Evaluation of genetic markers for prediction of preharvest sprouting tolerance in hard white winter wheats

Preharvest sprouting of wheat results in significant financial loss at all steps in the production and marketing chain. Due to its intermittent nature in many wheat‐growing regions, direct selection for tolerance to preharvest sprouting is difficult. DNA markers linked to genes conditioning tolerance offer a more consistent and reliable approach to genetic improvement in tolerance. This investigation assessed the value of previously identified markers linked to quantitative trait loci contributing to tolerance, across multiple genetic backgrounds. A significant contribution to tolerance was demonstrated for QPhs.pseru‐3AS, previously identified from the hard white winter wheat ‘Rio Blanco’. Marker alleles for this locus were associated with enhanced tolerance in three of four investigated populations. In addition, positive contributions of QPhs.pseru‐2B1 and QPhs.pseru‐2B2 also were documented. Simultaneous selection for putative marker alleles at two independent loci resulted in significantly higher mean tolerance scores. DNA markers linked to loci contributing to variation in preharvest sprouting tolerance offer an efficient and effective alternative to direct phenotypic selection.     

Evaluating Predictive Values of Various Physiological Indices for Salinity Stress Tolerance in Wheat

Soil salinity is a worldwide issue that affects agricultural production. The understanding of mechanisms by which plants tolerate salt stress is crucial for breeding varieties for salt tolerance. In this work, a large number of wheat (Triticum aestivum and Triticum turgidum) cultivars were screened using a broad range of physiological indices. A regression analysis was then used to evaluate the relative contribution of each of these traits towards the overall salinity tolerance. In general, most of the bread wheats showed better Na⁺ exclusion that was associated with higher relative yield. Leaf K⁺/Na⁺ ratio and leaf and xylem K⁺ contents were the major factors determining salinity stress tolerance in wheat. Other important traits included high xylem K⁺ content, high stomatal conductance and low osmolality. Bread wheat and durum wheat showed different tolerance mechanisms, with leaf K⁺/Na⁺ content in durum wheat making no significant contributions to salt tolerance, while the important traits were leaf and xylem K⁺ contents. These results indicate that Na⁺ sequestration ability is much stronger in durum compared with bread wheat, most likely as a compensation for its lesser efficiency to exclude Na⁺ from transport to the shoot. We also concluded that plant survival scores under high salt stress can be used in bread wheat as a preliminary selection for Na⁺ exclusion gene(s).     

人工合成小麦幼苗耐低温特性鉴定

为了鉴定不同小麦品种的耐低温特性,筛选耐低温种质资源,本文以59个栽培二粒小麦/节节麦和硬粒小麦/节节麦人工合成小麦,在室温（18℃）和低温（4℃）处理下测定萌发15天的幼苗形态指标,采用性状相对值（各性状低温与室温下测定值的比值）和隶属函数法相结合的方法,综合评价人工合成小麦品种的抗低温特性。结果表明,栽培二粒小麦/节节麦人工合成小麦的耐低温特性总体较硬粒小麦/节节麦人工合成小麦强;筛选出一批耐低温特性强的栽培二粒小麦-节节麦人工合成小麦材料,可用于小麦耐低温育种。     

有效利用土壤磷的小麦种质筛选方法研究

利用由不同地点采集的土壤样品布置了9次土培试验, 对437份不同小麦品种 在不同有效磷含量土壤中的磷营养特性表现进行了较全面的鉴定。 发现, 施磷处理和减 磷处理土壤有效磷含量的差距即选择压力是土培试验鉴定成败的关键因素。 施磷处理的土 壤有效磷含量为24 mg/kg左右, 减磷处理的土壤有效磷含量为8 mg/kg左右是利用     

不同小麦品种芽期耐盐性鉴定研究

为研究不同小麦品种在芽期的耐盐性,本研究以6 种小麦品种为研究对象,用不同浓度NaCl （盐浓度分别为0%(CK)、1%、1.5%、2.0%）胁迫处理后,分别测定并分析小麦芽期的发芽率、芽长、根长、芽鲜重。试验结果表明：在盐胁迫下,不同小麦品种随着盐浓度的升高,小麦的发芽率、芽长、根长、芽鲜重都随之降低。其中,在高盐(1.5% NaCl)处理下,‘宁春4 号’、‘Drasdal’在芽期比较敏感,‘红芒麦’、‘毛火麦’在芽期表现出一定的耐盐性,‘宁春27号’、‘山融3号’表现出比较强的耐盐性。因此,在高盐胁迫下‘宁春27号’、‘山融3号’芽期具有较强的耐盐性。     

Genetic variation in drought tolerance at seedling stage and grain yield in low rainfall environments in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Genetic architecture of seedling drought tolerance is complex and needs to be better understood. To address this challenge, we developed a protocol to identify the most promising drought-tolerant genotypes at the seedling stage in winter wheat. A population of 146 recombinant inbred lines (F₉) derived from a cross between wheat cultivars, ‘Harry’ (seedling drought tolerant) and ‘Wesley’ (seedling drought susceptible) were used in this study. All genotypes were sown in three replications in a randomized complete block design under controlled conditions in a greenhouse. Seven traits were scored and grouped into tolerance traits; days to wilting, leaf wilting, and stay green and survival traits; days to regrowth, regrowth, drought survival rate, and recovery after irrigation. Three selection indices were calculated (1) tolerance index, (2) survival index, and (3) drought tolerance index (DTI). The same set of genotypes were also tested for grain yield in two low rainfall environments for two seasons. High genetic variation was found among all genotypes for all seedling traits scored in this study. Correlations between tolerance and survival traits were weak or did not exist. Heritability estimates ranged from 0.53 to 0.88. DTI had significant phenotypic and genotypic correlations with all seedling traits. Genotypes were identified with a high drought tolerance at the seedling stage combined with high grain yield in low rainfall. Breeding for tolerance and survival traits should be taken into account for improving winter wheat drought tolerance at seedling stage. The selected genotypes can be used for to further improve drought tolerance in high yielding wheat for Nebraska.     

Validation of quantitative trait loci for aluminum tolerance in Chinese wheat landrace FSW

Aluminum (Al) toxicity is one of the major constraints for wheat production in acidic soils worldwide and use of Al-tolerant cultivars is one of the most effective approaches to reduce Al damage in the acidic soils. A Chinese landrace, FSW, shows a high level of tolerance to Al toxicity and a mapping population of recombinant inbred lines (RILs) was developed from a cross between FSW and Al-sensitive US spring wheat cultivar Wheaton to validate the quantitative trait loci (QTL) previously identified in FSW. The mapping population was evaluated for net root growth (NRG) during Al stress in a nutrient solution culture and hematoxylin staining score (HSS) of root tips after Al stress. After 132 simple sequence repeat (SSR) markers from three chromosomes that were previously reported to have the QTLs were analyzed in the population, two QTLs for Al tolerance from FSW were confirmed. The major QTL on chromosome 4DL co-segregated with the Al-activated malate transporter gene (ALMT1), however, sequence analysis of the promoter region (Ups4) of ALMT1 gene indicated that FSW contained a marker allele that is different from the one that was reported to condition Al tolerance in the Brazilian source. Another QTL on chromosome 3BL showed a minor effect on Al tolerance in the population. The two QTLs accounted for about 74.9 % of the phenotypic variation for HSS and 72.1 % for NRG and demonstrated an epistatic effect for both HSS and NRG. SSR markers closely linked to the QTLs have potential to be used for marker-assisted selection (MAS) to improve Al tolerance in wheat breeding programs.     

Evaluation of a semi‐controlled test as a selection tool for frost tolerance in durum wheat (Triticum durum)

Most durum wheat (Triticum durum) varieties possess only low winter hardiness due to their frost susceptibility. In North America and Central Europe, durum wheat is therefore typically sown in spring to circumvent the local winter conditions. However, the yield potential of durum in these regions could be much better exploited if durum varieties with increased frost tolerance were available, which could be sown in autumn. A factor limiting breeding for increased frost tolerance is the variation in the occurrence of frost stress across years. The ‘Weihenstephaner Auswinterungsanlage’ is a semi‐controlled test that exposes the plants to all weather conditions. Snow coverage of the plants, serving as frost protection, is prevented by the movable glass lid of the semi‐controlled test. In this study, different scorings for frost tolerance based on this semi‐controlled test were evaluated and compared with frost tolerance data in the field. Our results illustrate the potential of the ‘Weihenstephaner Auswinterungsanlage’ as an indirect selection tool for frost tolerance in durum breeding programmes, especially when regular frost tolerance data from the field are not available.     

Combining frost tolerance,high grain yield and good pasta quality in durum wheat

Growing in Central Europe winter instead of spring durum wheat would substantially increase yield potential but is currently hampered by the lack of knowledge of frost tolerance present in elite material. The objectives of our survey were to (i) study the genetic variability and heritability of frost tolerance and its association with other important agronomic and quality traits in durum wheat, (ii) examine the potential to combine frost tolerance with high quality and high grain yield and (iii) investigate the consequences of the heritabilities and associations among traits on the optimum design of a multistage selection programme for winter durum wheat. We investigated 101 elite winter durum wheat lines and four commercial checks in field trials at four locations. Four agronomic as well as nine quality traits were recorded. In addition, frost tolerance was evaluated using a semi‐controlled test resulting in high‐quality phenotypic data. Genotypic variances (σ²_G) were significantly larger than zero for all traits, and heritabilities were moderate to high. Several elite durum wheat lines exhibited a frost tolerance comparable to that of two frost‐tolerant Triticum aestivum varieties. Frost tolerance was not negatively associated with other important agronomic and quality traits. The high quality of the phenotypic data for frost tolerance evaluated in a semi‐controlled test suggests that this is a cost‐efficient approach to consider frost tolerance at early stages of a multistage durum wheat breeding programme.     

Varietal variation and physiological basis for inhibition of wheat seed germination after excessive water treatment

Soaking the seeds of most upland plants in water before sowing results in poor germination. Varietal differences in flooding tolerance of seeds have been reported in maize, soybean, barley and so on. This study was conducted to evaluate the varietal difference in wheat (2n = 42) seeds to soaking injury and to examine the importance of ethanol accumulation and seed coat as determinants of flooding tolerance. Of 342 varieties tested, many from Asia appeared more tolerant of flooding than the varieties from the Middle East. Soak-induced inhibition of germination and amounts of ethanol excreted were increased with soaking duration. Seeds of 26 wheat varieties were soaked 8 days at 20 °. Subsequent germination was correlated with amounts of ethanol excreted. Seeds with a red-colored coat exhibited higher tolerance to flooding than white ones, however, a varietal difference existed even in the case where the seed coat was peeled. These data suggest that soak-induced inhibition of wheat seed germination relates to accumulation of ethanol rather than seed coat color. This revised version was published online in July 2006 with corrections to the Cover Date.     

穗发芽抗性STS标记Vp1B3在中国小麦微核心种质中的检测

小麦在临近收获前发生穗发芽,不仅劣化小麦加工品质,而且降低小麦产量。提高小麦穗发芽抗性水平是小麦育种工作的重要目标之一。本实验以258份中国小麦微核心种质为试材,利用已报道的小麦穗发芽抗性标记Vp1B3对其进行多态性检测,以了解该抗性标记在中国小麦微核心种质中的分布规律,寻找新的等位变异类型,并结合部分品种的发芽指数,分析不同等位变异类型与穗发芽抗性之间的关系。结果表明：检测的258份供试材料中,a带型（13．9％）、c带型（41．1％）和e带型（34．5％）等3种带型为主要扩增带型,占总变异类型的89．5％;b、d、f带型为本研究所发现的新的等位变异类型,占总变异类型的2．4％。此外,杂合带型以及无扩增产物的分别占总变异类型的3．5％和4．6％。对选取的部分穗发芽抗性不同的材料进行统计分析,结果显示,c带型品种的发芽指数（GI,47．9％）明显高于a带型（GI,22．6％）和e带型（GI,24.3％）的品种,但c带型的品种中也存在GI值较低的高抗穗发芽品种,而a带型和e带型的品种中同时也出现了GI值较高的感穗发芽品种,说明小麦穗发芽的遗传机制比较复杂,其抗性不仅仅受Vp1B3基因控制,而是多种因素共同作用的结果。     

不同浓度盐胁迫对小麦萌发和幼苗生长的影响

提高以盐渍化为代表的中低产田的产量,已成为进一步提高小麦总产量的主要途径,对于保障中国粮食安全具有重要意义。笔者依据300 mmol/L盐浓度下的发芽率和水培苗期在200 mmol/L和400 mmol/L两个盐浓度梯度水平下的株高、根长、根数变化,对选自不同生态类型区的21份冬小麦资源及育成品种进行了耐盐性鉴定,并依据盐胁迫下的小麦发芽率和苗期植株变化对供试材料的耐盐力进行综合评判。研究结果表明：从供试材料中筛选出了1级耐盐材料3份;2级耐盐材料3份;3级耐盐材料5份,丰富了小麦耐盐种质资源。该方法与田间盐池鉴定方法相比,具有工作量小、速度快的优点,且鉴定结果与田间表现吻合度高,研究结果可为小麦耐盐育种提供理论和技术支撑,同时也可为进一步提高盐渍化土壤小麦产量提供技术支撑。     

黄淮冬麦区不同年代旱地小麦萌发期抗旱性与根系活力研究

为了调查黄淮冬麦区不同年代旱地小麦品种萌发期抗旱性与根系活力的变化规律,选择具有调研性的实验材料12个,利用GB/T 21127-2007小麦抗旱性鉴定评价技术规范,对12个供试材料进行种子萌发期抗旱性鉴定,同时对供材料进行根系活力测定。结果表明,供试12个品种小麦的抗旱性从20世纪50年代以来呈现“马鞍型”演变趋势;根系活力对照组呈现平缓下降,而高渗胁迫处理组小麦的根系活力却呈现上升的趋势;抗旱性与高渗胁迫下根系活力呈显著正相关关系。     

Salt Tolerance of an Amphiploid between Triticum aestivum and Agropyron junceum

The main objective of this work is to demonstrate the expression of salt tolerance genes in a wheat-Agropyron amphiploid. Salt tolerance tests were carried out on wheat varieties, ‘Chinese Spring,’ and ‘Glenn-son 81’ the amphiploid between ‘Chinese Spring’ and A. junceum, A. junceum and amphiploid × wheat hybrids, Apart from germination in petridishes all other tests were carried out on plants grown in saline hydroculture tanks. Fresh weight measurements are given for stressed and non-stressed plants as well as measurements of harvest ripe plants. The utility of A. junceum as a source of salt tolerance genes for wheat is discussed.     

Expression of barley yellow dwarf virus and Russian wheat aphid resistance genes in and fertility of spring wheat × triticale hybrids and backcross lines

Summary The Barley Yellow Dwarf Virus disease (BYDV) and the Russian wheat aphid (RWA) Diuraphis noxia (Mordvilko) have caused significant losses to wheat and barley in several areas of the world. Important sources of resistance to both BYDV and RWA have been found in Triticale. Different generations of interspecific wheat x Triticale crosses were produced and the progenies were screened for BYDV and RWA tolerance. Plants with equal chromosome numbers showed different levels of fertility. A significant correlation was observed between pollen fertility and seed set in primary florets (r=0.57). In generaL, pollen fertility, seed set and the number of euploid plants (2n=42) increased from one generation to the next. The expression of BYDV tolerance varied from population to population. Additive effects were predominant in F₁ and some backcross populations. A dominant effect of rye tolerance genes was also observed in few populations. A monogenic trait or a quantitative (polygenic) character would not agree with the observed segregation patterns. The heritability of this oligogenic tolerance was quite different between populations and in many populations the tolerance genes were only partially expressed. Some transgressive segregation for tolerance and sensitivity was demonstrated. The genes controlling tolerance to RWA in Triticale lines, Muskox 658 and Nord Kivu were not expressed in advanced lines resistant to BYDV. This indicates that tolerance genes for BYDV and RWA in these lines are located on different chromosomes.     

Pedigree analysis of the origin of manganese tolerance in Canadian spring wheat (Triticum aestivum L.) cultivars

Summary Breeding wheat (Triticum aestivum L.) for tolerance to manganese (Mn) might be in some cases more feasible and economical than use of soil amendments. As part of research on the heritability of Mn tolerance, a study on the level of Mn tolerance in Canadian wheat cultivars and its probable origin was accomplished by analysis of cultivar pedigrees and drawing phylogenetic maps to discern filial relationships. Cultivar tolerance to Mn was determined by relative root weight (RRW) in solution culture in the presence of 500 M Mn. A total of 91 cultivars were screened, 76 of which were Canadian. These data, together with data from another 28 cultivars reported in the literature, were used to draw two pedigree maps, a map for Canadian cultivars only, and a map for the Mn-tolerant Canadian cultivars Norquay and Laura. Results indicated a range of tolerance to Mn among Canadian cultivars. Manganese tolerance, found in either Canadian or foreign germplasm, and of either recent or older selection or origin, seems to have originated from land races from Rio Grande do Sul, the southernmost state of Brazil. Tolerance may have been introduced into Canadian germplasm directly by the use of Brazilian cultivars as parents, or indirectly by the introduction of Mexican germplasm with Brazilian parentages. This information will help the plant breeder to develop plant breeding systems, and may also help in the study of the mechanisms for Mn tolerance in wheat.     

Enhancement of aluminum tolerance in wheat by addition of chromosomes from the wild relative Leymus racemosus

Aluminum (Al) toxicity is the key factor limiting wheat production in acid soils. Soil liming has been used widely to increase the soil pH, but due to its high cost, breeding tolerant cultivars is more cost-effective mean to mitigate the problem. Tolerant cultivars could be developed by traditional breeding, genetic transformation or introgression of genes from wild relatives. We used 30 wheat alien chromosome addition lines to identify new genetic resources to improve wheat tolerance to Al and to identify the chromosomes harboring the tolerance genes. We evaluated these lines and their wheat background Chinese Spring for Al tolerance in hydroponic culture at various Al concentrations. We also investigated Al uptake, oxidative stress and cell membrane integrity. The L. racemosus chromosomes A and E significantly enhanced the Al tolerance of the wheat in term of relative root growth. At the highest Al concentration tested (200 μM), line E had the greatest tolerance. The introgressed chromosomes did not affect Al uptake of the tolerant lines. We attribute the improved tolerance conferred by chromosome E to improved cell membrane integrity. Chromosome engineering with these two lines could produce Al-tolerant wheat cultivars.     

小麦燕大1817×北农6号重组自交系群体在正常和盐胁迫水培条件下苗期性状的QTL定位

小麦苗期性状能够指示品种的耐盐性。本研究以小麦骨干亲本燕大1817与品系北农6号衍生的230个重组自交系为材料,利用2013年3个不同时间的水培试验数据和已经构建的SSR和SNP高密度遗传连锁图谱分别对正常和盐胁迫条件下根数和最长根长等7个苗期性状进行QTL定位。利用完备复合区间作图法(ICIM)共检测到69个加性效应QTL(LOD≥2.5),分布于除1A染色体外的所有20条染色体上,单个QTL解释的表型变异率为2.70%~19.00%。有46个QTL的增效效应来自于燕大1817,有23个QTL的增效效应来自于北农6号。有12个QTL能够在3个或3个以上的环境中被检测到,在燕大1817中定位到稳定的多分蘖主效QTL QTn.cau-7BS.1和盐胁迫条件下特异表达的根数QTL QRn.cau-2A,解析了小麦骨干亲本燕大1817的繁茂性和抗逆性遗传基础,为解析小麦品种耐盐遗传机制和耐盐性的分子标记辅助选择提供了重要信息。     

小麦品质性状分子标记多重PCR体系的建立

小麦高分子量谷蛋白亚基组成、1B/1R易位、籽粒硬度、直链淀粉含量和穗发芽抗性等性状与加工品质密切相关，建立相关性状的多重PCR体系在小麦品质分子育种中具有重要意义。本研究利用现有品质性状基因的分子标记，建立了适合不同品质类型品种评价和分子聚合育种的3个多重PCR体系，并用已知基因的品种（系）进行验证。多重PCR体系Ⅰ包括ω-secalin（1B/1R）、Vp1B3和Pinb-D1b基因的分子标记检测，可用于一般的品质检测；体系Ⅱ包括ω-secalin、Ax2*、Bx17和Dx5 基因的检测，可望用于强筋小麦品种的选育；体系Ⅲ包括Wx-A1、Wx-B1和Wx-D1位点的检测，可用于淀粉品质或糯小麦的选育。每个体系内的引物之间不存在相互抑制作用和错配，检测品种（系）的结果可靠、重复性好，成本低。3个多重PCR体系用于小麦品质育种的亲本评价和杂交后代优质基因的聚合，将会提高优质专用小麦品种评价和选育的效率。