Assessment of genetic diversity in bread wheat genotypes for tolerance to drought using AFLPs and agronomic traits

Moisture stress greatly limits the productivity of wheat in many wheat-growing regions of the world. Knowledge of the degree of genetic diversity among parental materials for key selection traits will facilitate the development of high yielding, stress tolerant wheat cultivars. The objectives of this study were to: (i) use amplified fragment length polymorphisms (AFLPs) to assess genetic diversity among bread wheat lines and cultivars with different responses to drought stress in two distinct environments and, (ii) compare genetic diversity estimated by AFLPs with diversity evaluated on agronomic performance under drought stress. Twenty-eight genotypes, 14 from Iran and 14 developed or obtained by CIMMYT, were evaluated in the study. Phenotypic data on the 14 Iranian lines were obtained in Iran, and data on the 14 CIMMYT lines were collected in Mexico. Ten AFLP primer pairs detected 335 polymorphic bands among the 28 cultivars. At the 5th fusion level of the resulting dendrogram, 6 genotype clusters were identified. Thirteen of the 14 CIMMYT genotypes grouped into one cluster while 4 of the remaining groups were comprised only of Iranian genotypes. When the agronomic performance of the Iranian materials was compared with the AFLP diversity analysis, 5 of the 6 drought susceptible genotypes clustered together in the agronomic dendrogram, and were located in the same cluster in the AFLP dendrogram. However, the drought tolerant Iranian materials did not show the same degree of relationship. The CIMMYT materials did not demonstrate a significant association between agronomic performance and genetic diversity determined using AFLPs. Clearly these data show that there are genotypes with similar agronomic performance and different genetic constitutions in this study that can be combined in a breeding program to potentially improve tolerance to drought stress.     

应用ISSR分子标记分析裸大麦的遗传多样性

为研究裸大麦的遗传多样性,利用筛选得到的16条ISSR引物对收集的国内外102份裸大麦材料和1份皮大麦材料进行了遗传多样性分析,并分析了裸大麦地理分布与遗传多样性的关系。结果表明,16条ISSR引物共扩增出133条条带,大小在100~2000bp。不同引物扩增的条带数在3?15条,平均每条引物扩增出8.31条,多态性条带为113条,多态性的平均百分率为85.1%,103份材料的遗传相似系数(GS)在0.2817~6,提示裸大麦的遗传多样性较高。利用NTsys 2.1软件进行聚类分析,103份材料分为四大类,第一大类只分布在中国青海,第二大类分布在亚洲、欧洲、北美洲和非洲,第三大类分布在亚洲、北美洲和南美洲,第四大类仅分布在亚洲和北美洲,表明亚洲,尤其中国地区具有较高的遗传多样性。裸大麦的遗传多样性与其地理来源的相关性,为进一步研究裸大麦尤其是青稞起源提供了参考。     

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.     

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.     

Development of common bean (Phaseolus vulgaris L.) lines resistant to the bean pod weevil,Apion godmani Wagner,in Central America

Summary The larva of the bean pod weevil (BPW), Apion godmani Wagner (Coleoptera: Curculionidae), causes serious yield losses in common bean (Phaseolus vulgaris L.) in Mexico and Central America, by consuming the seed as it develops in the immature pod. Resistance to the BPW was identified in bean germplasm of highland Mexican origin, and these sources of resistance were incorporated into a pedigree breeding program to recover locally adapted lines resistant to Bean Common Mosaic Virus and BPW, with commercial grain for Guatemala, Honduras and El Salvador. These lines yielded as well as or better than local cultivars in the absence of the insect, and better than local cultivars when the BPW was present. Resistance appeared to be governed by several genes, and was stable across geographic areas, seasons and planting systems.     

Phenotypic variation in boron-toxicity tolerance at seedling stage in durum wheat (Triticum durum)

Summary Nineteen durum wheat landraces, cultivars or advanced lines of different origins in West Asia and North Africa (WANA), and three barley and two bread wheat varieties were evaluated for their boron (B) toxicity tolerance. Seedlings were grown at five levels of soluble soil B in a plastic house under controlled temperatures. Significant differences existed between the durum wheat entries in days-to-symptom appearance and foliar symptom score. Under the highest soil B treatment, large differences existed between entries for dry weight per plant (P<0.05) but differences were non-significant for shoot B concentrations. Days-to-symptom appearance was highly correlated with symptom score, which was not correlated with shoot B concentrations. Boron toxicity symptom scores of the durum wheat entries ranged from the sensitive barley check to the moderately sensitive bread wheat check. As expected, days-to-symptom appearance decreased and symptom severity increased as the soil B concentrations increased.The result of this study supported the preliminary finding that small, though statistically significant, variation in B toxicity symptom scores exist in durum wheat. The higher CV of symptom scores found here was mainly due to one sensitive entry, Cakmak. If Cakmak was excluded from the analysis, the CV would be reduced by half, to 10%. Durum wheat genotypes which are more tolerant to B toxicity should be sought. Based on the results of this study, and of soil surveys and information collected in WANA, germplasm collected from Algeria, Iraq, Libya, Syria, and the Anatolian Plateau of Turkey should be screened first.Abbreviations B boron - WANA West Asia and North Africa     

Geographical variation of β-amylase thermostability among varieties of barley (Hordeum vulgare) and β-amylase deficiency

Investigations onto the thermostability of β-amylase in 274 varieties of barley (Hordeum vulgare L.) indicated that all varieties except one were distributed into three types of high (type A), intermediate (type B), and low (type C) thermostability, respectively. One variety (TB29) from China showed no β-amylase activity. Geographical variation was observed in the thermostability of β-amylase. Type C varieties were not observed in East Asia (Japan, the Korean Peninsula, China and Nepal), although 36 out of 37 varieties in Ethiopia were type C. Most of the varieties were Type A in Japan, the Korean Peninsula and China, whereas the frequency of type A and type B were nearly equal in Nepal. Varieties in the other five areas (North America, North Africa, Southwest Asia, Turkey and Europe) consisted of types A, B and C. These results support the fact that East Asian cultivars are genetically different from those of the western regions, as previously reported.     

Relationship between cold resistance,heading traits and ear primordia development of wheat cultivars

Summary For breeding early heading wheat cultivars with resistance to frost damage which are well adapted to dry areas of West Asia and North Africa, the relationships between winter hardiness, ear primordia development and heading traits, i.e. veernalization requirement, photoperiodic response and narrow-sense earliness, were assessed using a total of 30 genotypes of wheat (Triticum aestivum L.) grown in an experiment in Syria. The results of artificial freezing tests indicated that cultivars with good winter hardiness were to be found only in the winter wheat cultivars which required 50 or more days of vernalization treatment. These winter wheat cultivars did not initiate internode elongation without vernalization even at 95 days after planting. Thus their ear primordia were still underground and were protected from frost injury at this stage. Photoperiodic response and narrow-sense earliness were not associated with winter hardiness and earliness of internode elongation, but were related to the number of days to heading after planting. This indicated the possibility for breeding early heading cultivars with winter hardiness and tiller frost avoidance by combining high vernalization requirement, short narrow-sense earliness and neutral response to photoperiod.     

Adaptability and phenotypic stability of Lolium perenne L. cultivars of diverse origin grown at the margin of the species distribution

In northern countries, Lolium perenne L. generally survives poorly when grown inland and north of 60°N because of extensive winter damage. With the projected future climate change, it could become a promising option for improving production efficiency of the agricultural sector in these regions. Here, we compare the biomass production potential of cultivars of diverse origin across five locations stretching from Estonia to Iceland over a period of three harvest years, and their freezing tolerance under artificial conditions. The aim was to relate the observed pattern of adaptation to the geographic origin of the cultivars and their response to prevailing agroclimatic conditions. Significant interactions were observed between cultivars and test environments (locations × years), and significant interactions between cultivars and years were detected at four of the five locations. Models of joint regression, additive main effects and multiplicative interaction (AMMI) and factorial regression using several agroclimatic indices showed that cultivars developed in northern countries showed greater yield potential across the test environments and were, thus, generally better adapted than cultivars from Central Europe. Diploid cultivars were more frost tolerant than tetraploid cultivars giving them an advantage in locations which were characterized by low temperatures during the hardening period in autumn and mild and rainy winters, such as at the Icelandic location. Only a few cultivars showed general adaptability to the environmental conditions at the test sites, the most stable cultivar being an admixture of diploids and tetraploids. In future breeding, the best strategy would be to hybridize cultivars developed in northern countries with more exotic materials that combine high yield potential, adequate winter survival and superior disease resistance under northern conditions.     

Improved drought tolerance and root development as components of a scheme to breed blueberries for mineral soil adaptability

Blueberry breeding in North America started at the beginning of the 20th century and present cultivars are adapted to irrigated, high organic, acidic, sandy soils. However, sites meeting these requirements are limited, which has forced breeders to develop germplasm that is adapted to unamended mineral soils. Wild Vaccinium species can be found growing on a number of different soil types under a variety of climatic conditions, which indicates that genetic variability for mineral soil adaptability is present in Vaccinium germplasm. However, for a number of reasons progress in the development of mineral soil-adapted blueberry cultivars has been slow. In this paper a breeding scheme is presented that would allow the user to more efficiently access the variability that exists for mineral soil adaptability. The scheme is composed of two different seedling screening techniques (drought and seedling rooting screen) that are designed to eliminate the less vigorous individuals in a population before field testing. The field environment would be used primarily to evaluate individuals for fruit quality and yield characteristics. In blueberries, both general and specific combining ability can be fully exploited because they are vegetatively propagated which immediately fixes any unique combination of genes.     

东南亚茄子种质资源ISSR遗传多样性分析

为探讨东南亚和中国华南地区茄子育种资源的遗传差异,研究采用ISSR分子标记对来自泰国和马来西亚的10份茄子材料及中国和南美的8份材料进行遗传多样性分析。结果表明,17条ISSR引物共扩增出433条谱带,其中多态性条带390条,平均多态率为92%。17条引物在18份材料中的平均观测等位基因数、平均有效等位基因数、平均Nei’s基因多样度和平均香农信息指数分别为1.8971、1.4778、0.2850、0.4336,18份材料间的遗传相似系数GS在0.55~0.81之间。运用NTSYSpc2.10软件的UPGMA方法进行聚类分析,结果表明在遗传相似系数0.67时18份材料可分为2个类群,其中来自于东南亚的10份材料在第1类群,来自于南美的3份材料在第2类群。研究结果表明,东南亚茄子材料与中国和南美茄子材料间遗传多样性丰富,可为茄子种质资源的进一步研究和利用提供理论依据。     

Sources of resistance to Pyrenophora tritici-repentis in bread wheats

Summary No complete resistance to Pyrenophora tritici-repentis has been located in more than 1400 bread wheats examined. Incomplete resistance, however, occurs at different levels in many spring and winter types and data are presented for the strongest sources of resistance detected. In particular, there is a high frequency of Brazilian spring wheats with appreciable levels of resistance to this pathogen. Recent international nurseries from CIMMYT, Mexico, also contain numerous potentially valuable sources of resistance and these wheats may be shorter and higher yielding in Australia than the Brazilian wheats. The resistances in many Brazilian cultivars may be largely common because the cultivars are often strongly interrelated. Some of the Brazilian wheats resistant to P. tritici-repentis are also resistant to one or more of the septoria diseases and/or possess tolerance to aluminium toxicity.     

Development of unique and novel lines for early-maturing hybrids: moving GEM germplasm northward and westward

Future maize (Zea mays L.) genetic gains are dependent on the incorporation of unique and useful genetic diversity to breeding programs actively improving germplasm and developing cultivars. Our ultimate goal is to increase the genetic diversity currently available in early maturing maize hybrids by developing novel lines that can be utilized competitively in the northern US Corn Belt. A long-term breeding project (EarlyGEM) was initiated to move US Germplasm Enhancement Maize (GEM) germplasm northward and westward. Nine out of 152 breeding crosses were adapted and data from one breeding cross is presented. Five hundred BC₁:S₁ lines derived from (AR16026:S17-66-1-B × ND2000) × ND2000 were advanced, selected, and crossed to several commercial testers for early and late generation hybrid testing. Experiments were arranged in various partially balanced lattice designs and grown across 23 North Dakota (ND) environments. Data showed experimental GEM-derived hybrids had better grain yield (10.4 vs. 9.2 t ha^?1), test weight (72.5 vs. 70.1 kg h L^?1), extractable starch (67.8 vs. 64.2%) and fermentable starch, grain oil (4.3 vs. 3.5%), and grain protein (10.5 vs. 9.4%) when compared to popular hybrids at similar grain moisture at harvest. This is the first research incorporating GEM-derived tropical and late-temperate genetic materials for inbred line development representing a relative maturity (RM) below 90 days. As a consequence of these breeding efforts GEM materials were adapted to the northern US Corn Belt and are not only sources of useful and unique novel genetic diversity but also competitive products for industry use as requests for experimental EarlyGEM lines have been extensive. This research has practical implications with regards to new ways of conducting maize breeding for high latitudes.     

Photoperiod sensitivity gene controlling heading date in rice cultivars in the northernmost region of Japan

Rice is grown in diverse environments at latitudes ranging from 53^°N to 40^°S. In Japan, Hokkaido is the northernmost rice cultivation region(42–45^°N latitude). Only extremely early maturing (heading) varieties that have extremely low photoperiod sensitivity are adapted to this area. Heading date is the most important trait in adaptation to this particular environment. Also, the efficient manipulation of heading date is a crucial component of rice improvement. To determine the genetic basis for heading date among cultivars grown in Hokkaido, the heading behaviour was analyzed. Clear segregations were observed. To estimate the photoperiod sensitivity of the genes involved, the cultivars and F₁ plants from crosses between the cultivars were grown under different daylength conditions. The results indicated that the genes controlling heading date are photoperiod sensitive, suggesting they play important roles in the northernmost rice cultivation regions in Japan, to which only cultivars with extremely low photoperiod sensitivity are adapted. This revised version was published online in August 2006 with corrections to the Cover Date.     

The inheritance of seed colour and vernalization requirement in Brassica napus using doubled haploid populations

Summary In the Mediterranean coastal region, spring barley cultivars are sown in the autumn, corresponding with the rainy season. Thirty eight cultivars out of 44 spring which were collected from North African countries including Morocco, Algeria, Tunisia, Libya and Egypt were of a single dominant spring gene type (+Sh ₂+). Almost the same situation was found in Spain, Italy and Greece, with exceptions for France and Turkey. Kernel row of North African cultivars was characterized by six-rowed type, though there was one exception in Egypt. In the South European countries of Spain, Italy and Greece, six-rowed type varieties were also prevalent. As to non-brittle rachis, in North African countries oriental type cultivars (Btbt ₂) were much higher in frequency than occidental type cultivars (btBt ₂), while in European countries, occidental type cultivars were rather dominant, except for Italian cultivars. In Turkey, located in the joint area between Europe and Asia, cultivars tested were mostly occupied by spring genotype other than +Sh ₂+, and also characterized by tworowed head and occidental type for non-brittle rachis. In the Mediterranean coastal region, especially in North Africa, restricted genotypes, +Sh ₂+ for spring growth habit and v for six-row may indicate adaptability favorable to the growth conditions in these areas. Furthermore, North African cultivars were characterized by the oriental type of non-brittle rachis. This may give us information about the migratory routes of the original landrace to North Africa.     

Pan bread and dry white Chinese noodle quality in Chinese winter wheats

Improvements in pan bread quality and Chinese dry white noodle (DWCN) quality are the major breeding objectives in the north China winter wheat region. Eighty-one wheat cultivars and advanced lines were sown in two locations in the 2000–2001 season to evaluate the quality of winter wheat germplasm and investigate the association between pan bread quality and DWCN quality. Significant variability was observed for grain, pan bread, and DWCN quality attributes. Six cultivars and lines showed very good pan bread quality, 23 showed excellent DWCN quality in both locations, and the cultivars Yumai 34 and Sunstate showed superior quality for both food products. Protein content and grain hardness were significantly associated with pan bread quality, while the gluten quality-related parameters SDS-sedimentation value, Farinograph stability, and Extensograph maximum resistance, were significantly associated with pan bread quality score, and accounted for 59.3–72.3% of its variation. Yellow colour (b, CIE Lab) showed a strong negative association with pan bread and DWCN quality largely due to the strong and negative association between yellow colour and gluten strength parameters in this germplasm pool. Flour ash content and polyphenol oxidase (PPO) had a negative moderate effect on noodle colour, while protein content and grain hardness were negatively associated with noodle colour, appearance, and smoothness. The association between SDS-sedimentation volume, Farinograph stability, and Extensograph maximum resistance and DWCN score fitted a quadratic regression model, accounting for 31.0%, 39.0%, and 47.0% of the DWCN score, respectively. The starch pasting parameters, peak viscosity and paste breakdown, contributed positively to DWCN quality, with r = 0.57 and 0.55, respectively. Quality requirements for pan bread and DWCN differ in colour, gluten strength, and pasting viscosity. It is suggested that PPO, yellow pigment, SDS sedimentation volume, and peak viscosity are parameters that could be used to screen for DWCN quality in the early generations of a wheat-breeding program.     

北方冬麦区新育成优质品种的面包和馒头品质性状

本研究旨在了解近年北方冬麦区育成优质小麦品种的品质状况, 为优质小麦新品种选育和推广提供重要信息。2013—2014和2014—2015年度将52份国内及6份国外代表性优质品种种植于河北高邑和山东济宁, 测定粉质仪和拉伸仪参数及面包和馒头品质性状, 并分析蛋白质组分含量对面团流变学特性及面包和馒头成品品质的影响。结果表明, 大部分参试品种的粉质仪稳定时间在7 min以上, 品种间面筋强度、面包和馒头成品品质均存在显著差异。CA0493、师栾02-1、12品404、新麦26和Karl 5个品种面包品质好, 其中师栾02-1和Karl的馒头品质也较好, 可以作为兼用型品种在品质育种中应用。拉伸仪品质特性是反映强筋品种面包品质的重要指标, 建议在进行面包品质改良时, 重视拉伸特性。不溶性谷蛋白聚合体含量与面筋强度和面包品质呈显著正相关, 可作为品质育种的选种指标。     

Reworking the frame: analysis of current discourses on North Korea and a case study of North Korean labour in Dandong,China

North Korea remains a place of obscurity, mystery and even of imminent threat in popular imagination of East Asia and America. In this article, we explore existing representations of and discourses around North Korea and argue for a different framework to consider how North Korea is a critical participant in the contemporary world. Drawing on our respective fieldwork in Dandong, China, throughout 2006 to 2014, the article suggests a new way of thinking about issues surrounding North Korea.     

Genes conferring low seedling reaction to Mexican pathotypes of Puccinia recondita f. sp. tritici,and adult-plant responses of recent wheat cultivars from the former USSR

Fifty-five spring bread wheat (Triticum aestivum L.) cultivars, mostly released between 1975 and 1991 in eight leaf rust-prone spring wheat growing regions of the former USSR, were tested in the seedling growth stage for reaction to 15 Mexican pathotypes of Puccinia recondita f. sp. tritici. In total, seven known and at least two unknown genes were identified, either singly or in combinations: Lr3 (7 cultivars), Lr10 (14), Lr13 (5), Lr14a (1), Lr16 (1), Lr23 (3); the unknown genes were identified in 14 cultivars. The first unknown gene could be either Lr9, Lr19, or Lr25; however, the second unknown gene in 9 cultivars was different from any named gene. Twelve of the 15 pathotypes are virulent for this gene, hence its use in breeding for resistance will be limited. The cultivars were also evaluated at two field locations in Mexico with two pathotypes in separate experiments. The area under the disease progress curve and the final disease rating of the cultivars indicated genetic diversity for genes conferring adult plant resistance. based on the symptoms of the leaf tip necrosis in adult plants, resistance gene Lr34 could be present in at least 20 cultivars. More than half of the cultivars carry high to moderate levels of adult plant resistance and were distributed in each region.