Do fumonisin mycotoxins occur in wheat?

The fumonisin mycotoxins are mainly produced by the fungi Fusarium verticillioides and Fusarium proliferatum, which are both field pathogens of maize. The natural occurrence of fumonisins has been verified in maize and a large range of maize-based products in many countries of the world. However, occasional reports have emerged of fumonisins being detected in wheat, despite the main producing fungi not being pathogens of this cereal. An investigation was conducted into a recent report of the natural occurrence of fumonisins in the 2003/2004 South African wheat crop at levels up to 1.7 mg/kg, as determined by immunoaffinity column cleanup and direct fluorometric measurement. An AOAC International high-performance liquid chromatographic (HPLC) method for the determination of fumonisins in maize was modified and validated for the determination of fumonisins in spiked wheat samples. HPLC analysis of the wheat samples previously found to be positive for fumonisins revealed no detectable (<5 microg/kg) fumonisins in the 30 samples analyzed. These results, which lay doubt on previous reports of fumonisins in wheat, emphasize the fact that screening methods, especially if used outside their range or matrix of applicability, can produce false positive results despite the use of immunoaffinity cleanup. Such results should be validated and confirmed with a more definitive technique.     

Winter wheat fertilizing using nitrogen–sulphur fertilizer

Precise field experiments were established on two sites with winter wheat under different soil-climatic conditions in the Czech Republic. Four treatments were fertilized with same dose of nitrogen (200 kg N ha^?1) and increasing dose of sulphur (0, 10, 20 and 40 kg S ha^?1) using nitrogen–sulphur (N–S) fertilizer with calcium sulphate form. Soil and plant aboveground biomass samples were taken in the stages of development BBCH 26–28; 30–32; 37–39; 49–51. The winter wheat grain yield ranged between 7.20 and 10.86 t ha^?1 and had an increasing trend with increasing sulphur dose. Although the differences were usually not statistically significant, there were found increasing tendencies of bioavailable sulphur content in soil with increasing S split doses. Soil S content decreased with time probably due to plant uptake. Sulphur dose did not influence the S content in plant aboveground biomass. The total S contents in grain after harvest ranged between 0.09% and 0.14% and were not significantly influenced with the fertilizing treatment. The same statement is valid for the S content in straw, which ranged between 0.03% and 0.11%. Both, S content in winter wheat seeds and straw were strongly influenced by the site conditions.     

Carbon dioxide assimilation in urea‐treated wheat leaves

Application of 10 mM urea to the flag leaf of wheat plants enhanced in vivo urease activity several fold. Photosynthetic rate was also increased considerably. There were significant differences in the leaf internal carbon dioxide (CO₂) concentrations between the urea‐treated and untreated leaves. The finding that carbon (¹⁴C) was detected in the ethanol extract of the leaves fed with ¹⁴C‐urea suggests that CO₂ released from urea is re‐fixed by the leaves.     

Trait phenotyping and SSR markers characterization of wheat (Triticum aestivum L.) germplasm for breeding early maturing wheat’s for Western-Himalayas

Genetic Resources and Crop Evolution - The study involved evaluation of 96 wheat genotypes for early maturity and related traits and molecular characterization of trait specific candidate genotypes...     

Response of dryland wheat to ρ rates and placement methods

Abstract

In Morocco,response of dryland wheat (Triticum aestivuro) to ? has not been related to soil ? availability index. The objectives of the experiments reported were to determine the critical NaHCO₃‐extractable ? level in soils of Settat Province in Morocco and to compare the effect o‐f banding with broadcasting of concentrated superphosphate (CSP) for wheat, crops. Eighteen ?‐P factorial experiments were conducted on three different soil types (Rendolls, Caloixerolls and Chromoxererts) with different ? availability indexes and lime levels in 1985–86 and 1986–87. The ? rates were 0, 9, and 18 in 1985–86 and an additional 36 kg P/ha rate in 1986–87. The rainfall levels were 300 mm with an excellent distribution and 220 mm with a poor distribution in the above years, respectively. In the latter year, a P placement study was conducted on a Rendoll with a NaHCO₃‐P level of 4.5 mg/kg. For the placement study the rates were 0, 9, 18, 36, and 54 kg P/ha. The grain yield response to ? averaged 8% in the wet year and 40% in the drier year. The maximum yields obtained were close to 3 and 1 Mg/ha for the above years, respectively. A critical level of 5 mg/kg of NaHCO₃‐P was obtained, separating responsive from nonresponsive soils for a relative yield of 90%. The ? placement study showed that yield response to broadcast ? reached a plateau at 9 kg P/ha, but the response to banded ? continued up to the highest rate. This shows that the banding effect of CSP is more than a simple ? nutrition effect     

Summer fallow soil management – impact on rainfed winter wheat

Summer fallow soil management is an important approach to improve soil and crop management in dryland areas. In the Loess Plateau regions, the annual precipitation is low and varies annually and seasonally, with more than 60% concentrated in the summer months from July to September, which is the summer fallow period in the winter wheat-summer fallow cropping system. With bare fallow in summer as a control, a 3-year location-fixed field experiment was conducted in the Loess Plateau to investigate the effects of wheat straw retention (SR), green manure (GM) planting, and their combination on soil water retention (WR) during summer fallow, winter wheat yield, and crop water use and nitrogen (N) uptake. The results showed that SR increased soil WR during summer fallow by 20 mm on average compared with the control over 3 experimental years but reduced the grain yield by 8% in the third year and the grain N content by 6–15% in all 3 years. In contrast, GM planting markedly reduced soil WR by 16 mm and 33 mm in the first and third year, respectively, but increased water use efficiency (WUE) by 16% in the third year and nitrate N accumulation in 0–100 cm soil at winter wheat sowing. Their combination did not significantly affect the soil WR or the soil nitrate N content in any of the 3 years, but did increase WUE by 11% in the third year and grain yield by 2.6% in the second year. In conclusion, the combination of SR and GM planting mitigated the negative effects of the individual measures, providing a feasible method for summer fallow management in the semiarid Loess Plateau in China and other similar regions.     

Microsatellite markers – a new tool for distinguishing diploid wheat species

Triticum baeoticum and T. urartu are very similar morphologically. By using microsatellite markers it was possible to distinguish between these two species. Microsatellite markers are, therefore, a powerful new tool to support the determination of critical races in diploid wild wheat species. They also allow the discussion of evolutionary pathways within Triticum.     

Cool‐Season annual legume effects on wheat forage nutritive value

Hard red winter wheat (Triticum aestivum L. emend. Thell.) is an important cool‐season winter forage used primarily for increasing weight gain on growing beef cattle in the southern Great Plains. ‘Karl’ hard red winter wheat grown alone or grown with either hairy vetch (Vicia villosa Roth) or pea [(Pisum sativum L. subsp. arvense) var. ‘Austrian winter'] was sampled for forage nutritive value. The interplanted legume forage was also sampled for forage nutritive value. Ruminally degradable nitrogen (RDN):ruminally degradable organic matter (RDOM) ratios were highest for legume forage and exceeded the National Research Council (NRC) recommendation of 26.13 g RDN: 1 kg RDOM for peak ruminai microbial efficiency during March, April, and May sample periods over the 2‐year study. Wheat grown alone met the NRC requirement only during March. Wheat grown with either hairy vetch or pea had higher (P<0.05) RDN:RDOM ratios and crude protein (CP) values when compared to wheat grown alone during May. There were no differences (P>0.05) in dry matter (DM) yield between wheat grown alone or grown with the legumes except when analyzed by individual date, and then only for 1 of 6 sample dates. Undegraded intake protein (UIP) was generally higher (PO.05) for wheat compared to the legumes and higher (PO.05) for wheat grown alone during May compared to wheat grown with the legumes during May. The decline of the RDN:RDOM values to 40% below the NRC recommendation of wheat grown alone during May indicates a possible need for protein supplementation for growing beef cattle grazing wheat during this period. These data also indicate that interplanting legumes with wheat may enhance animal performance by providing forage of higher nutritive value. More information regarding grazing tolerance of these selected cool‐season annual legumes and subsequent animal performance is required.     

Evolution of tetraploid wheat based on variations in 5′ UTR regions of Ppd-A1: evidence of gene flow between emmer and timopheevi wheat

Previous study showed that tetraploid wheat was divided into two groups (Type AI and Type AII) based on sequences around Ppd-A1 gene (Takenaka and Kawahara in Theor Appl Genet 125(5):999–1014, 2012). That study focused on domesticated emmer wheat and used only 19 wild emmer wheats, so could not be clear the evolutional relationship between Type AI and Type AII. Here, a total of 669 accessions comprising 65 einkorn wheats, 185 wild emmer wheats, 107 hulled emmer wheats, 204 free-threshing (FT) emmer wheats, and 108 timopheevii wheats were studied by PCR assay and DNA sequencing for Type AI/AII. Type AII was an older type than Type AI because all einkorn accessions had Type AII. In wild emmer, Type AI was distributed in the northeast regions of its distribution and Type AII was found to be centered on Israel. A total of 37.4 % of hulled emmer accessions were Type AI, while 92.2 % of FT emmer accessions were Type AI. Differences in the proportion of Type AI/AII in domesticated emmer suggested a strong bottle-neck effect. We also found two MITE-like sequence deletion patterns from a part of Type AII accessions (dic-del and ara-del). Dic-del was found from only Israeli wild emmer accessions and ara-del was found from almost all timopheevii wheat accessions. Only three timopheevii accessions did not have ara-del, and one wild emmer accession and ten hulled emmer accessions had ara-del. These accessions suggested gene flow between emmer and timopheevii wheat.     

Variation of plant‐test phosphorus for individual lupin and wheat tops

Abstract

Two field experiments measured variation of phosphorus (P) concentration in dried tops (plant‐test P) of individual lupin (Lupinus angustifolius cv. Merrit) and wheat (Triticum aestivum cv. Cadoux) plants collected from random locations in experimental plots treated with different levels of superphosphate. Plant‐test P for the individual tops varied by between 4 to 65% of mean values. Coefficient of variation for the 10 individual plants per plot varied from 10 to 24%. For each plot, mean plant‐test P for the 10 individual tops were similar to values for bulk samples of 30 plants collected at random within the plot. It is concluded that a bulk sample of 30 lupin or wheat plant tops need to be collected from uniform areas in farmer paddocks to provide a representative estimated of the current P status of the crop.     

Free amino acids in unhardened and cold‐hardened winter wheat crowns

The free amino acids proline and glutamic acid increased in the crown of winter wheat in all treatments when exposed to cold‐hardening. Glutamine also increased except when 90–80 N‐P fertilizer was applied. The increase of proline and glutamic acid was enhanced with the application of P but counteracted by N. This enhancement was smaller with glutamine. The decrease of threonine, tyrosine, phenylalanine, lysine and α‐aminobutyric acid with cold‐hardening was not counteracted by application of N and P. However, isoleucine in cold‐hardened winter wheat increased with the application of 180–0 fertilizer and aspartic acid increased when P was added. The increase in alanine with cold‐hardening was enhanced by P alone but counteracted by N‐P treatments. The marked increase in proline during cold‐hardening could be useful in the detection of cold‐hardiness in winter wheats.     

Sensitivity of soft red winter wheat cultivars to chlorate‐induced toxicity

The use of chlorate as a nitrate analogue to screen soft red winter wheat (Triticum aestivum L.) cultivars for differences in nitrate reductase activity (NRA) was studied by adding potassium chlorate to a hydroponic nutrient solution in which wheat seedlings were growing. After 14 days, leaf symptoms indicating chlorate‐induced toxicity were rated. It was hypothesized that wheat plants which were susceptible to chlorate‐induced toxicity reduced chlorate and nitrate more rapidly than did resistant plants. In experiments testing the potential of this assay, wheat and barley (Hordeum vulgare L.) cultivars previously reported to have low NRA were less susceptible to chlorate‐induced toxicity than were cultivars reported to have high NRA. The assay was used to screen 15 soft red winter wheat cultivars for differences in sensitivity to chlorate‐induced toxicity. Variable toxic reactions were observed both among and within the cultivars. To determine whether the within‐cultivar variation was environmental or genetic, single plant selections for contrasting chlorate response were made, and bulked progeny were rescreened. In eight of 15 cultivars, the contrasting selections were different for chlorate‐induced toxic response, indicating heterogeneity for this trait within these eight cultivars. These chlorate‐selected lines may also be near‐isogenic lines for NRA. Seedling screening of wheat for chlorate response may be useful for identification of high NRA breeding lines.     

Reduced‐till spring wheat response to fertilizer sources and placement methods

Abstract

Field studies were conducted to determine the effect of nitrogen (N) and phosphorus (P) fertilizer sources and placement configurations on spring wheat growth, yield and quality. Different standard and experimental N and P sources at two rates and in different placement methods provided 32 fertilizer treatments at three locations. Banding of N and P together resulted in the greatest yields. Of the fertilizer combinations where N and P were applied separately, only broadcast N with deep banded P gave similar yields to N and P together. Banding fertilizer with the seed at these levels damaged seedling growth and limited yield. Elevated protein levels, when found, were likely due to lower yields and subsequent concentration of N in grain protein. Careful consideration of fertilizer rate, source and placement strategies to optimize production and water utilization are essential in dryland environments.     

Tolerance of durum wheat lines to an acid,aluminum‐toxic subsoil

Durum wheat, Triticum durum Desf., is reportedly more sensitive to aluminum (Al) toxicity in acid soils than hexaploid wheat, Triticum aestivum L. em. Thell. Aluminum‐tolerant genotypes would permit more widespread use of this species where it is desired, but not grown, because of acid soil constraints. Durum wheat germplasm has not been adequately screened for acid soil (Al) tolerance. Fifteen lines of durum wheat were grown for 28 days in greenhouse pots of acid, Al‐toxic Tatum subsoil at pH 4.5, and non‐toxic soil at pH 6.0. Aluminum‐tolerant Atlas 66 and sensitive Scout 66 hexaploid wheats were also included as standards. Based on relative shoot and root dry weight (wt. at pH 4.5/wt. at pH 6.0 X 100), durum entries differed significantly in tolerance to the acid soil. Relative shoot dry weight alone was an acceptable indicator of acid soil tolerance. Relative dry weights ranged from 55.1 to 15.5% for shoots and from 107 to 15.8% for roots. Durum lines PI 195726 (Ethiopia) and PI 193922 (Brazil) were significantly more tolerant than all other entries, even the Al‐tolerant, hexaploid Atlas 66 standard. Hence, these two lines have potential for direct use on acid soils or as breeding materials for use in developing greater Al tolerance in durum wheat. Unexpectedly, the range of acid soil tolerance available in durum wheat appears comparable to that in the hexaploid species. Hence, additional screening of durum wheat germplasm for acid soil (Al) tolerance appears warranted. Durum lines showing least tolerance to the acid soil included PI 322716 (Mexico), PI 264991 (Greece), PI 478306 (Washington State, USA), and PI 345040 (Yugoslavia). The Al‐sensitive Scout 66 standard was as sensitive as the most sensitive durum lines. Concentrations of Al and phosphorus were significantly higher in shoots of acid soil sensitive than in those of tolerant lines, and these values exceeded those reported to cause Al and phosphorus (P) toxicities in wheat and barley.     

Does no-till wheat sowing in a rice-wheat cropping sequence cause surface-soil compaction?

Wheat planting in rice-harvested fields without land preparation is more economical, but the physical characteristics of the plant root sphere are not well documented. Comparative changes in the soil compaction in parallel fields used for no-till and conventional tillage were measured in replicated field trials for two soil types and in three randomly selected farmers’ fields. Weakly to moderately developed soils on recent to old Pleistocene calcareous alluvium were studied. They differed in their clay content. No-till wheat sowing resulted in a greater soil bulk density and a lower total porosity in the heavy-textured soils compared to the light-textured soil. In the light-textured Jhakkar soil, the no-till regime resulted in a greater infiltration at the saturated state and under most suction levels and a greater macroporosity compared to the conventional tillage. The silty clay Kotly soil had greater macroporosity in the conventional tillage than in the no-till regime. The wheat root growth and penetration seemed to be favored by the relatively low bulk density resulting from the conventional tillage, particularly in the silty clay loam soil. The dense layer restricted root penetration in the silty clay loam soil, while there was less resistance in the sandy loam soil. The study demonstrated the suitability of the no-till regime for specific soil types. Published in Russian in Pochvovedenie, 2008, No. 11, pp. 1362–1370. The text was submitted by the authors in English.     

Foliar uptake of volatilized ammonia from surface‐applied urea by spring wheat

Abstract

Large volatile losses of NH₃ can occur from surface‐applied urea in semi‐arid areas. Our objective was to determine possible absorption of this volatilized N by the crop canopy under field conditions. At two different times during crop growth, ¹⁵N‐enriched urea was surface‐applied at rates equivalent to 100 kg N ha^‐1 to soil contained in trays placed between two rows of spring wheat. Seven days after application, the soil in the trays was removed from the field and analyzed for ¹⁵N content. Addition of HC1 during soil air drying was necessary to prevent volatile losses of ¹⁵N. Of applied urea‐N, 13% was volatilized over seven days at both application times. Of the urea‐N that was volatilized, 15% was absorbed by wheat at the first application time and 7% was absorbed by wheat at the second application time. Plant absorption of urea N (Y, mg) declined with distance from the source (x, cm) following the equation Y=10.95*10^(‐0.0142x). About 90% of absorbed N was within the first three wheat rows. Our findings suggest that a significant portion of ammonia volatilized from top‐dressed urea might be captured by plant foliage.     

Water‐retention capability as a selection criteria for drought resistance in wheat

Four durum wheat cultlvars (Triticum turgidum spp. durum Desf.) from different countries of origin (Austria, Ethiopia, and Italy) were investigated. Plants were grown in pots under glasshouse conditions. Immediately after the full development of the flag leaves, these leaves were detached for the screening. Distinct differences in water‐retention capabilty among the cultivars was observed. The drought‐resistant (hardy) types, Valgerardo and Boohai, showed better water retention capabilty than the drought‐sensitive ones, such as DZ‐04–688. Poor yielding cultivars under field conditions were also found to be poor in water‐retention capability and vice versa. The applied method is simple and inexpensive. It adds another procedure when screening for drought resistance. However, it needs further confirmation by cultivars covering a broader range of genetic diversity.     

Evaluation of soil extractants to estimate available micronutrients under wheat‐field conditions

Abstract

Three extracting reagents were evaluated by correlation analyses to provide the best index of Zn, Cu, Mn and Fe availability to wheat (Triticum aestivum L.) plants growing under open field conditions. Twenty one soils were selected to obtain the widest range in properties of soils of the land wheat cultivated. The magnitude of the extractive power varied in the following order: 6NHCl ? EDTA + NH₄OA_C, pH4.65 > DTPA‐TEA, pH 7.3. The mild extractants, EDTA and DTPA, gave the same order of removal of micronutrients being Zn < Cu < Fe < Mn. The acid extractant was on the contrast more effective on Cu and Fe with respect to Zn and Mn, respectively. Wheat concentrations of Zn, Mn and Fe were significantly correlated to soil micronutrients. Highly significant relationships were found for Zn extracted by DTPA solution (r = 0.737***) and for Mn and Fe extracted by EDTA solution (r = 0.710*** and r = 0.564**). Plant Zn and Mn were also well predicted by the acid extraction. The absence of correlation for plant Cu vs. soil Cu occurred probably because of wheat concentrations almost constant, ranging from 5.0 to 8.0 mg/kg.     

Polymorphisms in two homeologous γ-gliadin genes and the evolution of cultivated wheat

The polymorphisms in two -gliadin genes GAG56D and GAG56B on the D- and B-genomes of polyploid wheat, respectively, were investigated by sequencing PCR products and by PCR-RFLP. Of GAG56D, two alleles fo and ok were previously known to occur in hexaploid wheat. Here, we found that 16 sequenced fragments of GAG56D from six recognized subspecies of Triticum aestivum, including 13 contributed by this study, were identical to either the fo or the ok allele. Considering published evidence, it was concluded that the investigated alleles of GAG56D stemmed from two different Aegilops tauschii plants and thus two independent origins of hexaploid wheat. Compared to GAG56D-sequences obtained from 10 accessions of Ae. tauschii, the fo and ok alleles clustered with fragments from three accessions collected in the Caspian region. By sequencing fragments of GAG56B, four distinct allelic groups were found among cultivated wheats, typical of bread wheat (p-aes), durum wheat of gliadin 45-type (a), durum wheat of gliadin 42-type (p-dur) and Timopheev's wheat (p-tim), respectively. Interestingly, the a allele found in gliadin 45-type durum wheat was shared by European spelt cultivars, which strongly supported the hypothesis that European spelt originated from a hybridization event between a tetra- and hexaploid wheat. The data also suggested that emmer might have been domesticated more than once. Phylogenetic analysis of GAG56-fragments obtained from putative B/G-genome donors excluded all candidate species as immediate donors of the B/G-genome, but instead indicated a monophyletic origin of all GAG56B alleles found in polyploid wheat, i.e. including T. timopheevii.