Analysis of wheat-Thinopyrum intermedium derivatives with BYDV-resistance

Chromosome compositions of seven lines, derived from hybrids between a wheat cultivar and the wheat-Thinopyrum intermedium addition line Z6, with barley yellow dwarf virus (BYDV) resistance, were determined by genomic in situ hybridization, cytogenetic and SSR assays. The results showed that line N522 was a disomic addition line, lines N420 and N439 were 2Ai-2(2B) chromosome substitution lines, lines N431 and N452 were 2Ai-2(2D) chromosome substitution lines, line N523 was a 2Ai-2S(2D) ditelosomic substitution line, and line N530 was a double ditelosomic line with the mitotic chromosome number of 2n = 40 + 4t. One pair of telosomes in line N530 lacked several proximal SSR markers of chromosome 2AS, but possessed certain terminal markers, which were consistent with an acrocentric structure, and the other pair of chromosome arms were presumably 2Ai-2S telosomes with BYDV-resistance. These wheat-Th. intermedium lines provide useful genetic resources for developing alien chromosome translocation lines.     

Molecular and agronomic characterization of wheat-Agropyron intermedium recombinant chromosomes

Thirty‐six wheat‐Agropyron intermedium (host) Beauv. [Syn. Trichopyrum intermedium (host) A. Love, Elytrigia intermedia (host) Nevski, Thinopyrum intermedium (host) Barkworth and Dewey] 7A/7Ai‐1 recombinant chromosomes were characterized using DNA markers. Analysis of recombinant chromosomes using 15 restriction fragment length polymorphism probes identified the homoeologous crossover products that had varying length of A. intermedium chromatin introgressed onto chromosome 7A of common wheat. The linear order of the probe loci was established along the lengths of the chromosomes. The short arm recombinants that had A. intermedium chromatin distal to the locus Xpsr108 and proximal to the locus Xpsr119 were resistant to wheat stem rust, indicating that the rust resistance gene (Sr44) was located on the distal part of chromosome arm 4Ai‐1s. The barley yellow dwarf virus (BYDV) resistance gene reported to be present on the long arm of chromosome 7Ai‐1 was found to be ineffective against the BYDV serotype used in the present study.     

抗黄矮病小麦种质的分子标记

应用基因组原位杂交技术分析了抗小麦黄矮病种质的遗传组成,研究表明小麦一中间但麦草部分双二倍体无芒中4(2n=56)具有40条小麦染色体、5对中间僵麦草染色体、3对小麦/中间僵麦草易位染色体,其中1对是罗伯逊氏易位染色体。结果表明无芒中4与远中5的遗传组成有明显差异,是两种不同类型的材料。抗黄矮病小麦种质F940418, T10     

Identification of wheat–Thinopyrum intermedium 2Ai-2 ditelosomic addition and substitution lines with resistance to barley yellow dwarf virus

Among the regenerated plants derived from immature hybrid embryos of wheat–Thinopyrum intermedium disomic addition line Z6 × common wheat variety ‘Zhong8601’, a plant with a telocentric chromosome and barley yellow dwarf virus (BYDV) resistance was obtained. The telocentric chromosome paired with an entire Thinopyrum chromosome to form a heteromorphic bivalent at meiotic metaphase I. Genomic in situ hybridization showed that the telosome originated from Th. intermedium. Two ditelosomic additions and one disomic substitution were identified among the offspring of the plant. Two random amplified polymorphic DNA molecular markers were identified among 150 random primers used to detect the different arms of the alien chromosome. These might be useful for developing translocation lines with BYDV resistance.     

Characterization of wheat-Thinopyrum partial amphiploids for resistance to barley yellow dwarf virus

Resistance to viruses such as wheat streak mosaic virus (WSMV) and barley yellow dwarf virus(BYDV) is lacking in the primary gene pool of wheat, and therefore resistance is being introgressed from wild relatives such as Thinopyrum species. Resistance to BYDV was found in partial amphiploids (2n = 8x = 56, consisting of 42 wheat and14 alien chromosomes) obtained in hybrids between wheat and both Th. intermedium and Th.ponticum. GISH analysis revealed that the alien genomes of all but one resistant partial amphiploid were heterogeneous consisting of different ratios of St, J^s and J genome chromosomes obtained from theThinopyrum parent. Translocated chromosomes consisting of Robertsonian, interstitial and terminal translocations between the different genomes were also detected. The tissue blot immunoassay showed that partial amphiploids having resistance could be inoculated with the virus but both virus multiplication and spread were completely blocked. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identifying the alien chromosomes in wheat – Leymus multicaulis derivatives using GISH and RFLP techniques

Genomic in situ hybridization (GISH) and restriction fragment length polymorphism (RFLP) were used to identify the Leymus multicaulis (XXNN, 2n = 28) chromosomes in wheat-L. muliticaulis derivatives. Fifteen lines containing L. multicaulis alien chromosomes or chromosomal fragments were identified. All alien chromosomes or fragments in these 15 lines were from the X genome and none were from the N genome. Eleven L. multicaulis disomic addition lines and four translocation-addition lines were identified with chromosome rearrangements among homoeologous groups 2, 3, 6 and 7. Only homoeologous group 1 lacked rearrangements in addition or translocation chromosomes. The results revealed that translocation in non-homoeologous chromosomes widely exists in the Triticeae and therefore it is necessary to identify the alien chromosomes (segments) in a wheat background using these combined techniques. During the course of the work, probe PSR112, was found to detect X genome addition lines involving L. multicaulischromosomes. This may prove to be a valuable probe for the identification of alien chromosomes in a wheat background. This revised version was published online in August 2006 with corrections to the Cover Date.     

Segregation distortion in common wheat of a segment of Thinopyrum intermedium chromosome 7E carrying Bdv3 and development of a Bdv3 marker

Yellow dwarf (YD) disease is one of the most destructive diseases of cereals worldwide. Wheat (Triticum aestivum L.)–Thinopyrum intermedium 7E(7D) substitution line P29 carries resistance to YD, known as Bdv3, that originates on the long arm of chromosome 7E of Th. intermedium, and the resistance was introgressed into wheat chromosome 7D as T7DS.7DL–7EL in the translocation lines P961341 and P98134. Until now, quantification of YD viruses in cereal crops was usually done by enzyme‐linked immunosorbent assay (ELISA), which is time consuming and laborious. To facilitate this analysis, SSR‐Bdv3, a diagnostic molecular marker, was developed in this study. The transmission of the Th. intermedium segment with Bdv3 was investigated using the SSR‐Bdv3 marker and ELISA in F₂ and testcross progeny derived by crossing two wheat–Th. intermedium translocation lines to four common wheat cultivars. A Th. intermedium chromosome 7E segment in the translocation line P98134 was preferentially transmitted through male gametes in all of its crosses with the four wheat cultivars. However, the transmission frequency of the Th. intermedium 7E segment in another wheat–Th. intermedium translocation line, P961341, varied in different genetic backgrounds. The F₂ populations from reciprocal crosses of Chinese Spring and P961341 showed good fits to the expected ratio of 1 : 2 : 1. In this study, male preferential transmission for either chromosome 7E or chromosome 7D was observed in the progeny derived by crossing P961341 to other wheat cultivars.     

应用GISH与STS标记鉴定小麦-中间偃麦草抗黄矮病端体系

由大麦黄矮病毒引起的小麦黄矮病毒病是一个严重病害,至今在小麦属内还没有发现抗源。中间偃麦草2Ai-2染色体携带一个高抗黄矮病基因,对该基因的染色体臂定位将为制定抗病基因向小麦转移策略,筛选、开发特定的、与抗性连锁的分子标记的研究提供重要信息。本文对由小麦-中间偃麦草二体附加系Z6衍生的3个抗黄矮病端体系进行鉴定,通过分析端体的遗传构成、筛选与端体共分离的STS标记以确定端体在遗传上的染色体臂归属,从而明确BYDV抗病基因的染色体位置。以拟鹅冠草基因组[Pseudoroegneria strigosa (M. Bieb.) Löve,St]DNA为探针,中国春基因组(Triticum aestivum L., ABD) DNA作封阻分别对抗病亲本Z6及抗病端体系N530的根尖体细胞染色体进行原位杂交,结果表明,N530体细胞中有2个端体显示出与Z6中外源染色体2Ai-2短臂相似, 而与长臂不同的杂交信号。以小麦第2同源群的5个RFLP探针的DNA序列为基础,设计了6对PCR引物,对小麦-中间偃麦草二体异附加系、二体代换系和端体系进行扩增,结果表明,基于短臂探针psr126,psr131序列设计的2对引物,可在含有2Ai-2染色体及端体的抗黄矮病材料中特异扩增,而基于长臂探针psr112序列设计的1对引物,可在含有2Ai-2染色体的抗黄矮病材料中特异扩增,但不能在端体系进行特异扩增,证明外源端体为2Ai-2染色体的短臂。本研究不仅将黄矮病抗性基因定位于2Ai-2染色体的短臂上, 而且由RFLP探针psr126、psr131和psr112序列转化的标记STS₁₂₆ (sequence tagged site) STS₁₃₁和STS₁₁₂还可分别作为追踪2Ai-2染色体短臂和长臂的分子标记,用于抗病易位系辅助选择。     

Comparison of TAF46 and Zhong 5 resistances to barley yellow dwarf virus from Thinopyrum intermedium in wheat

Barley yellow dwarf virus (BYDV) is one of the most important plant viruses in the world. Two sources of resistance to BYDV derived from Thinopyrum intermedium were compared in wheat backgrounds. A source of resistance was confirmed in the partial amphiploid TAF46, the group 7 addition line L1, and translocation TC14. The other source of resistance derives from the partial amphiploid Zhong 5 and is present in the group 2 addition line Z6. Six ditelosomic addition lines have been derived from Z6. The resistance of genotypes derived from Zhong 5 is more effective at reducing virus multiplication throughout plant growth than that of genotypes derived from TAF46. The translocation line TC14, derived from TAF46 showed 30% plants escaping virus infection whereas all plants derived from Zhong 5 were infected. This suggests that the two sources of resistance are associated with differing mechanisms of resistance. Methods to better understand the genetic control and the mechanisms of these two resistances are suggested. The pyramiding of different sources of resistance to construct durable resistance is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characterization of a partial amphiploid between Triticum aestivum cv. Chinese Spring and Thinopyrum intermedium ssp. trichophorum

A partial amphiploid, TE-3, between Triticum aestivum cv. Chinese Spring (CS) and Thinopyrum intermedium ssp. trichophorum was characterized by cytological observation, genomic in situ hybridization (GISH), seed storage protein electrophoresis and disease resistance screening. The TE-3 plants were deeply covered with pubescence, which is characteristic of the Th. intermedium ssp. trichophorum parent. Feulgen staining of the somatic metaphases revealed that the chromosome number varied from 52 to 56. TE-3 pollen mother cells (PMCs) regularly showed two to four univalents and 25 to 27 bivalents, indicating a degree of cytological instability. Giemsa-C banding showed that the Thinopyrum chromosomes in TE-3 produced strong heterochromatin bands. GISH analysis suggested that the alien chromosomes in TE-3 consisted of eight St chromosomes, four J^s chromosomes, and two J genome chromosomes, as well as two St-J translocation chromosomes. Seeds storage proteins separated by acid polyacrylamide gel electrophoresis (APAGE) and sodium dodecyl sulphate – polyacrylamide gel electrophoresis (SDS-PAGE) showed that TE-3 expressed some of Th. intermedium ssp. trichophorum specific gliadin and glutenin bands. When inoculated with stripe rust and powdery mildew isolates, TE-3 expressed resistance derived from its Thinopyrum parent. It appears that TE-3 can be used as a donor source in wheat breeding programs to introduce novel variation for quality and disease resistance.     

Identification for H. villosa chromatin in wheat lines using genomic in situ hybridization, C-banding and gliadin electrophoresis techniques

Detection of H. villosa chromosomes in telosomic addition and translocation lines of common wheat was undertaken using genomic in situ hybridization (GISH), C-banding techniques and polyacrylamide gels electrophoresis. The result of GISH on mitotic metaphase cells of the addition line `95039' indicated that the added telochromosomes originated from H. villosa, and it was probably 6VS or 7Vs of H. villosa according to the C-banding pattern. Furthermore, the analysis of gliadin profiles demonstrated that the telochromosome was 6VS. A pair of 1RS/1BL translocation chromosome was also found in `95039'. In addition, mitotic GISH analysis showed that the 6VS/6AL translocation chromosome remained unchanged after being transferred into new wheat background. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genomic constitution of a partial amphiploid OK7211542 used as a source of immunity to barley yellow dwarf virus for bread wheat

A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of crosses between a series of 2n= 56 partial amphiploids confirmed that the alien genome of the BYDV-immune Agro-tricum line OK7211542 is derived from Thinopyrum ponticum and not from Thinopyrum intermedium. The evidence from meiotic pairing analysis indicated that the chromosome constitution of OK7211542 is similar to another Agrotricum line, ORRPX, which was derived from a cross of wheat and Th. ponticum, but different from other Agrotricum lines, Zhong 5 and TAF 46 which were derived from the crosses between wheat and Th. intermedium. The GISH analysis confirmed that OK7211542 contained one complete set of 14 Th. ponticum chromosomes, in which no S chromosome was present in the alien genome. GISH also detected a small alien translocation attached to one of the wheat chromosomes, a result that was consistent with the pairing data.     

Inheritance of traits associated with seed size in groundnut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

A new wheat-Thinopyrum substitution line AS1677, developed from a cross between wheat line ML-13 and wheat-Thinopyrum intermedium ssp. trichophorum partial amphiploid TE-3, was characterized by fluorescence in situ hybridization (FISH), sequential Giemsa-C banding, genomic in situ hybridization (GISH), seed storage protein electrophoresis, molecular marker analysis and disease resistance screening. Sequential Giemsa-C banding and GISH using Pseudoroegneria spicata genomic DNA as probe indicated that a pair of St-chromosomes with strong terminal bands were introduced into AS1677. FISH using pTa71 as a probe gave strong hybridization signals at the nuclear organization region and in the distal region of the short arms of the St chromosome. Moreover, FISH using the repetitive sequence pAs1 revealed that a pair of wheat 1D chromosomes was absent in accession AS1677. Seed storage proteins separated by acid polyacrylamide gel electrophoresis (APAGE) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) confirmed that AS1677 lacked the gliadin and glutenin bands encoded by Gli-D1 and Glu-D1, further confirming the absence of chromosome 1D. The introduced St chromosome pair belonging to homoeologous group 1 was identified by newly produced genome specific markers. AS1677 is a new 1St (1D) substitution line. When inoculated with stripe rust and powdery mildew isolates, AS1677 expressed stripe rust resistance possibly derived from its Thinopyrum parent. AS1677 can be used as a donor source for introducing novel disease resistance genes to wheat in breeding programs aided by molecular and cytogenetic markers.     

RFLP mapping of the three major genes, Vrn1, Q and B1, on the long arm of chromosome 5A of wheat

Chromosome 5A of wheat carries several major genes of agronomic importance, including Vrn1 controlling spring/winter wheat difference, Q determining spike morphology and B1 inhibiting awn development. A population of single-chromosome recombinant lines from the cross between two chromosome substitution lines, 'Chinese Spring' (Cappelle-Desprez 5A) and 'Chinese Spring' (Triticum spelta 5A) was developed to map these genes on the long arm of chromosome 5A relative to RFLP markers. Using 120 recombinant lines, a map of approximately 230 cM in length was constructed. The gene order was centromere– Vrn1– Q– B1. The Vrn1 locus was tightly linked to two RFLP markers, Xbcd450 and Xrz395 with 0.8 cM, and to Xpsr426 with 5.0 cM. The Vrn1-adjacent region was located in the central of the long arm, approximately 90 cM from the centromere. The chromosome region around Q and the 5A/4A translocation break-point were mapped by three RFLP markers, and their order was found to be Q– Xpsr370– Xcdo457–4A/5A break-point– Xpsr164. The B1 locus was located on the most distal portion of the long arm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mapping quantitative trait loci in wheat for resistance against greenbug and Russian wheat aphid

Breeding for genetic resistance against greenbug and Russian wheat aphid (RWA) is the most effective way of controlling these widespread pests in wheat. Earlier work had shown that chromosome 7D of a synthetic hexaploid wheat, ‘Synthetic’ (T. dicoccoides × Ae. squarrosa) (AABB × DD) gave resistance when transferred into the genetic background of an aphid‐susceptible cultivar, ‘Chinese Spring’, as the recipient. To map the genes involved, a set of 103 doubled haploid recombinant substitution lines was obtained from crossing the 7D substitution line with the recipient, and used to determine the number and chromosomal location of quantitative trait loci (QTL) controlling antixenosis and antibiosis types of resistance. Antixenosis to RWA was significantly associated with marker loci Xpsr687 on 7DS, and Xgwm437 on 7DL. Antibiosis to greenbug was associated with marker loci Xpsr490, Rc3 (on 7DS), Xgwm44, Xgwm111, Xgwm437, Xgwm121 and D67 (on 7DL). Similarly, antibiosis to RWA was linked to loci Xpsr490, Rc3, Xgwm44, Xgwm437 and Xgwm121. At least two QTL in repulsion phase, one close to the centromere either on the 7DS or 7DL arms, and a second distal on 7DL could explain antibiosis to RWA and, partially, this mechanism against greenbug.     

A new secondary reciprocal translocation discovered in Chinese wheat

A new wheat-rye secondary reciprocal translocation involving T1RS·7DL and T7DS·1BL was detected by chromosome C-banding and genomic in situ hybridization (GISH). The meiotic configuration analysis combined with C-banding and GISH on F₁ hybrids of this newly discovered translocation with T1RS·1BL and Chinese Spring Dt7DS indicated that the new translocation probably resulted from a secondary reciprocal translocation between the primary translocation T1RS·1BL and 7D in the progenies of Aifeng3//Mengxian201/Neuzucht. On the basis of the cytological analysis of progenies and recombinant inbred lines (RILs) (derived from a cross between T1RS·7DL, T7DS·1BL and T1RS·1BL), the translocation chromosomes T1RS·7DL and T7DS·1BL transmitted readily, and appeared in most of the progenies.     

Characterization of a wheat–Thinopyron intermedium substitution line with resistance to powdery mildew

Among the progenies of a hybrid between common wheat Triticum aestivum L. cv. Yannong 15 and Thinopyron intermedium, plant E99018 was identified with the chromosome number 2n = 42 and stable agronomic traits. An analysis of the metaphase chromosome pairing indicated that it formed 21 bivalents but that 2 univalents were present in the F₁ hybrid of this plant with common wheat. Resistance verification by race 15 and with mixed races of Blumeria graminis f. sp. tritici at the seedling and adult stages showed that at both stages, the plant was immune to powdery mildew. In situ hybridization with the genomic Th. intermedium and the St genome DNAs as probes and wheat DNA as a block has shown that it contained a pair of Th. intermedium chromosomes. On the basis of the hybridization pattern of the St genome probe to the critical chromosome, a conclusion was reached that this pair of chromosomes belonged to the E genome. Therefore, plant E99018 was a spontaneously formed substitution line. An analysis by 116 SSR markers indicated that the substituted wheat chromosome was 2D and the most likely substitution in E99018 is 2E(2D).     

Genetic variation for tolerance or resistance to barley yellow dwarf virus in durum wheat

Summary One durum wheat line (Triticum durum), cv. 82PCD476, with useful BYDV tolerance or resistance, was singled out of 5 152 lines evaluated between 1979 and 1986. A few other lines such as cv. Boohai and cv. 12th IDSN 227, slightly inferior to cv. 82PCD476, also showed some value. With an hybrid of cv. 12th IDSN227 with the susceptible cv. 84PCY-S531, broad-sense heritability values of 0.37–0.41 were obtained for symptoms and a heritability value of 0.55 was obtained for the total weight of spikes. The weight of spikes was considered as a good indicator of wheat tolerance to BYDV. Although BYDV resistance or tolerance genes are not very common in durum wheat, sources of heritable resistance could be found. However, the resistance ofT. aestivum to BYDV was superior to the one found inT. durum.Cintribution no. 323     

Molecular cytogenetic characterization of wheat-Thinopyrum ponticum translocations bearing blue-grained gene(s) induced by r-ray

Eight γ-irradiation-induced Triticum aestivum – Thinopyrum ponticum translocations conveying the blue aleurone were characterized using molecular cytogenetic approach. The size of alien chromosome segments was estimated by genomic in situ hybridization (GISH). The wheat chromosome segments involved in these translocations were clearly identified by two-color fluorescence in situ hybridization (FISH) with the probes of pAs1 and pSc119.2 (or pHvG38). Most of the detected translocations were reciprocal translocations involving wheat chromosomes 1B, 2D, 3A, 4A, 5B, 6B, 6D and 7A. This series of blue-grained wheat translocation lines would be useful in theoretical studies and wheat chromosome engineering breeding.     

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.