Value and utilization of alloplasmic common wheats with Aegilops crassa cytoplasm

Differences between alloplasmic lines and euplasmic controls indicated consistent beneficial effects of Aegilops crassa cytoplasm on common wheats. In general, the agronomic performance of alloplasmic lines was superior to that of euplasmic controls; the significant differences observed were ascribed to nucleus‐cytoplasmic (NC) interactions. A number of useful genetic attributes, for example, high yield, good quality and salt tolerance, were identified. A new NC hybrid variety ‘Xiaoshan 2134’ was bred. Field trials showed that the yield NC heterosis of ‘Xiaoshan 2134’ was 13.9% and the yield of ‘Xiaoshan 2134’ was at least 20% higher than that of a control variety widely grown in North China. The results suggested that Ae. crassa cytoplasm could broaden the genetic base of common wheat and improve common wheat cultivars by utilizing NC heterosis.     

Comparison of two fertility restoration systems against photoperiod-sensitive cytoplasmic male sterility in wheat

A ‘two‐line system’ using photoperiod‐sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm under a long‐day photoperiod ( 15 h) has been proposed as a new means of producing hybrid varieties in common wheat. The PCMS line is maintained by self‐pollination under short‐day conditions, and hybrid seeds can be produced through outcrossing of the PCMS line with a pollinator under long‐day conditions. Two kinds of fertility restoration systems against the PCMS are known. One is involved with a set of multiple fertility‐restoring (Rf) genes in the wheat cultivar ‘Norin 61’ located on (at least) chromosomes 4A, 1D, 3D and 5D. The other is controlled by a single dominant major Rf gene, Rfd1, located on the long arm of chromosome 7B in the wheat cultivar ‘Chinese Spring’. To examine the degree of fertility restoration by these two systems, nine PCMS lines were crossed with ‘Norin 61’ and ‘Chinese Spring’ as the restorer lines, and the F₁ hybrids were investigated. The degree of fertility restoration was estimated by comparing the seed set rates in the F₁ hybrids having the Ae. crassa cytoplasm and those with normal cytoplasm. The results revealed that the fertility restoration ability of a set of multiple Rf genes in ‘Norin 61’ was higher than that of the Rfd1 gene in ‘Chinese Spring’.     

Transfer of powdery mildew resistance from Aegilops variabilis into bread wheat

Winter hexaploid wheat (Triticum aestivum L.) was crossed with Aegilops variabilis to transfer resistance to powdery mildew into wheat. Following two backcrosses to wheat and from 5 to 9 generations of selfing, several disomic addition and substitution lines of hexaploid wheat resistant to the mildew pathogen were isolated. A pair of short satellited chromosomes was always observed in the resistant lines. Further evidence utilizing as markers for homoeologous group 1 HMW glutenin subunits and DNA hybridization with probe pGBX 3076 showed that an alien substitution involved this homoeologous group.     

Selection and genetic improvement of pollen fertility restorer lines with Triticum timopheevii cytoplasm in common wheat

The paper summarizes the selection and improvement of pollen fertility restoration in cytoplasmic male-sterile lines during the past 30 years at Jiangsu Province, China. A fertility restorer line (R16) with a good history of strong and stable restoring ability to different sterile lines was bred by accumulating fertility-restoring genes from derivatives of T797 and other restorer lines such as Primepi. A series of well-performing restorer lines with similar fertility-restoring ability has been bred by improving agronomic characters, disease-resistance and kernel size of R16. The restoring ability of these restorer lines using different male-sterile lines demonstrates that fertility restoration is no longer an obstacle for commercial utilization of hybrid wheat with the Triticum timopheeviii cytoplasmic male-sterile system. Line 2114 is a restorer with a single restoring gene transferred from Aegilops umbellulata. Its restoring ability, using both difficult and easily restored lines was 82% and 93.3% respectively. Maiyou No. 5, one hybrid variety, showed 13.2% yield advantage over the control variety in the Jiangsu Province registration test in 1997-1998 and was superior to nine other varieties adapted to the Jiangsu Province.     

Gliadins as biochemical markers for Aegilops turcomanica genes in wheat lines

An Aegilops turcomanica-typical gliadin was discovered in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of ethanol-soluble seed proteins from wheat lines Tr. 476, 482 and 492, which had been derived from a direct cross of Ae. turcomanica and Triticum aestivum and which revealed powdery mildew resistance due to a putative Ae. turcomanica-introgression. This Ae. turcomanica-derived gliadin was tested for its suitability as biochemical marker. For this purpose, doubled-haploid lines were produced via anther culture from crosses of Tr. 482 and Tr. 492 with actual winter wheat cultivars and breeding lines. Until now, 173 lines with Ae. turcomanica-gene(s) have been selected from 297 doubled haploid wheat lines.     

Improving male fertility restoration of common wheat for Triticum timopheevii cytoplasm

The fertile pure line R3‐37 of common wheat with cytoplasm of Triticum timopheevii Zhuk. is an R‐line (restorer) that can restore the male fertility of A‐lines (male sterile lines) with T. timopheevii cytoplasm. In breeding hybrid wheat, the hybrid of the cross R3‐37/ Baimian3 was found to be completely male sterile, indicating that Baimian3 has some genes that are epistatic to the Rf genes in R3‐37. In order to elucidate the essence of this phenomenon, the male fertilities of the hybrids of 27 crosses including R3‐37 and/or Baimian3 were studied. The results show that inheritance of male fertility of the hybrid R3‐37/Baimian3 involves interactions among Rf alleles, male fertility‐inhibiting genes and genetic background. Although more than 70 different kinds of male sterile cytoplasm to common wheat have been discovered, the systems of hybrid wheat production based on male sterile cytoplasm are all the A‐line/R‐line type and all have similar problems of hybrid fertility restoration. This study confirmed that there is a new model (A‐line/R*‐line//R‐line) for producing hybrid wheat with high fertility restoration. In the new model, the completely male sterile hybrids of A‐line/R*‐line can act as common A‐line.     

Genetic analysis of fertility restoration against photoperiod-sensitive cytoplasmic male sterility in Triticum aestivum cv. Norin 61

Triticum aestivum cv. Norin 26 with the Aegilops crassa cytoplasm becomes almost completely male sterile when grown under a long-day condition (15 h of light or longer), but is highly male fertile under a short-day condition (14.5h or less). This type of male sterility is called photoperiod-sensitive cytoplasmic male sterility (PCMS). Genetic analyses were made of the fertility-restoring (Rf) genes effective against PCMS that are present in T. aestivum cv. Norin 61. Conventional and monosomic studies indicated that restoration of fertility is controlled by multiple Rf genes located on at least four chromosomes: 4 A, 1D, 3D and 5D. The genetic mechanism of fertility restoration by the genes of‘Norin 61’differs from the mechanisms reported for‘Chinese Spring’and a‘Norin 26’mutant line.     

Eyespot resistance in wheat ×Aegilops kotschyi backcross lines

In wheat, eyespot caused by PseudoCercosporella herpotrichoides, is one of the main foot‐rot diseases. Yield losses up to 40% occur in some years. Plant protection by fungicide application is possible, but a better way is through resistance breeding. Two resistance sources are currently used: Aegilops ventricosa and the old French variety ‘Cappelle Desprez’. A new source of resistance has been found in the accession AE120 of Ae. kotschyi from the Gatersleben gene bank with the genome constitution UUSvSv. This accession has been crossed and backcrossed twice to susceptible wheat varieties, and in each generation, plants with a relatively high level of resistance have been selected. From this material, lines have been developed and tested in F₆ to F₈. Finally, several lines could be classified as moderately resistant, such as the French variety ‘Cappelle Desprez’ after resistance determination during milk ripeness (DC75). No line reached the high resistance level achieved with Pch‐1 from Ae. ventricosa. The yield of these lines under infection conditions was higher compared with ‘Cappelle Desprez’. The line 6018‐96‐3 showed a high yield of 64.3 dt/ha compared with 59.6 dt/ha, on the average, in combination with the best expression of eyespot resistance in the adult growth stage over 3 years.     

Location of Pm3g, a powdery mildew resistance allele in wheat, by using a monosomic analysis and by identifying associated molecular markers

A segregating population of doubled-haploid lines issued from the cross between the wheat (Triticum aestivum L. em. Thell) cultivars Courtot, resistant to several isolates of powdery mildew (Blumeria graminis DC. f. sp. tritici Em. Marchal), and Chinese Spring (susceptible) was used to map Mlar, a gene carried by Courtot and conferring resistance to this pathogen. The assignation of Mlar using monosomic lines of Courtot was confirmed by the mapping analysis. Mlar was located on the short arm of the chromosome 1A, in the vicinity of the locus XGli-A5 coding for storage proteins. This result was in accordance with those demonstrating that Mlar was an allele of the Pm3 locus (Pm3g), a gene also involved in the resistance to powdery mildew. This revised version was published online in August 2006 with corrections to the Cover Date.     

Basic studies on hybrid wheat breeding using the 1BL-1RS translocation chromosome / Aegilops kotschyi cytoplasm system 1. Development of male sterile and maintainer lines with discovery of a new fertility-restorer

The Aegilops kotschyi cytoplasm and a 1BL-1RS translocation chromosome that consists of the long arm of wheat chromosome 1B and the short arm of rye chromosome 1R were transferred to six spring common wheat cultivars by repeated backcrossing. Resistance to leaf rust race 21B conditioned by the Lr26 gene and a secalin subunit encoded by the Sec-1 gene, both on the 1RS arm, were used as the selection markers of the translocation chromosome. Five of the six cultivars used were converted to complete male steriles, whereas the remaining one, cv. Kitamiharu 48, retained normal fertility, after transfer of both the 1BL-1RS chromosome and Ae. Kotschyi cytoplasm. Conventional gene analysis suggested that Kitamiharu 48 carries an incompletely dominant fertility-restoring gene. The F₁ hybrids between the male steriles and ordinary common wheat cultivars recovered fertility only at a low level, indicating that a single dose of the Rfv1 gene on the 1BS arm of wheat is insufficient for full fertility restoration under spring-sowing condition. Our results are in clear contrast to complete fertility restoration under fall-sowing condition reported by Nonaka et al. (1993). Combination of the 1BL-1RS chromosome / Ae. Kotschyi cytoplasm system with a new fertility-restoring gene discovered in Kitamiharu 48 may provide a breakthrough for spring-type hybrid wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Identification of powdery-mildew-resistance genes in common wheat (Triticum aestivum L.). VI. Wheat cultivars grown in China

A total of 26 common wheat cultivars and advanced breeding lines grown in China were tested with a set of 11 differential powdery-mildew isolates. Seven cultivars were susceptible. Another seven cultivars showed the response pattern of resistance gene Pm2, either individually or in combination with genes Pm3d or Pm4a. Five cultivars expressed the resistance of gene Pm4b singly or in combination with Pm6. Another four cultivars exhibited the response patterns of genes Pm5, Pm6 and Pm8, respectively. Three cultivars, which included one breeding line with a pair of substituted chromosomes from Haynaldia villosa, presumably carrying the resistance gene Pm21, showed resistance-response patterns to all the isolates tested.     

First-division restitution in hybrids of Langdon durum disomic substitution lines with rye and Aegilops squarrosa

Durum wheat ‘Langdon’(LDN) caused a high frequency of first‐division restitution (FDR) and partial fertility in hybrids with rye, Secale cereale L., and Aegilops squarrosa L. In order to determine the genetic control of FDR, a complete set of 14 Langdon durum D‐genome disomic substitution lines (LDNDS) was crossed with ‘Gazelle’ rye and one accession (RL5286) of A. squarrosa. The microsporogenesis and fertility of the hybrids were studied. The results showed that most of the hybrids expressed a high frequency of FDR and partial fertility. However, the hybrids of 2D(2A), 4D(4A), 5D(5B) and 6D(6B) crossed with both rye and A. squarrosa, as well as 1D(1A) with A. squarrosa, had either little or no FDR and were completely sterile. These hybrids had different types of first meiotic divisions compared with LDN control hybrids. The hybrids with 2D(2A), 4D(4A) and 6D(6B) had a high frequency of random segregation of chromosomes at the first division. The hybrids with 5D(5B), as expected, showed high homoeologous pairing. The hybrid of 1D(1A) with A. squarrosa had a high frequency of equational division at first division. These results suggest that the reduced or absent FDR in such hybrids might be related to the substitution of chromosomes with an FDR gene and poor compensation ability of the D‐genome chromosomes for their homoeologous A‐ or B‐ genome chromosomes. Cytological analysis suggested that chromosome 4A in LDN most likely carries a gene for high frequency of FDR in hybrids. In addition, some monads were observed at the end of meiosis in the hybrids of 3D(3A) and 6D(6A) crossed with rye. They were formed from FDR cells that failed to divide at second division, suggesting that the LDN 3A and 6A chromosomes might carry genes for normal second division of FDR cells in the rye crosses.     

The study of introgressive lines of Triticum aestivum × Aegilops speltoides by in situ and SSR analyses

Fluorescence in situ hybridization (FISH) with a genome‐specific repeat, Spelt1, and wheat simple sequence repeat (SSR) markers were used to analyse the chromosome constitution of two Triticum aestivum×Aegilops speltoides introgressive lines. The lines 170/98i and 178/98i carried one and two subtelomeric regions of Ae. speltoides (per haploid genome), respectively, marked by Spelt1 repeats according to FISH data. SSR analysis detected homoeologous substitution of wheat chromosome 7D with Ae. speltoides chromosome 7S in the lines 178/98i and 170/98i as well as the assumed terminal translocation in the short arm of chromosome 3A in the line 178/98i. Anthocyanin pigmentation of the coleoptiles was found in the lines 170/98i and 178/98i and resulted from the 7S (7D) substitution. It was demonstrated that Spelt1 could be effectively used for the rapid identification (without DNA isolation) of terminal translocations of T. aestivum×Ae. speltoides introgressive lines as well as for further analysis of the stability of the hybrid plants.     

Identification of powdery-mildew-resistance genes in common wheat (Triticum aestivum L. em. Thell.). V. Old German cultivars and cultivars released in the former GDR

A total of 59 old wheat cultivars grown in Germany prior to 1960 were tested for mildew response using a collection of 12 differential isolates of Erysiphe graminis DC f. sp. tritici Marchal (Blumeria graminis (DC) Speer f. sp. tritici). Nineteen cultivars did not possess any major resistance gene and 25 were characterized by susceptible or intermediate responses. Fifteen cultivars revealed isolate-specific response patterns that could not be attributed to known major resistance genes or gene combinations. Many of the old German cultivars inherited a mildew-resistance gene from the Canadian cultivar ‘Garnet’ which is tentatively designated M1-Ga. Cultivars ‘Bretonischer Bartweizen’ (designated M1-Br) and ‘Adlungs Alemannen’ (designated M1-Ad) appeared to carry unknown resistance genes. Among 18 winter wheat cultivars released in the former GDR. eight showed susceptibility to all isolates used. Cv. “Borenos” carries resistance gene Pm3c. Five cultivars possess gene Pm4b. two cultivars gene pm5 and one cultivar a combination of genes Pm2 and Pm4b. Cultivar ‘Zentos’ was resistant to almost all isolates used. Its resistance might be conditioned by different unknown major resistance genes.     

Agronomic and qualitative characteristics of ten bread wheat hybrids produced using a chemical hybridizing agent

Summary Ten experimental hybrids derived from the crossing of representative Italian pure-line varieties were grown at three locations in 1984–85. The amount of F₁ seed produced from the crossings ranged from 1.5 up to 4 kg per plot of 20 m². Hybrid purity was on average 88% when estimated through the growout test and 82% when estimated through acid polyacrylamide gel electrophoresis (A-PAGE) of gliadin.All the hybrids showed high-parent heterosis for plant height. Grain yield was higher in the hybrids (71.1 q/ha) than in the female parents (66.5 q/ha); the range of mid-parent heterosis being-10% to +17%. Four hybrids showed standard heterosis (yield advantage). The highest value (+6%) was obtained with the combinations Chiarano x Leopardo and Claudia x Leopardo. Among yield components, the number of spikelets/spike proved to be an important trait and may explain the superiority of the hybrids over the traditional varieties.The bread-making quality appeared intermediate to that of the parents or closer to that of the poorest parental variety.     

Genetic suppression of the cereal rye-derived gene Pm8 in wheat

The location of wheat gene Pm8 for resistance to powdery mildew in the 1RS chromosome segment derived from cereal rye cultivar Petkus was confirmed. There was reduced transmission of the 1BL.1RS chromosome relative to its wheat homologue in four of the five crosses examined. Pm8 was not expressed in some wheat cultivars and selections which possessed the 1RS chromosome identified by the presence of relevant genes for resistance to the three rusts, due to the presence of a dominant suppressor gene(s) in the wheat genome. The frequency of suppression in 1BL.1RS wheats from Mexico was significantly higher than in a group of wheats (both local and exotic) introduced from China and was probably much higher than in European wheats. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic polymorphisms at Gli-Dt gliadin loci in Aegilops tauschii as revealed by acid polyacrylamide gel and capillary electrophoresis

Gliadin variation at Gli‐D^t1 and Gli‐D^t2 loci in 198 Aegilops tauschii accessions was studied by acid polyacrylamide gel electrophoresis (A‐PAGE) and capillary electrophoresis (CE). High genetic polymorphisms were found at both gliadin coding loci, revealing a total of 184 and 169 gliadin variants at the Gli‐D^t1 and Gli‐D^t2 loci, respectively. In particular, 12 gliadin blocks encoded by different alleles were apparently expressed and readily identified in six synthetic hexaploids produced by hybridization between Triticum durum and Ae. tauschii accessions. Compared with Ae. tauschii ssp. eusquarrosa, the gliadin profile of the D genome in Ae. tauschii ssp. strangulata more resembles that of T. aestivum, supporting the view that the subspecies strangulata is the most likely progenitor of bread wheat. Capillary electrophoresis analysis showed that the method is capable of separating and characterizing gliadins with speed, in high resolution using small sample amounts, and is well‐suited to detect protein alleles and to identify desirable genotypes in wheat quality improvement.     

Chromosome location and microsatellite markers linked to a powdery mildew resistance gene in wheat line 'Lankao 90(6)'

Wheat lines known as 'Lankao 90(6)', derived from the cross 'Mzalenod Beer' (hexaploid triticale)/'Baofeng 7228'//'90 Xuanxi', carry a recessive powdery mildew resistance gene temporarily named PmLK906 . Gene PmLK906 appears to be different from known wheat powdery mildew resistance genes. PmLK906 was tagged using microsatellite markers in a segregating population derived from the cross 'Chinese Spring'/'Lankao 90(6)21-12'. The dominant microsatellite marker Xgwm265-2AL was linked in repulsion with PmLK906 at a genetic distance of 3.72 cM, whereas the co-dominant Xgdm93-2AL was linked to PmLK906 at a genetic distance of 6.15 cM. Both markers were placed on chromosome arm 2AL using 'Chinese Spring' nulli-tetrasomic lines. The recessive PmLK906 has a different specificity to the dominant resistance alleles located at the Pm4 locus and appeared to be located to a locus different from Pm4 .     

Photoperiod-sensitive cytoplasmic male sterility in wheat with Aegilops crassa cytoplasm

Summary Triticum aestivum cv. Norin 26 with Aegilops crassa, Ae. juvenalis or Ae. vavilovii cytoplasm (all D² type) has been studied relative to its photoperiodic response of male sterility and fertility restoration patterns. Alloplasmic lines of Norin 26 with a D² type cytoplasm showed almost complete male sterility under long-day conditions (15 h), but high male fertility under short-day conditions (14.5 h). No significant influence of temperature on reduction in male fertility was observed. Thus, this type of male sterility is called photoperiod-sensitive cytoplasmic male sterility (PCMS). The PCMS is expressed in the form of pistillody of stamens. Histological studies revealed that there were incomplete ovule-like structures instead of tapetal cells and pollen grains in the pistillate stamens. The floret differentiation stage of the plant is the stage that is sensitive to photoperiod. The PCMS can be used as a new means for hybrid wheat production, named two-line system. The PCMS line is maintained and multiplied by self-fertilization under short-day conditions, and hybrid seed can be produced by crossing the PCMS line with a pollinator line under long-day conditions. In contrast to the system of hybrid wheat production using the T. timopheevi cytoplasm, the present system requires only PCMS and pollinator lines.Abbreviation CS Chinese Spring - N26 Norin 26 - PCMS photoperiod-sensitive cytoplasmic male sterility