Transmission of chromosomes through the eggs and pollen of triticale × wheat F1 hybrids

Summary The substitution patterns of rye chromosomes in hexaploid triticale × wheat F₂ hybrids, along with the transmission patterns of rye chromosomes through egg cells and pollen when several of the F₁ hybrids were test crossed to triticale and wheat were investigated. The data indicated that the rye chromosome transmission through both the egg and pollen was random in number and in composition. The test crosses suggested that it was best to use wheat pollen for the transmission of rye chromosomes through the egg cells of the F₁ hybrids and triticale egg cells for the transmission of rye chromosomes through F₁ hybrid pollen. A deviation from random segregation in the F₂ and the transmission rate was observed for rye chromosomes 1R, 4R/7R, and 6R. The transmission rates of 1R and 6R varied depending on the direction in which the cross was made. The results also indicated that there was little or no compensation between the R- and D-genomes and that the chromosomes of these two genomes appeared to be transmitted independently of each other.     

Mapping of novel salt tolerance QTL in an Excalibur × Kukri doubled haploid wheat population

Key message

Novel QTL for salinity tolerance traits have been detected using non-destructive and destructive phenotyping in bread wheat and were shown to be linked to improvements in yield in saline fields.

Abstract

Soil salinity is a major limitation to cereal production. Breeding new salt-tolerant cultivars has the potential to improve cereal crop yields. In this study, a doubled haploid bread wheat mapping population, derived from the bi-parental cross of Excalibur?×?Kukri, was grown in a glasshouse under control and salinity treatments and evaluated using high-throughput non-destructive imaging technology. Quantitative trait locus (QTL) analysis of this population detected multiple QTL under salt and control treatments. Of these, six QTL were detected in the salt treatment including one for maintenance of shoot growth under salinity (QG_(1–5).asl-7A), one for leaf Na⁺ exclusion (QNa.asl-7A) and four for leaf K⁺ accumulation (QK.asl-2B.1, QK.asl-2B.2, QK.asl-5A and QK:Na.asl-6A). The beneficial allele for QG_(1–5).asl-7A (the maintenance of shoot growth under salinity) was present in six out of 44 mainly Australian bread and durum wheat cultivars. The effect of each QTL allele on grain yield was tested in a range of salinity concentrations at three field sites across 2 years. In six out of nine field trials with different levels of salinity stress, lines with alleles for Na⁺ exclusion and/or K⁺ maintenance at three QTL (QNa.asl-7A, QK.asl-2B.2 and QK:Na.asl-6A) excluded more Na⁺ or accumulated more K⁺ compared to lines without these alleles. Importantly, the QK.asl-2B.2 allele for higher K⁺ accumulation was found to be associated with higher grain yield at all field sites. Several alleles at other QTL were associated with higher grain yields at selected field sites.

     

Assessment of testcross performance and genetic diversity of yellow endosperm maize lines derived from adapted × exotic backcrosses

Introduction of exotic maize (Zea mays L.) into adapted tropical germplasm may enhance genetic variability and lead to greater progress from selection. The first objective of this study was to determine if yellow endosperm lines derived from adapted × exotic backcrosses contain exotic alleles that are superior to the recurrent adapted parental line for yield and other agronomic traits in tropical environments. Thirteen exotic yellow maize inbred lines were crossed to an adapted orange line (KUSR) and the F₁s were backcrossed to KUSR to generate the first backcrosses. Fifty BC₁F₄ lines derived from these backcrosses and the recurrent parent were crossed to a common inbred tester (L4001) to form testcrosses, which were evaluated at eight environments in Nigeria. Testcrosses of the BC-derived lines differed significantly for grain yield and other agronomic traits. Only two testcrosses yielded significantly less than L4001 × KUSR, with the best 15 testcrosses producing between 289 and 1,056 kg/ha more grain yield than L4001 × KUSR. The best testcrosses were similar to or better than L4001 × KUSR for other agronomic traits. The second objective of this study was to assess the extent of genetic diversity present among the BC-derived lines. We genotyped 46 BC-derived lines including KUSR and L4001 with 10 AFLP primer pairs and found 491 polymorphic fragments. The average allelic diversity of the lines was 0.30 ± 0.01. The genetic distance of each BC-derived line from KUSR ranged between 0.49 and 0.91. The average genetic distance for all pairs of the BC-derived lines was 0.68 ± 0.004, varying from 0.34 to 0.92. The increased grain yield and genetic diversity observed in these studies provide evidence that exotic germplasm can contribute new alleles to expand the genetic base of tropical maize and develop high-yielding hybrids.     

An evaluation of some morphological traits in doubled haploid lines and their F1 hybrids of head cabbage Kamienna Głowa in the vegetative phase

The internal stump length, head mass and head shape of doubled haploid (DH) lines and their F1 hybrids of head cabbage Kamienna G?owa were compared. It was found that the range of variation in the investigated traits of DH lines was higher than that of their F1 hybrids. The head mass of the DH lines indicated some level of inbreeding depression, but their F1 hybrids showed a significant effect of heterosis. Genes responsible for flattened head shape were dominant over rounded shape genes. The longer internal stump trait was dominant over the shorter one.     

Production of trigeneric (barley × wheat) × rye hybrids

Summary Rye (Secale cereale cv. Prolific 2n=14 and 2n =14 + 2B was crossed onto hybrids between barley (Hordeum vulgare 2n = 14) and wheat (Triticum aestivum 2n= 42). Pollinated florets were injected with GA₃ to promote fertilization and hybrid embryo development. At 16 days after pollination the watery caryopses were removed, embryos dissected and cultured on a modified B₅ medium. Approximately 20% of the cultured embryos produced both roots and coleoptile and developed into viable seedlings. Viable seeds were also obtained at a low frequency from the same cross combinations. The hybrids were wheat-like except for the hairy neck characteristic of rye. There were 35 chromosomes in somatic tissue; 21 wheat, 7 barley and 7 rye. The rye chromosomes were distinguishable by their larger size and terminal C-bands. A lower seed set was obtained using pollen from rye plants with 2n=14 + 2B chromosomes than from plants without B chromosomes.Contribution No. 577, Ottawa Research Station     

QTL mapping of stripe,leaf and stem rust resistance genes in a Kariega × Avocet S doubled haploid wheat population

Adult plant resistance to stripe (yellow) rust in the wheat cultivar Kariega has previously been ascribed to a major quantitative trait locus (QTL) on each of chromosomes 2B and 7D, along with a number of minor QTL. We have extended both the size of the cv. Kariega × cv. Avocet S mapping population, and the marker coverage within it, by assembling a set of Diversity Array Technology (DArT) markers. This has allowed for the analysis of the genetic basis of the adult plant and seedling resistances to stripe, leaf and stem rust present in the two mapping population parents. The stripe rust reactions of the segregating material were assessed in both field (three scoring dates) and greenhouse experiments. The chromosome 2B QTL became more important than the Lr34/Yr18 complex on chromosome 7D as the plants aged. As the infection progressed, the two QTL explained an increasing proportion of the variance for percentage leaf area infected. The cv. Kariega allele at the minor chromosome 4A QTL had a consistent effect on the severity of stripe rust infection and the overall plant reaction at the earlier scoring dates, but lost importance as the disease progressed. Several rust resistances were detected using an improved greenhouse-based test.     

Mapping QTLs with epistatic effects and QTL×environment interactions for plant height using a doubled haploid population in cultivated wheat

Quantitative trait loci (QTLs) for plant height in wheat (Triticum aestivum L.) were studied using a set of 168 doubled haploid (DH) lines, which were derived from the cross Huapei 3/Yumai 57. A genetic linkage map was constructed using 283 SSR and 22 EST-SSR markers. The DH population and the parents were evaluated for wheat plant height in 2005 and 2006 in Tai'an and 2006 in Suzhou. QTL analyses were performed using the software of QTLNetwork version 2.0 based on the mixed linear model. Four additive QTLs and five pairs of epistatic effects were detected, which were distributed on chromosomes 3A, 4B, 4D, 5A, 6A, 7B, and 7D. Among them, three additive QTLs and three pairs of epistatic QTLs showed QTLxenvironment interactions (QEs). Two major QTLs, QphAB and Qph4D, which accounted for 14.51 % and 20.22% of the phenotypic variation, were located similar to the reported locations of the dwarfing genes Rhtl and Rht2, respectively. The Qph3A-2 with additive effect was not reported in previous linkage mapping studies. The total QTL ef fects detected for the plant height explained 85.04% of the phenotypic variation, with additive effects 46.07%, epistatic effects 19.89%, and QEs 19.09%. The results showed that both additive effects and epistatic effects were important genetic bases of wheat plant height, which were subjected to environmental modifications, and caused dramatic changes in phenotypic effects. The information obtained in this study will be useful for manipulating the QTLs for wheat plant height by molecular marker-assisted selection (MAS).     

Mapping QTLs with epistatic effects and QTL×environment interactions for plant height using a doubled haploid population in cultivated wheat

Quantitative trait loci (QTLs) for plant height in wheat (Triticum aestivum L.) were studied using a set of 168 doubled haploid (DH) lines, which were derived from the cross Huapei 3/Yumai 57. A genetic linkage map was constructed using 283 SSR and 22 EST-SSR markers. The DH population and the parents were evaluated for wheat plant height in 2005 and 2006 in Tai’an and 2006 in Suzhou. QTL analyses were performed using the software of QTLNetwork version 2.0 based on the mixed linear model. Four additive QTLs and five pairs of epistatic effects were detected, which were distributed on chromosomes 3A, 4B, 4D, 5A, 6A, 7B, and 7D. Among them, three additive QTLs and three pairs of epistatic QTLs showed QTL×environment interactions (QEs). Two major QTLs, Qph4B and Qph4D, which accounted for 14.51% and 20.22% of the phenotypic variation, were located similar to the reported locations of the dwarfing genes Rht1 and Rht2, respectively. The Qph3A-2 with additive effect was not reported in previous linkage mapping studies. The total QTL effects detected for the plant height explained 85.04% of the phenotypic variation, with additive effects 46.07%, epistatic effects 19.89%, and QEs 19.09%. The results showed that both additive effects and epistatic effects were important genetic bases of wheat plant height, which were subjected to environmental modifications, and caused dramatic changes in phenotypic effects. The information obtained in this study will be useful for manipulating the QTLs for wheat plant height by molecular marker-assisted selection (MAS).     

Response of wheatgrasses and wheat × wheatgrass hybrids to barley yellow dwarf virus

Summary Resistance to barley yellow dwarf virus (BYDV), manifested by low enzyme-linked immunosorbent assay (ELISA) values in plants exposed to viruliferous aphids, was identified in several wheatgrasses (Agropyron spp.). ELISA results were similar for root and leaf extracts of infested plants. No difference in reaction to BYDV was found between plants grown in the field and those in the growth chamber. Interspecific hybrids were generated using pollen from single resistant plants of Agropyron spp. to pollinate soft red winter wheat spikes. Resistance in hybrids appeared to be at the level of virus replication rather than at the level of vector inoculation. The hybrids varied in their reaction to BYDV. Expression of BYDV resistance in hybrids was influenced not only by wheat genotype and Agropyron species but, in some cases, reaction varied even among hybrids between the same wheat genotype and Agropyron plant. Implications of these results are discussed.Contribution from the Purdue Univ. Agric. Exp. Stn., West Lafayette, IN 47907, and USDA-ARS. The research was supported in part by Public Varieties of Indiana. Purdue Univ. Agric. Exp. Stn. Journal No. 11656     

Morphological, molecular and cytological analyses of Carica papaya×C. cauliflora interspecific hybrids

 Morphological, molecular and cytological analyses were performed to assess the hybridity of 120 putative interspecific hybrids of Carica papaya L.×C. cauliflora Jacq. In the putative interspecific hybrids the number of main leaf veins was intermediate between the two parents while the hermaphrodite flower sex form and the low vigour were distinctive features of these hybrids. Petiole length, stem diameter, leaf length, leaf width and flower colour were similar to C. papaya, whereas leaf shape, type, serration, venation, petiole hairiness and flower shape were similar to C. cauliflora. Markers generated by the polymerase chain reaction using 72 10-mer primers (random amplified polymorphic DNA) revealed a high level of polymorphism (64%) between C. papaya and C. cauliflora. Seventeen of these primers yielded reliable and easily scorable polymorphic banding patterns that were further screened to reveal hybrids. A range of 1–5 RAPD primers consistently confirmed that all 120 plants were genetic hybrids, with all of them containing at least one band from the male parent. Cytological analysis revealed that 7–48% of the cells in many of the interspecific hybrids were aneuploid suggesting that chromosome elimination was occurring. The frequency of aneuploid cells was negatively associated (r=0.88) with the number of bands from the male parent integrated into the hybrid. Pollen fertility of the hybrids was from 0.5 to 14.0% while C. papaya and C. cauliflora had 88.0–99.0% and 90.0–97.0% fertile pollen, respectively. Received: 28 February 1996 / Accepted: 27 September 1996     

Gametoclonal variation detected in the nuclear ribosomal DNA from doubled haploid lines of a spring wheat (Triticum aestivum L., cv. ‘César’)

Summary The organization of the nuclear ribosomal DNA from a parental line of wheat (Triticum aestivum L., cv. César) and its anther-derived first cycle and second cycle doubled haploid lines has been analyzed by DNA-DNA molecular hybridization. Restricted DNA has been probed by three subclones of wheat nuclear ribosomal DNA covering the entire repeat unit. No significant difference was detected in the extent of methylation of ribosomal DNA of the doubled haploid lines with respect to the parental line. On the other hand, a variation has been found in the organization of the nontranscribed spacer region of ribosomal DNA of the first cycle doubled haploid line. This variation remains stable after a second cycle of in vitro androgenesis. However, one out of five second cycle doubled haploid lines so far tested showed an additional hybridization band present in the parental line but lacking in the first cycle doubled haploid line.     

High-frequency generation and characterization of intergeneric hybrids and haploids from new wheat–barley crosses

Key message

Hybrid plants and a high frequency of maternal haploids were obtained using an efficient wheat–barley hybridization system (with new genotype combinations) and confirmed by several cytological and molecular tools.

Abstract

An efficient hybridization system between wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) is presented on the basis of three new genotype combinations. A particularly high, 14 % frequency of plant regeneration per florets was achieved in the wheat–barley genotype combination of ‘Sichuan’ × ‘Morex’. The genome composition in 42 of the 95 plants regenerated by embryo rescue was determined using ploidy analysis, genomic in situ hybridization and the application of chromosome arm-specific molecular markers (SSR and STS). A high overall frequency (76 %) of maternal (wheat) haploids was observed in all the tests for all three cross combinations. A major implication of this observation is that this new hybridization system represents a useful tool to study the mechanism of uniparental chromosome elimination in cereals.     

Production and characterization of alloplasmic lines of a triticale ‘Rosner’

Summary The transfer of cytoplasms of various Triticum and Aegilops species to a hexaploid triticale (Rosner) has been attempted using 30 alloplasmic lines and a euplasmic line of common wheat as cytoplasmic donors. The average rate of F₁ hybrid production (seed setting rateXgermination rate) following an ordinary method of crossing is only 0.09%, whereas this rate is increased to 3.1% by use of embryo culture. The first backcross of the F₁ plants with triticale pollen is again difficult, the hybrid production being 0.9%. Further backcrosses proceed smoothly in most cases. As a consequence, the following seven cytoplasms have been transferred to triticale: T. dicoccum, T. aestivum, Ae. squarrosa, Ae. cylindrica, Ae. juvenalis, Ae. ovata and Ae. speltoides. None of these alien cytoplasms causes more meiotic instability than does the triticale's own cytoplasm. Two cytoplasms of T. dicoccum and T. aestivum, both belonging to the B plasma type, have no effect upon any of triticale's characters. Two D type cytoplasms of Ae. squarrosa and Ae. cylindrica cause about 50% reduction of male fertility but exert no other remarkable effects. This fact suggests a partial functional compensation of the effect of a 1D chromosome upon interacting with D cytoplasm by a rye chromosome substituting for it in triticale. A D² cytoplasm of Ae. juvenalis causes earlier heading and complete male sterility, accompanied by some reduction of growth vigor. An M⁰ type cytoplasm of Ae. ovata and an S type cytoplasm of Ae. speltoides cause a great heading delay, complete male sterility, and severe reduction of vigor. From the viewpoint of triticale breeding, none of these cytoplasms appears superior to the triticale's own cytoplasm. However, from the viewpoint of genetics, the hexaploid triticale is an effective tester for differentiating the B, S, and D plasma types.Contribution No. 466 from the Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Japan     

Current applications of wheat and wheat–alien precise genetic stocks

A comprehensive collection of wheat aneuploids, whole chromosome substitutions (both intervarietal and interspecific) and wheat–alien addition lines, along with various introgression and near-isogenic lines, has been created over a period of years, primarily to provide the means of localizing the genes underpinning traits and to introduce novel genes into the bread wheat genome. For a time, interest in this class of genetic material was on the wane, but more recently it has revived in the context, for example, of localizing DNA-based markers, designing chromosome-specific bacterial artificial chromosome libraries, and establishing functional differences between alleles and homoeoalleles. Here, a brief review is provided of recent applications of precise genetic stocks in the field of molecular genetics, functional genetics and genomics of the Triticeae species.     

Genome merger: from sequence rearrangements in triticale to their elimination in wheat–rye addition lines

Genetic and epigenetic modifications resulting from different genomes adjusting to a common nuclear environment have been observed in polyploids. Sequence restructuring within genomes involving retrotransposon/microsatellite-rich regions has been reported in triticale. The present study uses inter-retrotransposon amplified polymorphisms (IRAP) and retrotransposon microsatellite amplified polymorphisms (REMAP) to assess genome rearrangements in wheat–rye addition lines obtained by the controlled backcrossing of octoploid triticale to hexaploid wheat followed by self-fertilization. The comparative analysis of IRAP and REMAP banding profiles, involving a complete set of wheat–rye addition lines, and their parental species revealed in those lines the presence of wheat-origin bands absent in triticale, and the absence of rye-origin and triticale-specific bands. The presence in triticale × wheat backcrosses (BC) of rye-origin bands that were absent in the addition lines demonstrated that genomic rearrangement events were not a direct consequence of backcrossing, but resulted from further genome structural rearrangements in the BC plant progeny. PCR experiments using primers designed from different rye-origin sequences showed that the absence of a rye-origin band in wheat–rye addition lines results from sequence elimination rather than restrict changes on primer annealing sites, as noted in triticale. The level of genome restructuring events evaluated in all seven wheat–rye addition lines, compared to triticale, indicated that the unbalanced genome merger situation observed in the addition lines induced a new round of genome rearrangement, suggesting that the lesser the amount of rye chromatin introgressed into wheat the larger the outcome of genome reshuffling.     

Comparative analysis of the meiotic effects of wheat ph1b and ph2b mutations in wheat×rye hybrids

 Wheat-wheat and wheat-rye homoeologous pairing at metaphase I and wheat-rye recombination at anaphase I were examined by genomic in situ hybridization (GISH) in wild-type (Ph1Ph2) and mutant ph1b and ph2b wheat×rye hybrids. The metaphase-I analysis revealed that the relative contribution of wheat-rye chromosome associations in ph2b wheat×rye was similar to that of the wild-type hybrid genotype but differed from the effect of the ph1b mutation. The greater pairing promotion effect of the ph1b mutation appears to be relatively more on distant homoeologous partner metaphase-I associations, whereas the lower promoting effect of ph2b is evenly distributed among all types of homoeologous associations. This finding reveals that distinct mechanisms are involved in the control of wheat homoeologous pairing by the two Ph genes. The frequency of wheat-rye recombination calculated from anaphase-I analysis was lower than expected from the metaphase-I data. A greater discrepancy was found in ph2b than in ph1b wheat×rye hybrids, which may suggest a more distal chiasma localization in the former hybrid genotype. Received: 20 June 1997 / Accepted: 9 December 1997     

High-density genetic map of durum wheat × wild emmer wheat based on SSR and DArT markers

A genetic linkage map of tetraploid wheat was constructed based on a cross between durum wheat [Triticum turgidum ssp. durum (Desf.) MacKey] cultivar Langdon and wild emmer wheat [T. turgidum ssp. dicoccoides (K?rn.) Thell.] accession G18-16. One hundred and fifty-two single-seed descent derived F(6) recombinant inbred lines (RILs) were analyzed with a total of 690 loci, including 197 microsatellite and 493 DArT markers. Linkage analysis defined 14 linkage groups. Most markers were mapped to the B-genome (60%), with an average of 57 markers per chromosome and the remaining 40% mapped to the A-genome, with an average of 39 markers per chromosome. To construct a stabilized (skeleton) map, markers interfering with map stability were removed. The skeleton map consisted of 307 markers with a total length of 2,317 cM and average distance of 7.5 cM between adjacent markers. The length of individual chromosomes ranged between 112 cM for chromosome 4B to 217 cM for chromosome 3B. A fraction (30.1%) of the markers deviated significantly from the expected Mendelian ratios; clusters of loci showing distorted segregation were found on chromosomes 1A, 1BL, 2BS, 3B, and 4B. DArT markers showed high proportion of clustering, which may be indicative of gene-rich regions. Three hundred and fifty-two new DArT markers were mapped for the first time on the current map. This map provides a useful groundwork for further genetic analyses of important quantitative traits, positional cloning, and marker-assisted selection, as well as for genome comparative genomics and genome organization studies in wheat and other cereals.     

Electrophoretic protein analysis for the identification of doubled haploid 1A–1R, 1B–1R wheat-rye double translocation lines and for the assessment of their genetic stability

Eighteen available doubled haploid wheat lines with a cytologically proven 1A–1R, 1B–1R double translocation, which where derived via anther culture from four crosses of the 1A–1R wheat-rye translocation cv Amigo with several 1B–1R wheat-rye translocation forms, were subjected to electrophoretic seed protein analysis. Besides, the five parents used in the crosses and some other wheat cultivars and doubled haploid lines (19 with a 1B–1R single translocation, 10 with a 1A–1R translocation and 7 without any 1R translocation) were also included in the investigation. It was found that the gliadin patterns visualized after SDS polyacrylamide gel electrophoresis of alcohol-soluble seed protein extracts can differentiate not only 1B–1R and 1A–1R translocation forms from wheats without any 1R-translocation chromosome, but also 1B–1R and 1A–1R wheats from each other. Moreover, 1A–1R, 1B–1R double translocation lines can be distinguished as well due to characteristic differences revealed between 1A–1R and 1B–1R translocation forms. Thus, all of tested dh₁- and dh₂-grains of the double translocation lines showed the expected doublet: the 1A–1R translocation (Amigo)-typical rye band and the 1B–1R translocation (Kawkas)-typical rye band. Consequently, gliadin patterns estimated after SDS electrophoresis may be used as markers for the fast detection of the desired 1A–1R, 1B–1R double translocation forms among 1A–1R single translocation lines, 1B–1R single translocation lines and lines without any 1R-translocation in the progenies of appropriate crosses. Furthermore, by means of gliadin tests on the dh₂-generation the excellent stability of the double translocation 1A–1R, 1B–1R during more than one propagation phase has been proven. Estimations of high-molecular weight (HMW) glutenin subunits coded by 1A and 1B chromosomes are compatible with the double translocation constitution. A few deviating results can be explained by crossing-over events. Seed protein analysis revealed that it is possible to produce 1A–1R, 1B–1R double translocation lines with good glutenin compositions provided that adequate favourable parents are used.Former name: Department of Physiology of Institute for Cereal Research     

The polyphyly of Neotragus – Results from genetic and morphometric analyses

Dwarf antelope species were commonly united in the tribe “Neotragini” (Bovidae, Mammalia) due to their general morphological appearance. However, phylogenetic analyses have shown that not all dwarf antelopes are closely related, so it was suggested to restrict the name Neotragini to the type genus Neotragus. In our study we use mitochondrial cytochrome b sequences and linear skull measurements to further investigate the similarity of all three Neotragus species. Our analyses support the close relationship of N. moschatus and N. batesi. However, N. pygmaeus – the type species, which was never before included in phylogenetic analyses – is not closely related. It might share a most recent common ancestor with another “dwarf antelope”, the Klipspringer Oreotragus oreotragus, and the duikers in the taxon Cephalophini. Hence, we suggest resurrecting the genus Nesotragus von Dueben, 1846 for Nesotragus moschatus and N. batesi.