Influence of water activity on deoxynivalenol accumulation in wheat

The influence of water activity (a_w) on deoxynivalenol accumulation in wheat at 25°C was studied. Gnotobiotic grains were conditioned at different a_w levels, inoculated with a toxigenic Fusarium graminearum strain, and incubated for ten weeks. The highest accumulation of deoxynivalenol (1130 ug/kg) was detected at a_w 0.980. At a_w 0.945 and 0.925 the maximum quantities of toxin accumulated were 113 ug/kg and 93 ug/kg respectively. Deoxynivalenol was not detected in the substrate at a_w 0.900. Results suggest that intermediate a_w levels (0.97 – 0.92) are particularly critical at post harvest time because those are conditions under which deoxynivalenol production is most likely to be initiated naturally.     

Investigation of the distribution of deoxynivalenol and ochratoxin A contamination within a 26 t truckload of wheat kernels

A study was conducted to determine the distribution of deoxynivalenol (DON) and ochratoxin A (OTA) in a lot of 261 of wheat kernels. Within this study, two different sampling and sample preparation strategies were carried out. On the one hand, following the official commission regulation 401/2006/EC, an aggregate sample out of 100 incremental samples was build, homogenized and prepared for laboratory analysis. On the other hand each individual subsample was investigated for its deoxynivalenol and ochratoxin A content. The determined concentration of DON in the individual samples was in a range from 830 up to 2655 (μg/kg, for OTA results ranged from < 0.2 up to 8.6 μg/kg. Thus, a coefficient of variance of 25% for DON and 200% for OTA was achieved. From this, a spot formation for OTA was observed and the average value of the 100 incremental samples did not correspond to the achieved value for the aggregate sample. While the DON contamination at this concentration range seems to be more even, consequently the result of the aggregate sample was in accordance with the average value. In addition a sample communition study was performed to answer the question whether the time consuming process of grinding of the whole aggregate sample is necessary or not. The results of this study show that contamination of whole wheat kernels with DON is at the same level within a 1 kg sample (CV 16%), while OTA contamination shows high variability (CV 94%). At least for OTA this study indicated that an extensive and complete sample communition of the high volume aggregate sample is necessary.     

Saturation and mapping of a majorFusarium head blight resistance QTL on chromosome 3BS of Sumai 3 wheat

Fusarium head blight (FHB) is a destructive disease in wheat. The major quantitative trait locus (QTL) on 3BS from Sumai 3 and its derivatives has been used as a major source of the resistance to FHB worldwide, but the discrepancy in reported location of the major QTL could block its using in map based cloning and marker assisted selection. In this study, Chinese Spring-Sumai 3 chromosome 3B substitution line was used as resistant parent of the mapping population to reduce the confounded effect of genetic background in Sumai 3. The major QTL region was saturated with the Sequence Tagged Microsatellite (STM) and Sequence Tagged Site (STS) markers. A linkage map of chromosome 3B with 36 markers covering a genetic distance of 112.4 cM was constructed. Twelve new markers were inserted into the chromosome region where the major QTL was located. The average interval distance between markers was 1.5 cM. Multiple QTL Models (MQM) mapping indicated that the major QTL was located in the interval ofXgwm533 — Xsts9-1, and explained 45.6% of phenotypic variation of the resistance to FHB. The SSR (simple sequence repeat) markerXgwm533 and STM markerXstm748tcac are closely linked to the major QTL.     

Detection of QTL linked to Fusarium head blight resistance in Sumai 3-derived North Dakota bread wheat lines

During the past decade Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe has resulted in severe grain yield and quality losses of wheat (Triticum aestivum L.) in the Northern Great Plains of the U.S. Given the complexity of breeding for FHB resistance, molecular markers associated with this trait will be valuable in accelerating efforts to breed resistant cultivars. The objective of this study was to identify molecular markers linked to quantitative trait loci (QTL) for FHB resistance in wheat using a set of lines obtained by several cycles of crossing to North Dakota adapted genotypes, which derived their resistance from cv. Sumai 3. Microsatellite markers spanning the wheat genome were used to screen parents and derived lines. Polymorphisms for parental alleles were compared to disease scores for Type II resistance. The probability of linkage between markers and introgressed resistance genes was calculated using a binomial probability formula based on the assumption that a molecular marker at a specific distance from the introgressed gene, in a near-isogenic line (NIL), will carry the donor-parent allele as a function of the distance between marker and gene and the number of backcrosses/selfs performed in deriving the NIL. Microsatellite loci Xgwm533 and Xgwm274 were significantly associated with QTL for FHB resistance.     

Molecular mapping of novel genes controlling Fusarium head blight resistance and deoxynivalenol accumulation in spring wheat.

Fusarium head blight of wheat is an extremely damaging disease, causing severe losses in seed yield and quality. The objective of the current study was to examine and characterize alternate sources of resistance to Fusarium head blight (FHB). Ninety-one F1-derived doubled haploid lines from the cross Triticum aestivum 'Wuhan-1' x Triticum aestivum 'Maringa' were examined for disease reaction to Fusarium graminearum by single-floret injection in replicated greenhouse trials and by spray inoculation in replicated field trials. Field and greenhouse experiments were also used to collect agronomic and spike morphology characteristics. Seed samples from field plots were used for deoxynivalenol (DON) determination. A total of 328 polymorphic microsatellite loci were used to construct a genetic linkage map in this population and together these data were used to identify QTL controlling FHB resistance, accumulation of DON, and agronomic and spike morphology traits. The analysis identified QTL for different types of FHB resistance in four intervals on chromosomes 2DL, 3BS, and 4B. The QTLs on 4B and 3BS proximal to the centromere are novel and not reported elsewhere. QTL controlling accumulation of DON independent of FHB resistance were located on chromosomes 2DS and 5AS. Lines carrying FHB resistance alleles on 2DL and 3BS showed a 32% decrease in disease spread after single-floret injection. Lines carrying FHB resistance alleles on 3BS and 4B showed a 27% decrease from the mean in field infection. Finally, lines carrying favourable alleles on 3BS and 5AS, showed a 17% reduction in DON accumulation. The results support a polygenic and quantitative mode of inheritance and report novel FHB resistance loci. The data also suggest that resistance to FHB infection and DON accumulation may be controlled, in part, by independent loci and (or) genes.     

Evaluation and precise mapping of QFhb.nau-2B conferring resistance against Fusarium infection and spread within spikes in wheat (Triticum aestivum L.)

Leaf color mutants are valuable resources for studying regulatory mechanisms of photosynthetic pigment metabolism. In this study, a chlorophyll-deficient golden leaf mutant lcm1 of Chinese cabbage was identified from its wild-type “FT” by ethyl methanesulfonate (EMS) mutagenesis. The phenotype of the golden leaf mutant lcm1 was that the leaves remained golden throughout development. Pigment measurements showed that the chlorophyll content of the mutant lcm1 was less than that of the wild-type “FT”. There were no obvious grana lamellae observed in the chloroplast microstructure of the mutant lcm1. Genetic analysis revealed that the mutant lcm1 phenotype was controlled by a single recessive nuclear gene, lcm1 (BrChlH). The MutMap method and Kompetitive Allele Specific PCR genotyping were used to predict that Bra006208 encoding a Mg-chelatase H subunit, the candidate gene for the mutant lcm1. The 4249-bp lcm1 gene had five exons and a single nucleotide substitution (G to A) in the third exon that resulted in an amino acid substitution (A to V). This SNP2523351 occurred in the highly conserved CobN-Mg_chel domain of the LCM1 (BrCHLH) protein. This study suggests that lcm1 gene plays an important role in the function of CHLH and provides a solid foundation for further studies on the development of plant leaf color.

     

The effects of chromosomes 3A and 3B on resistance to Fusarium head blight in tetraploid wheat

Fusarium head blight (FHB) caused by Fusarium graminearum is one of the most destructive diseases of wheat in areas where the weather is warm and humid after heading. Previous studies indicate that the level of resistance to FHB varies not only among wheat cultivars but also among some of their wild relatives. No accession, however, has yet been identified to be completely immune to FHB among the Gramineae. It is known that durum wheat (Triticum turgidum L. conv. durum) is consistently more susceptible to FHB than common wheat (T. aestivum L.). The importance of the D genome in conferring resistance to FHB has been emphasized. Meanwhile, recent studies using molecular markers report effective QTLs on chromosome 3BS in a hexaploid population and on 3A in tetraploid recombinant inbred chromosome lines. In this study, we performed an evaluation of the effects of homoeologous group 3 chromosomes of T. turgidum ssp. dicoccoides on resistance to FHB using a set of chromosome substitution lines of a durum wheat cultivar 'Langdon'. The accession of T. turgidum ssp. dicoccoides examined in this study was more susceptible for Type II resistance (resistance to spread of FHB in the head) than 'Langdon'. Both of the chromosome substitution lines of 3A and 3B showed the same level of resistance with 'Langdon', but bleaching of the heads was completely prevented in the substitution lines of chromosome 3A without relationship to rachis fragility. It was concluded that the chromosome 3A of T. turgidum ssp. dicoccoides carries resistance gene(s) to head bleaching caused by FHB.     

Effect of plant water deficit on the deoxynivalenol concentration in Fusarium-infected maize kernels

In current climate change scenarios, mean air temperatures and summer droughts are expected to increase over the long-term average in large parts of Europe. These changes will strongly affect the growth and health of cultivated plants. In a field experiment in 2009 and 2010 in rain-out shelters, the consequences of plant water availability under three water regimes on the severity of Fusarium ear rot, deoxynivalenol (DON) contamination and yield of maize were investigated. Water was provided exclusively to the plants by a mobile sprinkler system installed in the rain-out shelter. Three maize cultivars were supplied with 50, 75, and 125% of the long-term average monthly precipitation of the experimental site. In 2009, Fusarium graminearum-infected oat kernels were placed on the soil surrounding maize plants to promote ear infection, whereas in 2010, the maize silks were directly inoculated with suspensions of F. graminearum conidia. Heavy drought stress in the 50% water regime was reflected in the average ear yield of the three maize cultivars of 75?dt ha^-1 compared with 192?dt ha^-1 at 125% water. In this comparison, the DON concentrations in the kernels were fivefold higher at 50% water than at the high water regime: 380 compared with 75???g DON kg^-1 DM. In 2010, the drought stress symptoms were less pronounced than in 2009, and a much lower ear yield loss from 128 to 108?dt DM ha^-1 was observed with decreasing water supply. The DON contamination of the kernels was at a higher level than in 2009, but a similar upward trend from 330???g?kg ^-1 DM at 125% water supply to about 3.5-fold higher DON levels at 75 and 50% water supply was observed. These different yield responses presumably resulted from variable climatic conditions at the experimental site in the 2?years. The results of this study suggest that the risk of DON contamination of maize kernels increases when plants are grown under conditions of long-term water deficit.     

Mycotoxins in cereal grain (part 15). Distribution of deoxynivalenol in naturally contaminated wheat kernels

The analysis of deoxynivalenol (DON) in naturally infected wheat samples, after having been separated into four fractions through laboratory sieves, showed very low levels of DON in the fraction of largest kernels >2.8 mm (0 up to 1 mg/kg). The highest concentration of DON was found in fractions 2.2 to 2.5 mm and <2.2mm with up to 14mg/kg and 15mg/kg DON, respectively. In two samples (fractions <2.2mm) nivalenol was detected in concentrations up to 1,4mg/kg.     

Identification of a UDP-glucosyltransferase conferring deoxynivalenol resistance in Aegilops tauschii and wheat

Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.     

Effect of cleaning, milling, and baking on deoxynivalenol in wheat

Samples of wheat naturally infected by Fusarium graminearum Schwabe were obtained from mills in Oklahoma, Missouri, Kansas, and Minnesota and fields in Nebraska and Kansas in 1982; they were analyzed for deoxynivalenol (DON). The wheat was milled, and DON was found throughout all the milling fractions (bran, shorts, reduction flour, and break flour). The DON recoveries for each mill run ranged from 90 to 98%. These samples, regardless of DON concentration, also gave similar fractional distributions of DON. The greatest (21 ppm [21 micrograms/g]) concentration of DON was found in the bran, and the smallest (1 ppm) was found in the break flour. Cleaning and milling were not effective in removing DON; DON was not destroyed in the bread baked from the naturally contaminated whole wheat flour, but the effect on its concentration in the samples analyzed varied, the reduction ranging from 19 to 69%. The percent reduction found in the cleaned wheat ranged from 6 to 19%. DON concentrations in the following commercially made breads, caraway rye, seedless rye, and pumpernickel, were 45 ppb (ng/g), 39 ppb, and 0 ppb, respectively. The limits of detection by gas chromatography-mass spectrometry and high-pressure liquid chromatography for DON were 0.5 and 10 ng, respectively.     

QTL analysis of resistance to Fusarium head blight in the novel wheat germplasm CJ 9306. II. Resistance to deoxynivalenol accumulation and grain yield loss

Fusarium head blight (FHB or scab) caused by Fusarium species is a destructive disease in wheat, not only causing dramatic decrease of grain yield and quality, but also leading to serious mycotoxin contamination in the infected grains. This study was conducted to identify and quantify quantitative trait loci (QTLs) contributing to resistance to deoxynivalenol (DON) accumulation as well as to grain yield loss in a population of 152 F₇ recombinant inbred lines (RILs) derived from the cross Veery/CJ 9306. DON content in scabby grains and relative decreases of yield components were analyzed. Two new QTLs (QFhs.nau-2DL and QFhs.nau-1AS) for resistance to DON accumulation caused by FHB in wheat were detected, and QTLs QFhs.ndsu-3BS and QFhs.nau-5AS were also validated in CJ 9306, based on a constructed genetic linkage map. On the average of three experiments, major QTLs QFhs.ndsu-3BS and QFhs.nau-2DL explained up to 23 and 20% of phenotypic variation, respectively. QFhs.nau-1AS and QFhs.nau-5AS separately explained 4–6% of phenotypic variation. The differences among years/experiments were significant for all the four QTLs. However, the QTL × environment interaction was significant only for QFhs.nau-2DL, but not for the others. The results suggest that simple sequence repeat (SSR) markers Xgwm533b associated with QFhs.ndsu-3BS, and Xgwm539 associated with QFhs.nau-2DL could be used in marker-assisted selection to enhance resistance to DON accumulation. QFhs.ndsu-3BS + QFhs.nau-2DL and QFhs.nau-2DL + QFhs.nau-5AS would be the optimum choices for two-locus combinations. QFhs.ndsu-3BS was also validated in CJ 9306 for resistance to grain yield loss, explaining 8–15% of phenotypic variation. No QTLs for resistance to DON accumulation or grain yield loss independent of Type II resistance were found. By comparison, however, either of QFhs.nau-2DL or QFhs.nau-5AS alone and their combination were more contributive to resistance to DON accumulation than to Type II resistance.     

Deoxynivalenol accumulation and other scab symptoms in six romanian wheat genotypes inoculated withFusarium graminearum

At anthesis, under field conditions at Fundulea, each of 6 Romanian winter wheat genotypes was inoculated with 3Fusarium graminearum isolates used individually.Fusarium head blight (FHB) was assessed according to the following traits: relative weight of spikes (RWS), percentage of Fusarium damaged kernels (FDK), relative weight of kernels per head (RWKH), area under the disease progress curve (AUDPC) and deoxynivalenol (DON) content in total sample of kernels. Correlations between these traits and parameters revealed important differences between examined wheat genotypes in: DON accumulation, progress of FHB development, yield reduction, and models of host — pathogen interactions in theTriticum - Fusarium pathosystem. Significant correlations between different attributes of FHB were found forFusarium isolate 1 which is a moderate producer of DON (0.89 μg g^-1). Weight of spike was significantly correlated with weight of kernels per spike (r = 0.93**) and with percentage of damaged kernels (r = - 0.87**), while FDK was highly correlated with RWKH (r = - 0.85*) and with DON content (r = 0.82*). Area under the disease progress curve was also found to be significantly correlated with DON content (r = 0.86*).     

Genetic analysis of dry matter and nitrogen accumulation and protein composition in wheat kernels

The maximum rate and duration for grain dry matter (DM) and nitrogen (N) accumulation were evaluated in 194 recombinant inbred lines (RILs) from a cross between the two French wheat cultivars Récital and Renan. These cultivars were previously identified as having contrasting kinetics of grain DM and N accumulation. Grain protein composition was analysed by capillary electrophoresis (CE), which enabled quantification of the different storage protein fractions (-gliadins, -gliadins, LMW glutenins, HMW glutenins, and each of their subunits). Correlation analyses revealed that DM and N accumulation rates were closely correlated and repeatable over several years, which was not the case for DM and N accumulation durations, and that protein composition was primarily influenced by the N accumulation rate. This was particularly true for the LMW-glutenins and the -gliadins, the most abundant protein fractions. A genetic map of 254 molecular markers covering nearly 80% of the wheat genome was used for quantitative trait loci (QTL) analysis. A total of seven QTLs were found. Five QTLs were significantly associated with the kinetics of DM and N accumulation, and two of them also influenced protein composition. Two QTLs affected only the protein composition. One major QTL explained more than 70% of the total variation in HMW-GS Glu1B-x content.     

Effect of cleaning, milling, and baking on deoxynivalenol in wheat.

Samples of wheat naturally infected by Fusarium graminearum Schwabe were obtained from mills in Oklahoma, Missouri, Kansas, and Minnesota and fields in Nebraska and Kansas in 1982; they were analyzed for deoxynivalenol (DON). The wheat was milled, and DON was found throughout all the milling fractions (bran, shorts, reduction flour, and break flour). The DON recoveries for each mill run ranged from 90 to 98%. These samples, regardless of DON concentration, also gave similar fractional distributions of DON. The greatest (21 ppm [21 micrograms/g]) concentration of DON was found in the bran, and the smallest (1 ppm) was found in the break flour. Cleaning and milling were not effective in removing DON; DON was not destroyed in the bread baked from the naturally contaminated whole wheat flour, but the effect on its concentration in the samples analyzed varied, the reduction ranging from 19 to 69%. The percent reduction found in the cleaned wheat ranged from 6 to 19%. DON concentrations in the following commercially made breads, caraway rye, seedless rye, and pumpernickel, were 45 ppb (ng/g), 39 ppb, and 0 ppb, respectively. The limits of detection by gas chromatography-mass spectrometry and high-pressure liquid chromatography for DON were 0.5 and 10 ng, respectively.     

The effects of alien chromosomes on common wheat resistance to biotrophic fungal pathogens

Effective, perhaps new genes of resistance to brown rust and powdery mildew expressed in common wheat genome in plant ontogenesis were revealed on additive chromosomes of Aegilops searsii, Aegilops longissima, Secale montanum and Elytrigia elongata.     

Genetic analysis of scab resistance QTL in wheat with microsatellite and AFLP markers.

Three chromosomal regions associated with scab resistance were detected in a common cultivar, Ning7840, by microsatellite and AFLP analysis. Six microsatellites on chromosome 3BS, Xgwm389, Xgwm533, Xbarc147, Xgwm493, Xbarc102, and Xbarc131, were integrated into an amplified fragment length polymorphism (AFLP) linkage group containing a major quantitative trait locus (QTL) for scab resistance in a mapping population of 133 recombinant inbred lines (RILs) derived from 'Ning7840' x 'Clark'. Based on single-factor analysis of variance of scab infection data from four experiments, Xgwm533 and Xbarc147 were the two microsatellite markers most tightly associated with the major scab resistance QTL. Interval analysis based on the integrated map of AFLP and microsatellite markers showed that the major QTL was located in a chromosome region about 8 cM in length around Xgwm533 and Xbarc147. Based on mapping of six microsatellite markers on eight 3BS deletion lines, the major QTL was located distal to breakage point 3BS-8. In total, 18 microsatellites were physically located on different subarm regions on 3BS. Two microsatellites, Xgwm120 and Xgwm614, were significantly associated with QTL for scab resistance on chromosome 2BL and 2AS, respectively. The resistance alleles on 3BS, 2BL, and 2AS were all derived from 'Ning7840'. Significant interaction between the major QTL on 3BS and the QTL on 2BL was detected based on microsatellite markers linked to them. Using these microsatellite markers would facilitate marker-assisted selection to improve scab resistance in wheat.     

Effect of individual chromosomes on sex behavior of Drosophila

Dependence of intensity of Drosophila virilis male sexual behaviour on age-related differences was studied. Most active proved to be those age periods which correlated with the time of S-esterase elevated activity. Courtship displays were compared in strains 101 and 160, interstrain differences correlating with the S-esterase activity level. As S-esterase plays an important role in fertilization, this relationship seems to be non-random. It is quite possible that the level of S-esterase activity regulates male sexual activity in natural populations. Some variations in male courtship display in interspecies hybrids (D. virilis x D. littoralis) were demonstrated which depended on the gene dose of respective species. It may well be that in the bk and dt gene regions those genes are localized which are responsible for courtship behaviour. The analysis of sexual behaviour in interstrain and interspecies hybrids proved to be successful approach to elucidating possible role of separate chromosomes in sexual behaviour determination.     

Influence of alien chromosomes on the resistance of soft wheat to biotrophic fungal pathogens

The resistance of 77 disomic chromosome-addition and chromosome-substitution lines of soft wheat that had been created on the base of the Chinese Spring variety to Belorussian populations of powdery mildew and brown leaf rust is studied. The lines possess a chromosome pair introduced from 13 species of cereals as well as three amphiploids. New genes that express resistance to biotrophic fungal pathogens in chromosomes 2S^s and 5S^s from the Aegilops searsii species and chromosome 6R^m from the Secale montanum species were discovered. We do not exclude the possibility that the new resistance gene against powdery mildew is carried by chromosome 6S¹ from the species Aegilops longissima (line No. 4), and that the new resistance gene against brown leaf rust is carried by chromosome 3E from the species Elytrigia elongata.     

Potential new sources of wheat curl mite resistance in wheat to prevent the spread of yield-reducing pathogens

The wheat curl mite (WCM), Aceria tosichella Keifer (Trombidiformes: Eriophyidae), is a major pest in cropping regions of the world and is recognised as the primary vector of several yield-reducing pathogens, primarily affecting wheat. Management of WCM is complicated due to several aspects of the mite’s biology and ecology; however, commercially viable mite resistant wheat varieties may offer practical long-term management options. Unfortunately, mite populations have adapted to previously identified sources of resistance, highlighting the need for further sources of resistance and the value of stacking different resistances to give greater degrees and longevity of control. In this study we assessed the susceptibility of 42 wheat-derived genotypes to mite population growth using a new experimental method that overcomes methodological limitations of previous studies. Experimental wheat lines included a variety of wheat genotypes, related Triticeae species, wheat-alien chromosome amphiploids, and chromosome addition or substitution lines. From these we identify new promising sources of WCM resistance associated with Thinopyrum intermedium, Th. ponticum and Hordeum marinum chromosomes. More specifically we identify group 1J and 5J chromosomes of the L3 and L5 wheat-Th. intermedium addition lines as new sources of resistance that could be exploited to transfer resistance onto homoeologous wheat chromosomes. This study offers new methods for reliable in situ estimations of mite abundance on cereal plants, and new sources of WCM resistance that may assist management of WCM and associated viruses in wheat.