Synthetic Amphiploids Research Articles

Molecular cytogenetic identification and nutritional composition evaluation of newly synthesized Triticum turgidum-Triticum boeoticum amphiploids (AABBAbAb).

Triticum boeoticum Boiss. (AbAb, 2n = 2x = 14) is a wheat-related species with the blue aleurone trait. In this study, 18 synthetic Triticum turgidum-Triticum boeoticum amphiploids were identified, which were derived from crosses between T. boeoticum and T. turgidum. Three probes (Oligo-pTa535, Oligo-pSc119.2, and Oligo-pTa713) for multicolor fluorescence in situ hybridization (mc-FISH) were combined with genomic in situ hybridization (GISH) to identify chromosomal composition. Seven nutritional indices (anthocyanins, protein, total essential amino acids TEAA, Fe, Zn, Mn and Cu) were measured, and the nutritional components of 18 synthetic amphiploids were comprehensively ranked by principal component analysis (PCA). The results showed that all three synthetic amphiploids used for cytological identification contained 42 chromosomes, including 14A, 14 B, and 14 Ab chromosomes. The average anthocyanin content was 82.830 μg/g to 207.606 μg/g in the whole meal of the 17 blue-grained lines (Syn-ABAb-1 to Syn-ABAb-17), which was obviously higher than that in the yellow-grained line Syn-ABAb-18 (6.346 μg/g). The crude protein content was between 154.406 and 180.517 g/kg, and the EAA content was 40.193-63.558 mg/g. The Fe, Zn, Mn and Cu levels in the 17 blue-grained lines were 60.55 to 97.41 mg/kg, 60.55-97.41 mg/kg, 35.11 to 65.20 mg/kg and 5.74 to 7.22 mg/kg, respectively, which were higher than those in the yellow-grained line. The contribution of the first three principal components reached 84%. The first principal component was mainly anthocyanins, Fe, Zn and Mn. The second principal component contained protein and amino acids, and the third component contained only Cu. The top 5 Triticum turgidum-Triticum boeoticum amphiploids were Syn-ABAb-11, Syn-ABAb-17, Syn-ABAb-5, Syn-ABAb-8 and Syn-ABAb-4. These amphidiploids exhibited the potential to serve as candidates for hybridization with common wheat, as indicated by comprehensive score rankings, toward enhancing the nutritional quality of wheat.

Generation of spontaneous Triticum durum ×Aegilops tauschii wheat synthetic amphiploids and their characterization

Aegilops tauschii (2n=2x=14), the D-genome donor is the closest progenitor to modern wheat representing a large proportion of unexplored genetic variation. Flourishing in the adverse climatic conditions it can be utilized in the wheat improvement programmes. We targeted to develop and characterize the primary synthetics amphiploids from nine different accessions of Ae. tauschii and one Triticum durum cv. PBW114 through spontaneous chromosomal doubling. Being fertile with ~50% survival rate, the amphiploids were selfed for five generations without any selection and 38 F6 amphiploids were obtained. They were evaluated for chromosome number and pairing behaviour, different agro-morphological traits and diseases of leaf rust, yellow rust and powdery mildew. Nineteen amphiploids had 2n = 42 chromosomes, four had 2n=28, two had 41 chromosomes. While in the remaining 12 amphiploids, the chromosome number varied from 24 to 42, some with abnormal pairing. Large variations were observed in agromorphological traits with 32 amphiploids showing better thousand grain weight than the hexaploid check varieties and PBW114. Response to the three targeted diseases varied widely across the panel. Twenty-four D-genome specific SSRs used to assess the genetic diversity showed that the amphiploids from same cross combinations were grouped differently. We observed that development of a new species is a complex event, and combining divergent genomes into one nucleus with chromosome doubling inflicts considerable stress on a newly emerged species with rapid genomic instability in nascent allopolyploid individuals to enable their immediate survival. However, this is an effective and novel means of creating new diversity for wheat improvement programmes.

Molecular cytogenetic identification of a new synthetic amphiploid (Triticum timococcum, AtAtGGAmAm) with a seed setting rate comparable with that of natural Triticum zhukovskyi

AbstractTriticum timopheevii (AtAtGG) was previously cultivated in western Georgia, and Triticum zhukovskyi (AtAtGGAmAm) is a natural allohexaploid originating from hybridization of T. timopheevii and Triticum monococcum (AmAm). In this study, two synthetic amphiploids (Triticum timococcum, AtAtGGAmAm), Syn‐AtGAm‐20 and Syn‐AtGAm‐21, were developed by chromosome doubling of F1 hybrids between T. timopheevii and T. monococcum. Chromosomes of these two amphiploids were identified by fluorescence in situ hybridization (FISH) utilizing oligonucleotide probes Oligo‐pSc119.2‐1, Oligo‐pTa535‐1, Oligo‐pTa71‐2 and Oligo‐(AAC)7. Each amphiploid had 42 chromosomes derived from its parents, but the Glu‐A1mx subunits from einkorn were both not expressed. Syn‐AtGAm‐20 had low average seed setting rates of 19.86% and 20.50% in two different years, with abnormal spikes similar to those reported before. Syn‐AtGAm‐21 had normal spikes with average seed setting rates of 65.88% and 61.56% in two different years, comparable with those of natural T. zhukovskyi. However, the relationship between Syn‐AtGAm‐21 and natural T. zhukovskyi requires further study. This research provides new materials for studying the origin of T. zhukovskyi.

Investigation of the effects of different genotypes on regeneration capacity in Triticale

Triticale (x Triticosecale Wittmack) is a synthetic amphiploid cereal that grows on about 3 million hectares in the world. It is grown mostly for forage or animal feed, although some triticale-based foods can be purchased at health food stores or are found in some breakfast cereals. Mature embryos of two triticale cultivars (Ümran Hanım and Melez 2001) were used as the resources explants. The effects of one auxin type (2,4-D) and three various concentrations, (4.0 mg/l; 8mg/l; 12.0mg/l) callus formation and plant regeneration were determined. Callus formation values were detected over 85% in three concentrations. In terms of results, the highest embryogenic callus formation rate was determined 46.91 % at 12 mg/l of Ümran Hanım dicamba. However, the lowest embryogenic callus formation rate was found with a value of 12.86% in Ümran Hanım's 2,4-D 8.0 mg/l hormone application. The highest regeneration capacity was determined at 12.09% at a dose of 12.0 mg/l of Mikham 2001 2,4-D. However, the lowest regeneration capacity was determined at 2.2% at the dose of 4 mg/l of Ümran Hanım 2,4-D. Our results displayed that auxin type and hormone dosage were very significant on the triticale mature embryos.

Genome-Wide Introgression and Quantitative Trait Locus Mapping Reveals the Potential of Asian Cotton (Gossypium arboreum) in Improving Upland Cotton (Gossypium hirsutum).

Gossypium arboreum (2n=2x=26, A2), the putative progenitor of the At-subgenome of Gossypium hirsutum (2n=4x=52, AD), is a repository of genes of interesting that have been eliminated during evolution/domestication of G. hirsutum. However, its valuable genes remain untapped so far due to species isolation. Here, using a synthetic amphiploid (AADDA2A2) previously reported, we developed a set of 289 G. arboreum chromosome segment introgression lines (ILs) in G. hirsutum by expanding the backcrossing population and through precise marker-assisted selection (MAS) although complex chromosomal structural variations existed between parents which severely hindered introgression. Our results showed the total coverage length of introgressed segments was 1,116.29 Mb, representing 78.48% of the At-subgenome in the G. hirsutum background, with an average segment-length of 8.69 Mb. A total of 81 co- quantitative trait loci (QTLs) for yield and fiber quality were identified by both the RSTEP-ADD-based QTL mapping and the genome-wide association study (GWAS) analysis, with 1.01–24.78% of the phenotypic variance explained. Most QTLs for boll traits showed negative additive effects, but G. arboreum still has the potential to improve boll-number traits in G. hirsutum. Most QTLs for fiber quality showed negative additive effects, implying these QTLs were domesticated in G. hirsutum compared with G. arboreum and, a small quantity of fiber quality QTLs showing positive additive effects, conversely; however, indicates that G. arboreum has the underlying genes of enhancing fiber quality of G. hirsutum. This study provides new insights into the breeding genetic potential of G. arboreum, lays the foundation for further mining favorable genes of interest, and provides guidance for inter-ploidy gene transference from relatives into cultivated crops.

Production of synthetic wheat lines to exploit the genetic diversity of emmer wheat and D genome containing Aegilops species in wheat breeding

Due to the accumulation of various useful traits over evolutionary time, emmer wheat (Triticum turgidum subsp. dicoccum and dicoccoides, 2n = 4x = 28; AABB), durum wheat (T. turgidum subsp. durum, 2n = 4x = 28; AABB), T. timopheevii (2n = 4x = 28; AAGG) and D genome containing Aegilops species offer excellent sources of novel variation for the improvement of bread wheat (T. aestivum L., AABBDD). Here, we made 192 different cross combinations between diverse genotypes of wheat and Aegilops species including emmer wheat × Ae. tauschii (2n = DD or DDDD), durum wheat × Ae. tauschii, T. timopheevii × Ae. tauschii, Ae. crassa × durum wheat, Ae. cylindrica × durum wheat and Ae. ventricosa × durum wheat in the field over three successive years. We successfully recovered 56 different synthetic hexaploid and octaploid F2 lines with AABBDD, AABBDDDD, AAGGDD, D1D1XcrXcrAABB, DcDcCcCcAABB and DvDvNvNvAABB genomes via in vitro rescue of F1 embryos and spontaneous production of F2 seeds on the Fl plants. Cytogenetic analysis of F2 lines showed that the produced synthetic wheat lines were generally promising stable amphiploids. Contribution of D genome bearing Aegilops and the less-investigated emmer wheat genotypes as parents in the crosses resulted in synthetic amphiploids which are a valuable resource for bread wheat breeding.

Production and cytological characterization of a synthetic amphiploid derived from a cross between Oryza sativa and Oryza punctata.

Oryza punctata Kotschy ex Steud. (BB, 2n = 24) is a wild species of rice that has many useful agronomic traits. An interspecific hybrid (AB, 2n = 24) was produced by crossing O. punctata and Oryza sativa variety Punjab Rice 122 (PR122, AA, 2n = 24) to broaden the narrow genetic base of cultivated rice. Cytological analysis of the pollen mother cells (PMCs) of the interspecific hybrids confirmed that they have 24 chromosomes. The F1 hybrids showed the presence of 19-20 univalents and 1-3 bivalents. The interspecific hybrid was treated with colchicine to produce a synthetic amphiploid (AABB, 2n = 48). Pollen fertility of the synthetic amphiploid was found to be greater than 50% and partial seed set was observed. Chromosome numbers in the PMCs of the synthetic amphiploid were 24II, showing normal pairing. Flow cytometric analysis also confirmed doubled genomic content in the synthetic amphiploid. Leaf morphological and anatomical studies of the synthetic amphiploid showed higher chlorophyll content and enlarged bundle sheath cells as compared with both of its parents. The synthetic amphiploid was backcrossed with PR122 to develop a series of addition and substitution lines for the transfer of useful genes from O. punctata with least linkage drag.

Use of the synthetic Oligo-pTa535 and Oligo-pAs1 probes for identification of Hordeum chilense-origin chromosomes in hexaploid tritordeum

The synthetic oligonucleotide probes Oligo-pTa535 and Oligo-pAs1 were previously developed by other authors based on the repetitive sequences of clones pTa535 and pAs1 available in GenBank, and have been used as probes in fluorescence in situ hybridization (FISH) experiments allowing the identification of wheat and rye chromosomes. Their suitability as nondenaturing fluorescence in situ hybridization (ND-FISH) probes turned the hybridization procedure less time consuming, easier and more affordable. Contrastingly to conventional FISH, ND-FISH does not require DNA denaturing, preserving the chromosomal morphology and being adequate for successive hybridizations on the same chromosome spread. In this study, we hybridized, for the first time, the Oligo-pTa535 and Oligo-pAs1 probes on mitotic chromosomes of hexaploid tritordeum using ND-FISH. Tritordeum (HchHchAABB) is the synthetic amphiploid resultant from crosses between wild barley (HchHch) and cultivated durum wheat (AABB). Both Oligo-pTa535 and Oligo-pAs1 hybridized on all H. chilense-origin chromosomes of tritordeum, allowing their identification and the construction of an ideogram based on their hybridization patterns and on the physical location of the 45S ribosomal DNA (rDNA) loci detected by pTa71. We are confident that this ideogram will be further useful for the identification of H. chilense-origin chromosomes in other tritordeum lines or allopolyploids involving the Hch-genome.

A New Synthetic Amphiploid (AADDAA) between Gossypium hirsutum and G. arboreum Lays the Foundation for Transferring Resistances to Verticillium and Drought.

Gossypium arboreum, a cultivated cotton species (2n = 26, AA) native to Asia, possesses invaluable characteristics unavailable in the tetraploid cultivated cotton gene pool, such as resistance to pests and diseases and tolerance to abiotic stresses. However, it is quite difficult to transfer favorable traits into Upland cotton through conventional methods due to the cross-incompatibility of G. hirsutum (2n = 52, AADD) and G. arboreum. Here, we improved an embryo rescue technique to overcome the cross-incompatibility between these two parents for transferring favorable genes from G. arboreum into G. hirsutum. Our results indicate that MSB2K supplemented with 0.5 mgl-1 kinetin and 250 mg-1 casein hydrolysate is an efficient initial medium for rescuing early (3 d after pollination) hybrid embryos. Eight putative hybrids were successfully obtained, which were further verified and characterized by cytology, molecular markers and morphological analysis. The putative hybrids were subsequently treated with different concentrations of colchicine solution to double their chromosomes. The results demonstrate that four putative hybrid plants were successfully chromosome-doubled by treatment with 0.1% colchicine for 24 h and become amphiploid, which were confirmed by cytological observation, self-fertilization and backcrossing. Preliminary assessments of resistance at seedling stage indicate that the synthetic amphiploid showed highly resistant to Verticillium and drought. The synthetic amphiploid between G. hirsutum × G. arboreum would lay the foundation for developing G. arboreum-introgressed lines with the uniform genetic background of G. hirsutum acc TM-1, which would greatly enhance and simplify the mining, isolation, characterization, cloning and use of G. arboreum-specific desirable genes in future cotton breeding programs.

Caracterización del genoma de un Triticum x Thinopyrum (Poaceae) sintético amfiploide utilizando hibridación in situ.

Caracterización del genoma de un Triticum x Thinopyrum (Poaceae) sintético amfiploide utilizando hibridación in situ. Los “Trigopiros” derivan de cruzamientos entre diferentes especies deTriticum y Thinopyrum. El objetivo es obtener cereales con características similares al trigo, perennes,resistentes a enfermedades y a la salinidad de los suelos. Además estos híbridos sintéticos son útilespara transferir al trigo atributos agronómicos de Thinopyrum. “Trigopiro” Don Noé INTA, que se cultiva actualmente en Argentina, presenta rasgos agronómicos valiosos, así como un alto contenido deproteínas seminales. En el presente trabajo se confirmó que el número de cromosomas de “Trigopiro”Don Noé es 2n = 56. Técnicas de hibridación in situ (FISH-GISH) permitieron postular su composicióngenómica desconocida hasta el momento. Este híbrido artificial posee 14 cromosomas del genoma J deThinopyrum y 2 pares de cromosomas con posibles translocaciones entre Triticum y Thinopyrum. El restode los cromosomas pertenecen a los genomas A, B y D de Triticum.

Molecular cytogenetic identification and phenotypic description of a new synthetic amphiploid, Triticum timococcum (AtAtGGAmAm).

A recently developed synthetic amphiploid, Triticum timococcum Kost., nom. nud. (2n = 6x = 42, AtAtGGAmAm) is described in the present study. This hexaploid taxon was developed by colchicine treatment in Martonvásár from the hybrid of a selected accession of Triticum timopheevii Zhuk. (2n = 4x = 28, AtAtGG) and a prebred semi-dwarf line of Triticum monococcum L. (2n = 2x = 14, AmAm). A detailed cytomolecular examination was carried out using the sequential multicolour fluorescence and genomic in situ hybridization techniques (FISH and mcGISH). It was proved that T. timococcum has 42 chromosomes originating from its parents. The chromosomes of the A genomes of T. monococcum and T. timopheevii could be distinguished in the amphiploid using FISH. The successful discrimination of the chromosomes was supported by the karyotypes of the three genomes and the successful optimization of the mcGISH technique for the A and G chromosomes achieved in the present study. A phenotypic evaluation was also carried out under natural and artificial growing conditions in 2012 and 2013. Based on the results, T. timococcum has intermediate characteristics in terms of spike (spikelet) shape and plant height, while it is similar to the female parent, T. timopheevii regarding pubescence. Like its parents, T. timococcum showed outstanding resistance to the main fungal diseases of wheat. T. timococcum headed later and developed longer and looser spikes, fewer tillers and only a third as many seeds than its parents. The third generation of T. timococcum was able to develop an acceptable number of seeds, even taking into account the reduced germination ability in the field.

Cytomorphological Characterization of the Backcross Progeny of Synthetic Amphiploid Rice (AABB) and Tetraploid Oryza sativa (AAAA)

DCW008, a synthetic allopolyploid rice (2n = 4X = 48, AABB), was obtained from chromosome doubling of interspecific hybrids between Oryza sativa (2n = 24, AA) and O. punctata (2n = 24, BB). The F1 and backcross (BC1) hybrids were produced by crossing DCW008 as a female parent with a high seed set tetraploid rice Sg99012 - 4X (2n = 4X = 48, AAAA). BC1F1 and BC1F2 overcame many of the wild-type traits of DCW008; they had yellow-hulled grains, seed set ranged from 0% to 71.31% and the grain morphology was similar to that of cultivated rice. Variable numbers of chromosomes were observed in pollen mother cells (PMCs) from the BC1 plant. Genomic in situ hybridization (GISH) revealed that the majority of somatic cells and PMCs contained six chromosomes of O. punctata with fragment recombination observed in two of them. The backcross selection method employed in this study to generate allopolyploid progeny provides a reliable way of transferring useful genes from wild species into cultivated rice.

Characterization of Triticum timopheevii Zhuk. gene bank accessions for the development of synthetic amphiploid wheat lines

In recent years 56 accessions of Triticum timopheevii Zhuk. (2n=4x=28, AtAtGG) were characterized for the main phenotypic and resistance characters. Among these accessions 38 originated from the base species together with subspecies and varietas forms thereof, and 18 belong to the subspecies armeniacum group. After the evaluation of field assessment data gathered over 12 years, the most promising 11 accessions were selected for a crossability trial with cultivated einkorn. As a result of this trial, the accession with the highest seed set (Acc. No.: MVGB845) was chosen for the development of a new synthetic amphiploid using the same semi-dwarf line of diploid cultivated einkorn (Triticum monococcum L. ssp. monococcum 1T-1, 2n=2x=14, AmAm) as in the crossability trial. This einkorn line was bred in Martonvásár, and has both outstanding resistance and other promising phenotypic and agronomic characters.After crossing the accession MVGB845 with 1T-1, the triploid hybrids were treated with colchicine to obtain fertile progenies with a doubled genome. The newly developed synthetic hexaploid wheat breeding stock (named Triticum timococcum Kost., 2n=6x=42, AtAtGGAmAm) could ease the introgression of valuable resistance genes into bread wheat at the hexaploid level (bridge-crossing).The aim of the present research was to redevelop Triticum timococcum based on a detailed characterization of gene bank accessions, and to introduce this new material into wheat breeding.

Development and characterization of synthetic amphiploid (AABB) between Oryza sativa and Oryza punctata

AbstractOryza punctata, a wild relative of cultivated rice, belongs to the BB genome of Oryza. Interspecific hybrids (CW008, AB) between Oryza sativa (2n = 24 AA) and O. punctata (2n = 24 BB) were obtained using embryo rescue technique. Synthetic allopolyploid (DCW008, AABB) were produced through chromosome doubling by colchicine. Hybrids overcame many wild traits except the shattering and awn. The synthetic amphiploid plants showed obvious superiority in growth and production. Interspecific hybrids CW008 were completely infertile but DCW008 had better seed set after selfing. Genomic in situ hybridization investigations were performed on DCW008. The result indicated that the A genome was closed to the B genome and translocations occurred between some chromosomes of cultivated and wild rice. Meiosis was nearly normal in the amphiploid hybrid but was disrupted in the diploid hybrid, which resulted in different fertility of them.

Development of synthetic amphiploids based on Triticum turgidum × T. Monococcum crosses to improve the adaptability of cereals

Cultivated einkorn (Triticum monococcum L. ssp. monococcum) is an excellent source of resistance against several wheat diseases and quality parameters. Semi-dwarf einkorn lines with good crossability were identified in order to produce Triticum turgidum × T. monococcum synthetic amphiploids. Two combinations were used to develop the amphiploids: durum × einkorn and emmer × einkorn.After the genome duplication of F1 seeds, highly fertile amphiploids were developed. The AuBAm genome structure of the progenies was confirmed by genomic in situ hybridization (GISH).Lines derived from durum × einkorn and emmer × einkorn crosses were studied for agronomic performance, disease resistance and genetic variability. Both amphiploid combinations showed excellent resistance against certain wheat diseases (leaf rust, powdery mildew), but not against fusarium. The durum-based synthetic amphiploid lines showed a higher level of phenotypic diversity. The newly produced T. turgidum × T. monococcum synthetic hexaploids are promising genetic resources for wheat breeding. Selected durum × einkorn lines are currently used in bread wheat improvement to transfer the useful properties of einkorn into cultivated hexaploid wheat via ‘bridge-crossing’.

Screening of wild crucifers for resistance to mustard aphid, Lipaphis erysimi (Kaltenbach) and attempt at introgression of resistance gene(s) from Brassica fruticulosa to Brassica juncea

A diverse array of wild and weedy crucifers was screened under laboratory conditions for their resistance to Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae). Among these, Brassica fruticulosa and Brassica montana were found to be the most promising. The availability of a synthetic amphiploid, AD-4(B. fruticulosa × Brassica rapa var. brown sarson) as well as a set of Brassica juncea lines carrying genomic introgressions from B. fruticulosa allowed us to investigate B. fruticulosa resistance in greater detail. This assessment was carried out along with susceptible check B. rapa ssp. brown sarson cv. BSH-1 in a series of choice and no choice experiments. The mustard aphid showed maximum preference for feeding on BSH-1 while least preference was recorded for B. fruticulosa followed by AD-4 as evidenced by the number of aphids that settled on circular leaf bits of these genotypes 24 and 48 h after release in a choice experiment. Brassica fruticulosa exhibited strong antibiosis against mustard aphid in no choice experiment and all the released aphids died within 5–8 days of their release, while the maximum survival (76.7%) was recorded on BSH-1. The survival on AD-4 (40%) was significantly lower than that on BSH-1. Almost similar trend was observed with respect to other demographic parameters of L. erysimi viz. development time, fecundity and longevity. In the screen house studies, there was no seedling mortality in B. fruticulosa and AD-4 after 30 days of aphid release while 80% mortality was observed on BSH-1. Excellent variation for aphid resistance was recorded in B. juncea introgression lines, emphasizing heritable nature of fruticulosa resistance. The biochemical analysis suggested the possibility of high concentration of lectins to be associated with low aphid infestation in B. fruticulosa.

Random chromosome elimination in syntheticTriticum–Aegilopsamphiploids leads to development of a stable partial amphiploid with high grain micro- and macronutrient content and powdery mildew resistance

Synthetic amphiploids are the immortal sources for studies on crop evolution, genome dissection, and introgression of useful variability from related species. Cytological analysis of synthetic decaploid wheat (Triticum aestivum L.) - Aegilops kotschyi Boiss. amphiploids (AABBDDUkUkSkSk) showed some univalents from the C1 generation onward followed by chromosome elimination. Most of the univalents came to metaphase I plate after the reductional division of paired chromosomes and underwent equational division leading to their elimination through laggards and micronuclei. Substantial variation in the chromosome number of pollen mother cells from different tillers, spikelets, and anthers of some plants also indicated somatic chromosome elimination. Genomic in situ hybridization, fluorescence in situ hybridization, and simple sequence repeat markers analysis of two amphiploids with reduced chromosomes indicated random chromosome elimination of various genomes with higher sensitivity of D followed by the Sk and Uk genomes to elimination, whereas 1D chromosome was preferentially eliminated in both the amphiploids investigated. One of the partial amphiploids, C4 T. aestivum 'Chinese Spring' - Ae. kotschyi 396 (2n = 58), with 34 T. aestivum, 14 Uk, and 10 Sk had stable meiosis and high fertility. The partial amphiploids with white glumes, bold seeds, and tough rachis with high grain macro- and micronutrients and resistance to powdery mildew could be used for T. aestivum biofortification and transfer of powdery mildew resistance.

Fate of Aegilops speltoides-Derived, Repetitive DNA Sequences in Diploid Aegilops Species, Wheat-Aegilops Amphiploids and Derived Chromosome Addition Lines

The present study reports the cloning and characterization of an Aegilopsspeltoides-derived subtelomeric repeat, designated as pSp1B16. Clone pSp1B16 has 98% sequence homology with the previously isolated Ae. speltoides repeat Spelt1. The distribution of pSp1B16 and another Ae. speltoides repeat, pGc1R1, was analyzed in diploid Aegilops species, tetra- and hexaploid wheats, wheat-Aegilops amphiploids and derived chromosome addition lines by fluorescence in situ hybridization (FISH). Clones pSp1B16 and pGc1R1 revealed FISH sites in Ae. speltoides, Ae. sharonensis and Triticumtimopheevii, whereas additional pGc1R1 FISH sites were observed in Ae. longissima and Ae. caudata. The pSp1B16 and pGc1R1 FISH patterns of the Aegilops chromosomes in the wheat-Aegilops amphiploids and chromosome addition lines are similar to those present in the Aegilops parent accession. We did not observe any evidence of pSp1B16 and pGc1R1 sequence elimination, which is in contrast to previous studies using similar hybrids and repeats. The presented data suggest that the genomic changes in synthetic amphiploids observed in previous studies might be caused by homoeologous recombination, which was suppressed in the amphiploid analyzed in this study.

The synthesis of trigeneric Aegilops X Triticum X Secale hybrids

Synthetic amphiploids, Aegilops X Triticum and Triticum X Aegilops, were crossed with Secale cereale and Secale montanum. Trigeneric hybrids with genomic constitutions ADRc, ADMvRc, ADMvRm, ABDRc, ABDRm, ABDMvRm and ABDMvRcRc were produced and studied. All these hybrids except the hybrid with genomes ABDMvRcRc were taller and had bigger leaves and spikes than parents. The relative proportion of Secale genomes appears to be critical in the survival and subsequent development of these hybrids. The key characters of the genera Aegilops, Triticum and Secale (Pilger 1954) were examined by studying nine different trigeneric combinations. The trigeneric hybrids had characters from all the three genera. In general appearance, however, the spikelets of all the trigeneric hybrids resembled those of the Triticum parent more closely than those of the Secale and Aegilops parent. The trigeneric hybrids behaved like perennial forms, but were completely sterile. There was evidence that the sterility of the hybrids was genic as well as chromosomal. The induction of polyploidy and restoration of fertility in these hybrids might yield useful polygenomic forms.

Development and characterization of Triticum aestivum– Aegilops kotschyi amphiploids with high grain iron and zinc contents

Synthetic amphiploids betweenTriticum aestivum(AABBDD) landrace Chinese Spring (PhI) and cultivar WL711 with different accessions ofAegilops kotschyi(UUSlSl) were developed through colchicine treatment of sterile hybrids. TheF1hybrids and amphiploid plants were intermediate between the parents for plant morphology and spike characteristics. Meiotic metaphase chromosome analysis of theF1hybrids (ABDUSl) showed the expected chromosome number (35) and very little but variable homoeologous chromosome pairing. The amphiploids (AABBDDUUSlSl), however, had variable frequency of univalents at meiotic metaphase-I. The SDS–PAGE of high molecular weight glutenin subunits of amphiploids along with the parents showed the presence and expression of all the parental genomes in the amphiploids. The amphiploids with seeds as large as that of wheat cultivars had higher grain, flag leaf and grain ash iron and zinc concentrations than the wheat parents and comparable with those of theirAe. kotschyiparents suggest thatAe. kotschyipossesses a distinctive genetic system for the micronutrient uptake, translocation and sequestration than the wheat cultivars. This could, however, be demonstrated unequivocally only with comprehensive data on biomass, grain yield and harvest index of theAegilopsdonors and the synthetic amphiploids, which is not feasible due to their shattering and hard threshing. The use of amphiploids for the transfer of high iron and zinc concentrations and development of alien addition and substitution lines in wheat is in progress.