Mineral bioavailability in grains of Pakistani bread wheat declines from old to current cultivars

Estimating variation in grain mineral concentration and bioavailability in relation to grain yield and the year of cultivar release is important for breeding wheat with increased content of bioavailable minerals. The grain yield and yield components, grain phytate concentration, and concentration and bioavailability of minerals (zinc Zn, iron Fe and calcium Ca) in wheat grains were estimated in 40 wheat cultivars released in Punjab (Pakistan) during the last five decades. Mean grain Zn and Ca concentrations in current-cultivars were significantly lower (≥14%) than in obsolete cultivars released during the Green Revolution (1965–1976). Much of this variation was related to increased grain weight in current-cultivars. There was a positive correlation among minerals (r = 0.39 or higher, n = 40) and minerals with phytate in wheat grains (r = 0.38 or higher, n = 40). The tested cultivars varied widely in grain yield and grain phytate-to-mineral molar ratios (phytate:mineral). Compared to obsolete cultivars, the current-cultivars had a higher phytate:mineral ratio in grains, indicating poor bioavailability of minerals to humans. The study revealed a non-significant relationship between grain yield and phytate:mineral ratios in grains. Therefore, breeding for lower phytate:mineral ratios in wheat grains can ensure increased mineral bioavailability without significant reduction in the yield potential. Future breeding should be focused on developing new genotypes suitable for mineral biofortification and with increased mineral bioavailability in grains.     

Unique gliadin patterns in Chinese winter wheat cultivars

Cultivated Chinese wheat germplasm has been a valuable genetic resource in international plant breeding. Patterns of gliadin among cultivated Chinese accessions are unknown, despite the proven value and potential novelty. The objective of this work was to analyse the diversity within improved Chinese wheat germplasm. The electrophoretic banding patterns of gliadin in winter wheat cultivars and advanced lines were determined by acid-polyacrylamide gel electrophoresis. For 148 leading commercial cultivars and promising advanced lines used in this study, 48 patterns were identified, 29 corresponding to ω -gliadin, nine to γ -gliadin, five to β -gliadin and five to α -gliadin. The most frequent patterns were A6 in ω ; B in γ ; B in β and A in the region of α . A total of 116 band types appeared in the 148 samples: 94 accessions had unique gliadin types, and 22 gliadin, types while not unique, were found in 54 accessions. The gliadin patterns of Chinese wheat cultivars and lines greatly differed from the patterns of wheat lines from other countries. Three patterns, E, J, H, M, N and O in the ω -zone had not been reported previously. Three wheat zones of China, the Northern Winter Wheat Region, the Yellow and Huai Valley River valleys Winter Wheat Region and the Southwestern Winter Wheat Region, showed different frequencies in their gliadin patterns. This information can be used to monitor genetic diversity with Chinese wheat germplasm.     

Suitability of Chinese wheat cultivars for production of northern style Chinese steamed bread

Fifty-six bread wheat cultivars and advanced lines from major Chinese wheat growing regions and 10 Australian cultivars were grown in Anyang located in Yellow and Huai Valleys and Chengdu located in Yangtze region. The genotypes were examined for their suitability to produce northern style Chinese steamed bread (CSB) and used to investigate the association between wheat quality traits and performance of northern style CSB under manual and mechanized processing conditions. Anyang-sown wheat samples showed better grain quality characteristics and CSB quality than the Chengdu-sown materials. These differences were largely due to adverse climatic conditions prevailing in Chengdu that resulted in the deterioration of flour whiteness, Farinograph stability, and starch quality. Therefore, Chengdu was generally unfavorable for producing good quality wheat. However, significant variability among cultivars was observed in Chengdu, and Batavia, Dollar bird, and Tasman from Australia and Jing 411, Xiaoyan6, and Shaan 229 from China showed very good CSB quality under manual conditions, and Hartog, Batavia, Tasman, and Vulcan from Australia, and Jing 411 and Dongfeng 1from China were identified to confer good CSB quality under mechanized conditions. The wide range of CSB quality variations indicates that genetic improvement of CSB quality is possible in both environments. Protein content, gluten strength, and extensibility were positively associated with loaf volume and steamed bread elasticity. The relationship between gluten strength, extensibility, and appearance and stickiness were highly dependent on processing methods, i.e., negatively using a manual method and positively or slightly negatively using a mechanized process. Therefore, wheat quality requirement for CSB depends on CSB processing conditions. Medium protein content and medium-to-strong gluten strength with good extensibility is desirable for mechanized methods, but weak-to-medium gluten type for manual methods. High flour whiteness and RVA peak viscosity was found desirable for CSB quality regardless of the processing method used. Flour whiteness, falling number, and peak viscosity appeared to be more crucial in determining CSB quality in Chengdu, although protein content and Farinograph stability also contributed to appearance, elasticity, and stickiness. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relationship between yield and mineral nutrient concentrations in historical and modern spring wheat cultivars

The diet of approximately three billion people worldwide is nutrient deficient and most of the world’s poorest people are dependent on staple food crops as their primary source of micronutrients. One component of the solution to nutrient deficiencies is collaboration among plant breeders, cereal chemists and nutritionists to produce staple crop cultivars with increased mineral nutrient concentration. Sixty-three historical and modern wheat cultivars were evaluated for grain yield and concentration of calcium, copper, iron, magnesium, manganese, phosphorus, selenium, and zinc. While grain yield has increased over time, the concentrations of all minerals except calcium have decreased. Thus a greater consumption of whole wheat bread from modern cultivars is required to achieve the same percentage of recommended dietary allowance levels contributed by most of the older cultivars. The decrease in mineral concentration over the past 120 years occurs primarily in the soft white wheat market class, whereas in the hard red market class it has remained largely constant over time. This suggests that plant breeders, through intentional selection of low ash content in soft white wheat cultivars, have contributed to the decreased mineral nutrient concentration in modern wheat cultivars. These results contradict the theory that there exists a genetically based, biological trade-off between yield and mineral concentrations. Therefore, using the abundant variation present in wheat cultivars, it should be possible to improve mineral concentrations in modern cultivars without negatively affecting yield.     

Stripe rust resistance and genes in Chinese wheat cultivars and breeding lines

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases on wheat in China. To assess resistance in wheat cultivars and breeding lines in China, 330 leading cultivars and 164 advanced breeding lines were evaluated with stripe rust. In the greenhouse tests, seedlings of the entries were inoculated separately with several Pst pathotypes. In the field tests, the entries were evaluated for stripe rust resistance in Yangling, Shaanxi Province artificially inoculated and in Tianshui, Gansu Province under natural infection of Pst. The oversummering/wintering and spring epidemic zones of resistance genes were postulated using molecular markers for Yr5, Yr9, Yr10, Yr15, Yr17, Yr18, and Yr26, in combination with resistance spectra. Out of the 494 wheat entries, 16 (3.24 %) entries had all-stage resistance (ASR) in all race tests, 99 (20.04 %) had adult-plant resistance (APR), 28 (5.67 %) were considered to have slow-rusting (SR), and 351 (71.05 %) were susceptible to one or more races in both seedling and adult-plant stages. Advanced breeding lines had a higher percentage (37.2 %) of resistant entries (The sum of ASR, APR and SR) than leading cultivars (24.85 %). Among the epidemic regions, southern Gansu had a higher percentage of resistant entries than any other regions. Based on stripe rust reactions and molecular markers, two cultivars were found to possibly have Yr5 while no entries have Yr10 or Yr15. Resistance genes Yr9, Yr17, Yr18, and Yr26 were found in 134 (29.4 %), 45 (9.1 %), 10 (2 %), and 15 (3 %) entries, respectively.     

Are synthetic hexaploids a means of increasing grain element concentrations in wheat?

Element concentration in wheat grains is an important objective of plant breeding programs. For this purpose, synthetic hexaploid lines (Triticum durum ×Aegilops tauschii) have been identified as potential sources of high element concentration in grains. However, it is not known if these lines reach higher element concentrations in grains as the consequence of a dilution effect due to lower grain yield. In addition, most of the studies carried out with these lines did not evaluate above-ground element uptake. The objective of this study was to improve understanding of grain element concentrations as a function of grain yield, element uptake and biomass and element partitioning to grains in synthetic and conventional cultivars of wheat. One experiment with two standard sowing dates was carried out under field conditions. Biomass, grain yield, and macronutrient(Ca, Mg, K, P and S) and micronutrient (Cu,Fe, Mn and Zn) concentrations in grains and vegetative tissues were measured in two cultivars and one synthetic (chosen from ten lines). The synthetic showed higher element concentration in grains, e.g. between 25 and 30% for Fe, Mn and Zn across sowing dates, than cultivars while grain yield was similar or lower, depending on the sowing date. On the contrary, the synthetic showed lower concentration of Cain grains. This line showed also higher uptake of Fe, Mn, K and P than cultivars. The superior grain element concentration of the synthetic line was not only due to a dilution effect but also to a higher uptake efficiency. Therefore, synthetics would bea valuable source of germplasm for increasing element grain concentration, at least in this case for Fe, Mn, K and P. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dough stickiness in rye-derived wheat cultivars

Summary Rye-derived wheat cultivars are being used in many breeding programmes throughout the world in order to achieve improvements in yield and disease resistance. However, the serious quality defect of intense dough stickiness associated with many of these wheat cultivars is limiting the usefulness of their flour in large mechanised bread bakeries. A dough preparation procedure was developed which enabled the dough surface properties of a range of rye-derived wheat cultivars to be assessed on doughs mixed quantitatively to their optimum mixing time. Intense dough stickiness was found in samples of 1AL/1RS and 1DL/1RS translocation lines tested and in all of the 1BL/1RS wheat cultivars examined except the West German cultivar, Disponent. Most of the 1BL/1RS wheat cultivars were derived from the Russian cultivars, Kavkaz, Aurora and Skorospelka 35 and included the CIMMYT-bred cultivars such as the Veery lines (Glennson, Ures, Genaro and Seri) and the Nebraskan cultivar, Siouxland. Based on the results of studying selected 1BL/1RS wheat cultivars in detail, this intense dough stickiness appeared to be independent of growing season, trial location, protein content, mixing tolerance, milling process and extraction rate. In addition pilot bakery trials confirmed that our laboratory testing procedures can be used to detect this intense dough stickiness.     

Adaptation of wheat rusts to the wheat cultivars in former Czechoslovakia

Summary In former Czechoslovakia virulence of rusts attacking wheat was studied since the sixties. Since the same time genes for resistance in the registered cultivars were identified. The role of Berberis and Thalictrum as alternate hosts for stem rust and leaf rust, respectively, was investigated as well. Determined changes of virulence in rust populations could only partially be ascribed to changes of resistance genes in the grown cultivars. Unnecessary genes for virulence had no negative effect on the fitness of the pathogen. All tested samples of aeciospores from barberries attacked rye, not wheat. None of Thalictrum species occurring in the Czech and Slovak Republics was found to host wheat leaf rust. However, the sexual stage of wheat stem rust and wheat leaf rust could be induced on Berberis vulgaris and Thalictrum speciosissimum, respectively. General epidemiological conclusions are drawn from the results and experience of the last 35 years.     

Partial resistance to wheat leaf rust in 18 spring wheat cultivars

Summary Eighteen spring wheat cultivars were tested in microfields and race nurseries for their partial resistance PR to wheat leaf rust under low and high disease pressure respectively. Large differences existed between the 18 cultivars, Skalavatis 56 being the most susceptible and Ponta Grossa 1 being the most resistant cultivar. Of the three epidemic parameters, disease severity (DS) at the time that the susceptible check was severely diseased and area under the transformed disease severity curve (AUTC) and the logistic growth rate (r), AUTC and DS were highly correlated. Both seemed to be reliable estimators of PR but DS should be preferred for economical reasons. The logistic growth rate seemed to be unsuitable as an estimator of partial resistance.High and low disease pressure gave similar cultivar ranking. PR can be screened and selected equally well in race nurseries with low space, low time and low cost input as in microfields with high space, time and cost input.Cultivar differences in development rate had a large impact on the cultivar differences for amount of disease and can therefore greatly bias the estimation of cultivar resistance. The resistance of early cultivars tended to be underestimated whereas the resistance of late cultivars tended to be overestimated. The effect of differences in developmental rate was most pronounced in the flag leaf. It is advisable to avoid the assessment of disease levels on the flag leaf only and to incorporate in the tests several susceptible and resistant checks that cover the range of development rates in the material to be selected, because otherwise selection for resistance will tend to select also for lateness.Regression of the epidemiological parameters on three components of partial resistance revealed that latency period (LP) is an important factor in determining the resistance observed in the field explaining on average 67% of the observed variation. Adding infection frequency (IF) and urediosorus size (US) to the linear model increased the proportion of the observed variation in the field explained by the components to 80%. This result supports the idea that the components of PR inherit independently, at least, in part.     

小麦籽粒钙元素含量的研究进展

提高矿物质营养元素含量正在成为世界主要粮食作物的重要研究方向和育种目标。钙元素是人体必需的矿物质元素,在人类骨骼形成和新陈代谢中发挥着重要作用。全球约35亿人缺钙,缺钙已成为影响人类健康的国际性重大问题。主食是一种最优安全的矿物质元素补充途径。小麦是我国乃至全世界主要粮食作物,是全球35%~40%人口主要的食物来源,是摄入钙的主要来源,是矿物质元素生物强化的重要作物。通过遗传改良方法提高小麦籽粒钙元素含量被认为是解决缺钙最经济、有效、可持续的措施,目前已引起了国内外学者的高度关注。本文综述了近年来小麦籽粒钙元素含量的研究进展,主要包括籽粒钙含量的遗传差异、影响因素以及与相关性状关系、调控机理。此外,我们还提出了将来进行钙营养强化小麦研究的方向,此研究内容为加快通过主粮实现有效补钙、倡导健康营养的膳食模式、满足由“量”的需求向“质”的需求转变的粮食安全、改善国民健康状况以及减少因缺钙造成的经济损失提供了解决方案。     

小麦籽粒钙元素含量的研究进展

Increasing the mineral content is becoming the important research direction and major target for crops breeding in the world. Calcium is an essential mineral element for human health and plays a pivotal role in skeletogenesis and metabolism. It is estimated that about 3.5 billion people was suffered from calcium deficiencies. Calcium deficiency has become a major international problem harming human health. The staple food is an optimal and safe way to mineral supplement. Wheat, one of the main food crops in China and even in the world, is the main source of food for 35%-40% of global population, a main source for human’s calcium intake as well as an important crop of mineral element biofortification. Improving the calcium content in wheat grains through genetic improvement is considered to be the most economical, effective and sustainable measure to solve the calcium deficiency, which has aroused great concern from international scholars. This paper summarized the recent advances in the study of calcium content in wheat grains, mainly including the genetic variation, affecting factors, the relationship with related traits and regulation mechanism of calcium content in grain. Furthermore, we also put forward the direction of future research on calcium-fortified wheat, which provides solutions for accelerating the effective calcium supplementation through staple food, promoting the healthy and nutritious dietary pattern, ensuring the food security to meet the transition from “quantitative” to “qualitative” demands, improving people’s health, and reducing economic losses caused by calcium deficiency.     

Capillary zone electrophoresis analysis of gliadin proteins from Chinese and Yugoslav winter wheat cultivars

Gliadin proteins extracted from fifteen Chinese and Yugoslav winter wheat cultivars were fractionated using a new separation technique – Capillary Zone Electrophoresis (CZE). Different CZE conditions were defined to optimize resolution and reproducibility of gliadin separations. Excellent resolution and high reproducibility of gliadin CZE patterns were obtained by using 47 cm length, 50 μm i.d. capillaries at 15 kV and 30° C in sodium borate buffer system with acetonitrile (ACN) and sodium dodecyl sulfate. By using these CZE conditions, gliadin proteins from each cultivar were easily separated into more than 35 components. This resolution is generally superior to that of one- and two-dimensional electrophoresis and RH-HPLC. Analysis of reproducibility of gliadin CZE patterns from Chinese cultivar ‘Lumai 6’ showed that the average relative standard deviation (RSD) for peak migration times and heights was 0.21% and 4.06%, respectively. Gliadin electrophoregrams of all cultivars studied showed clear qualitative and quantitative differences, including presence or absence of some major peak, migration times and heights of peaks. Specifically, some closely related cultivars that were not differentiable by A-PAGE, were readily differentiated by CZE. In addition, winter wheat cultivars from China and Yugoslavia showed greater differences in gliadin compositions revealed by CZE. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differences between spring wheat cultivars in early growth

Summary Twelve spring wheat cultivars were grown as isolated plants in the field and their pre-anthesis growth was interpreted in terms of plant growth analysis. Relative growth rate (RGR) decreased steadily with time due to a decline of leaf area per unit plant weight (LAR), which could be explained by the reduction of the portion of leaf weight in total plant weight (LWR). Growth per unit leaf area (NAR) and leaf area per unit leaf weight (SLA) changed only little with time.Differences between cultivars for NAR and LAR were of similar magnitude: both 8% when measured by the genetic coefficient of variation. Because both quantities were negatively correlated, the genetic variation of RGR was only 5%. Genetic variation for LWR and SLA were also of similar size, both about 4%. Estimates of genetic variances and covariances based on cultivar means appeared to be biased strongly when the error variation of the means was neglected.Special attention is paid to the methodology of plant growth analysis.     

Virulence of wheat yellow rust races and resistance genes of wheat cultivars in Ecuador

Virulence factors of the yellow rust, Puccinia striiformis, populations in bread wheat were studied in Ecuador between 1973 and 2004. The number of virulence factors has increased markedly from very few in the early seventies to 16 at the end of the 90s. Isolates belonging to race 0E0 seem to be the ancestor of a rapid virulence evolution of yellow rust in Ecuador. This evolution can be explained by a single step mutation pattern. Virulence to the resistance genes Yr1, Yr2, Yr2+, Yr3V, Yr3ND, Yr4+, Yr6, Yr6+, Yr7, Yr7+, Yr9, Yr9+, Yr11, Yr12, Yr18, Yr24, Yr26 and those in the cultivars Carstens V (YrCV) Strubes Dickkopf (YrSD), Suwon92/Omar (YrSU), Spaldings Prolific (YrSP), Anza (YrA+) and Selkirk (YrSK). was identified. Virulence to Yr5, Yr8, Yr10, and Yr15 was not found. Postulation of resistance genes at the seedling stage of 14 Ecuadorian wheat cultivars indicated that these cultivars carry alone or in combinations the resistance factors Yr1, Yr2, Yr3, Yr6, Yr9 and/or other undesignated resistance factors. Yellow rust evolution in Ecuador has been associated with deployment of these resistance genes. None of these deployed Yr resistance genes are effective to the present yellow rust population in Ecuador.     

Adaptation of semidwarf wheat cultivars to rainfed conditions

Summary With a view to determining the comparative adaptation of semidwarf wheats to rainfed conditions, adaptation analyses were carried out on grain yield data of the 6th and 7th International Spring Wheat Yield Nurseries of the International Maize and Wheat Improvement Centre. Sites were chosen which had not received irrigation: across a combined total of 44 such sites, yield variation was closely related to growing seasonal rainfall. Using these sites, yields of thirty-three common cultivars. Norin 10-derived semidwarf cultivars plus tall ones, were regressed against site mean yield to give a regression slope (b) and deviations from the regression (s_d ²) for each cultivar.Semidwarf cultivars generally showed higher mean yields and larger regression slopes (b > 0.9) than tall cultivars from lower latitudes. Tall cultivars from higher latitudes showed the lowest mean yields and the lowest b values (< 0.7). No consistent trends in s_d ² were evident. Despite the greater regression slopes of semidwarf wheats, the best yields under all but the lowest yielding (driest) conditions were given by certain semidwarf cultivars; these had high mean yields and b values close to 1.0 (for example Tobari 66, Inia 66, Pato ArGentino and Sonalika). In contrast other semiwdarfs (notably Chenab 70) of similar mean yield, plant height and phenology, were not well adapted to the drier conditions as indicated by b values close to 1.3. The usefulness of the regression technique and the implications of these results for selection of semidwarf wheats adapted to drier conditions are discussed.Joint contribution from the Department of Agronomy, University of Sydney, N.S.W. 2006, Australia and the International Maize and Wheat Improvement Centre (CIMMYT), Londres 40. Mexico 6, D.F.     

南阳特殊粒色小麦品种选育

为了强化小麦的营养品质,南阳市农科所利用常规育种、诱变育种、航天育种及远缘杂交等方法选育出的特殊粒色小麦新系列品系,在产量、抗性、营养品质等方面具有明显优势,可以加工成纯天然无公害传统食品和功能食品,满足人们崇尚天然、追求绿色环保,对营养、保健的要求。     

Allelic changes in bread wheat cultivars were associated with long-term wheat trait improvements

Genetic impacts under selective breeding of agricultural crops have been frequently investigated with molecular tools, but inadequate attention has been paid to assess genetic changes under long-term genetic improvement of plant traits. Here we analyzed allelic changes with respect to wheat trait improvement in 78 Canadian hard red spring wheat cultivars released from 1845 to 2004 and screened with 370 mapped SSR markers. The improvements in quality, maturity, yield, disease, stem rust, leaf rust, sawfly resistance, and agronomy were considered. A total of 154 (out of 370) loci with significant allelic changes across 21 chromosomes were detected in the 78 wheat cultivars separated into improved versus non-improved groups for eight traits. The number of significant loci for improving a trait ranged from four for quality to 68 for yield and averaged 35. Many more loci with significant allelic reduction for improving a trait were detected than those with significant allelic increase. Selection for early maturity introduced more alleles, but improving the other traits purged more alleles. Significantly lower numbers of unique alleles were found in the cultivars with improved traits. The distributions of unique allele counts also varied greatly across the 21 chromosomes with respect to trait improvement. Significant SSR variation between two cultivar groups was observed for improvement in seven traits, but not in stem rust. The proportional SSR variation residing between two groups ranged from 0.014 to 0.118. The proportional SSR variations within the improved cultivar groups consistently were much lower than those within the non-improved groups. These findings clearly demonstrate the association between allelic changes and wheat trait improvements and are useful for understanding the genetic modification of the wheat genome by long-term wheat breeding.     

Gliadin allele composition of Yugoslav winter wheat cultivars

Summary The complete gliadin allele composition of 57 Yugoslav common winter wheat cultivars was studied. Large differences were found in gliadin genotypes among cultivars bred at different Yugoslav breeding centres as well as between early and recent wheats bred in the Novi Sad breeding centre. Yugoslav wheats have limited variation in gliadin alleles, of which Gli-A1a, Gli-B1b, Gli-B1l, Gli-D1b, Gli-A2e, Gli-B2b, Gli-D2a are shown to be the most frequent. Examples of favoured alleles to new cultivars are described. 40% of the studied wheat cultivars have natural biotypes differing in gliadin allele composition. The frequency of cultivars with the biotypes differs greatly among breeding centres.     

Resistance to leaf rust in cultivars of bread wheat and durum wheat grown in Spain

A set of bread wheat and durum wheat cultivars adapted to Spanish conditions was tested for resistance against leaf rust caused by different pathotypes of Puccinia triticina in field trials and in growth chamber studies. Lower levels of resistance were found in durum wheat than in bread wheat. The most frequent Lr genes found in bread wheat were Lr1, Lr10, Lr13, Lr20, Lr26 and Lr28. In durum wheat, additional resistance genes that differed from the known Lr genes were identified. The level of partial resistance to leaf rust was in general low, although significant levels were identified in some bread wheat and durum wheat cultivars.