Chromosome location of the gene for brittle rachis in the Tibetan weedrace of common wheat

The brittle rachis of the Tibetan weedrace (Triticum aestivum var. tibetanum) was found to be governed by a single dominant gene on the short arm of chromosome 3D. The new brittle rachis gene was designated Br₁. This study also discovered that the type of disarticulation is governed by many genes that may differ from brittle rachis genes. In other words, the same brittle rachis gene may exhibit various types of disarticulation in various genetic backgrounds. So, after the brittle rachis gene (barrel type) in Aegilops tauschii entered hexaploid wheat through the amphidiploid path, it might exhibit the wedge type of disarticulation.     

Sources of Resistance to Stem Rust (<Emphasis Type="Italic">Puccinia graminis</Emphasis> f. sp. <Emphasis Type="Italic">tritici</Emphasis>) in Ethiopian Tetraploid Wheat Accessions

Seedlings of 41 emmer (Triticum dicoccon Schrank) and 56 durum (T. durum Desf.) wheat accessions were evaluated for their response to stem rust (Puccinia graminis f. sp. tritici) infection under greenhouse condition at Kulumsa Agricultural Research Center, Ethiopia. The objectives were to identify tetraploid wheat accessions that could serve as sources of resistance to stem rust, and postulate the stem rust (Sr) resistance genes through multipatotype testing. The test included screening of accessions for stem rust resistance and multipatotype testing. To ensure vigorous screening, a mixture of six isolates (Si-1a, Am-2, Ku-3, Dz-4a, Ro-4 and Na-22) that were collected from severely infected emmer, durum, and bread wheat (Triticum aestivum L.) varieties of major wheat growing areas of Ethiopia was used as inocula. Out of the tested accessions, 18 emmer and 6 durum accessions exhibited low infection types (0–2) response and hence selected as a source of resistance to stem rust infection. Multipatotype testing was done to postulate Sr genes in the selected accessions. In the test, 10 different stem rust races (A2, A9, A11, A14, A16, A17, B3, B7, B15, and B21), 33 stem rust differential lines, and a universal susceptible check variety, Morocco were used, The high (3–4) and low infection type reaction patterns of the tested accessions and differential lines were used to postulate the genes that exhibit gene-for-gene relationship. The presence of Sr 7b, 8b, 9a, 9b, 10, 14, 24, 27, 28, 29, 30, 31, 32 and Tt-3+10 genes were postulated in 16 selected emmer and 5 durum wheat accessions. Efforts to transfer these valuable Sr genes from cultivated tetraploid wheats could be rewarding to get stem rust resistant varieties and boost wheat production.     

Inheritance of the Triple-spikelet Character in a Tibetan Landrace of Common Wheat

The Tibetan triple-spikelet wheat (TTSW) (Triticum aestivum L. concv. tripletum nom. nud.) is a landrace of common wheat collected from Tibet, China. It possesses a genetic stable character of triple-spikelets, and produces more than 50 spikelets and about 150 florets per spike. The plant has normal number of tillers, normal length of spikes, and well-developed seeds. The inheritance of the triple-spikelet trait in TTSW was genetically analyzed. The results indicate that the triple-spikelet character in TTSW is controlled by two recessive genes. Therefore, we suggest designating the genes controlling this character of triple-spikelets as Ts1 and Ts2. These genes could be used for increasing the number of spikelets per spike for high-yield breeding in common wheat.     

Genetic mapping of the gene for brittle rachis in a <Emphasis Type="Italic">Triticum aestivum</Emphasis>—<Emphasis Type="Italic">Aegilops triuncialis</Emphasis> introgression line

Aegilops triuncialis L. (2n = 4x = 28, genome formula UUCC) has been used to obtain one of the “Arsenal collection”, the distant hybridization of Triticum aestivum L. The introgression line 124/00ⁱ, which was derived from the cross of T. aestivum ‘Rodina' with γ-irradiated pollen of an accession of Ae. triuncialis. However, undesirable genes can be incorporated into the cultivated varieties from Ae. triuncialis. The spikes of Ae. triuncialis disarticulate from stems at a single node at the bottom of the spikes. It was defined as a synaptospermic diaspore. However, the spike of 124/00ⁱ unexpectedly disarticulate below each spikelet showing wedge type of disarticulation. The brittle rachis gene Br ¹²⁴ (B rittle r achis of 124 /00 ⁱ ) of 124/00ⁱ was allelic to Br2 located on the short arm of chromosome 3A. From the microsatellite mapping, the Br ¹²⁴ gene was bracketed by Xbarc19 (20.3 cM) and Xgwm779.1(14.3 cM) on the short arm of chromosome 3A. The present study suggested that the dominant mutation from synaptospermic diaspore to wedge type disarticulation occurred in the gamete of Ae. triuncialis when Ae. triuncialis pollen was treated with γ-irradiation.     

The Positive Effect of Sulfur on Selenium Detoxification Under Selenite Condition in Wheat

An experiment was performed to evaluate the regulatory effects of varied amounts of sulfur (S) on selenium (Se) uptake and distribution within wheat (Triticum aestivum L.) in response to selenite (SeO₃^2-). The results showed that an appropriate amount of SeO₃^2- (≤5 mg kg^?1) improved the agronomic traits of wheat, and the addition of S significantly alleviated wheat growth inhibition caused by excessive SeO₃^2- (≥15 mg kg^?1). The Se concentration of different fractions in wheat grain showed a tendency of alkali-soluble Se > alcohol-soluble Se > water-soluble Se > salt-soluble Se. The use of S significantly reduced Se accumulation in each wheat part when the addition of SeO₃^2- was ≤15 mg kg^?1, but the Se distribution ratio of various wheat parts was not influenced by S supply. Overall, the application of S fertilizer is an effective technical measure to promote wheat production safety in high-Se areas.     

Use of Italian wheat varieties in China

Summary Italian wheat varieties (Triticum aestivum L.) have played an important role in Chinese wheat production and improvement, especially in the 1950's to 1970's. In the history of wheat introduction in China, three series of Italian germplasms making great impact on the development of wheat production and improvement are recognized. This paper describes the brief history of introduction of Italian varieties into China and the detailed use of them for wheat production and wheat improvement in China.     

Cloning and phylogenetic analysis of polyphenol oxidase genes in common wheat and related species

Cloning and phylogenetic analysis of polyphenol oxidase (PPO) genes in common wheat and its relatives would greatly advance the understanding of molecular mechanisms of grain PPO activity. In the present study, six wheat relative species, including T. urartu, T. boeoticum, T. monococcum, T. dicoccoides, T. durum and Ae. tauschii, were sampled to isolate new alleles at Ppo-A1 and Ppo-D1 loci corresponding to common wheat PPO genes, and seven new alleles were identified from these species, which were designated as Ppo-A1c (from T. urartu), Ppo-A1d (T. boeoticum), Ppo-A1e (T. monococcum and T. durum), Ppo-A1f (T. dicoccoides), Ppo-A1g (T. durum), Ppo-D1c (Ae. tauschii) and Ppo-D1d (Ae. tauschii), respectively. Five out of the seven alleles detected in the wheat relatives contained an open reading frame (ORF) of 1,731 bp, encoding a polypeptide of 577 residues, which is the same as those of Ppo-A1 and Ppo-D1 genes in common wheat, whereas, the full-length ORF of the allele Ppo-A1g from T. durum was not obtained, and a 73-bp deletion occurred in the third exon of Ppo-D1d, an allele from Ae. tauschii, resulting in a shorter polypeptide of 466 amino acids. The 191-bp insertion in the first intron reported previously in common wheat was also found in T. dicoccoides lines, implying that more than one tetraploid wheat lines may be involved in the origination of common wheat. Phylogenetic trees were constructed using the genomic DNA sequences of the seven alleles, together with four from common wheat and four partial PPO gene sequences deposited in GenBank. The genome tribe A was divided into two clusters, one of which contained Ppo-A1d and Ppo-A1e, and the other included the remaining five alleles at Ppo-A1 locus. The alleles from different clusters showed high sequence divergences, indicated by dozens of SNPs and five to six InDels. The genome tribe D comprised the alleles Ppo-D1a, Ppo-D1c, Ppo-D1d and Ppo-D1b, and the former three were clustered together, showing significant sequence divergence from Ppo-D1b. In addition, the relationships between these allelic variants and grain PPO activities were also discussed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Carbon isotope discrimination and water use efficiency in Iranian diploid,tetraploid and hexaploid wheats grown under well-watered conditions

Carbon isotope discrimination (Δ) has been proposed as physiological criterion to select C₃ crops for yield and water use efficiency. The relationships between carbon isotope discrimination (Δ), water use efficiency for grain and biomass production (WUE_G and WUE_B, respectively) and plant and leaf traits were examined in 20 Iranian wheat genotypes including einkorn wheat (Triticum monococcum L. subsp. monococcum) accessions, durum wheat (T. turgidum L. subsp. durum (Desf.) Husn.) landraces and bread wheat (T. aestivum L. subsp. aestivum) landraces and improved cultivars, grown in pots under well-watered conditions. Carbon isotope discrimination was higher in diploid than in hexaploid and tetraploid wheats and was negatively associated with grain yield across species as well as within bread wheat. It was also positively correlated to stomatal frequency. The highest WUE_G and grain yield were noted in bread wheat and the lowest in einkorn wheat. Einkorn and bread wheat had higher WUE_B and biomass than durum wheat. WUE_G and WUE_B were significantly negatively associated to Δ across species as well as within bread and durum wheat. The variation for WUE_G was mainly driven by the variation for harvest index across species and by the variation for Δ within species. The quantity of water extracted by the crop, that was closely correlated to root mass, poorly influenced WUE_G. Environmental conditions and genetic variation for water use efficiency related traits appear to highly determine the relationships between WUE_G and its different components (water consumed, transpiration efficiency and carbon partitioning).     

Grain Quality of Emmer Wheat Derived Synthetic Hexaploid Wheats

The wild diploid goat grass (Aegilops tauschii Cosson), and the cultivated tetraploid emmer wheat (Triticum turgidum L. subsp. dicoccon (Schrank) Thell.) may be important sources of genetic diversity for improving hexaploid bread wheat (Triticum aestivum L.). Through interspecific hybridization of emmer wheat and Ae. tauschii, followed by chromosome doubling, it is possible to produce homozygous synthetic hexaploid wheat. Fifty-eight such synthetic hexaploids were evaluated for grain quality parameters: grain weight, length, and plumpness, grain hardness, total protein content, and protein quality (SDS-Sedimentation volume, SDS-S). Most synthetics showed semi-hard to hard grain texture. Results showed significant genetic variation among the synthetic hexaploids for protein content, SDS-S values, and grain weight and plumpness. Quality measurement values of synthetic hexaploids were regressed on corresponding values of the emmer wheat parents. With this offspring-parent regression, protein content and SDS-S values explained 8.7 and 28.8%, respectively, of the variation among synthetics, indicating a significant contribution from the emmer wheat parents for these traits. The synthetic hexaploids, in general, had significantly higher protein content (15.5%, on average) and longer grains than ‘Seri M82’, the bread wheat control (13.1% protein content). Synthetics with SDS-S values and grain weights higher than those of ‘Seri M82’ were also identified. Protein content among synthetics showed significantly negative correlations with grain weight and plumpness, but no correlation with SDS-S values. Despite these negative correlations, 10 superior synthetic hexaploid wheats, derived from nine different emmer wheat parents and with above average levels of protein content, SDS-S values, and either grain weight or plumpness, were identified. This study shows that genetic variation for quality in tetraploid emmer wheat can be transferred to synthetic hexaploid wheats and combined with plump grains and high grain weight, to be used for bread wheat breeding.     

Identification of molecular markers linked to the genes for purple grain color in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>)

Pericarp color in wheat is an important trait related to nutrients and health benefits. Identification of molecular markers closely linked to the grain color genes will help utilize pericarp trait in wheat breeding. Genetic studies involving F₁, F₂, and F₃ populations from the cross Jizi 439 (purple grain)/Gao8901 (white grain) showed that the purple grain color was controlled by two genes. By using the bulked segregant analysis (BSA) approach, two DNA pools were established from the dark purple-grain and white-grain plants respectively. Among the 230 pairs of microsatellite primers used in this study, two markers showed polymorphism in DNA pools, parents, F₁ and F₂ populations. Linkage analysis indicated that the two markers Xgwm47 and Xgwm155 were linked with two purple pigment genes. One of the purple pigment genes is located on chromosome 2AS and is 34.7cM away from the marker Xgwm47, whereas another gene is mapped on 3AL with 14.7cM away from marker Xgwm155.     

Genetic diversity in Ethiopian hexaploid and tetraploid wheat germplasm assessed by microsatellite markers

The genetic diversity of a subset of the Ethiopian genebank collection maintained at the IPK Gatersleben was investigated applying 22 wheat microsatellites (WMS). The material consisted of 135 accessions belonging to the species T. aestivum L. (69 accessions), T. aethiopicum Jacubz. (54 accessions) and T. durum Desf. (12 accessions), obtained from different collection missions. In total 286 alleles were detected, ranging from 4 to 26 per WMS. For the three species T. aestivum, T. aethiopicum and T. durum on average 9.9, 7.9 and 7.9 alleles per locus, respectively, were observed. The average PIC values per locus were highly comparable for the three species analysed. Considering the genomes it was shown that the largest numbers of alleles per locus occurred in the B genome (18.4 alleles per locus) compared to A (10.1 alleles per locus) and D (8.2 alleles per locus) genomes. Genetic dissimilarity values between accessions were used to produce a dendrogram. All accessions could be distinguished, clustering in two large groups. Whereas T. aestivum formed a separate cluster, no clear discrimination between the two tetraploid species T. durum and T. aethiopicum was observed.     

Genetic Diversity and Relationships of Wheat Landraces from Oman Investigated with SSR Markers

Little is known about genetic diversity and geographic origin of wheat landraces from Oman, an ancient area of wheat cultivation. The objectives of this study were to investigate the genetic relationships and levels of diversity of six wheat landraces collected in Oman with a set of 30 evenly distributed SSR markers. The total gene diversity, (H_T), conserved in the three durum wheat (Triticum durum desf.) landraces (H_T = 0.46) was higher than in the three bread wheat (Triticum aestivum L.) landraces (H_T = 0.37), which were similar to Turkish and Mexican bread wheat landraces calculated in previous studies. Genetic variation partitioning (G_ST) showed that variation was mainly distributed within rather than among the durum (G_ST = 0.30) and bread wheat (G_ST = 0.19) landraces. Based on modified Rogers’ distance (MRD), the durum and bread wheat landraces were distinct from each other except for a few individuals according to principal coordinate analysis (PCoA). One bread wheat landrace (Greda) was separated into two distinct sub-populations. A joint cluster analysis with other landraces of worldwide origin revealed that Omani bread wheat landraces were different from other landraces. However, two landraces from Pakistan were grouped somewhat closer to Omani landraces indicating a possible, previously unknown relationship. Implications of these results for future wheat landrace collection, evaluation and conservation are discussed.     

Genetic characterization of Lens ervoides from Ethiopia

Summary A single population of the Mediterranean species Lens ervoides was located in Ethiopia and seeds were collected. Based on chromosomal arrangement and isozyme profile the Ethiopian L. ervoides is similar to populations of this species in the Mediterranean region. All hybrids between L. ervoides from Ethiopia and an accession of this species from Israel were dwarf, whereas hybrids between the former and an accession from Algeria were normal. Segregation in F₂ and BC generations indicated that the dwarf habit in lentil is governed by dominant alleles of two complementary genes designated df ₁ and df ₂. The dominant allele of another gene, dfi, inhibits the dwarf phenotype. The evolution of L. ervoides from Ethiopia and its potential as a genetic resource are briefly discussed.     

Differences in CO2 and N2O emission rates following crop residue incorporation with or without field burning: A case study of adzuki bean residue and wheat straw

In the context of sustainable soil-quality management and mitigating global warming, the impacts of incorporating raw or field-burned adzuki bean (Vigna angularis (Willd.) Ohwi & Ohashi) and wheat (Triticum aestivum L.) straw residues on carbon dioxide (CO₂) and nitrous oxide (N₂O) emission rates from soil were assessed in an Andosol field in northern Japan. Losses of carbon (C) and nitrogen (N) in residue biomass during field burning were much greater from adzuki bean residue (98.6% of C and 98.1% of N) than from wheat straw (85.3% and 75.3%, respectively). Although we noted considerable inputs of carbon (499 ± 119 kg C ha^–1) and nitrogen (5.97 ± 0.76 kg N ha^–1) from burned wheat straw into the soil, neither CO₂ nor N₂O emission rates from soil (over 210 d) increased significantly after the incorporation of field-burned wheat straw. Thus, the field-burned wheat straw contained organic carbon fractions that were more resistant to decomposition in soil in comparison with the unburned wheat straw. Our results and previously reported rates of CO₂, methane (CH₄) and N₂O emission during wheat straw burning showed that CO₂-equivalent greenhouse gas emissions under raw residue incorporation were similar to or slightly higher than those under burned residue incorporation when emission rates were assessed during residue burning and after subsequent soil incorporation.     

Agronomic and economic efficiency of ground tire rubber and rubber ash used as zinc fertilizer sources for wheat

The aim of this 2-year field experiment was to investigate agronomic and economic efficiency of ground tire rubber and rubber ash as zinc (Zn) sources for wheat (Triticum aestivum L. cvs. Kavir and Back Cross) compared with a commercial zinc sulfate (ZnSO₄). A similar rate of Zn was used by soil incorporation of 40 kg/ha ZnSO₄, 200 kg/ha waste tire rubber ash, and 1000 kg/ha ground rubber. A no Zn added treatment was also considered as control. All Zn fertilizers significantly increased grain yield of wheat over the control, although effectiveness of rubber ash was greater than the other Zn sources. Wheat plants treated with rubber ash accumulated higher Zn in their grains compared with those treated with ground rubber and ZnSO₄. Tire rubber ash had the highest agronomic and economic efficiency and contained low levels of cadmium (Cd) and lead (Pb). Therefore, it can be used as an economic substitution for commercial ZnSO₄.     

Fortification of Bread Wheat Using Synthesized Zn-Glycine and Zn-Alanine Chelates in Comparison with ZnSO4 in a Calcareous Soil

ABSTRACT

Calcareous soils typically suffer from zinc deficiency and zinc sulfate is incorporated in many cultivated soils. Utilization of ZnSO₄ has some kinds of interaction with soil particles and organic matter. In this study, the efficacy of two znic(Zn)-amino acid chelates (Zn-ACs) i.e., Zn-alanine (Zn-Ala) and Zn-glycine (Zn-Gly) on wheat (Triticum aestivum, cv. N91-8) growth characteristics and zinc concentration in wheat was examined under greenhouse conditions and compared to the a commercial ZnSO₄. Results showed that Zn-Ala and Zn-Gly significantly increased the dry weight and shoot length of wheat in comparison to ZnSO₄ treatment. Soil application of Zn-Amino acid chelates proved to be the most influential source of zinc in increasing wheat growth and yield indices. Number of fertile spikelet and grain yield increased significantly respectively compared to ZnSO₄ treatment. Zn concentration and protein content of wheat grain in Zn-ACs treatment was significantly higher than the ZnSO₄ treatment. Soil application of Zn-ACs caused a significant decrease in the grain phytic acid (PA) concentration and also phytic acid to zinc molar ratio in comparison with ZnSO₄ treatment. According to the results, Zn-ACs could be utilized as a zinc fertilizer source for improving the zinc bioavailability in wheat.     

Rapid Estimation of Potentially Mineralizable N in Early Spring Following Fall Biosolids Applications to Winter Wheat

The amount of potentially mineralizable nitrogen (PMN) in early spring is critical to winter wheat production because maximum nitrogen (N) uptake begins then. We evaluated the Haney-Brinton CO₂-burst method for quantifying PMN in early spring from biosolids fall-applied to soft red winter wheat (Triticum aestivum L.). Anaerobically digested and lime stabilized biosolids were fall-applied at 0, 50 and 100 kg PAN ha^?1 at six locations in the Virginia Coastal Plain in 2013. The Haney-Brinton CO₂-burst method did not provide an accurate estimation of spring PAN for biosolids applied in the fall for no-till winter wheat. The sum of preplant soil inorganic N and PMN of the unamended soil was better related to grain yield than PMN alone. The Haney-Brinton CO₂-burst method is inadequate for use in no-till management but may provide an accurate mid-season estimate of winter wheat yield potential when used in combination with pre-plant soil inorganic N.     

Functional traits associated with nitrogen use efficiency in wheat

The association between functional traits and nitrogen use efficiency (NUE) was investigated to assist the breeding of nitrogen (N) use-efficient bread wheat (Triticum aestivum ssp. aestivum) varieties. This study combined results from a climate chamber experiment involving 41 spring wheat varieties and a field experiment involving six winter and six spring wheat varieties grown with and without the application of mineral N fertiliser. The climate chamber experiment was analysed by partial least squares (PLS) regression, with several predictors and NUE as response, to identify traits related to NUE. Specific hypotheses were then tested in the field experiment. The PLS indicated six traits of particular importance for overall NUE: leaf chlorophyll (SPAD value) of the top leaf at stem elongation, grains ear^?1, ears pot^?1, straw biomass pot^?1, days between emergence and anthesis, and days between emergence and completed senescence. In the field experiment, the SPAD value of flag leaves of winter wheat around anthesis was positively correlated with NUE and total grain N, at both N levels. Fast development was positively correlated with high NUE and N uptake efficiency in spring wheat. Early senescence of the flag leaf was positively correlated with grain N concentration and negatively correlated with grain-specific N efficiency in winter wheat at low N fertilisation levels. The results indicate that high SPAD value of the top leaf might be a candidate trait that could be used in wheat breeding for improved NUE, while genetic variation in senescence could possibly be used to tailor varieties for different end-use quality when grown at low N. More studies are needed to validate these findings in other environments and for other genotypes.     

Effect of assay conditions and field exposure on urease activity associated with cereal residues

Abstract

Urea fertilisers are often applied to soil with cereal residues on the surface. Although the urease properties of soils have been investigated, the urease activities associated with cereal residues have not been thoroughly studied. Two experiments were performed to develop an acceptable urease assay for cereal residues, and to determine the effect of field exposure and concomitant saprophytic colonization on urease levels.

Two acceptable assays were found: 1) incubation in the presence of THAM‐H₂SO₄ buffer (pH 8), toluene, and urea, and 2) incubation only in the presence of urea. In both assays substrate concentration was 0.05 M, incubation temperature was 37°C, incubation length was 2 hours, and urea hydrolysis was determined by ammonium production. Although both assays were highly correlated (r² = 0.992), the buffer method gave higher values. Subsequent investigations illustrated that urease activity associated with cereal residues is dramatically increased by saprophytic colonization after harvest. Freshly‐harvested winter wheat (Triticum aestivum, L.), winter rye (Secale cereale, L.), and spring wheat residues had urease activities (by the buffer method) of 4.3, 6.9, and 3.1 μmol urea g^‐1 h^‐1, respectively. After field exposure of 67–77 days, the urease activities had increased to 69.1, 101.9, and 74.3, respectively. The latter are far higher than literature values for U.S. mineral soils or the dried green leaves of plants.     

Soil quality effects of tillage and residue under rice–wheat cropping on a Vertisol in India

Soil quality in rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping systems is governed primarily by the tillage practices used to fulfill the contrasting soil physical and hydrological requirements of the two crops. The objective of this study was to develop a soil quality index (SQI) based on bulk density (BD), penetration resistance (PR), water stable aggregates (WSA) and soil organic matter (OM) to evaluate this important cropping system on a Vertisol in India. Regression analysis between crop yield and SQI values for various tillage and crop residue management treatments indicated SQI values of 0.84–0.92, 0.88–0.93 and 0.86–0.92 were optimum for rice, wheat and the combined system (rice + wheat), respectively. The maximum yields for rice and wheat were 5806 and 1825 kg ha⁻¹ occurred at SQI values of 0.85 and 0.99, respectively. Using zero tillage (ZT) for wheat had a positive effect on soil quality regardless of the treatments used for rice. Regression analyses to predict sustainability of the various tillage and crop residue treatments showed that as puddling intensity for rice increased, sustainability without returning crop residues decreased from 6 to 1 years. When residue was returned, the time for sustainable productivity increased from 6 to 15 years for direct seeded rice, 5 to 11 years with low-intensity puddling (P₁) and 1 to 8 years for high-intensity (P₂) puddling. For sustainability and productivity, the best practice for this or similar Vertisols in India would be direct seeding of rice with conventional tillage and residues returned.