The Transfer of Thinopyrum-Derived Leaf-rust Resistance from Common Wheat to Durum Wheat.

The leaf rust resistance gene on chromosome 7AL of ‘Chinese Spring’ transfer no. 12 derived from Thinopyrum ponticum, was transferred to durum wheat by standard backcrossing. In ‘Agatha’ and ‘Indis’ a leaf rust resistance gene from Thinopyrum ponticum and Thinopyrum ponticum respectively, is found on a translocated segment on chromosome arm 7DL. The use of the ‘Langdon’ disomic D-chromosome substitution lines for 7A and 7B resulted in the recovery of tetraploid leaf-rust resistant lines from the crosses with ‘Agatha’ in the B₂F₁ generation. Tetraploid lines carrying the ‘Indis’ translocation segment were recovered in the B₂F₂ generation. The F₂ segregation ratios for rust resistance after selfing or back-crossing generally fitted a 1: 1 ratio indicating non-transmission of the translocation segments in the male gametes. Homozygous resistant plants were not obtained. Meiotic instability was observed in 28 chromosome B₂ F₂ derivatives of the crosses between ‘Chinese Spring’ transfer no. 12 and durum wheat.     

Genetic control of a response to the segregation distortion allele,Sd-1d,in the common wheat line ‘Indis’

Summary A translocated chromosome segment, derived from Thinopyrum distichum, carries the leaf rust resistance allele Lr19d and a segregation distorter allele, Sd-1d. In translocation heterozygotes, male and female gametophytes lacking the translocation are aborted, the severity of the effect depending on the genotype of the hybrid. The selective abortion of the gametophytes with a normal chromosome 7D appears to be based on the absence of the translocated chromosome rather than the presence of the normal chromosome. The magnitude of the gametocidal response, elicited by Sd-1d, is under multigenic control. A number of chromosomes, the individual effects of which are generally small, may act to suppress or promote the response. Chromosome arms 2AL, 2BL, 5BL and 5DL of Chinese Spring were found to reduce sensitivity to the presence of the gametocidal chromosome. Chromosome 3B of Inia 66-1 also reduce the gametocidal response while chromosome arm 6DS of Chinese Spring may promote the effect     

Transfer of the Glu-D1 Gene from Chromosome 1D of Breadwheat to Chromosome 1R in Hexaploid Triticale

The use of hexaploid triticale as a crop for human consumption has been limited by its inferior bread-making quality. To ameliorate this problem, a segment of chromosome ID of breadwheat with the Glu-D1d allele encoding for high molecular weight glutenin subunits 5 7plus; 10 was translocated to chromosome 1R of the hexaploid triticale ‘Rhino’ through a combination of a centric break-fusion translocation followed by 5D(5B)-induced homoeologous pairing. The resulting recombinant chromosome 1R has a small interstitial segment of ID with the Glu-D1d allele. The maximum physical length of the translocated segment is estimated at about 16.5 % of 1DL. Frequency of translocations involving the long arms of homoeologous group-1 chromosomes in the analyzed progeny suggested that homoeologous recombination in triticale was substantially higher than that previously reported in hexaploid wheat.     

Evidence of allelism between genes Pm8 and Pm17 and chromosomal location of powdery mildew and leaf rust resistance genes in the common wheat cultivar'Amigo'

TIBL-1RS wheat-rye translocation cultivars utilized in wheat programmes worldwide carry powdery mildew resistance gene Pm8. Cultivar‘Amigo’possesses resistance gene Pm17 on its TIAL-1RS translocated chromosome. To be able to use Pm17efficiently in breeding programmes, this gene was transferred to a TIBL-1RS translocation in line Helami-105, and allelism between Pm8 and Pm17was studied. The progenies of the hybrids in the F₂ generation and F₃ families provided evidence that the two genes are allelic. Genetic studies using monosomic analyses confirmed that in cultivar‘Amigo', Pm17 and leaf rust resistance gene Lr24 are located on a translocated chromosome involving 1 A and 1B, respectively.     

Transfer of the Glu-D1 locus encoding high molecular weight glutenin subunits 5+10 from breadwheat to diploid rye

A fragment of chromosome 1DL of breadwheat (Triticum aestivum L.) with the locus Glu-D1 encoding high molecular weight glutenin subunits 5+10 was translocated in hexaploid triticale (× Triticosecale Wittmack) to chromosome 1RL of rye (Secale cereale L.) where it replaced a corresponding fragment containing locus Sec-3 encoding rye secalins. The translocated chromosome 1R was transferred to diploid rye through backcrosses. During the transfer, at least two crossover events must have taken place that reduced the lengths of the 1DL inserts to about 5–8% of 1RL. These short inserts were selected on the basis of normal male transmission from heterozygotes and by low pairing with chromosome 1D in the F₁ hybrids with wheat, and tested by the in situ hybridization with total genomic DNA. While the wheat introgression in rye did not affect plant morphology or fertility, preliminary observations of the first population of homozygotes suggested that grain yield was lower, probably as a result of about 15% reduction of the 1000 kernel weight. The presence of a single wheat glutenin locus was insufficient to create rye with wheat-like breadmaking properties. However, relative to controls, the SDS-sedimentation value increased by about 75% and loaf volume was greater in test bakes using the procedure adapted for wheat-rye blends. Loaf volume for bread baked using the procedure for rye flour was not affected. Ryes with various glutenin subunits could be used in wheat-rye blends. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic basis of seedling-resistance to leaf rust in bread wheat 'Thatcher'

The bread wheat cultivar ‘Thatcher’ is documented to carry the gene Lr22b for adult‐plant resistance to leaf rust. Seedling‐resistance to leaf rust caused by Puccinia triticina in the bread wheat cultivar ‘Thatcher’, the background parent of the near‐isogenic lines for leaf rust resistance genes in wheat, is rare and no published information could be found on its genetic basis. The F₂ and F₃ analysis of the cross ‘Agra Local’ (susceptible) × ‘Thatcher’ showed that an apparently incompletely dominant gene conditioned seedling‐resistance in ‘Thatcher’ to the three ‘Thatcher’‐avirulent Indian leaf rust pathotypes – 0R8, 0R8‐1 and 0R9. Test of allelism revealed that this gene (temporarily designated LrKr1) was derived from ‘Kanred’, one of the parents of ‘Thatcher’. Absence of any susceptible F₂ segregants in a ‘Thatcher’ × ‘Marquis’ cross confirmed that an additional gene (temporarily designated LrMq1) derived from ‘Marquis’, another parent of ‘Thatcher’, was effective against pathotype 0R9 alone. These two genes as well as a second gene in ‘Kanred’ (temporarily designated LrKr2), which was effective against all the three pathotypes, but has not been inherited by ‘Thatcher’, seem to be novel, undocumented leaf rust resistance genes.     

Fine mapping of qSS‐9, a major and stable quantitative trait locus,for seed storability in rice (Oryza sativa L.)

Seed storability in rice (Oryza sativa L.) is an important agronomic trait. We previously showed a quantitative trait locus of seed storability, qSS‐9, on chromosome 9 in a backcross population of ‘Koshihikari’ (japonica) / ‘Kasalath’ (indica) // ‘Koshihikari’. In this study, fine mapping of the chromosomal location of qSS‐9 was performed. Effect of ‘Kasalath’ allele of qSS‐9 was validated using a chromosome segment substitution line, SL36, which harboured the target quantitative trait loci (QTL) from ‘Kasalath’ in the genetic background of ‘Nipponbare’ under different ageing treatments in different environments. Subsequently, an F₂ population from a cross between ‘Nipponbare’ and SL36 was used for fine mapping of qSS‐9. Simultaneously, four subnear isogenic lines (sub‐NILs) that represented different recombination breakpoints across the qSS‐9 region were developed from F₃ progeny. Finally, the qSS‐9 locus was located between the Indel markers Y10 and Y13, which delimit a region of 147 kb in the ‘Nipponbare’ genome. These results provide a springboard for map‐based cloning of qSS‐9 and possibilities for breeding rice varieties with strong seed storability.     

Pleiotropic effects of the ea7 photoperiod response gene on the morphology and agronomic traits in barley

The photoperiod‐insensitive barley mutant ‘Atsel’, carrying the recessive gene ea₇, was studied together with the donor variety ‘Atlas’ (wild‐type, Ea₇) under different daylengths with the aim of analysing pleiotropic effects. Grown under long and short photoperiods ‘Atsel’ flowered about 10 days and 34 days, respectively, earlier than ‘Atlas’. The significantly shorter life‐cycle of the photoperiod‐insensitive mutant resulted in several changes of plant morphology. Tillering, plant height, number of leaves and number of internodes were reduced. A lower number of florets per main spike was observed for ‘Atsel’, but only in the long photoperiod experiment. Finally, photoperiod insensitivity combined with a lower grain yield per plant was most pronounced under long‐day treatment. The data are comparable with results obtained from single chromosome recombinant lines of wheat that have differences in their photoperiod response caused by the genes Ppd1 or Ppd2.     

A polymorphic microsatellite in the 3'end of 'waxy' genes of wheat, Triticum aestivum

Potential polymorphism of an (AT)_N microsatellite at the 3’end of waxy genes in bread wheat was examined. Primers were designed from a published cDNA sequence of a wheat waxy gene. Polymerase chain reaction (PCR) amplification of genomic DNA from 135 mainly Australian cultivars revealed eight alleles on chromosome 7A. This polymorphic microsatellite is a potential codominant marker for the Wx-A1 locus in breeding programmes. A distinguishable fragment was also amplified from chromosome 7D. This fragment was absent where a plant was null for the waxy gene on chromosome 7D, being a dominant marker for the Wx-D1 locus. The primers were also useful for amplifying genomic DNA from barley, rye and triticale and can be used to detect potential polymorphism in these species.     

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.     

Detection of molecular markers linked to the durable adult plant stripe rust resistance gene Yr18 in bread wheat (Triticum aestivum L.)

Stripe rust of wheat caused by Puccinia striiformis West. f. sp. tritici presents a serious problem for wheat production worldwide, and identification and deployment of resistance sources to it are key objectives for many wheat breeders. Here we report the detection of simple sequence repeat (SSR) markers linked to the durable adult plant resistance of cv. ‘Otane’, which has conferred this resistance since its release in New Zealand in 1984. A double haploid population from a cross between ‘Otane’ and the susceptible cv. Tiritea’ was visually assessed for adult plant infection types (IT) in the glasshouse and field, and for final disease severity in the field against stripe rust pathotype 106E139A⁺. At least three resistance loci controlled adult plant resistance to stripe rust in this population. Quantitative trait loci (QTL) mapping results revealed that two of these, one on chromosome 7DS corresponds to the durable adult plant resistance gene Yr18 and other on chromosome 5DL were contributed from ‘Otane’; while the remaining one on chromosome 7BL, was contributed from the susceptible ‘Tiritea’. Interval mapping placed the ‘Otane’‐resistant segment near the centromere of chromosome 7DS at a distance of 7 cM from the SSR marker gwm44. The stability of QTL in the two environments is discussed. SSR gwm44 is potentially a candidate marker for identifying the durable resistance gene Yr18 in breeding programmes.     

长穗偃麦草1E附加系与杀配子染色体2C附加系杂交后代的细胞学及形态学分析

长穗偃麦草是小麦的野生近缘种属,具有抗寒、抗旱、抗病等优异性状。为了利用长穗偃麦草的优异基因,将‘中国春’-长穗偃麦草1E二体附加系与‘中国春’-柱穗山羊草2C二体附加系杂交、自交和回交,观察其后代的细胞学和形态学特性。结果表明,在杂交后代有丝分裂和减数分裂中观察到了染色体畸变现象;统计F1代自交结实率,发现与亲本相比,这些杂种后代的结实率明显降低;杂种后代的穗型发生了分离,除正常穗型外还观察到了密穗型,说明杀配子染色体2C可以诱导染色体畸变并对结实率和穗型均有一定的影响。本研究为进一步创制小麦-长穗偃麦草1E染色体易位系和缺失系奠定了基础。     

The Aegilops ventricosa segment on chromosome 2AS of the wheat cultivar 'VPM1' carries the cereal cyst nematode resistance gene Cre5

Previous studies showed that the intermediate level of resistance in bread wheat line ‘VPM1’ to pathotype Ha12 of the cereal cyst nematode could be conferred by an Aegilops ventricosa‐derived gene, CreX, in chromosome arm 2AS, which also carries the rust resistance genes Yrl7, Lr37 and Sr38. Near isogenic lines (NILs) differing for the presence and absence of the Ae. ventricosa‐derived linked genes Yrl7/Lr37/Sr38 were tested with cereal cyst nematode. Lines carrying Yr17 produced significantly fewer nematode cysts than the controls. An infested soil experiment produced better differentiation among resistant and susceptible genotypes. Susceptibility of ‘Trident’ indicated that linkage between CreX and Yr17 is incomplete. Microsatellite markers did not differentiate between ‘Trident’ and CreX‐carrying genotypes. However, Xgwm636 (104) was associated with the presence of Yr17 in all six genetic backgrounds. Since none of the reported cereal cyst nematode resistance genes is located in chromosome 2AS, CreX was designated as Cre5.     

Intrachromosomal mapping of genes for dwarfing (Rht12) and vernalization response (Vrn1) in wheat by using RFLP and microsatellite markers

For intrachromosomal mapping of the dominant GA-sensitive dwarfing gene Rht12 and the vernalization response gene Vrn1 on chromosome 5 A, an F₂ population was established using a wide (synthetic) wheat cross. In addition to restriction fragment length polymorphism (RFLP) probes four microsatellite markers were incorporated. Rht12 was mapped distally to four RFLP loci (Xmwg616, Xpsr164, Xwg114, Xpsr1201) and three microsatellite markers (Xgwm179, Xgwm410, Xgwm291), known to be located on the segment of chromosome SAL which was ancestrally translocated and is homoeologous to Triticeae 4 L. The map position of Rht12 suggests that it is homoeologous to the dominant GA-sensitive dwarfing gene Ddw1, present on chromosome 5RL. The vernalization response gene Vrn1 showed linkage to Xwg644, as might be expected from comparative maps.     

Effects of Wheat Chromosome 1D Telosomes on Hybrid Seed Development in Wheat × Rye Crosses

Pollination of ‘Chinese Spring,’ monosome 1D plants with rye results in failure of hybrid seed development in a proportion of the F₁ seeds corresponding to the transmission rate of the nullisomic 1D egg cells. Development and viability of these hybrid seeds closely resemble that normally observed in T. aurum× rye crosses. Using ‘Chinese Spring’ chromosome ID telosomic plants in crosses with rye, it was possible to illustrate that the observed effect was associated with the long arm of this chromosome.     

Chromosomal location of powdery mildew resistance gene Pm16 in wheat using SSR marker analysis

The use of resistant cultivars is a most economical way to control powdery mildew (Blumeria graminis f.sp. tritici) in wheat (Triticum aestivum L.). Identification of molecular markers closely linked to resistance genes can greatly increase the efficiency of pyramiding resistance genes in wheat cultivars. The objective of this study was to identify molecular markers closely linked lo the powdery mildew resistance gene Pm16. An F₂ population with 156 progeny was produced from the cross‘Chancellor’(susceptible) ב70281’ (resistant), A total of 45 SSR markers on chromosomes 4A and 5B of wheat and 15 SSRs on chromosome 3 of rice was used lo lest the parents, as well as the resistant and susceptible bulks: the resulting polymorphic markers were used to genotype the F₂ progeny. Results indicated that the SSR marker Xgwm159, located on the short arm of chromosome 5B, is closely linked to Pm16 (genetic distance: 5.3 CM). The cytogenetical data presented in an original report, in combination with this molecular analysis, suggests that Pm16 may he located on a translocated 4A.5BS chromosome.     

Association of leaf rust and powdery mildew resistance in a recombinant derived from a Hordeum vulgare × Hordeum bulbosum hybrid

While studying powdery mildew resistance in a recombinant line (code 81882) derived from a Hordeum vulgare (cv. ‘Vada’) ×Hordeum bulbosum hybrid, a low infection type of resistance to leaf rust was observed. To determine the mode of inheritance of the leaf rust resistance and whether there was linkage between the two resistances, F₂ and F₃ progenies from crosses between 81882 and ‘Vada’ were inoculated with the leaf rust and powdery mildew pathogens. Southern blots were prepared using restricted DNA extracted from leaves of 82 F₂ plants and four chromosome 2HS sequences were hybridized with the blots to define the length of the introgression. The leaf rust resistance appears to be inherited as a single dominant gene on chromosome 2HS, which co-segregates with the powdery mildew resistance. There was an almost complete association between the resistances and the respective molecular markers, but it is likely that the strong linkage results from the frequent inheritance of the introgressed H. bulbosum DNA as an intact segment of chromatin with only low levels of recombination within the segment.     

Genetical Studies of Gibberellic Acid Insensitivity in Rye (Secale cereale L.)

Genetic analysis of three semi-dwarf genotypes of rye (Secale cereale L.)—‘Moskowskij Karlik’, ‘Gülzow kurz’ and ‘R 18’, which were shown to be insensitive to applied gibberellic acid (GA₃), has been carried out by using a seedling test. It could be demonstrated that all of the three genotypes are carrying recessive alleles for GA-insensitivity. Whereas the alleles of ‘Moskowskij Karlik’ and ‘R 18’ seem to have the same locus on chromosome 5R, the GA-insensitivity of ‘Gülzow kurz’ is governed by a different gene, most probably located on chromosome 7R. The relationship between the genes (alleles) for GA-insensitivity and semi-dwarfness, including the symbolization of the Gai-genes as well as their utilization in rye breeding is discussed.     

Molecular cytogenetic characteristics of a translocation line between common wheat and Thinopyrum intermedium with resistance to powdery mildew

Powdery mildew caused by Blumeria graminis (DC) Speer f. sp. tritici Em. Marchal is a serious disease of wheat (Triticum aestivum L.) in Southwestern China. A line of common wheat designated 08-723 isolated from the progeny of a hybrid between common wheat and Thinopyrum intermedium (Host) Barkworth & Dewey, was highly resistant to the existing powdery mildew races in the region. This line had a similar phenotype to its wheat parent, and it showed normal bivalent pairing at metaphase I of meiosis. It was analyzed by genomic in situ hybridization, fluorescence in situ hybridization and sequential C-banding-GISH to determine the amount, location and origin of the alien chromatin present. The results revealed that line 08-723 is homozygous for a two-point translocation replacing chromosome 6A of wheat. The translocation chromosome appears to have a normal 6AL arm; its short arm has a short terminal segment of ca. 10 % in length originating from an unidentified B-genome chromosome of wheat and a long proximal segment of ca. 90 % of the arms’ length originating from one of the St-genome chromosomes of Th. intermedium. Genetic analysis of powdery mildew resistance in F₁, F₂ and F_2:3 populations from a cross of 08-723 with a susceptible wheat line indicated that the resistance was controlled by a single dominant gene and in a sample of F2 plants it always associated with the translocated chromosome. The gene responsible for resistance on the translocated chromosome may provide an alternate source of resistance in wheat breeding programs.     

Intergeneric Transfer (Rye to Wheat) of a Gene(s) for Russian Wheat Aphid Resistance

An octoploid triticale was derived from the F, of a Russian wheat aphid-resistant rye, ‘Turkey 77’, and ‘Chinese Spring’ wheat. The alloploid was crossed to common wheat, and to ‘Imperial’ rye/‘Chinese Spring’ disomic addition lines. F₂, progeny from these crosses were tested for Russian wheat aphid resistance and C-banded. A resistance gene(s) was found to be associated with chromosome arm IRS of the ‘Turkey 77’ rye genome. A monotelosomic IRS (‘Turkey 77’) addition plant was then crossed with the wheat cultivar ‘Gamtoos’, which has the 1BL.1RS ‘Veery’ translocation. Unlike the IRS segment in ‘Gamtoos’, the ‘Turkey 77’-derived 1 RS telosome did not express the rust resistance genes Sr31 and Ar26, which could then be used as markers. From the F, a monotelosomic 1 RS addition plant that was also heterozygous for the 1BL. 1 RS translocation was selected and testerossed with an aphid-susceptible common wheat, ‘Inia 66’ Meiotic pairing between the rye arms resulted in the recovery of five euploid Russian-wheat-aphid-resistant plants. One recombinant also retained Sr31 and Lr26 and was selfed to produce translocation homozygotes.