Percentage Of Fusarium-damaged Kernels Research Articles

Responses of Wheat (Triticum aestivum) Constitutively Expressing Four Different Monolignol Biosynthetic Genes to Fusarium Head Blight Caused by Fusarium graminearum.

The Fusarium head blight (FHB) pathogen Fusarium graminearum produces the trichothecene mycotoxin deoxynivalenol and reduces wheat yield and grain quality. Spring wheat (Triticum aestivum) genotype CB037 was transformed with constitutive expression (CE) constructs containing sorghum (Sorghum bicolor) genes encoding monolignol biosynthetic enzymes caffeoyl coenzyme A (CoA) 3-O-methyltransferase (SbCCoAOMT), 4-coumarate-CoA ligase (Sb4CL), or coumaroyl shikimate 3-hydroxylase (SbC3'H) or monolignol pathway transcriptional activator SbMyb60. Spring wheats were screened for type I (resistance to initial infection, using spray inoculations) and type II (resistance to spread within the spike, using single-floret inoculations) resistances in the field (spray) and greenhouse (spray and single floret). Following field inoculations, disease index, percentage of Fusarium-damaged kernels (FDK), and deoxynivalenol measurements of CE plants were similar to or greater than those of CB037. For greenhouse inoculations, the area under the disease progress curve (AUDPC) and FDK were determined. Following screens, focus was placed on two each of SbC3'H and SbCCoAOMT CE lines because of trends toward a decreased AUDPC and FDK observed following single-floret inoculations. These four lines were as susceptible as CB037 following spray inoculations. However, single-floret inoculations showed that these CE lines had a significantly reduced AUDPC (P < 0.01) and FDK (P ≤ 0.02) compared with CB037, indicating improved type II resistance. None of these CE lines had increased acid detergent lignin compared with CB037, indicating that lignin concentration may not be a major factor in FHB resistance. The SbC3'H and SbCCoAOMT CE lines are valuable for investigating phenylpropanoid-based resistance to FHB.

Evaluation of Inoculation Methods for Determination of Winter Wheat Resistance to Fusarium Head Blight

One of the most severe winter wheat (Triticum aestivum L.) diseases is Fusarium head blight (FHB). It is believed that selection for resistance to FHB is better in high disease pressure environments, for which various methods of artificial inoculation are used. The standard spray method of artificial inoculation is believed to be technically demanding and labour intensive. Therefore, scattering Fusarium-infected maize stalks onto trial plots after wheat emergence is suggested as a suitable alternative. The aim of this study was to compare the mean values and heritability of the visual rating index (VRI) and the percentage of Fusarium-damaged kernels (FDK) between the two abovementioned methods of artificial inoculation and natural infection, and to determine the phenotypic correlations between the three methods for the studied traits. The achieved levels of VRI and FDK were comparable for the two methods of artificial inoculation and considerably lower under natural conditions. Heritability for VRI ranged over four years from 0.68 to 0.91 for the spray method, from 0.73 to 0.95 for the infected maize stalks, and from 0.26 to 0.65 for natural infection, whereas for FDK it ranged from 0.56 to 0.85, 0.38 to 0.83, and 0.11 to 0.44 for the three inoculation methods, respectively. The strong positive correlation between the two applied methods of artificial inoculation for studied traits suggests that scattering infected maize stalks could serve as a reliable supplement for the technically and labor-intensive spray method of artificial inoculation.

Foliar fungicides provide chemical control of Fusarium head blight of wheat in South Africa

Chemical control of a yield-limiting, quality-reducing wheat disease like Fusarium head blight (FHB) is an important management strategy; however, no fungicides are registered against it in South Africa. The aim of this study was to determine foliar fungicides and seed treatment efficacy for FHB management. Three commercial fungicides and two seed treatments were evaluated in a naturally infested field during 2011 and 2012. Significant interactions between the seed treatments and the foliar fungicides were obtained for FHB incidence and yield. When the fungicide Abacus® was sprayed in combination with either of the two seed treatments, FHB incidence was significantly decreased compared with use of the fungicide alone. Prosaro® sprayed in combination with Galmano® Plus as a seed treatment significantly decreased yield compared with the use of Prosaro alone or in combination with Vitavax® Plus as a seed treatment. The fungicide treatments significantly reduced FHB incidence and the percentage of Fusarium-damaged kernels (%FDK) when compared with control treatments, and significantly increased the yield. A weak but significant correlation was recorded between deoxynivalenol (DON) and %FDK. Strong negative correlations were observed between hectolitre mass (HLM) and FHB incidence and %FDK, respectively, and between yield and %FDK. These results indicate that the chemical control of FHB of wheat can be used to manage the disease in South Africa. Future research, therefore, must focus on integrating chemical control with host resistance to obtain optimal results.

Resistance to Fusarium Head Blight, Kernel Damage, and Concentrations of Fusarium Mycotoxins in the Grain of Winter Wheat Lines

Fusarium head blight (FHB) can contaminate cereal grains with mycotoxins. Winter wheat can also become infected with FHB and is more resistant than durum wheat to head infection but less than other small-grain cereals. The aim of this study was to identify winter wheat lines that combine low levels of head infection and kernel damage with low levels of grain contamination with mycotoxins. Resistance of 27 winter wheat lines (four with resistance gene Fhb1) and cultivars to FHB was evaluated over a three-year (2017–2019) experiment established in two locations (Poznań and Radzików, Poland). At the anthesis stage, heads were inoculated with Fusarium culmorum isolates. The FHB index was scored, and the percentage of Fusarium-damaged kernels (FDKs) was assessed. The grain was analyzed for type B trichothecenes (deoxynivalenol and derivatives and nivalenol) and zearalenone content. The average FHB index of both locations was 12.9%. The proportion of FDK was 6.9% in weight and 8.5% in number. The average content of deoxynivalenol amounted to 3.543 mg/kg, and the average amount of nivalenol was 2.115 mg/kg. In total, we recorded 5.804 m/kg of type B trichothecenes. The zearalenone content in the grain was 0.214 mg/kg. Relationships between the FHB index, FDK, and mycotoxin contents were highly significant for wheat lines; however, these relationships were stronger for FDK than for FHB index. Breeding lines combining all types of FHB resistance were observed, five of which had resistance levels similar to those of wheat lines with the Fhb1 gene.

Resistance to Fusarium Head Blight, Kernel Damage, and Concentration of Fusarium Mycotoxins in Grain of Winter Triticale (x Triticosecale Wittmack) Lines

Fusarium head blight (FHB) can cause contamination of cereal grain with mycotoxins. Triticale is also infected with FHB; however, it is more resistant than wheat to head infection. The aim of this study was to identify triticale lines that combine low head infection with low toxin contamination. Resistance to FHB of 15 winter triticale and three winter wheat lines was evaluated over a three-year experiment established in two locations. At the anthesis stage, heads were inoculated with Fusarium culmorum isolates. The FHB index was scored and the percentage of Fusarium-damaged kernels (FDKs) assessed. The grain was analysed for type B trichothecenes (deoxynivalenol and derivatives, nivalenol) and zearalenone content. The average FHB index was 10.7%. The proportion of FDK was 18.1% (weight) and 21.6% (number). An average content of deoxynivalenol amounted to 7.258 mg/kg and nivalenol to 5.267 mg/kg. In total, it was 12.788 mg/kg of type B trichothecenes. The zearalenone content in the grain was 0.805 mg/kg. Relationships between FHB index, FDK, and mycotoxin contents were statistically significant for triticale lines; however, they were stronger for FDK versus mycotoxins. Triticale lines combing all types of FHB resistance were found, however the most resistant ones were less resistant that wheat lines with the Fhb1 gene.

Differential accumulation of deoxynivalenol in two winter wheat cultivars varying in FHB phenotype response under field conditions

Fusarium head blight (FHB) or scab, caused by Fusarium graminearum Schwabe [sexual stage Gibberella zeae (Schwein.) Petch], is a destructive disease of small grain cereals. Fusarium graminearum produces the mycotoxin deoxynivalenol (DON), which accumulates in and lowers the value and quality of grain. Field experiments were conducted from 2007 to 2009 to determine if two winter wheat cultivars varying in FHB phenotype response differentially accumulated DON. Secondary objectives were to model the relationship between FHB severity and DON, determine if environment (= year) influenced DON accumulation in the two cultivars, and measure the percentage of Fusarium-damaged kernels (FDK) in the two cultivars. The cultivar ‘Harry’ with a moderately resistant FHB phenotype consistently accumulated more DON (P ≤ 0.0358) than ‘2137’ with a susceptible phenotype. The relationship between FHB severity and DON was linear and positive for both cultivars in all three years (0.32 ≤ R2 ≤ 0.60; 0.0053 ≤ P ≤ 0.1092). Environment (= year) had a significant effect (P < 0.0001) on DON accumulation in both cultivars, and this effect was attributed to differences in rainfall amount and duration in the months of May and June. DON accumulation was highest in 2008 (average of 33.2 ppm in ‘Harry’ and 21.2 ppm in ‘2137’) when there was steady, above-average rainfall in May and June. FDK was highest in 2008 and was higher in ‘Harry’ (64%) than in ‘2137’ (46%). The results from this study suggest that a winter wheat cultivar with a moderately resistant FHB phenotype can be susceptible to FDK and DON accumulation. Based on these results, there is a need to standardize the criteria (FHB intensity, FDK, DON) for characterizing wheat cultivars as resistant or susceptible to FHB.

Effects of Integrating Cultivar Resistance and Fungicide Application on Fusarium Head Blight and Deoxynivalenol in Winter Wheat.

Fusarium head blight (FHB) or scab, incited by Fusarium graminearum, can cause significant economic losses in small grain production. Five field experiments were conducted from 2007 to 2009 to determine the effects on FHB and the associated mycotoxin deoxynivalenol (DON) of integrating winter wheat cultivar resistance and fungicide application. Other variables measured were yield and the percentage of Fusarium-damaged kernels (FDK). The fungicides prothioconazole + tebuconazole (formulated as Prosaro 421 SC) were applied at the rate of 0.475 liters/ha, or not applied, to three cultivars (experiments 1 to 3) or six cultivars (experiments 4 and 5) differing in their levels of resistance to FHB and DON accumulation. The effect of cultivar on FHB index was highly significant (P < 0.0001) in all five experiments. Under the highest FHB intensity and no fungicide application, the moderately resistant cultivars Harry, Heyne, Roane, and Truman had less severe FHB than the susceptible cultivars 2137, Jagalene, Overley, and Tomahawk (indices of 30 to 46% and 78 to 99%, respectively). Percent fungicide efficacy in reducing index and DON was greater in moderately resistant than in susceptible cultivars. Yield was negatively correlated with index, with FDK, and with DON, whereas index was positively correlated with FDK and with DON, and FDK and DON were positively correlated. Correlation between index and DON, index and FDK, and FDK and DON was stronger in susceptible than in moderately resistant cultivars, whereas the negative correlation between yield and FDK and yield and DON was stronger in moderately resistant than in susceptible cultivars. Overall, the strongest correlation was between index and DON (0.74 ≤ R ≤ 0.88, P ≤ 0.05). The results from this study indicate that fungicide efficacy in reducing FHB and DON was greater in moderately resistant cultivars than in susceptible ones. This shows that integrating cultivar resistance with fungicide application can be an effective strategy for management of FHB and DON in winter wheat.

Estimating deoxynivalenol contents of wheat samples containing different levels of Fusarium-damaged kernels by diffuse reflectance spectrometry and partial least square regression

Fusarium head blight is a fungal disease causing yield losses and mycotoxin contamination in wheat and other cereals. Wheat kernels (cultivar Ritmo) were sampled in 2001, 2002, 2003, and 2006 and Fusarium-damaged kernels were separated from sound grain based on visual assessment. Subsequently, grain lots containing 0, 20, 40, 60, 80, and 100% of damaged kernels were compiled. Each lot was split and the spectrometric reflectance (wavelengths 350–2500 nm) was measured using subgroup one, while the concentration of the mycotoxin deoxynivalenol (DON) was determined by high-performance liquid chromatography in subgroup two. DON concentrations in batches classified as sound were not significantly different from 0. Estimating DON contents from the percentage of Fusarium-damaged kernels was impeded by vast variability, resulting in a coefficient of determination of 0.49. Using spectrometric data subjected to partial least square regression allowed estimating DON contents with higher accuracy, in particular at elevated percentages of damaged kernels. The coefficient of determination was 0.84 for the relationship between DON contents estimated based on spectrometric data and the DON contents measured. The intercept of a regression line fitted through a plot of estimated versus measured DON contents was 0.89 ± 3.61 mg/kg. Since intercept + standard error was larger than the actual legal limit (1.25 mg DON per kg dry grain in the European Union), the spectrometric procedure was still not precise enough to allow a reliable separation of grain samples with DON contents below 1.25 mg/kg from samples with DON contents above the limit. However, spectrometric data also allowed estimating the DON content of the average damaged kernel within a given lot composed of sound and damaged kernels, which is probably the reason for the reduction of the fraction of unexplained variance by 35% compared to the visual approach and illustrates that spectrometric approaches can make a contribution to reducing DON contents of wheat grain.

Effects of Fusarium infection on the amino acid composition of winter wheat grain

Winter wheat (susceptible cultivar Ritmo) was grown in 2006 near Kiel and in 2007 near Heide in northern Germany. Plants were inoculated at anthesis using a Fusarium graminearum macroconidial suspension. The percentage of Fusarium-damaged kernels (FDK) ranged from 0 ± 2% to 28 ± 2%. The contents of the Fusarium mycotoxin deoxynivalenol (DON) and wheat amino acids were determined in the grain. Levels of the amino acids alanine, lysine, and tyrosine increased with the percentage of FDK or DON contents whereas glutamic acid contents decreased. Aspartic acid and threonine were not related to the percentage of FDK or DON contents. Effects of Fusarium infection on other amino acids were significant only at the sampling site with the higher degree of Fusarium-damage. Interestingly, those amino acids that increased consistently and significantly with the degree of Fusarium-damage are derived from phosphoenolpyruvate or pyruvate, suggesting that pathogen-induced changes in the glycolytic input for amino acid biosynthesis play a significant role for the amino acid composition of Fusarium-damaged winter wheat grain. On average, amino acid contents decreased by 0.13% compared to the amino acid content of sound kernels upon an increase of 1% of FDK.

Mapping QTLs associated with Fusarium-damaged kernels in the Nanda 2419 × Wangshuibai population

Fusarium head blight (FHB), or scab, is a devastating wheat disease worldwide, reducing both grain yield and quality. The percentage of Fusarium-damaged kernels (FDK) directly reflects the damage level caused by scab on wheat grains and its variation represents the so-called type IV scab resistance in germplasm. To identify genes governing type IV resistance and investigate its relationship with other scab resistance types, we mapped QTLs associated with percent FDK using data from three different field evaluations of the recombination inbred line (RIL) population derived from the susceptible cultivar Nanda 2419 × the scab-resistant cultivar Wangshuibai. Five QTLs related to percent FDK were identified in at least two different trials, for which Wangshuibai contributed four of the resistance alleles. Most of the FDK-related QTLs, including the three with larger effects, QFdk.nau-2B, QFdk.nau-3B and QFdk.nau-4B, mapped to intervals associated with either type IV resistance or type II resistance. Moreover, most of the major type I and type II resistance QTLs detected previously were associated with type IV resistance, suggesting that resistance to initial infection and disease spread play major roles in conditioning less FDK. Therefore, breeders have options to choose inoculation methods based on their expertise and resources without risking significant loss of information when using percent FDK as the disease index. The most useful scab resistance QTLs for breeding would be those with stable influences on FDK and/or deoxynivalenol (DON) accumulation besides the initial infection and disease spread.

Estimating mycotoxin contents of Fusarium-damaged winter wheat kernels

Winter wheat ( Triticum aestivum L., cultivars Ritmo and Dekan) grain was sampled in Northern Germany between 2001 and 2006. Kernels damaged by fungi of the genus Fusarium were separated from sound grain by visual assessment. Samples containing 0%, 20%, 40%, 60%, 80% and 100% of Fusarium-damaged kernels were compiled and analyzed for the Fusarium type B trichothecenes deoxynivalenol (DON, 2001–2006), nivalenol (NIV, 2006), 3-acetyl-deoxynivalenol (3AcDON, 2006) and 15-acetyl-deoxynivalenol (15AcDON, 2006). The relationship between mycotoxin contents and the percentage of Fusarium-damaged kernels was calculated for each lot of grain. Apart from one exception, relationships between the percentage of Fusarium-damaged kernels and NIV, 3AcDON or 15AcDON were non-significant. In contrast, close relationships between the percentage of Fusarium-damaged kernels and the DON content were observed ( r 2 = 0.93–0.99). The y-axis intercepts were not significantly different from zero, but the DON content of the damaged kernels varied by a factor of 11.59 between years and by a factor of 1.87 between cultivars. Fusarium-damaged kernels contained between 0.21 and 2.39 μg DON kernel − 1 . The overall average DON content of a Fusarium-damaged wheat kernel was 1.29 ± 0.11 μg. The DON content of diseased kernels was affected by environment and wheat genotype but not by genotype × environment interaction. On average, Fusarium-damaged kernels contained 9.7-fold more DON than 15AcDON, 19.5-fold more DON than NIV, and 26.9-fold more DON than 3AcDON. 3AcDON and 15AcDON contents per wheat kernel were not significantly different between cultivars. On average, 4.27% of Fusarium-damaged kernels were sufficient to reach the 1.25 mg DON kg − 1 grain limit for unprocessed cereals in the EU. Given the low percentages of Fusarium-damaged kernels that are equivalent to current legal DON limits, grading accuracies > 96% would be needed when using automatic grading systems for separating sound from damaged kernels.

Comparison of the influence of inoculum sources on the development of fusarium head blight and the deoxynivalenol content in spring wheat in a disease nursery

The screening for genetic resistance to fusarium head blight (FHB) in wheat has been challenged by the lack of efficacy of various artificial inoculation techniques in disease nurseries. In 2001-2003, we examined the influence of inoculum sources (conidial suspension, infested barley and corn kernels, or infested wheat debris) and inoculation frequency on the development of FHB and the deoxynivalenol (DON) content. The study was conducted on three spring wheat genotypes in a disease nursery of Ottawa, Ontario. The development of FHB was monitored by visually estimating disease severity on a scale of 0 to 9, six times during each growing season. Severity of FHB over time was summarized as the area under the disease-progress curve (AUDPC). Symptoms of FHB were also rated, at a critical developmental stage (soft dough), as critical-time disease severity (DS), percentage of infected spikelets (IS), and FHB index. The percentage of Fusarium-damaged kernels (FDK) and DON content in the wheat kernels were assessed after harvesting. All inoculation treatments had significantly greater AUDPC and DS in 2002, FHB index and IS in 2001 and 2002, and FDK in all three years than the noninoculated control. Regardless of inoculum source, two inoculations produced as much FHB, FDK, and DON as three inoculations. Among the inoculum sources, the conidial suspension or infested kernels yielded significantly greater AUDPC, DS, FHB index, IS, and DON content than the infested debris. Inoculation with conidial suspension resulted in greater FDK than inoculation with infested kernels or infested debris, between which there were no differences. The results of the present study confirm that conidial suspension and infested kernels are equally effective inoculants for FHB nurseries. Infested debris, though a natural source of inoculum, is less effective.

Influence of Wheat Cultivar, Species of Fusarium, and Isolate Aggressiveness on the Efficacy of Fungicides for Control of Fusarium Head Blight.

Attempts to control Fusarium head blight (FHB) with fungicides have been highly variable. Variability is caused by cultivar resistance, fungicide efficacy, fungicide coverage, timing, and pathogen aggressiveness. In this research, fungicides were tested on winter wheat cultivars with different levels of resistance to FHB using different isolates of Fusarium graminearum and F. culmorum to evaluate the role of host resistance and isolate aggressiveness on severity of FHB. Fungicides were applied to groups of wheat heads to provide full coverage. Incidence and severity of FHB was measured by the severity of head symptoms, percentage of Fusarium-damaged kernels (FDK), yield loss, and deoxynivalenol (DON) contamination. Development of FHB was affected by fungicides, cultivars, fungal isolates, and most of the two-way interactions of these variables. Among the fungicides tested, those containing tebuconazole tended to be more effective in reducing FHB. Reduction of disease in susceptible cultivars may not be adequate to produce marketable yields under conditions of high disease pressure. In most cases, if a fungicide reduced FHB visual symptoms, similar decreases were detected in yield loss, DON concentration, and FDK reaction. In 1998, an increase in DON contamination compared with the Fusarium check was observed with azoxystrobin and carbendazim on the more susceptible cultivar. This increase in DON with some fungicide requires additional research. Research to develop more resistant cultivars, better spraying technology, and more effective fungicides is also needed.

Fusarium Head Blight Reactions and Accumulation of Deoxynivalenol (DON) and Some of its Derivatives in Kernels of Wheat, Triticale and Rye

Fifty‐three commercially grown cultivars and germplasm lines of winter triticale (n = 18), wheat (n = 13), and rye (n = 5) and spring triticale (n = 8), wheat (n = 7) and rye (n = 2) were inoculated at mid anthesis with a spore suspension consisting of a mixture of Fusarium culmorum, Fusarium avenaceum and Fusarium graminearum isolates of known toxinogenic activity. Reactions to Fusarium head blight were measured as disease severity, reductions of kernel number/head, kernel weight/head and 1000 kernel weight, number of Fusarium‐damaged kernels and kernel content of deoxynivalenol (DON) and its acetyl‐derivatives 3‐AcDON, 15‐AcDON, and moniliformin. None of the cereal genotypes was completely resistant to Fusarium head blight. Wheat suffered from the largest kernel weight reductions, and accumulated the largest amounts of deoxynivalenol (up to 39.5 mg/kg) and 3AcDON (up to 6.0 mg/kg) in kernels. Deoxynivalenol was not detected in grain samples of winter rye cv. Dańkowskie Z?ote, and spring rye cv. Ludowe. 15‐AcDON was only detected in genotypes of triticale, and 3AcDON only in a few genotypes of winter wheat and rye. Moniliformin was detected at low concentrations (up to 0.092 mg/kg) in kernels of some genotypes selected for the mycotoxin analysis. A moderately strong Pearson correlation was found between head blight severity parameters and the accumulation of deoxynivalenol and its derivatives in grain of the cereal genotypes studied. Fusarium head blight severity parameters were correlated with the percentage of Fusarium‐damaged kernels and reductions of yield components. However, some head blight‐susceptible genotypes realized their potential yields, but accumulated high levels of mycotoxins in kernels. Both Fusarium head blight resistant and susceptible genotypes of the three cereal species accumulated deoxynivalenol in kernels. This finding suggests that the system regulating deoxynivalenol accumulation may be independent of Fusarium head blight reaction.

A survey of the occurrence of deoxynivalenol in wheat from 1986–1988 harvests in the USSR

The occurrence of deoxynivalenol (DON; vomitoxin) in wheat from 1986-1988 harvests in the USSR was surveyed. A significant frequency of DON contamination (81.3% of samples analyzed) was observed. A correlation between levels of DON contamination and percentage of Fusarium-damaged kernels was demonstrated. It was shown that DON contamination did not exceed the maximum tolerated level (MTL) established in the USSR (1.0 mg/kg) if samples contained no more than 0.6% of Fusarium-damaged kernels.