent leaves and grain itself. This technique also reflects the more efficient use of N resources (fertilizer and native soil-N) when plants receive a late N amendment.

Foliar Fungicide Effects on Disease Severity, Yield, and Agronomic Characteristics of Modern Winter Wheat Genotypes

Core Ideas Foliar fungicide application at the flag leaf stage (Zadoks 39) improved grain yield and grain protein content.One time application of foliar fungicide resulted in economic returns up to US$204 ha–1.Grain volume weight, grain size, leaf area index, and leaf greenness were improved from foliar fungicide application at the flag leaf stage. Foliar diseases limit winter wheat (Triticum aestivum L.) production in the Great Plains of the United States. Farmers often use foliar fungicide application to counter yield loss. Two‐year field experiments were conducted at two locations in Nebraska to investigate the effects of foliar fungicide (Prosaro 421 SC [Bayer Crop Science, Leverkusen, Germany]: prothioconazole + tebuconazole) at the flag leaf stage on yield and agronomic characteristics of winter wheat. Foliar fungicide application increased grain yield, grain protein content, seed weight, grain volume weight, leaf greenness, and leaf area by up to 42, 1, 16, 6, 48, and 35%, respectively. Foliar fungicide at the flag leaf stage in the spring reduced disease severity (up to 84%), area under disease progress curve (up to 87%), and agronomic characteristics that resulted in economic returns of up to US$204 ha−1 excluding the premium farmers get from increased protein. Susceptible to moderately susceptible genotypes were more responsive to foliar fungicide on controlling disease severity and improving grain yield compared to moderately resistant to resistant genotype when disease pressure was high. This study showed that the economic benefit for all genotypes obtained from improved grain yield, grain volume weight, grain protein content, and grain size due to one‐time application of foliar fungicide at the flag leaf stage in winter wheat could have significant benefit to the farmer’s economy and wheat industry.

Wheat Pest Dynamics, Forecasting and Current Importance of the Attack, to Develop Integrated Control System in the Center of Transylvania (ARDS Turda, 2006-2016)

The paper presents data about wheat pest attack in Transylvania in the last 10 years, under the different climatic, phenological and technological conditions, with details of the correlations of the climatic factors with the bio-ecology of the species or pest groups. Such data may be important for modelling and forecasting wheat pest attacks. The climatic warming, represented strong environmental factors (R2 = 0.43), which led to changes in the species structure, favouring the development of the populations of a narrow spectrum of species becoming dominant and dangerous by numerical increases. In the years 2006-2015, the eudominance of thrips (58%), the dominance of aphids (14%) and of wheat flies (12%), the subdominant species of Chrysomelidae and the increase of entomophagus abundance were revealed. In the year 2016, the weight of the dominant groups of wheat flies (25%), aphids (21%), leafhoppers (18%), thrips (17%), of the subdominant group of Chrysomelidae (10.6%) and cereal bugs (4.5%) increased. Changes in entomocenotic interactions phytophagusentomophagus, changes in pest dynamics, and of optimal moments for treatments important in the development of integrated pest control systems, have occurred in wheat crops. In the conditions of the area, the annual abundance of entomophagus is determined by the annual abundance of phytophagous insects, as expressed by a positive correlation (R2 = 0.464 and D% = 46.4%). Under the conditions of the last 10 years, the annual ratio of the number of phytophagous / entomophagus fluctuated between 2.35 and 12.42. The size of the phytophagous / entomophagus ratio was strongly correlated with the increase of the average annual temperatures, with a percentage determination coefficient D% = 15.5%, having an optimum of the interactions at values of 6.3 phytophagous / 1 entomophagus, and less well correlated with the annual precipitations. These changes in wheat entomocenoses, the biological potential accumulated over the last 10 years and at the level of 2016 indicate the importance of adapting pest control strategies, which should include preventive methods (respecting the optimum sowing time, agro-technical and phytosanitary methods), insecticide treatments on seed and on vegetation, at optimal application times for the groups of pests whose attacks overlap, respectively the first treatment in the spring, no later than the end of tillering, for wheat flies, leafhoppers, Chrysomelidae etc.; the second treatment at the phenophase of flag leaf stage and ear appearance, for thrips, aphids, bugs etc.; and other treatments at warning. Given the importance of entomophagous arthropod fauna in limiting wheat pests it is necessary to protect and use the auxiliary entomophagus, flora biodiversity involved in achieving the productivity and stability of wheat crops.

Формування продуктивності сорго цукрового під впливом строків сівби

The scientifically based choice of sowing terms for sorghum depends on the climatic conditions, type, state and humidity of the soil, biological characteristics of varieties and hybrids, the economic purpose of sowing, rate of positive temperatures growth. The purpose of the research was to determine the effect of sowing terms on the growth, development and the yield of green mass of sugar sorghum. In the experiment, the variety of sugar sorghum Silosne 42 and the hybrid Dovista were sown in three terms when the soil temperatures at the depth of seeding were: І – 6–8 °С, ІІ – 8–10 °С, ІІІ – 10–12 °С. Biometric indexes of sugar sorghum depended both on sowing terms and varietal characteristics. The plants most intensively developed and formed the above-ground mass in a variant where the soil temperature at the depth of seeding was 10–12 °С, and plants height was 151.7 and 193.7 cm in the period of flowering – respectively in the Silosne 42 variety and the Dovista hybrid. The highest indexes of the leaf area (51.87 and 57.25 thousand m2/ha), photosynthetic potential (4.26 and 4.32 million m2×days/ha) and the net productivity of photosynthesis (3.50 and 3.54 g/m2 per day) of sugar sorghum were on varieties, sown when the soil temperature at the depth of seeding was 10–12 °С, respectively in the Silosne 42 variety and the Dovista hybrid. It was noted that the increase in the surface of leaf area and the duration of vegetation result in higher photosynthetic potential and, consequently, the growth of the green mass yield. Maximum indexes of pure productivity of photosynthesis are observed in the flowering period, that is, during the period of the most intense growth of the above-ground mass and the leaf surface of sugar sorghum. From the flag leaf stage until flowering stage there is an intense growth in sugar sorghum, and increment of green mass is 57.3-78.6% compared with the growing point differentiation stage. The sorghum biomass indexes had the highest values at all stages of the third sowing term. Increment of the green mass continues to the hard dough stage, while dry matter grows throughout the growing period. The highest yield of the green and dry mass of the Silosne 42 variety and the Dovista hybrid is observed in the hard dough stage, when the soil temperature at the depth of seeding was 10–12 °С – 74.8 and 17.4 t/ha and 83.7 and 20.2 t/ha. The Dovista hybrid prevailed on the yield of the green mass on 9.8–12.7% and dry matter on 4.5–7.8% than the Siloshne 42 variety.

Foliar application of benzovindiflupyr shows non-fungicidal effects in wheat plants.

BACKGROUNDThe fungicide benzovindiflupyr belongs to the class of succinate dehydrogenase inhibitors (SDHIs). Certain SDHIs have shown plant physiological effects, so‐called secondary effects, that appeared to be related to the plant water status. Therefore, the effect of benzovindiflupyr on transpiration of leaves and whole wheat plants was studied under controlled conditions. Furthermore, wheat yield trials under controlled and natural drought stress in the field were conducted.RESULTSTranspiration of detached wheat leaves was reduced by benzovindiflupyr in a dose‐dependent manner. Similarly, whole‐plant transpiration decreased for several days following application of this fungicide. In 16 field trials under drought stress conditions that were classified as disease‐free, treatment of wheat plants at the flag leaf stage or at heading with benzovindiflupyr showed a grain yield increase (+5.2%; P ≤ 0.01) that was partially attributed to an increased thousand‐grain weight.CONCLUSIONSWater saving during pre‐anthesis as a result of benzovindiflupyr application may be associated with better seed setting and filling under dry field conditions in wheat. The results of this research provide new insights into secondary effects of SDHIs that lead directly to yield improvements. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Genotype, environment, seeding rate, and top-dressed nitrogen effects on end-use quality of modern Nebraska winter wheat.

Fine-tuning production inputs such as seeding rate, nitrogen (N), and genotype may improve end-use quality of hard red winter wheat (Triticum aestivium L.) when growing conditions are unpredictable. Studies were conducted at the Agronomy Research Farm (ARF; Lincoln, NE, USA) and the High Plains Agricultural Laboratory (HPAL; Sidney, NE, USA) in 2014 and 2015 in Nebraska, USA, to determine the effects of genotype (6), environment (4), seeding rate (3), and flag leaf top-dressed N (0 and 34 kg N ha-1 ) on the end-use quality of winter wheat. End-use quality traits were influenced by environment, genotype, seeding rate, top-dressed N, and their interactions. Mixograph parameters had a strong correlation with grain volume weight and flour yield. Doubling the recommended seeding rate and N at the flag leaf stage increased grain protein content by 8.1% in 2014 and 1.5% in 2015 at ARF and 4.2% in 2014 and 8.4% in 2015 at HPAL. The key finding of this research is that increasing seeding rates up to double the current recommendations with N at the flag leaf stage improved most of the end-use quality traits. This will have a significant effect on the premium for protein a farmer could receive when marketing wheat. © 2017 Society of Chemical Industry.

Crop sequence and in-season nitrogen (N) application effects on organic winter wheat (Triticum aestivum L.) yield and quality

The objective of this study was to determine an optimum combination of N inputs for dryland organic winter wheat (Triticum aestivum L.) (WW). Trials were conducted on separate fields near Concord, Nebraska in 2008–2009 and 2010–2011. WW followed previous crops of alfalfa (Medicago sativa L.)/corn (Zea mays L.) and alfalfa/alfalfa. Cattle manure was applied at three rates (providing approximately 0, 58, and 112 kg ha−1 predicted plant available N [0, base, and double rates]), in either fall (autumn) or spring. An organic-approved foliar N was applied at three rates (0, 11, and 22 kg ha−1 N) in late spring (flag leaf stage). In Trial I, yield and N uptake were greater for fall (autumn) manure (4.0 Mg ha−1 and 82.9 kg N ha−1) than for spring manure (3.5 Mg ha−1 and 76 kg N ha−1). In Trial I, grain protein concentration was slightly improved (~2%) by both rates of foliar N and the double rate of spring manure, and slightly decreased (~2%) by both rates of fall manure. In Trial II no treatment had a clear effect on WW yield, grain protein concentration, or N uptake. In both trials the mean grain yield was 3.7 Mg ha−1 and protein concentration was above 130 g kg−1, which exceeded the requirement for bread flour. It was concluded that N was not limiting in this system; the alfalfa provided sufficient fertility for WW in both the alfalfa/corn/WW and alfalfa/alfalfa/WW crop sequences. The results indicated that livestock manure may be more effectively used for other phases of the rotation than for WW.

Grain sorghum transpiration efficiency at different growth stages

Transpiration efficiency (TE) is an important physiological trait associated with drought tolerance of plants. Currently, little is known about the grain sorghum TE and its dynamics with the age of plants. To compare the sorghum TE at different growth stages, four studies (two in the greenhouse and two in the growth chamber) were conducted under controlled environmental conditions. Plants were grown in lid-covered boxes and harvested at six-leaf, flag leaf, grain filling and maturity stages. The mean shoot TE values were 4.47 and 4.10 kg/m<sup>3</sup> for two greenhouse studies, and 4.85 and 4.30 kg/m<sup>3</sup> for two growth chamber studies, respectively. The shoot TE was not different among four growth stages within each study, suggesting that sorghum plants used the same amount of water per unit of biomass production for different growing periods. Because crops grown under dryland environments often run out of water during reproductive periods, result supports the ideas that soil water availability at later growth stages is crucial to achieve the yield potential of dryland sorghum.

Seeding Rate, Genotype, and Topdressed Nitrogen Effects on Yield and Agronomic Characteristics of Winter Wheat

Winter wheat (Triticum aestivum L.) yield produced in Nebraska is often inconsistent, mainly due to environmental variability. Managing production practices could partially mitigate this problem. The objective of this study was to determine the effects of seeding rate (0.5, 1, and 2 times of the normal seeding rate), genotype (6), and topdressed nitrogen (0 and 34 kg N ha−1 at the flag leaf stage) on the yield and agronomic characteristics of winter wheat. Experiments were conducted under rainfed conditions at the Agronomy Research Farm (ARF; Lincoln, NE) and the High Plains Agricultural Laboratory (HPAL; Sidney, NE) in 2014 and 2015. A randomized complete block design with a split factorial arrangement of four replicates was used. Nitrogen was applied to the whole plots and factorial combinations of the six genotypes and three seeding rates were applied to the split plots. Normal seeding rates were 186 seeds m−2 at HPAL and 252 seeds m−2 at ARF. Nitrogen fertilization significantly increased yield and net returns (US$101 at ARF to $96 at HPAL) in 2014. Grain yield increased in response to seeding rate for both sites and years. Twice, the seeding rate increased grain yield, by 5% in 2014 and 13% in 2015 at ARF. The corresponding yield increase was 9% in 2014 and 5% in 2015 at the HPAL site. Estimated net return was $17 and $21 ha−1 at ARF, and $10 and $81 ha−1 at HPAL in 2014 and 2015, respectively.

Evaluation of Different Wheat Genotypes Reaction to Stripe Rust (Puccinia striiformis f.sp. tritici) under Field Conditions in Ardabil Province

In order to assess the reaction of different wheat genotypes to 134E134A+ race of yellow rust at adult plant stage, 100 wheat genotypes were evaluated at Ardabil and Moghan under field and mist irrigation conditions. Infection type was recorded at flag leaf stage when disease appeared in susceptible genotypes (infection of around 80%). Disease severity on leaves was evaluated by Modified Cobb’s Scale in which 0: immune, 0%-5%: resistant, 5%-10%: moderately resistant, 10%-30%: moderately susceptible, more than 30%: highly susceptible. Mean coefficient of infection and mean area under disease progress curve (AUDPC) of flag leaf were calculated in each region separately. Analysis of variance indicated significant difference between genotypes for all traits. Results of this experiment according to coefficient of infection indicated that in Ardabil area, 1% of the genotypes were Immune, 29% were resistant, 52% were moderately resistant and 18% were susceptible. In Moghan area 25% of the genotypes were Immune, 59% were moderately resistant and 16% were susceptible to yellow rust disease. Cluster analysis based on infection type characteristics, disease severity and coefficient of infection in Moghan classified genotypes into four main groups. On the other hand, cluster analysis in Ardabil according to aforementioned traits, classified the varieties into three main groups. Compound analysis of variance according to infection type characteristics, disease severity and coefficient of infection in two regions indicated there is a significant difference between examined genotypes and interaction of genotype × region.

Photosynthetic efficiency parameters as indicators of agronomic traits of winter wheat cultivars in different soil water conditions

In an effort to find breeding methods for improving drought stress tolerance and grain yield, twelve photosynthetic efficiency parameters have been measured on ten cultivars of winter wheat (Triticum aestivum L.), along with water use (WU), water use efficiency (WUE) and agronomic traits of grain yield (GYP), biomass weight (BWP), harvest index (HI), yield stability index (YSI) and stress tolerance index (STI) in the vegetative pot trial with control (B1) and drought stress (B2) treatments. Drought stress induced in three different stages of development has caused decrease in water use efficiency based on biomass (WUEb) (B1: 2.94 g L-1; B2: 2.71 g L-1) and grain yield (WUEg) (B1: 1.03 g L-1; B2: 0.89 g L-1), as well as GYP and BWP. Dissipation energy flux per excited cross section (DI0/CS0) observed in the drought stress treatment in the tillering stage of growth gave significant negative correlation coefficient (P?0.05) with agronomic traits of tested wheat cultivars (GYP:-0.75; WUEg and STI: -0.74; YSI: -0.67). Performance index (PIABS) measured in the drought stress conditions in the flag leaf stage was in significant positive correlation with GYP and WUEg (r=0.64). Lower values of absorption flux per excited cross section (ABS/CS0), electron transport per excited CS (ET0/CS0) and dissipation energy flux per excited CS (DI0/CS0) and higher values of PIABS, measured on wheat genotypes (cultivars) in the drought stress conditions of pot trial, could indicate higher tolerance to drought stress conditions. Results of the studied photosynthetic efficiency parameters of wheat cultivars were also the good predictor for important agronomic traits, especially, when they were detected in the early stage of growth.

QTLs for earliness and yield-forming traits in the Lubuski\u2009\xd7\u2009CamB barley RIL population under various water regimes

Drought has become more frequent in Central Europe causing large losses in cereal yields, especially of spring crops. The development of new varieties with increased tolerance to drought is a key tool for improvement of agricultural productivity. Material for the study consisted of 100 barley recombinant inbred lines (RILs) (LCam) derived from the cross between Syrian and European parents. The RILs and parental genotypes were examined in greenhouse experiments under well-watered and water-deficit conditions. During vegetation the date of heading, yield and yield-related traits were measured. RIL population was genotyped with microsatellite and single nucleotide polymorphism markers. This population, together with two other populations, was the basis for the consensus map construction, which was used for identification of quantitative trait loci (QTLs) affecting the traits. The studied lines showed a large variability in heading date. It was noted that drought-treatment negatively affected the yield and its components, especially when applied at the flag leaf stage. In total, 60 QTLs were detected on all the barley chromosomes. The largest number of QTLs was found on chromosome 2H. The main QTL associated with heading, located on chromosome 2H (Q.HD.LC-2H), was identified at SNP marker 5880–2547, in the vicinity of Ppd-H1 gene. SNP 5880–2547 was also the closest marker to QTLs associated with plant architecture, spike morphology and grain yield. The present study showed that the earliness allele from the Syrian parent, as introduced into the genome of an European variety could result in an improvement of barley yield performance under drought conditions.

Transgenerational effects of temporal drought stress on spring barley morphology and functioning

Drought stress affects plants leaving a long-lasting imprint that may be passed onto progeny, affecting its growth and functioning. The aim of the research was to analyse the transgenerational effect of intense drought on alterations in functioning and changes in the growth of shoot and roots of spring barley. Barley seeds from a maternal generation that were affected by intense drought stress at the flag leaf stage or grown in the optimum conditions throughout the vegetation period were used as a sowing material to analyse the growth of a progeny generation at drought or in soil at optimum soil moisture. The difference in water availability during the growth of the progeny generation significantly affected all measured indicators of plant growth and functioning. However, significant differences were also found between offspring growing in the same conditions but characterised by different water availability during the growth of the maternal generation. The differences between plants with different stress histories in the maternal generation were more pronounced in barley offspring grown at drought than at optimum soil water availability. The drought induced during the growth of the barley maternal generation decreased the shoot-to-root mass ratio, enhanced growth of thin roots, and reduced the number of thick roots in the progeny grown at drought, compared to plants that were grown in the same conditions but without drought in the maternal generation. Maintenance of relatively long roots at low allocation of biomass to roots at drought in the progeny of the stressed maternal generation may be an adaptive response that can minimise carbon cost of water and nutrient acquisition.The results obtained may have implications in the prediction of responses of crops and ecosystems to drought and in proper design of scientific experiments on plant responses to water availability.

A DIGE proteomic analysis of wheat flag leaf treated with TERRA-SORB® foliar, a free amino acid high content biostimulant

The flag leaf is the most important source of carbohydrate during wheat kernel filling. Around a 75% of all sugars stored in the kernel come from carbon fixed by this leaf. Terra-Sorb® foliar is an L-α-amino acid-based product from enzymatic hydrolysis for foliar application with a high ratio of free to total amino acids. Previous agronomical studies carried out on grassy, horticultural and tree crops have shown that the application of Terra-Sorb® increases photosynthetic plant activity and chlorophyll content, promotes rapid recovery from stress and improves fruit set. In this work, we have undertaken a proteomic approach to explore molecular mechanisms potentially involved in the stimulating effect of Terra-Sorb® Foliar on wheat yield when applied in commercial fields. Wheat plants at the flag leaf stage were treated, and a DIGE approach was used to compare the proteomes of treated vs. control plants in four biological replicates. Thirty-seven protein spots were found to change in abundance (ANOVA p The deregulated proteins identified were mainly related to the life cycle of Rubisco. Importantly, two proteins involved in the positive regulation of Rubisco activity, namely Rubisco activase, and the large subunit of Rubisco binding protein, were found up-regulated in treated plants, suggesting a better performance of Rubisco. Down-regulated proteins were of metabolic and anti-stress enzymes, including Cu/Zn superoxide dismutase that protects photosystem II from photooxidation. In conclusion, significant changes were shown to occur in the wheat flag leaf proteome upon Terra-Sorb® Foliar application. The deregulated proteins identified are directly or indirectly involved in the CO fixation which may correlate with the known stimulating effect of Terra-Sorb® Foliar of wheat yield, although further functional experiments are needed to validate the proposed hypothesis.

Influence of production systems on return and risk from malting barley production in western Canada

Profitable malting barley (Hordeum vulgare L.) production systems are required to reverse the decline in area seeded to malting barley in western Canada. Systems that could increase the profitability of growing malting barley considered the previous crop, nitrogen (N) rate, and fungicide application. The net return (NR) and risk for these systems were computed from western Canada field data. Analysis of variance was used to evaluate the impact of systems on NR over 21 site-years of field data. Risk was evaluated with a stochastic simulation model. NR was higher and risk lower for malting barley when the preceding crop was field pea (Pisum sativum L.), when fungicide was applied at the flag leaf stage for leaf disease control, and when N was 50% of the recommended N rate. Therefore, malting barley should be grown on field pea stubble at a lower N rate, with fungicide applied when there are leaf diseases.

Роль агроекологічних умов у реалізації генетичного потенціалу продуктивності сортів озимої пшениці Triticum aestivum L.

Роль агроекологічних умов у реалізації генетичного потенціалу продуктивності сортів озимої пшениці Triticum aestivum L.

Assessing and modeling economic and environmental impact of wheat nitrogen management in Belgium

Future progress in wheat yield will rely on identifying genotypes and management practices better adapted to the fluctuating environment. Nitrogen (N) fertilization is probably the most important practice impacting crop growth. However, the adverse environmental impacts of inappropriate N management (e.g., lixiviation) must be considered in the decision-making process. A formal decisional algorithm was developed to tactically optimize the economic and environmental N fertilization in wheat. Climatic uncertainty analysis was performed using stochastic weather time-series (LARS-WG). Crop growth was simulated using STICS model. Experiments were conducted to support the algorithm recommendations: winter wheat was sown between 2008 and 2014 in a classic loamy soil of the Hesbaye Region, Belgium (temperate climate). Results indicated that, most of the time, the third N fertilization applied at flag-leaf stage by farmers could be reduced. Environmental decision criterion is most of the time the limiting factor in comparison to the revenues expected by farmers.

Real-time PCR quantification and spatio-temporal distribution of airborne inoculum of Puccinia triticina in Belgium

In order to better understand the epidemiology of Puccinia triticina and the relationship between airborne inoculum and disease severity, a method for quantifying airborne inoculum was developed using volumetric Burkard 7-day spore traps and real-time PCR. The method was applied using a spore trap network from 1 March to 30 June over a 5-year period. At one site, the inoculum was quantified continuously over 3 years, during which it showed a seasonal distribution, with the highest quantities and detection frequencies occurring between May and June. High mean daily quantities (65.8–121.2 spores/day) and detection frequencies (±20 % of days) were also reported after harvest from September to December. In the coldest months of the year, almost no detection was recorded (1–6 % of days). The study results indicate that the absence of inoculum in the air when upper leaves are emerging could be a limiting factor for the risk of epidemics. Mean daily quantities of airborne inoculum (0–131.4 spores/day) were measured from the beginning of stem elongation (GS30) to the flag leaf stage (GS39). These values were well correlated with the disease severity levels measured during grain development. A multiple regression analysis showed that total rainfall in late summer and autumn and mean minimum temperature in winter positively influence spore density between GS30 and GS39 in the following spring (R2 = 0.73). This relationship and the patterns of airborne inoculum observed in fields strongly suggest the existence of a ‘green bridge’ phenomenon in Belgium. Our study also showed that the quantification of airborne inoculum or its estimation using a weather-based predictive model could be useful for interpreting disease severity models and avoiding over-estimates of disease risk.