Inheritance of Carbon Isotope Discrimination in Bread Wheat (Triticum Aestivum L.)

Summary Reliable selection of families with increased grain yield is difficult in breeding programs targeting water-limited environments. Carbon isotope discrimination (Δ) is negatively correlated with transpiration efficiency, and low Δ is being used for indirect selection of high wheat yield in rainfed environments. Yet little is known of genetic control and opportunities for improving selection efficiency of Δ in wheat. Half-diallel and generation means mating designs were undertaken to provide estimates of the size and nature of gene action for Δ in a range of wheat genotypes varying for this trait. Significant (P < 0.01) differences were observed for leaf tissue Δ among parents (19.3 to 20.7‰) and F₁ progeny (19.4 to 20.9‰) in the half-diallel. General (GCA) and specific combining ability (SCA) effects were significant (P < 0.05), while Baker's GCA/SCA variance ratio of 0.89 was close to unity, indicating largely additive gene effects. GCA effects varied from −0.38 to + 0.34‰ for low and high Δ genotypes `Quarrion' and `Gutha', respectively. GCA effects and parental means were strongly correlated (r = 0.95, P < 0.01) while directional dominance and epistasis contributed to small, non-additive gene action for Δ. Smaller Δ in F₁ progeny was associated with accumulation of recessive alleles from the low Δ parent. Narrow-sense heritability was high (0.86) on a single-plant basis. Generation means analysis was undertaken on crosses between low Δ genotype Quarrion and two higher Δ genotypes `Genaro M81' and `Hartog'. The F₁, F₂ and midparent means were not statistically (P > 0.05) different, whereas backcrossing significantly changed Δ toward the mean of the recurrent parent. Gene action was largely additive with evidence for additive × additive epistasis in one cross. Narrow-sense heritabilities were moderate in size (0.29 to 0.43) on a single-plant basis. Genetic gain for Δ in wheat should be readily achieved in selection among inbred or partially inbred families during the later stages of population development.     

普通小麦及近缘粗山羊草α-醇溶蛋白基因的克降、定位与进化分析

通过特异PCR引物设计,从普通小麦品种(豫麦34和烟农19)和粗山羊草(T9、T197、T48、T176和T17)中扩增、克隆了7个新的α-醇溶蛋白基因,分别命名为Gli-YM34、Gli-YN19、Gli-T9、Gli-T197、Gli-T48、Gli-T176和Gli-T17,基因序列长度为846~891 bp,编码282~297个氨基酸残基,都具有α-醇溶蛋白的典型结构特点。其中Gli-YM34和Gli-YN19基因推导的醇溶蛋白都含有一个额外的半胱氨酸残基,可能对面筋品质有正向作用。根据α-醇溶蛋白氨基酸序列所具有的4种T细胞抗原表位和多聚谷氨酰胺重复区的平均长度以及中国春缺体四体分析,将来自普通小麦品种的Gli-YM34和Gli-YN19基因定位在6D染色体上的Gli-D2位点,而且Gli-YM34和Gli-YN19与来自粗山羊草的α-醇溶蛋白基因具有很高的序列相似性,进一步证明粗山羊草是普通小麦D基因组的供体。在克隆的4个典型α-醇溶蛋白基因中检测到21个SNP和1个9 bp的缺失。系统进化分析表明,α-醇溶蛋白基因与低分子量谷蛋白亚基基因关系较近,在大约43.69百万年时分化,与ω-醇溶蛋白和HMW-GS基因亲缘关系较远,它们的分化时间大约为79.39百万年。     

The Role of Phenolics and Peroxidase in Resistance to Alternaria triticina in Bread Wheat (Triticum aestivum L.)

Total phenolic content in eight diverse wheat lines showed that PF-70354 YACO'S' had the highest (802.90 ± 1.35 μg g⁻¹ fresh weight) and Agra Local possessed the lowest amount (684.72 ± 5.28 μg g⁻¹ fresh weight). However, for further experiments two lines namely, ACC-8226 and MP-845, with contrasting disease scores under field trials were assessed. Pre-infectional levels of total phenolics and peroxidase activity were higher in ACC-8226 than in MP-845. Furthermore, the amount of phenolics and peroxidase activity in each case increased after inoculation. The post-infectional levels of phenolics and peroxidase were again higher in ACC-8226 than in MP-845. The peroxidase activity decreased with age in both the varieties, with very little peroxidase activity after 35th day. However, the amount of phenolics started to decrease with the progress of disease and age in MP-845, whereas in ACC-8226 an elevated level of it was maintained. Our findings not only support that ACC-8226 is the resistant and MP-845 is the susceptible variety but also provide important biochemical parameters for plant breeders to authentically identify potential breeding material and plan effective breeding strategies using these tools.     

Cytology and Fertility of Hybrids and Amphiploids between Aegilops caudata L. ×Triticum turgidum (L.) Thell

Interspecific hybrids and amphiploids between Aegilops caudata L. (2n = 2x = 14, CC) and Triticum turgidum (L.) Thell. conv. durum Desf M. K. (2n = 4x = 28, AABB) were produced. Such hybrids can be used to introduce desirable traits such as disease resistance into cultivated durum wheats. One of the durum parents was a ph I mutation of the cv. ‘Cappelli’ used for testing the possibility of direct introduction of alien variation into cultivated species. The amphiploids were obtained both through colchicine chromosome doubling and as natural non-reductional mciosis products. In both hybrids and amphiploids, meiotic pairing and fertility were studied. Hybrids showed varying degrees of pairing and, in addition to the one involving the ph 1 mutant, one high pairing hybrid was found (Ae. caudata× cv. ‘Capinera’). Cytological examination of microsporogenesis in amphiploids revealed a high frequency of bivalent formation. Fertility proved to be a very variable character since some of the amphiploids were almost completely sterile. The use of amphiploids in breeding programmes is discussed in relation to meiotic and fertility data.     

Physiological and Yield Responses of Faba bean (Vicia faba L.) to Drought Stress in Managed and Open Field Environments

Water scarcity is threatening the sustainability of global food grain production systems. Devising management strategies and identification of crop species and genotypes are direly required to meet the global food demands with limited supply. This study, consisted of two independent experiments, was conducted to compare faba bean (Vicia faba L.) genotypes Giza Blanka, Goff‐1, Hassawi‐1, Hassawi‐2 and Gazira‐2 in terms of physiological attributes and yield under water‐limited environments. In first experiment, conducted in a growth chamber, osmotic stress of ?0.78, ?0.96, ?1.19 and ?1.65 MPa was induced using polyethylene glycol for 4 weeks. In second experiment, conducted in open field for two consecutive growing seasons, water deficit treatments were applied 3 weeks after sowing. In this experiment, irrigation was applied when an amount of evaporated water from the ‘class A pan’ evaporation reached 50 mm (well watered), 100 mm (moderate drought) and 150 mm (severe drought). Water deficit, applied in terms of osmotic stress or drought, reduced the root and shoot length, related leaf water contents, total chlorophyll contents and efficiency of photosystem‐II, plant height, grain yield and related attributes in faba bean; increased the leaf free proline, leaf soluble proteins and malondialdehyde contents, and triggered the maturity in tested faba bean genotypes. However, substantial genetic variation was observed in the tested genotypes in this regard. For instance, root length of genotypes Giza Blanka and Hassawi‐2 decreased gradually, whereas it was increased in genotypes Goff‐1, Hassawi‐1 and Gazira‐2 with increase in the level of osmotic stress. Genotypes Gazira‐2 and Hassawi‐2 had better relative leaf water contents, leaf free proline and soluble proteins under water deficit conditions; however, these were minimum in genotype Giza Blanka. Better accumulation of leaf free proline, soluble proteins, and maintenance of chlorophyll contents, tissue water, efficiency of photosystem‐II and grain weight in water‐limited conditions helped some genotypes like Hassawi‐2 to yield better. Future breeding programs for developing new faba bean genotypes for water‐limited environments may consider these traits.     

Deep Roots are Pivotal for Regulating Post‐Anthesis Leaf Senescence in Wheat (Triticum aestivum L.)

Root activity plays a dominant role in grain filling in cereal crops. However, the importance of deep roots for regulating post‐anthesis leaf senescence is not clearly understood in wheat (Triticum aestivum L.). In this study, we used ³²P tracing to estimate the difference in wheat root activity at soil depths of 30 and 70 cm and the root restriction method to investigate the effects of vertical distribution of deep roots on leaf senescence, with non‐restricted plants as controls. Recovery of radioactive ³²P indicated that deep roots had significantly higher activity than upper roots in wheat. Root restriction at a soil depth of 50 cm caused significant decreases in the activities of superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6) and ascorbate peroxidase (EC 1.11.1.11) at 16 days after anthesis and thereafter resulting in an increase in malondialdehyde. As a result, chlorophyll levels and net photosynthesis decreased. Ultimately, the root‐restricted wheat produced a significantly lower grain yield than the non‐restricted controls. These data suggest that deep roots are pivotal for regulating plant senescence, duration of grain filling, and yield formation.     

Yield Stability of Winter Wheat (Triticum sp.) Cultivars and Lines

The purpose of this study was to compare responsiveness to environment as well as the stability of newly developed promising lines with traditional commercial cultivars. Subject research was conducted in Ankara between 1983-1989 on common and durum wheat cultivars and lines. Regression coefficient (b) was used as the criterion of genotypes' responsiveness to environment whereas deviation from regression (S²d) and coefficient of determination (r²) were used as stability parameters. Each experiment year was regarded as an environment and yield average of each year was used as the environmental index.
In consequence of the research, it was determined that new varieties with high yield, adaptable to diverse environments could be developed by means of hybridizations between parents having different genetic characteristics which were provided from diverse ecological regions.     

Genetic control of boron efficiency in wheat (Triticum aestivum L.)

The genetic control of boron (B) efficiencyin wheat (Triticum aestivum L.) wasstudied for three genotypes representing Binefficient (I, Bonza), moderately Binefficient (MI, SW 41) and B efficient (E,Fang 60) categories. Boron efficiency wasexpressed as a partially dominant characterbut the phenotypes of F₁ hybrids,relative to parents, indicated geneticcontrol varying from recessive to additiveto completely dominant with different crosscombinations and B levels. Major geneswere identified from the evaluation ofF₂-derived F₃ populations derivedfrom intercrosses between the threeparents. Monogenic segregation was foundin Bonza × SW 41 and SW 41 × Fang 60crosses and digenic segregation resultedin Bonza × Fang 60. Among thethree wheat genotypes with widely differentB efficiency, genetic variation forresponse to B could be accounted for by twogenes, Bo _d 1 and Bo _d 2.     

Intraspecific Variation in Nitrogen Uptake and Nitrogen Utilization Efficiency in Wheat (Triticum aestivum L.)

Twenty wheat ( Triticum aestivum L.) varieties differing in plant height were grown in soil culture and evaluated for differences in nitrogen uptake and nitrogen utilization efficiency (NUE) at limited (40 kg N ha⁻¹) and normal (120 kg N ha⁻¹) nitrogen supply. Nitrogen uptake showed 1.4- and 1.5-fold varietal variation at harvest for limited and normal N supply, respectively. NUE for dry matter production (NE1) exhibited 1.28- and 1.38-fold genotypic variation while NUE for grain production (NE2) varied by 1.25- and 1.21-fold at limited and normal N supply, respectively. Tall varieties were found to have higher N uptake and NUE for dry matter production, while dwarf cultivars had greater NUE for grain production. Nitrogen uptake was found to be strongly positively associated with dry matter production (r=0.85 and r =0.77 at limited and normal N supply, respectively), indicating an important effect of growth rate on N uptake. NUE for biomass production, as well as for grain production, was reduced as the supply of nitrogen was increased.     

Productivity and Sustainability of Cotton (Gossypium hirsutum L.)–Wheat (Triticum aestivum L.) Cropping System as Influenced by Prilled Urea, Farmyard Manure and Azotobacter

Field experiments were conducted at Indian Agricultural Research Institute, New Delhi, during 2001–2002 and 2002–2003, to study the effect of inorganic, organic and Azotobacter combined sources of N on cotton (Gossypium hirsutum L.) and their residual effect on succeeding wheat (Triticum aestivum L.) crop. The results indicated considerable increase in yield attributes and mean seed cotton yield (2.33 Mg ha^?1) with the combined application of 30 kg N and farmyard manure (FYM) at 12 Mg ha^?1 along with Azotobacter (M₄). The treatment in cotton that included FYM, especially when fertilizer N was also applied could either improve or maintain the soil fertility status in terms of available N, P and K. Distinct increase in yield attributes and grain yield of wheat was observed with the residual effect of integrated application of 30 kg N ha^?1 + FYM at 12 Mg ha^?1 + Azotobacter. Direct application of 120 kg N ha^?1 resulted 67.4 and 17.7 % increase in mean grain yield of wheat over no N and 60 kg N ha^?1, respectively. Integrated application of organic and inorganic fertilizer is therefore, recommended for higher productivity and sustainability of the cotton–wheat system.     

Agronomic and Physiological Study of Cold and Flooding Tolerance of Spelt (Triticum spelta L.) and Wheat (Triticum aestivum L.)

Flooding of soil occurs all over the world in areas of crop production. The resulting lack of available oxygen in the soil can hinder the establishment of field crops such as wheat ( Triticum aestivum L.) and thus lead to a decrease in yield. The current study compares the tolerance of spelt ( Triticum spelta L.) and wheat to wet and cold stress during germination and early growth. Two specific traits seem to be related to the superior early flooding tolerance of spelt: (1) fast growth of the coleoptile, which reaches the soil surface rapidly, thus reducing the time span of hypoxia sensitivity, independent of temperatures between 10 and 20 °C; (2) the improved physiological adaptation for coleoptile growth under hypoxia is probably due to lower oxygen consumption between germination and emergence. Because of this high level of flooding tolerance, spelt would also be a good source for breeding for stress tolerance in wheat. These findings will help to detect quantitative trait loci (QTL) for characters such as growth rate, flooding tolerance and oxygen consumption in future studies. A marker-assisted introgression of spelt into wheat is necessary to avoid combination with undesirable agronomic traits of spelt.     

Comparative Responses of Wheat (Triticum aestivum L.) Cultivars to Salinity at the Seedling Stage

Seedling growth and ion content of Pakistani bread wheat cultivars was assessed in solution culture in the absence and presence of NaCl (100 and 200 mol m⁻³) to determine whether seedling traits could be used in breeding programs for salt-tolerance. Growth was recorded as seedling fresh weight, and the shoot and leaves analysed for major inorganic ions. Plants subjected to salt stress excluded Na⁺ and Cl⁻ ions from the shoot to varying extents. Exclusion preferentially maintained lower Na⁺ and Cl⁻ levels in the apical tissue, as the leaf to leaf gradient in Na⁺ and Cl⁻ became steeper as the external salinity increased, although there were significant differences between cultivars. Correlation analysis on individual plants indicated that excluding Na⁺ at low salinity, and Na⁺ and Cl⁻ at high salinity, were correlated significantly with growth performance, although it was clear that other factors were also involved. The relationship of tolerance to ion exclusion was stronger when the data were examined on an individual plant basis than when related to pooled cultivar data or to the cultivar rank order derived from field trials, probably due to large variations in Na⁺, and to a lesser extent, Cl⁻ transport in supposedly homozygous cultivars.     

Morphological Traits Associated with Lodging Resistance of Spring Wheat (Triticum aestivum L.)

Throughout the world, lodging in cereals causes great losses in yield each year. A two year field study was conducted to determine the relationship of morphological traits to lodging resistance in spring wheat ( Triticum aestivum L.) breeding lines and to find easily measurable traits related to lodging resistance. A set of 15 breeding lines, representing a wide range of combinations of plant height and lodging resistance, was evaluated.
During the first year, 29 morphological traits were measured at two growth stages and correlated with the lodging score. Higher correlations were found for traits measured at anthesis (DC 65) than for traits measured at maturity (DC 92); most of the fresh weight traits correlated better to lodging resistance than did the corresponding dry matter parameters. During the second year the six traits of plant height, stem length, stem diameter, ear weight, stem weight and stem weight per cm were measured at anthesis and correlated with the lodging score.
From the pooled data of four experiments, significant correlations between the lodging score and single morphological traits were found for stem diameter and stem weight per cm. Thicker stems and heavier stems (mg per cm) were indicative for better lodging resistance. Stem diameter and stem weight cm⁻¹ explained 48.5 % and 49.7 %, respectively, of the phenotypic variation in lodging resistance. Multiple linear regression equations indicated that 77.2 % of the variation in lodging resistance was based on stem weight cm⁻¹ and on the weight of the ear.     

低温积累与光周期对小麦发育特性调控的分子机理研究进展

温度和光照是影响小麦发育的主要因素,不但决定了小麦生态型的区域分布,也通过调控小麦的发育阶段、器官建成、穗分化起始及进程等因素而影响小麦的产量。本文介绍了低温春化和光周期对小麦发育特性影响的分子基础,对其调控机制及互作模式研究进展进行了综述。     

施氮水平对冬小麦旗叶光合特性的调控效应

在大田试验条件下,对大穗型小麦品种兰考矮早八旗叶光合特性及氮素调控效应进行了研究。结果表明,旗叶叶绿素含量随籽粒灌浆进程呈逐渐降低的趋势。PSⅡ潜在活性、PSⅡ光化学的最大效率、荧光光化学猝灭系数等随生育进程呈先升高后降低的变化趋势,且均在开花期达到最大值,之后逐渐下降;荧光非光化学猝灭系数则在成熟期达到最大值。氮肥对旗叶光合特性有一定的调控效应,Chl,F_v/F_o,F_v/F_m及qP均随施氮水平的增加呈增加的趋势,其中Chl和F_v/F_o以N3（180 kg hm^-2）处理最大,F_v/F_m和qP（除孕穗期外）以N4（360 kg hm^-2）处理最大;qN则随施氮水平增加呈降低的趋势,以N4处理最小。适宜的施氮量（180 kg hm^-2）改善了兰考矮早八的光合色素性状,提高PSⅡ潜在活性及PSⅡ光化学的最大效率,减少荧光非光化学猝灭系数,从而有助于籽粒产量的提高。     

小麦抗白粉病基因聚合体DH材料的分子标记鉴定

小麦白粉病是由Blumeria graminis f.sp. tritici引起的世界性病害,利用分子标记辅助选择进行抗白粉病基因累加,可延长品种抗病性寿命,有利于提高育种效率。本研究利用Pm4b的STS-PCR标记,Pm13和PmV的SCAR-PCR标记,以及与Pm12共分离的同功酶标记（α-Amy-1）对来自小麦与玉米杂交产生的双单倍体材料的7个株系和9个穗系的4     

Nitrogen Loss and Wheat (Triticum aestivum L.) Yields in Response to Zero-tillage and Sowing Time in a Semi-arid Tropical Environment

A net‐house experiment was conducted at the Indian Agricultural Research Institute, New Delhi, to study the effect of simulated zero‐tillage on the N loss through ammonia (NH₃) volatilization, and flux of inorganic N after the sowing of wheat and urea‐N application on two different dates. In addition, the effects of soil perturbation through simulated tillage vs. zero‐tillage, and of sowing time on the wheat yields (above and below‐ground) and N use were examined. Results showed significantly (P < 0.05) higher NH₃ volatilization loss of N in zero‐tillage than the tillage treatments, but no significant difference between early (18 November) or later (8 December) sowing wheat on such losses. Inorganic N, mostly NH‐N, was significantly higher in undisturbed soil on day 5, whereas on day 15, NO‐N was significantly higher in disturbed soil than the undisturbed (zero‐tilled) soil. There was little difference in NH‐N or NO‐N contents in soils between two dates of sowing. Plant parameters showed no significant (P > 0.05) differences among the treatments in terms of height, spike length, or number of grains per spike, grain and straw yields and root biomass and harvest index. Moreover, there were no significant differences among the treatments when N uptakes were compared. Our results thus suggest that after flooded rice, wheat can be grown successfully on zero‐tilled soils even when adopting sowing dates till early December. More N loss through NH₃ volatilization in zero‐tilled than tilled soils may not affect growth and yields of wheat, but needs to be reduced for N conservation and environmental reasons.