Effect of nitrogen fertilization on Fusarium head blight in spring barley

Nitrogen fertilization has been shown to influence the occurrence and the impact of Fusarium head blight in wheat. It also plays a key role in adjusting barley quality to the requirements of the malting industry, implying specific contents of protein. The present study investigated the effect of nitrogen input on the incidence of relevant Fusarium species in spring barley under field and greenhouse conditions. Grain material from differently fertilized field plots was analyzed for fungal DNA and mycotoxins by qPCR and LC-MS/MS, respectively. Under natural pathogen pressure no effect of nitrogen on infection was observed. When pathogen pressure (Fusarium culmorum and Fusarium avenaceum) was increased via species-specific soil-surface inoculation, nitrogen application reduced contents of Fusarium DNA and mycotoxins in barley grain. Nitrogen-dependent canopy parameters were recorded over the season and correlated with DNA and mycotoxin data. Apparently, sparser canopy permitted more Fusarium infections in unfertilized plots. In addition, well nitrogen-fertilized plants allowed less fungal development in the barley spike after spray inoculation in the greenhouse. These results suggest that nitrogen fertilization restricts Fusarium grain infection of barley by influencing canopy characteristics and possibly plant physiology.     

Reducing the incidence of cereal head infection and mycotoxins in small grain cereal species

Reducing the level of infection of cereal heads caused by Fusarium and associated mycotoxin accumulation in grains is of a high priority in order to secure the yield, agronomic performance, and food and feed safety from field to table. Strategies to tackle the problem have been proposed at many levels, including greater knowledge of the biology of toxigenic fungi and of plant–pathogen interactions, monitoring activities which extend from the field to the end-products, pre-breeding, breeding and transgenesis to develop new resistant plant varieties, crop protection based on synthetic or natural molecules, biocontrol of fungal populations, the development and use of models that take into account the climatic conditions, and the adoption of technological protocols for reducing or inactivating mycotoxins. This review article highlights that the problem is very complex but that the scientific community continues to produce important knowledge and potential solutions.     

大麦籽粒产量和氮积累的农艺因素效应

本试验研究了密度及氮肥运筹对大麦籽粒产量和氮积0累的影响。结果表明,在本地区以基本苗为172万／hm2的群体籽粒产量最高,增加壮蘖肥和穗肥比例可明显提高植株器官氮含量和籽粒产量。明确了生产上宜采用的基本苗密度和氮肥运筹比例。     

Influence of maize–wheat rotation systems on Fusarium head blight infection and deoxynivalenol content in wheat under low versus high disease pressure

Fusarium head blight (FHB) is one of the most destructive fungal diseases of small grain cereals resulting in a reduced grain yield and quality. FHB is the result of a complex interaction between weather conditions and agricultural practices including crop rotation, tillage, fungicide application and host resistance. This study deals with the results of field experiments conducted during the growing seasons 2009–2010 until 2011–2012 at Bottelare (Belgium). The experiments were set up to evaluate the influence of maize–wheat rotation on the visual symptoms of FHB and deoxynivalenol (DON) content in winter wheat. Using a randomised complete block design with four replications, we studied the impact of (a) maize variety as previous crop, (b) maize harvest method (grain or silage maize), (c) tillage method and (d) the influence of the wheat variety resistance on the FHB incidence and DON content. The experimental results showed that the susceptibility of the maize varieties for Fusarium and maize harvest method had only a minor effect on the FHB incidence and DON content of the wheat crop during the subsequent growing season. The tillage method and wheat variety resistance were more important; both factors had a significant influence on the FHB incidence and DON content. Furthermore, the quantitative effect of these factors depended on the disease pressure. The DON content reduction obtained by ploughing and by sowing moderately resistant wheat varieties was higher in case the weather conditions favoured FHB development. Furthermore, it was shown that repeated maize–wheat rotation in combination with favourable weather conditions for FHB could result in an accumulation of inoculum, which, for instance, led to DON contents up to 9.90 mg/kg in August 2012.     

Gramineous and non-gramineous weed species as alternative hosts of Fusarium graminearum,causal agent of Fusarium head blight of wheat,in Argentina

Weeds and wild plants around and within crops could serve as alternative hosts of fungal pathogens. In this work we describe the isolation of Fusarium graminearum, the main causal agent of Fusarium head blight (FHB) in Argentina from the inflorescences of healthy weed plants belonging to sixty seven gramineous and non-gramineous species, which showed no symptoms of Fusarium infection, sampled throughout a year. Fifty four of the weed species considered, belonging to 19 botanical families, were first identified as alternative hosts of F. graminearum in the present work. Furthermore, the trichothecene chemotype of a group of isolates was analysed and strains belonging to 15-acetyldeoxynivalenol, 3-acetyldeoxynivalenol and nivalenol chemotypes were found. The information provided could prove valuable to study further the epidemiological role of weeds in FHB epidemics, which might help to improve management of the disease in wheat growing areas.     

Folate in barley grain and fractions

Wholegrain cereals are good sources of folate. However, little is known about folate in barley. In this study, total folate was analysed in five hulled Finnish barley cultivars from three harvesting years (2006–2008). In addition, different fractions were produced from two hulled cultivars by scarification and from mixes of hulled cultivars by industrial milling. Total folate was determined in all samples with a microbiological method and vitamer distribution in scarification and industrial milling fractions, using HPLC or UPLC. Limited variation was observed in the total folate content of the five cultivars. The average contents of the three harvest years ranged from 563 to 773 ng/g dm. Fractions containing germ and outer layers were the richest in folate. The highest total folate content in the scarification fractions was up to 1710 ng/g dm. The total folate content of the hull fraction obtained by dehulling 10% of the grains with an industrial pearler was almost 4-fold compared to the corresponding dehulled grain. This hull fraction is normally not used as food. The main folate vitamers in the fractions were 5-HCO-H₄folate, 5-CH₃-H₄folate, 5,10-CH⁺-H₄folate, and 10-HCO-PGA. Folate content could be enhanced naturally by introducing folate-rich fractions of barley into cereal products.     

Integration of meta-QTL discovery with omics:Towards a molecular breeding platform for improving wheat resistance to Fusarium head blight

Fusarium head blight (FHB) is a global wheat disease that devastates wheat production. Resistance to FHB spread within a wheat spike (type II resistance) and to...     

Real-time quantitative PCR based method for the quantification of fungal biomass to discriminate quantitative resistance in barley and wheat genotypes to fusarium head blight

Fusarium head blight (FHB) caused by Fusarium graminearum is one of the devastating diseases of small grain crops, including barley and wheat. Breeding for resistance is one of the best and ecofriendly strategies to manage the FHB. However, the existing methods used for screening genotypes, both under field and greenhouse conditions, often resulted in high experimental error, leading to inconsistent ranking of genotypes over years. In the postgenomic era, precise assessment of resistance is crucial to identify candidate genes. Here, we report a pathogen inoculation procedure and a real-time quantitative polymerase chain reaction (qPCR) based protocol for the quantification and discrimination of quantitative resistance among barley and wheat genotypes to FHB. Using Fusarium specific primer pair Tri6_10, for the trichothecene biosynthetic cluster (Tri6) gene, we successfully quantified the relative fungal biomass in both spikelets and rachis. A qPCR of spikelets and rachis collected on 6 dpi, from inoculated three alternate spikelet regions, discriminated resistance with less experimental error than those based on the proportion of spikelets diseased (PSD) at 9 dpi. This method can be applied for medium to high-throughput barley and wheat breeding programmes to discriminate quantitative resistance among genotypes against FHB.     

大麦赤霉病抗源的发掘与评价

为了发掘新的大麦赤霉病抗源,2005、2006年利用禾谷镰刀菌单花滴注和喷雾接种相结合的方法,研究了287份大麦品种对赤霉病的抗扩展性和抗侵染性.结果表明,大麦赤霉病抗性除了抗初侵染类型外还存在抗扩展类型.比较两年单花滴注接种后21 d的病小穗率,筛选得到9个抗源,分别为盐96157、2000品12、秀9744、Vivar、Phoenix、盐94148、鉴35、盐97001、96AC20-30,占全部供试品种的3.44%.通过比较喷雾接种21 d后病小穗率、病穗率、病情指数、反应级等各项指标,发现9个抗源中存在三种类型:盐96157、2000品12、盐94148和Vivar属于既抗扩展又抗侵染的类型,秀977、鉴35和Phoenix属于抗侵染性较弱而抗扩展性强的类型,盐97001和96AC20-30属于抗侵染性强而抗扩展性较弱的类型.在9个抗源中96AC20-30抗侵染性也最强.     

Changes in some biochemical components of wheat grain that was infected with Fusarium graminearum

Wheat kernels that were lightly and moderately infected by Fusarium graminearum were analyzed in terms of their carbohydrate, lipid, and protein contents to determine any compositional changes. The significant compositional changes in lightly infected wheat were increases in reducing sugars (24%), non-starch lipids (5%), and decreases in cellulose (17%) and hemicellulose (20%) components. In moderately infected wheat, the increases in protein (6%), total sugars (26%), reducing sugars (14%), non-starch (20%) and starch (8%) lipids, and decreases in apparent and total amylose (11–20%), cellulose (43%) and hemicellulose (37%) components were also significant. Furthermore, infection with F. graminearum decreased the proportions of water-extractable protein (albumin) and storage protein (glutenin) by 33 and 80%, respectively, in moderately infected wheat.     

A disease survey of Fusarium wilt and Alternaria blight on sweet potato in South Africa

A disease survey was conducted on sweet potato in the major production areas of South Africa in 2006-2008 to determine the importance of wilt disease (WD) and Alternaria blight (AB) caused by Alternaria bataticola. The disease prevalence, incidence and severity were assessed for both WD and AB in 58 sweet potato fields in seven provinces, and included both commercial and resource-poor growers. The prevalence of WD in commercial fields was significantly higher than in resource-poor fields; while disease incidence and severity were very low in both commercial and resource-poor fields. Soil pH showed a moderate negative linear correlation to WD severity. WD is at present considered a minor disease of sweet potato in South Africa, although local outbreaks can be damaging. AB had very low disease prevalence, incidence and severity levels in both commercial and resource-poor fields countrywide. However, one of the fields had moderately high disease incidence and severity levels, showing that the disease can be destructive if not controlled. AB should be considered a potentially destructive disease of sweet potato in South Africa. Fusarium oxysporum was consistently isolated from WD plants, with F. oxysporum f. sp. batatas identified, but other formae speciales were also associated with the disease.     

Modeling plant carbon flow and grain starch accumulation in wheat

The process of starch accumulation in grain directly influences the yield and quality formation in wheat. Since few studies have been aimed at modeling the grain starch accumulation, this study was undertaken to develop a simplified process model for predicting the rate of starch accumulation in wheat grain by focusing on the variation of plant carbon dynamics post-anthesis. Five different experiments involving genotypes, nitrogen rates and water regimes were conducted to support model development and model evaluation. The model proposed that the starch accumulation rate (STR) in individual grain was determined by the availability of carbon source in plant (GCA_i) and the ability of starch synthesis in grain (f(A_i)), as influenced by the factors of temperature, water and nitrogen conditions within plants. The f(A_i) could be described in a two-section curve with post-anthesis growing degree days (GDD), first exponential increase and then linear decrease. The GCA_i was determined by post-anthesis carbon assimilation and carbon remobilization from vegetative organs to grains. A genotypic parameter was incorporated into the model algorithm, i.e. the maximum rate of individual grain starch accumulation, to differentiate the ability of starch accumulation among cultivars. The overall performance of the model was validated with different data sets from three field experiments spanning 3 years and comprising various genotypes, nitrogen and water levels. The RMSE values for all treatments were averaged as 12.51%, indicating a good fit between the simulated and observed data. It appears that the model can give a reliable prediction for grain starch accumulation of different wheat cultivars under various growing conditions.     

Determinants of barley grain yield in a wide range of Mediterranean environments

Barley grain yield in rainfed Mediterranean regions can be largely influenced by terminal drought events. In this study the ecophysiological performance of the ‘Nure’ (winter) × ‘Tremois’ (spring) barley mapping population (118 Doubled Haploids, DHs) was evaluated in a multi-environment trial of eighteen site–year combinations across the Mediterranean Basin during two consecutive harvest years (2004 and 2005). Mean grain yield of sites ranged from 0.07 to 5.43 t ha⁻¹, clearly dependent upon both the total water input (rainfall plus irrigation) and the water stress index (WSI) accumulated during the growing season. All DHs were characterized for possessing molecular marker alleles tagging four genes that regulate barley cycle, i.e. Vrn-H1, Vrn-H2, Ppd-H2 and Eam6. Grain yield differences were initially interpreted in terms of mean differences between genotypes (G), environments (E), and for each combination of genotype and environment (GE) through a “full interaction” ANOVA model. Variance components estimates clearly showed the greater importance of GE over G, although both were much lower than E. Alternative linear and bilinear models of increasing complexity were used to describe GE. A linear model fitting allelic variation at the four genes explained genotype main effect and genotype × environment interaction much better than growth habit itself. Adaptation was primarily driven by the allelic constitution at three out of the four segregating major genes, i.e. Vrn-H1, Ppd-H2 and Eam6. In fact, the three genes together explained 47.2% of G and 26.3% of GE sum of squares. Grain yield performance was more determined by the number of grains per unit area than by the grain weight (phenotypic correlation across all genotypic values: r = 0.948 and 0.559, respectively). The inter-relationships among a series of characters defining grain yield and its components were also explored as a function of the length of the different barley developmental phases, i.e. vegetative, reproductive, and grain filling stages. In most environments, the best performing (adapted) genotypes were those with faster development until early occurrence of anthesis. This confirmed the crucial role of the period defining the number of grains per unit area in grain yield determination under Mediterranean environments.     

Effects of different extraction methods on the structural properties and bioactivities of polysaccharides extracted from Qingke (Tibetan hulless barley)

In this study, four extraction methods, including ultrasonic assisted extraction (UAE), hot water extraction (HWE), microwave assisted extraction (MAE), and pressurized water extraction (PWE), were used to extract Qingke polysaccharides (THBs), and their physicochemical structures, in vitro antioxidant activities, and in vitro hypolipidemic activities were investigated and compared. Results demonstrated that the yields, the chemical compositions, the apparent viscosities, the molecular weights, and the molar ratios of constituent monosaccharides of THBs varied by different extraction methods. THB-P extracted by PWE possessed the highest molecular weight and apparent viscosity among all tested THBs. In addition, all THBs extracted by different methods exerted obvious in vitro antioxidant activities, in vitro binding capacities, and inhibitory effects on the pancreatic lipase. Indeed, both antioxidant activities and hypolipidemic activities of THB-P were higher than that of THB-H, THB-U, and THB-M obtained by HWE, UAE, and MAE, respectively, which might be due to the high molecular weight and apparent viscosity of THB-P. The findings indicated that the pressurized water extraction could be a convenient method for the extraction of polysaccharides from Qingke with high biological activities for applications in the functional food fields.     

Walnut blight: development of fruit infection in two orchards

Walnut is one of the major regional crops produced in Dauphiné (SE France). Unfortunately, walnut blight has been recorded as the main disease for years. Crop losses due to this disease may reach high levels in spite of repeated copper sprays. In order to monitor the bacterial contamination of the fruits, two orchards differing in soil, irrigation and treatment were selected. Fruit sampling was performed once a week for 11 weeks. Results showed that the percentage of contaminated fruits was more important at the beginning of a maturation, that bacterial populations rapidly reached a maximum level and that there was no obvious relation between the number of bacteria infecting a fruit and the occurrence of necrosis. These results did not indicate any significant difference between the two orchards, in these respects.     

Assessment of biochemical markers identified in wheat for monitoring barley grain tissue

The possible use of specific biochemical compounds identified in wheat grains was evaluated for monitoring barley grain tissues during fractionation. First barley grain anatomy was studied through microscopic observation and quantification of the relative proportion of each anatomical part in four distinct barley samples from both hulled and hulless genotypes. As expected from cereal phylogeny and irrespective of the possible presence of hull, common features were observed between barley and wheat grains, but the aleurone layer predominated in the outer layers. The specific location of the compounds identified in wheat was established. Phytic acid was specifically localized in the aleurone layer and alkylresorcinols in the composite layer containing the testa, even if their concentration differed from that observed in wheat grain tissues. Thus, these two markers identified in wheat can be used to monitor the corresponding barley tissues, independent of the presence of hulls. Conversely, phenolic compounds, either ferulic acid trimer or p-coumaric acid, cannot be used to monitor respectively the outer pericarp or the aleurone cell walls in barley grains. p-coumaric acid was identified as an efficient marker of the hull and could be used to distinguish hulled or hulless barley grains and to help monitor the dehulling process.     

Differences in metabolomic profiles of the naturally contaminated grain of barley,oats and rye

Studies of a spectrum of metabolites found in cereals are becoming one of the primary tools for evaluating their susceptibility to the effects of various environmental agents, such as: pathogens, temperature and precipitation. In order to reduce the effect of the environmental conditions, cultivars were grown under identical cultivation conditions.     

Differences in metabolomic profiles of the naturally contaminated grain of barley,oats and rye

Studies of a spectrum of metabolites found in cereals are becoming one of the primary tools for evaluating their susceptibility to the effects of various environmental agents, such as: pathogens, temperature and precipitation. In order to reduce the effect of the environmental conditions, cultivars were grown under identical cultivation conditions.This study aimed to construct a model to differentiate infected from non-infected cereals by developing the metabolomic profile of barley, oats and rye. Fungal and total microflora content, trichothecenes, fatty acids and volatile compounds were determined in the grains using GC/MS and en electronic nose. The most significant compounds in the construction of the model were established as the following volatiles: (E, E)-3,5 octadien 2-one, 1-heptanol, naphthalene, p-xylene and dimethyl sulphone; fatty acids: oleic acid (C18:1n-9), α-linolenic acid (C18:3n-3) and palmitoleic acid (C16:1n-7); mycotoxins: T-2, and HT-2 toxins and deoxynivalenol as well as the terpene: trichodiene. Chemometric techniques were established to enable the identification of the grains.Results indicate the necessity to extend the scope of analyses of cereals to include the metabolomic aspect. This will make it possible to identify a dependence between their most significant traits and will contribute to a better understanding of their cereal resistance mechanisms.