Oviposition deterrence in spring wheat, Triticum aestivum, against orange wheat blossom midge, Sitodiplosis mosellana: implications for inheritance of deterrence

Some spring wheat lines are known to be antixenotic to ovipositing orange wheat blossom midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae). The genetic basis of antixenosis, expressed in the plant as oviposition deterrence to S. mosellana , was explored using a population of 92 doubled-haploid wheat lines from a cross between a susceptible parent and a deterrent parent which also had antibiosis resistance. Wheat midge egg densities on wheat spikes were obtained from a standardized laboratory cage test and from the field in 2006 and 2007. Compared to the susceptible parent, egg densities on 55–88% of the lines were reduced by more than half in the laboratory and both years in the field. Twenty-five of the 92 lines were consistently at least as deterrent as the deterrent parent in all three environments. Frequency distribution of egg densities compared to the parents indicated that deterrence was conferred by more than one gene, with complementary interaction among genes. Heritability of deterrence was estimated at 67%, showing that environment had a substantial effect on the phenotypic expression of the trait. Consistently deterrent lines had a larger proportion of eggs laid on the rachis compared to the other lines in all environments, suggesting that the presence of deterrence affects where on the spikelet the females lay their eggs. There was no evidence for linkage between deterrence genes and the antibiosis gene, Sm1 . Oviposition deterrence is a promising means for suppressing wheat midge oviposition in commercial wheat crops; however, the multigenic nature of oviposition deterrence in wheat to S. mosellana and the influence of environment on its expression will provide challenges for incorporating this trait into wheat breeding programs.     

Inheritance of field resistance to Stagonospora nodorum leaf and glume blotch and correlations with other morphological traits in hexaploid wheat (Triticum aestivum L.)

Breeding for wheat varieties resistant to Stagonospora nodorum blotch (SNB) is the most sustainable strategy for controlling the disease. In order to map quantitative trait loci (QTLs) for SNB resistance we analysed 204 recombinant inbred lines of the cross between the winter wheat (Triticum aestivum L.) variety Forno and the winter spelt (Triticum spelta L.) variety Oberkulmer. We determined the level of resistance of adult plants to leaf blotch (SNL) and glume blotch (SNG) as well as morphological traits for 2 years after artificial inoculation with S. nodorum. Using composite interval mapping and LOD > 3.7, we detected ten QTLs for SNG blotch resistance (six inherited from the susceptible parent Forno) and 11 QTLs for SNL resistance (four inherited from Forno) across 2 years. Both resistance traits were moderately correlated (r = 0.52) and had only one common QTL. For SNL resistance, seven QTLs were not associated with QTLs for morphological traits. Among them, QSnl.eth-2D, QSnl.eth-4B and QSnl.eth-7B3 had major effects (R(2) > 13%) and were potential candidates for marker-assisted selection. For SNG, the major QTL on chromosome 5A, explaining 36% of the phenotypic variance for resistance, was associated with the q locus conferring the spelt morphology (long lax ear, long culm and hard glumes). Only QSng.eth-1BS, which explained 7% of the variance for resistance to SNG blotch, was not associated with QTLs for morphological traits. The consequences for breeding programmes are discussed.     

Cytological characteristics of F2 hybrids between Triticum aestivum L. and T. durum Desf. with reference to wheat breeding

Cytological and agronomic characteristics of a F2 population from Triticum aestivum L. x T. durum Desf. hybrids were analyzed plant by plant. Means of morphologic traits in the F2 population were similar to those of the low-value parent. On average, F2 hybrids had 36.54 chromosomes per plant, indicating that each gamete lost 2.73 chromosomes at meiosis of the F1 generation. More than half of plants had 36-39 chromosomes, so male gametes with 19-21 chromosomes seemed to be superior to the others. The distribution frequency of chromosomes in this study differed from that in a previous report, where a different tetraploid wheat was used. This shows that a different breeding strategy may need to be taken when exploiting a different tetraploid wheat. According to our results, some plants with 42 chromosomes, having all the wheat A, B and D chromosomes, would appear in the F3 population, which provides a chance to obtain stable bread wheat lines from the self-pollinated progenies. Alternatively, the desirable individuals of the F2 population were backcrossed to bread wheat, which is very useful and efficient for the improvement of bread wheat by exploiting desirable genes in durum wheat.     

Detection of QTLs for Stagonospora glume blotch resistance in Swiss winter wheat

Stagonospora nodorum is the causal agent of the Stagonospora glume blotch disease in hexaploid wheat. The Swiss winter bread wheat cv. 'Arina' has a highly effective, durable and quantitative glume blotch resistance. We studied 240 single seed descent (SSD)-derived lines of an 'Arina × Forno' F_5:7 population to identify and map quantitative trait loci (QTLs) for glume blotch resistance under natural infestation. Using composite interval mapping (CIM) and LOD>4.5, we detected two chromosomal regions on chromosome arms 3BS and 4BL which were specifically associated with glume blotch resistance. These identified QTLs were designated QSng.sfr-3BS and QSng.sfr-4BL, respectively. QSng.sfr-3BS peaked at the locus Xgwm389 in the telomeric region of the short arm of chromosome 3B and explained 31.2% of the observed phenotypic variance for the resistance within the population. The responsible QSng.sfr-3BS allele originated from the resistant parent 'Arina'. The QTL QSng.sfr-4BL (19.1%) mapped to chromosome arm 4BL ('Forno' allele) very close to two known genes, TaMlo and a catalase (Cat). Both QTL alleles combined could enhance the resistance level by about 50%. Additionally, they showed significant epistatic effects (4.4%). We found PCR-based microsatellite markers closely linked to QSng.sfr-3BS (gwm389) and QSng.sfr-4BL (gwm251) which make marker-assisted selection (MAS) for Stagonospora glume blotch resistance feasible. We also found one resistance QTL, QSng.sfr-5BL, on the long arm of chromosome 5B which overlapped with QTLs for plant height as well as heading time.Communicated by H. C. Becker     

A population of wheat multiple synthetic derivatives: an effective platform to explore,harness and utilize genetic diversity of <Emphasis Type="Italic">Aegilops tauschii</Emphasis> for wheat improvement

Key message

The multiple synthetic derivatives platform described in this study will provide an opportunity for effective utilization of Aegilops tauschii traits and genes for wheat breeding.

Abstract

Introducing genes from wild relatives is the best option to increase genetic diversity and discover new alleles necessary for wheat improvement. A population harboring genomic fragments from the diploid wheat progenitor Aegilops tauschii Coss. in the background of bread wheat (Triticum aestivum L.) was developed by crossing and backcrossing 43 synthetic wheat lines with the common wheat cultivar Norin 61. We named this population multiple synthetic derivatives (MSD). To validate the suitability of this population for wheat breeding and genetic studies, we randomly selected 400 MSD lines and genotyped them by using Diversity Array Technology sequencing markers. We scored black glume as a qualitative trait and heading time in two environments in Sudan as a quantitative trait. Our results showed high genetic diversity and less recombination which is expected from the nature of the population. Genome-wide association (GWA) analysis showed one QTL at the short arm of chromosome 1D different from those alleles reported previously indicating that black glume in the MSD population is controlled by new allele at the same locus. For heading time, from the two environments, GWA analysis revealed three QTLs on the short arms of chromosomes 2A, 2B and 2D and two on the long arms of chromosomes 5A and 5D. Using the MSD population, which represents the diversity of 43 Ae. tauschii accessions representing most of its natural habitat, QTLs or genes and desired phenotypes (such as drought, heat and salinity tolerance) could be identified and selected for utilization in wheat breeding.

     

How to build the non-host plant for stability in insect resistance management

We consider using non-host plants that express both a toxin and oviposition deterrence for to increase stability for insect resistance management. The two traits reinforce each other ecologically. We used a two-gene model to evaluate this combination of traits. When toxin resistance was recessive or partially recessive, even moderate levels of oviposition deterrence extended time to resistance. When sensitivity to oviposition deterrence started at a low frequency (0.001) selection pressure from the toxin caused the frequency of the gene for sensitivity to oviposition deterrence to increase and the time to resistance was extended beyond the 150-y timeline of the simulations. Even in the worst-case scenario, when toxin resistance was dominant, oviposition deterrence extended time to resistance up to 150 y. The genes for toxin and sensitivity to oviposition deterrence support each other ecologically to prevent resistance from developing to either trait. This creates a more stable insect resistance management strategy.     

Genetic architecture of quantitative trait loci associated with morphological and agronomic trait differences in a wild by cultivated barley cross.

Hordeum vulgare subsp. spontaneum is the progenitor of cultivated barley (Hordeum vulgare L.). Domestication combined with plant breeding has led to the morphological and agronomic characteristics of modern barley cultivars. The objective of this study was to map the genetic factors that morphologically and agronomically differentiate wild barley from modern barley cultivars. To address this objective, we identified quantitative trait loci (QTLs) associated with plant height, flag leaf width, spike length, spike width, glume length in relation to seed length, awn length, fragility of ear rachis, endosperm width and groove depth, heading date, flag leaf length, number of tillers per plant, and kernel color in a Harrington/OUH602 advanced backcross (BC2F8) population. This population was genotyped with 113 simple sequence repeat markers. Thirty QTLs were identified, of which 16 were newly identified in this study. One to 4 QTLs were identified for each of the traits except glume length, for which no QTL was detected. The portion of phenotypic variation accounted for by individual QTLs ranged from about 9% to 54%. For traits with more than one QTL, the phenotypic variation explained ranged from 25% to 71%. Taken together, our results reveal the genetic architecture of morphological and agronomic traits that differentiate wild from cultivated barley.     

Quantitative trait loci for lodging resistance in a segregating wheat×spelt population

 Lodging can strongly affect both the grain yield and the quality of wheat. Lodging represents a quantitative trait and is difficult to assess on a phenotypic basis. Marker-assisted selection (MAS) could therefore become an important tool in breeding for lodging resistance. In this study, we mapped and characterised quantitative trait loci (QTLs) for lodging resistance, as well as morphological traits correlated with lodging, in a segregating population of 226 recombinant inbred lines derived from the cross of the lodging-resistant wheat variety Forno with the susceptible spelt variety Oberkulmer. Lodging, plant height, leaf width, leaf-growth habit, culm stiffness, culm swinging, culm thickness, days to ear emergence and days to flowering were assessed in field trials at two locations in 1996 and at one location in 1997. Additionally, at one location weight and length parameters were also assessed. Plant height and culm stiffness explained 77% of the phenotypic variance of lodging in a multiple regression model over all three environments. QTL analysis of lodging and morphological parameters was based on a genetic map containing 230 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping nine QTLs for lodging resistance were detected, explaining 63% of the phenotypic variance in a simultaneous fit. Seven of these QTLs coincided with QTLs for morphological traits, reflecting the correlations between these traits and lodging. In our population the most efficient way to improve lodging resistance would be by a combination of indirect selection on plant height and culm stiffness together with MAS on the two QTLs for lodging resistance which did not coincide with QTLs for morphological traits. Received: 3 August 1998 / Accepted: 28 November 1998     

Morphological traits of wheat (Triticum aestivum L.) associated with resistance to shoot fly,Atherigona approximata Malloch

Shoot flies (Atherigona spp.) are the members of muscidae family which have got economic importance as pest of several crops of Gramineae family mostly cereals and millets. One of the most effective management strategies for controlling shoot fly is the use of resistant wheat cultivars carrying specific resistant traits. Among thirty wheat genotypes screened at the University of Agricultural Sciences, Dharwad-Karnataka (India), two advanced germplasms UAS BW-12417 and UAS BW-11110 recorded least oviposition and dead heart due to shoot fly and found to be less preferred by Atherigona approximata Malloch. The morphological traits of different wheat genotypes revealed a significant negative correlation of shoot fly oviposition and dead heart with leaf length, leaf length to breadth ratio, seedling height, average seedling growth rate, seedling vigour, leaf glossiness and trichome density of wheat leaves, which indicated the enhanced shoot fly infestation as decrease in the values of above-mentioned morphological traits. Meanwhile, increase in leaf breadth and leaf area of wheat genotype aggrandised the oviposition and dead heart damage by shoot fly. Under the changing climate where, the minor insect pests attaining major pest status, the present investigation would pave way for breeders to tailor future breeding programmes to evolve shoot fly resistant hybrids with high yielding traits.     

Mapping of quantitative trait loci determining agronomic important characters in hexaploid wheat ( Triticum aestivum L.)

A set of 114 recombinant inbred lines of the 'International Triticeae Mapping Initiative' mapping population was grown during the seasons 1997, 1998, 1999 and 2000 under several environments. Twenty morphological (glume colour, awn colour, waxiness, leaf erectness, peduncle length), agronomical (ear emergence time, flowering time, grain filling time, ear length, plant height, lodging, grain number, thousand-grain-weight, grain weight per ear, grain protein content, winter hardiness) and disease resistance (powdery mildew, yellow rust, leaf rust, fusarium) traits were studied. Not all traits were scored in each experiment. In total 210 QTLs with a LOD threshold of >2.0 (minor QTLs) were detected of which 64 reached a LOD score of >3.0 (major QTLs). Often QTLs were detected in comparable positions in different experiments. Homologous and homoeologous relationships of the detected QTLs, and already described major genes or QTLs determining the same traits in wheat or other Triticeae members, are discussed.     

Comparative performance of bread wheat and hexaploid triticale cytoplasms

Summary Thirteen wheat-like advanced-generation triticale x wheat derivatives, having tetraploid wheat cytoplasm from triticale, were reciprocally crossed with three improved bread wheats, and the resulting F₁s were evaluated for determining the comparative performance of the bread wheat and triticale cytoplasms for different traits. Significant reciprocal differences in the mean performance were observed for days to heading, days to maturity, spikes/plant, flag-leaf area, peduncle length, plant height, spike length, grains/spike, 1,000-grain weight, grain yield and grain protein content, and most of them were in favour of hexaploid wheat cytoplasm. However, this superiority of the hexaploid cytoplasm was not universal for a particular trait, implying that the differences in the performance of the evaluated reciprocal crosses depended not solely on the cytoplasmic background, but also on the interplay of the specific genotype with the cytoplasm.     

Inheritance of frost resistance and winter hardiness in distant hybrids of wheat and amphiploids

The data on inheritance of frost resistance and winter hardiness of bread wheat lines obtained as a result of distant hybridization of wheat-rye and wheat-elymus amphiploids with durum and bread wheat were presented. It was shown that selection of the donors of valuable traits is sensible to make in later progenies of hybrids (F6-F7). So, it is possible to obtain the new initial breeding material for winter bread wheat selection with high frost tolerance, winter hardiness and early maturity. Hypotheses explaining the high frost resistance of hybrids are presented. The crosses of the octoploid amphiploids with durum wheat are more preferable for the alien traits introgression into wheat than the crosses with bread wheat.     

Application of a new IBD-based QTL mapping method to common wheat breeding population: analysis of kernel hardness and dough strength

Mapping quantitative trait loci (QTL) in plants is usually conducted using a population derived from a cross between two inbred lines. The power of such QTL detection and the estimation of the effects highly depend on the choice of the two parental lines. Thus, the QTL found represent only a small part of the genetic architecture and can be of limited economical interest in marker-assisted selection. On the other hand, applied breeding programmes evaluate large numbers of progeny derived from multiple-related crosses for a wide range of agronomic traits. It is assumed that the development of statistical techniques to deal with pedigrees in existing plant populations would increase the relevance and cost effectiveness of QTL mapping in a breeding context. In this study, we applied a two-step IBD-based-variance component method to a real wheat breeding population, composed of 374 F₆ lines derived from 80 different parents. Two bread wheat quality related traits were analysed by the method. Results obtained show very close agreement with major genes and QTL already known for those two traits. With this new QTL mapping strategy, inferences about QTL can be drawn across the breeding programme rather than being limited to the sample of progeny from a single cross and thus the use of the detected QTL in assisting breeding would be facilitated.     

小麦品种冀麦24抗麦红吸浆虫QTL分析

麦红吸浆虫是影响小麦产量和品质的重要害虫,研究小麦对吸浆虫抗性的遗传及其连锁分子标记对于提高抗虫品种的选择效率具有重要意义。本研究以小麦感虫品系6218与抗虫品种冀麦24产生的重组近交系(RIL)群体为材料,利用SSR标记和人工虫圃对冀麦24的抗虫性遗传进行了研究。结果表明:6218与冀麦24的抗性差异显著,RIL群体在2年2点的鉴定中抗性稳定;所构建的遗传连锁图谱包含112个SSR位点,形成26个连锁群,图谱全长835.7 cM,标记间平均距离为7.5 cM。利用QTL IciMapping的完备区间作图法,在4A染色体上检测到1个加性效应位点(QSm.hbau-4A),该位点在2个鉴定年度的贡献率分别为9.67%、10.57%。该抗性QTL及其连锁SSR标记的发掘,将有助于提高小麦抗吸浆虫育种的选择效率。     

Identification and validation of quantitative trait loci conferring tan spot resistance in the bread wheat variety Ernie

Tan spot, caused by Pyrenophora tritici-repentis, is a foliar disease of wheat, and it can inflict serious reduction in grain yield and quality. The bread wheat variety Ernie was found to be immune to this disease in Australia, and its genetic control was investigated by quantitative trait loci (QTL) analysis using a doubled haploid population. Eight QTL were identified in this population from three independent trials, and four of them were derived from the parent Ernie. The most significant QTL was located on chromosome arm 2BS, explaining 38.2, 29.8 and 36.2% of the phenotypic variance, respectively, in these trials. The effects of the 2BS QTL were further validated in four additional populations. The presence of this single QTL reduced disease severity by between 29.2 and 67.1% with an average of 50.5%. The significant effects of this QTL and its consistent detection across all the trials with different genetic backgrounds make it an ideal target for breeding programmes as well as for its further characterization. Data from this study also showed that neither plant height nor heading date significantly affects tan spot resistance.     

The inheritance of the traits of resistance to fungal diseases by distant hybrids of wheat with amphiploids

The inheritance of resistance to powdery mildew, leaf rust and septorios of hybrids from crosses of wheat--rye and two wheat--Elymus amphiploids with durum and bread wheat was studied. Spontaneous hybridization was revealed to be a determining factor of the new available trait formation in the wide crosses. Control of the leaf rust and heary leaf traits by the same alien chromosome of Elytricum fertile is confirmed. While in the wheat--Aegilops amphiploid H74/90-258 these traits are not linked and controlled by one and two genes, respectively. The alien resistance is easier introgessed into wheat genome in the cross of 8x-amphiploid with durum wheat, than with bread wheat. Constant homozygous strains with group resistance to the studied diseases have been revealed.     

小麦-簇毛麦6VS/6AL易位染色体对小麦农艺性状的影响

南京农业大学细胞遗传研究所选育的小麦－簇毛麦6VS/6AL易位系在6VS上携有Pm21基因,用它作抗源已选育出一批高抗白粉病的新品系和新品种。为了研究6VS/6AL易位染色体对普通小麦农艺性状的影响,本研究选用由不同生态类型的推广品种与6VS/6AL易位系经过杂交回交选育的11个高代品系(种)及其轮回亲本和3份涉及6VS/6AL的高代分离品系以及5个F2群体,对产量、株高、穗长、穗粒数、穗粒重和千粒重等农艺性状进行比较分析。结果表明,6VS/6AL易位染色体对后代的小穗数、穗粒数、穗粒重和产量等农艺性状没有表现出明显的影响,对穗长和千粒重表现出一定的正向效应。多数6VS/6AL衍生品系的株高与亲本相比有所增加,但在同一组合的不同品系之间表现出一定的差异,在育种过程中通过选择能够改变增高趋势。6VS/6AL易位系对白粉病免疫,并且遗传稳定,对小麦的抗病育种是很有潜力的抗源亲本。     

High-resolution analysis of a QTL for resistance to Stagonospora nodorum glume blotch in wheat reveals presence of two distinct resistance loci in the target interval

Stagonospora nodorum glume blotch (SNG), caused by the necrotrophic fungus Stagonospora nodorum, is one of the economically important diseases of bread wheat (Triticum aestivum L.). Resistance to SNG is known to be quantitative and previous studies of a recombinant inbred line (RIL) population identified a major quantitative trait locus (QTL) for resistance to SNG on the short arm of chromosome 3B. To localize this QTL (QSng.sfr-3BS) with high resolution, we constructed a genetic map for the QTL target region using information from sequenced flow-sorted chromosomes 3B of the two parental cultivars ‘Arina’ and ‘Forno’, the physical map of chromosome 3B of cultivar ‘Chinese Spring’ and BAC-clone sequences. The mapping population of near-isogenic lines (NIL) was evaluated for SNG resistance in field infection tests. NILs segregated for disease resistance as well as for plant height; additionally, we observed a high environmental influence on the trait. Our analysis detected a strong negative correlation of SNG resistance and plant height. Further analysis of the target region identified two linked loci associated with SNG resistance. One of them was also associated with plant height, revealing an effect of QSng.sfr-3BS on plant height that was hidden in the RIL population. This result demonstrates an unexpectedly high genetic complexity of resistance controlled by QSng.sfr-3BS and shows the importance of the study of QTL in mendelized form in NILs.     

Sources of resistance and susceptibility to Septoria tritici blotch of wheat

An association genetics analysis was conducted to investigate the genetics of resistance to Septoria tritici blotch, caused by the fungus Zymoseptoria tritici (alternatively Mycosphaerella graminicola), in cultivars and breeding lines of wheat (Triticum aestivum) used in the UK between 1860 and 2000. The population was tested with Diversity Array Technology (DArT) and simple‐sequence repeat (SSR or microsatellite) markers. The lines formed a single population with no evidence for subdivision, because there were several common ancestors of large parts of the pedigree. Quantitative trait loci (QTLs) controlling Septoria resistance were postulated on 11 chromosomes, but 38% of variation was not explained by the identified QTLs. Calculation of best linear unbiased predictions (BLUPs) identified lineages of spring and winter wheat carrying different alleles for resistance and susceptibility. Abundant variation in Septoria resistance may be exploited by crossing well‐adapted cultivars in different lineages to achieve transgressive segregation and thus breed for potentially durable quantitative resistance, whereas phenotypic selection for polygenic quantitative resistance should be effective in breeding cultivars with increased resistance. The most potent allele reducing susceptibility to Septoria, on chromosome arm 6AL, was associated with reduced leaf size. Genes which increase susceptibility to Septoria may have been introduced inadvertently into UK wheat breeding programmes from cultivars used to increase yield, rust resistance and eyespot resistance between the 1950s and 1980s. This indicates the need to consider trade‐offs in plant breeding when numerous traits are important and to be cautious about the use of non‐adapted germplasm.     

沙生植物沙鞭不同居群形态变异研究

以沙鞭(Psammochloa villosa Bor.)20个自然居群为研究对象,对其株高、花序长度、旗叶长度、旗叶宽度和小穗长度等12个表型性状进行形态变异研究。结果显示,12个性状群体间F值为1.832~8.958,达到显著或极显著水平,表明沙鞭不同居群表型性状存在广泛变异,且变异程度各不相同;主成分分析结果显示,前4个主成分代表了沙鞭形态多样性的82.277%,其中旗叶长度、旗叶宽度、颖片长度、小穗长度等是造成不同居群表型性状差异的主要因素;依据欧式距离对参试居群进行的UPGMA聚类分析结果表明,当遗传距离为20.5时,可以将20个沙鞭野生居群划分为两类,且各表型性状并没有依居群地理分布而聚类。