Hexaploid Level Research Articles

Biosystematics of Indian Plants IV: <i>Portulaca oleracea</i> and <i>P. quadrifida</i> in Punjab

A large collection of two polymorphic weeds, Portulaca oleracea Linn. and P. quadrifida Linn., originating from diverse sources, was cultivated under uniform conditions. This experiment revealed the extent and nature of be genetic variation in the two species. In the former there were found three qualitatively distinguishable variants all at hexaploid (n=27) level, while in the latter there were only two quantitatively distinct variants at 6x (n=27) and 12x levels. All these have been evaluated biosystematically.

Chromosome numbers in 31 taxa of Asteraceae, Brassicaceae, Poaceae, Hypericaceae, Lamiaceae, Fabaceae and Plantaginaceae from wetlands of Hamadan region in Iran

In this study, we report the somatic chromosome numbers (2n) of 31 taxa belonging to Asteraceae, Brassicaceae, Poaceae, Hypericaceae, Lamiaceae, Fabaceae and Plantaginaceae families from wetlands of Hamadan region in Iran. The chromosome numbers of about half of these species have not been reported in the previous literature. Chromosome number of Ononis spinosa counted chromosomally for the first time at the world level and the chromosome numbers of Erigeron acer, Pulicaria dysenterica, Arctium lappa, Xanthium strumarium, X. spinosum, Barbarea plantaginea, Brachypodium sylvaticum, Polypogon fugax, Prunella vulgaris and Lathyrus chloranthus, are here reported for the first time from Iran. In all taxa 2n was 12, 14, 16, 18, 20, 24, 28, 30, 32 and 42, as a diploid, tetraploid and hexaploid levels. These newly available data are further compared with those previously published for the same or related species.

Genome Sizes, Ploidy Levels, and Base Compositions of Styrax Species and Cultivars

Styrax L. is a genus of ≈130 species, many with horticultural traits of interest, though sparsely represented in cultivation. Previous studies reporting chromosome counts have established a base chromosome number of x = 8 and provided evidence of diploid, tetraploid, pentaploid, and hexaploid levels within the genus, including the more commonly cultivated Styrax japonicus Siebold & Zucc. being reported as pentaploid. Little has been reported relative to genome size within the Styracaceae. We conducted flow cytometry using fluorochromes propidium iodide (PI) and 4′,6-diamidino-2-phenylindole (DAPI) to estimate relative 2C genome size and ploidy of 47 accessions representing 15 species of Styrax and base composition of a subset of 9 accessions representing 6 species. Cytologic analysis of chromosomes was completed on Styrax confusus Hemsl. for ploidy calibration to genome size. Diploids, tetraploids, pentaploids, hexaploids, and octoploids were identified. Relative 2C genome size ranged from 1.38 to 6.61 pg. This survey confirms published ploidy for Styrax americanus Lam., Styrax obassia Siebold & Zucc., Styrax redivivus (Torr.) L.C.Wheeler (diploid), and S. japonicus (pentaploid); suggests alternate ploidy levels and/or ploidy series for Styrax grandifolius Aiton (diploid) and Styrax hookeri C.B.Clarke (octoploid); and establishes ploidy levels for Styrax glabrescens Benth., Styrax odoratissimus Champ. ex Benth., Styrax officinalis L., Styrax platanifolius Engelm. ex Torr., Styrax ramirezii Greenm., Styrax wilsonii Rehder (diploid), Styrax confusus, Styrax hemsleyanus Diels (tetraploid), and Styrax fortunei Hance (diploid and hexaploid).

Effect of Meiotic Polyploidisation on Selected Morphological and Anatomical Traits in Interspecific Hybrids of Brassica oleracea × B. napus

In Brassica, interspecific hybridisation plays an important role in the formation of allopolyploid cultivars. In this study, the ploidy of F1 and F2 generations resulting from interspecific hybridisation between B. oleracea inbred lines of head cabbage (B. oleracea L. var. capitata) (2n = 18) and kale (B. oleracea L. var. acephala) (2n = 18) with inbred lines of rapeseed (B. napus L.) (2n = 38) was examined by flow cytometry analysis and chromosome observation. Furthermore, the effect of meiotic polyploidisation on selected phenotypic and anatomical traits was assessed. The F1 hybrids of head cabbage × rapeseed (S3) and kale × rapeseed crosses (S20) were allotriploids with 2n = 28 chromosomes, and nuclear DNA amounts of 1.97 (S3) and 1.99 pg (S20). These values were intermediate between B. oleracea and B. napus. In interspecific hybrids of the F2 generation, which were derived after self-pollination of F1 hybrids (FS3, FS20) or by open crosses between F1 generation hybrids (FC320, FC230), the chromosome numbers were similar 2n = 56 or 2n = 55, whereas the genome sizes varied between 3.81 (FS20) and 3.95 pg 2C (FC230). Allohexaploid F2 hybrids had many superior agronomic traits compared to parental B. napus and B. oleracea lines and triploid F1 hybrids. In the generative stage, they were characterised by larger flowers and flower elements, such as anthers and lateral nectaries. F2 hybrids were male and female fertile. The pollen viability of F2 hybrids was comparable to parental genotypes and varied from 75.38% (FS3) to 88.24% (FC320), whereas in triploids of F1 hybrids only 6.76% (S3) and 13.46% (S20) of pollen grains were fertile. Interspecific hybrids of the F2 generation derived by open crosses between plants of the F1 generation (FC320, FC230) had a better ability to set seed than F2 hybrids generated from the self-pollination of F1 hybrids. In the vegetative stage, F2 plants had bigger and thicker leaves, larger stomata, and significantly thicker layers of palisade and spongy mesophyll than triploids of the F1 generation and parental lines of B. oleracea and B. napus. The allohexaploid F2 hybrids analysed in this study can be used as innovative germplasm resources for further breeding new vegetable Brassica crops at the hexaploid level.

Molecular characterization of Algerian populations of cocksfoot and tall fescue: Ploidy level determination and genetic diversity analysis

AbstractAlgeria is a country rich in phytogenetic resources, especially those of pastoral and forage interest. Unfortunately, few studies have been conducted to characterize Algerian local ecotypes. Recently, advances in next‐generation sequencing technologies have allowed for robust genotyping by sequencing (GBS) for single nucleotide polymorphism (SNP) discovery, making the characterization of plant relationships with complex and unsequenced genomes more feasible. In the present study, we investigate the genetic diversity of cocksfoot and tall fescue ecotypes from different regions in Algeria, using the SNP variation supplied by a GBS analysis. We compared ecotypes to two common cultivars of both species. A total of 787 SNP markers for cocksfoot and 743 for tall fescue were obtained, and the diversity analysis revealed that 88% and 86% of overall variation in cocksfoot and tall fescue, respectively, were within populations rather than among them. Genetic structure analysis revealed a moderate genetic differentiation among accessions with a mean Fst value of 0.127 for cocksfoot and 0.140 for tall fescue, with high gene flow (NmOrchardgrass = 1.723, NmTall fescue = 1.535) and no significant isolation‐by‐distance pattern. A unweighted pair group method with arithmetic mean tree (UPGMA) and principal component analysis revealed the genetic distinctness of populations from cultivars for each species. The flow cytometry analysis confirmed the tetraploid level of cocksfoot and the hexaploid level of all tall fescue entries but one. Although the cocksfoot populations were distinct from the cultivars, the Ruines de djemila population had the broadest base and showed the closest relative relationship to the two cultivars. Similarly, the FE5729 tall fescue population showed the closest relationship to the two tall fescue cultivars.

News lines of winter common wheat (triticum aestivum L.) and winter triticale (xtriticosecale wittmack ex a. camus) in the conditions of the forest-steppe of Ukraine

The data on the analysis of new lines of common wheat and winter triticale hexaploid level by morphological characteristics, biochemical properties and markers grain created and studied during 2005–2019 are provided. in the conditions of the Forest-Steppe of Ukraine.A new breeding material of common wheat and winter triticale hexaploid level has been submitted for study to the National Center for Genetic Resources Plant of Ukraine of the Рlant Production Institute nd. a. V.Ya. Yuryev of NAAS of Ukraine and is used by us in breeding tasks.The purpose and objectives of the study – to create and give an agroecological and selection and economic assessment of the new starting material of hexaploid level of winter triticale adapted to the conditions of the Forest-Steppe and Polissia Ukraine.Materials and methods. The breeding work was carried out in the educational and scientific research center of Bila Tserkva NAU in 2007–2017. The source material was the triticale varieties of winter of various ecological and geographical origin of domestic and foreign selection (Slavetne, Pshenychne, Chayan, DAU 5, Uragan, Ladne, Rarytet, Poliske 7, Adas, Woltario, etc.) provided on a contractual basis to the NCGRP of Ukraine of the Рlant Production Institute nd. a. V.Ya. Yuryev of NAAS. Hybridization was performed by the method of manual castration of maternal components and fueling by the «fuel-method» 2–3 days after castration. All observations and evaluations were carried out according to the according to generally accepted methodology according to generally accepted methodology. Mathematical-statistical data processing was carried out according to B.A. Dospekhov and using computer software Statistica-5.5 and Excel-2003.The discussion of the results. It is shown that new wheat lines: Donzorna 1005, Sviatdonivka 1007/05, Kyivopolka 1016, Polezoriana 1021, Flonormyra 1017/05, Zoroariyivka 1024/05, and triticale Trygorsyz give good results, given the consistently high consistently high winter tolerance and drought tolerance (8.5 points on average), plant productivity (average grain weight per ear 2.5 g, weight 1000 grains 50 g) and grain yield (average 5.8 t/ha ) and grain quality (protein content: in wheat grain – 14%, triticale – 10.8%) and flour (gluten content 27–29%, including triticale – 19%).According to the results of environmental testing in the central and northern Forest-Steppe, new genotypes formed such an average grain yield: Donzorna 1005 – 5.32 t/ha, Sviatdonivka 1007/05 – 5.59 t/ha, Kyivopolka 1016 – 5.89 t/ha, Polezoriana 1021/09 ’ 5.87 t/ha, Flonormyra 1017/05 – 6.77 t/ha, Zoroariyivka 1024/05 – 5.93, and triticale Trygorsyz – 5.17 t/ha.Analysis of electrophoresis of storage proteins showed that the new Donzorna line 1005/05 is characterized by the presence of recombinant wheat-rye translocation 1BL.1RS from the Caucasus type secalinam. In addition, the genetic marker 1BL.1RS was also noted in the lines KC 14-05 (UA0123342), Zoriana Nosovskaya (UA0110603), L 3-95 (UA0107961), L 41-95 (UA0108030), L 4639/96 (UA 0108163) , which are samples of the Ukrainian Plant Gene Pool, which indicates the possibility of their study in breeding and genetic programs for the use of reserve proteins controlled by the Gli-Al, Gli-R1 loci as genetic markers for identifying genotypes with recombinant 1RS and determining the frequency of recombination between shoulders 1RS as part of various translocations within the framework of tasks on the formation of recombinantly inbred wheat lines with high resistance to a series of stem rusts.Conclusions. The materials of the article reflect the results of the formation and study of a new source material of winter common wheat and triticale of hexaploid level, which was transferred in 2019 to study in National Center for Genetic Resources Plant of Ukraine of the Рlant Production Institute nd. a. V.Ya. Yuryev of NAAS of Ukraine in order to register and replenish the country's genetic bank with genotypes valuable for agroecological, breeding and economic traits for long-term selection and genetic research.

Parameters of adaptability, biological and economical valuable traits of soft wheat promising lines

Results of research of soft winter wheat new lines of hexaploid level by morphological features, biological properties and biochemical parameters were given. During 2018–2020 in the Northern part of the Central Forest-Steppe of Ukraine the assessment of the general adaptive capacity by the yielding capacity and biological-agronomic traits are given and promising ones are highlighted (Donzorna, Flonormyra, Polezoriana). The new wheat lines have proved themselves well given the consistently high winter, drought resistance, and productivity, coefficient of variation is low, variance of stability, homeostaticity, and selection value – high. According to the biochemical composition of the grain, the studied lines are characterized by medium and high ‘raw’ protein content and gluten content. New selection wheat lines own by the technological indicators (the volumetric bread outut of 100 g of drough, the total baking rating), flour ‘quite satisfactory’, ‘good’, and ‘excellent’ score (Sviatdonivka, Flonormyra). The new wheat line Donzorna is characterized by the presence of 1BL/1RS wheat-rye translocation, which distinguishes it as a donor of resistance to biotic and abiotic factors and requires further more detailed study.

ВЫСОТА РАСТЕНИЙ-ОБРАЗЦОВ ТРИТИКАЛЕ РАЗЛИЧНОГО ПРОИСХОЖДЕНИЯ И УРОВНЯ ПЛОИДНОСТИ

The great attention that is now being paid to triticale by breeders is due to the hopes of combining in one organism all the valuable that wheat and rye can give. The study of morphological characters using the most typical samples of triticale, characterizing the ecologicalgeographic and genotypic diversity of this synthetic genus, allows us to reveal the patterns of their variability for use in breeding programs and in taxonomy. As a result of studying 36 samples of triticale of various origins and ploidy different levels in terms of plant height and resistance to lodging, it was found that there is a very close correlation between these two parameters. Spring and winter forms significantly differ from each other in terms of plant height. Spring forms are lower than winter ones. The largest number of spring triticale samples have plant height from 110 to 130 cm, and hexaploids – from 130 to 150 cm. The majority of hexaploid triticale spring forms were obtained in Mexico and Russia. Mexican triticale plants are much lower in height than Russian ones. A close correlation was established between the resistance to lodging of triticale plants and the length of the stem. As a rule, specimens with heights not higher than 115 cm are characterized by high resistance to lodging. The amplitude of variability in plant height in triticale is quite significant at all ploidy levels. The range of variation in plant height is greatest at the hexaploid level – from 50 to 200 cm. In tetraploids it ranges from 70 to 160 cm, in octoploids – from 80 to 170 cm. The highest average value of plant height in octoploid forms of triticale is 133.8 cm, in tetraploids – 122.7 cm, and the smallest in hexaploids – 114.5 cm. This is explained by intensive selection work carried out at this level of ploidy.

Ploidy of Seeds from Odd-polyploid American Elm

Seeds from two odd-polyploid Ulmus americana L., both open-pollinated from surrounding tetraploid trees, were analyzed for nuclear genome size by using flow cytometry. Seeds from the triploid were predominantly aneuploid, with DNA content intermediate between triploid and tetraploid levels, but substantial numbers of tetraploid and pentaploid seeds were observed. No seeds of even ploidy were found in progeny of the pentaploid; seeds of the pentaploid were pentaploid, aneuploid with DNA content intermediate between tetraploid and pentaploid levels, or aneuploid with DNA content intermediate between pentaploid and hexaploid levels. Seeds from both trees often gave two peaks via flow cytometry, indicating the presence of two genetically distinct embryos in the same seed. The frequency of polyembryony in the sample is much higher than the frequency of seeds that yield multiple seedlings, suggesting that the formation of two genetically distinct embryos, followed by abortion of one embryo, is common in elms.

Evidence of widespread hybridization among couch grasses (Elymus, Poaceae)

AbstractHybridization, polyploidization, and crop‐to‐wild gene transfer within the agriculturally important tribe Triticeae are well explored experimentally, but the true consequences of both phenomena under natural conditions remain understudied. The present paper reports on an investigation of three species of couch grasses (Elymus hispidus, E. repens, and E. caninus) examining the ploidy levels and absolute genome sizes (1081 plants from 302 natural populations in Central Europe, verified by chromosome counts) and their morphological delimitation. In the present study, the hexaploid level prevailed in E. hispidus and E. repens whereas E. caninus was exclusively tetraploid. Introgressive hybridization between hexaploid species, unidirectionally shifted towards E. hispidus, was indicated by a continual pattern of genome size values. We did not find any evidence for heteroploid hybridization involving tetraploid E. caninus; however, we detected minority cytotypes among both E. caninus plants (hexaploid) and E. repens–E. hispidus hybrids (heptaploid and nonaploid) suggesting the formation of unreduced gametes. Morphometric results (367 plants, redundancy analysis, principal component analysis, and correlation analysis) mirrored the continual homoploid pattern of absolute genome size (including the unidirectional shift), and a significant correlation between absolute genome size and morphology was confirmed. Moreover, morphometric analyses detected additional characteristics for the delimitation of the Elymus taxa under study. Considering the crossability of E. hispidus with Triticum aestivum (bread wheat), the revealed extent of introgressive hybridization has implications for assessing the potential risk of gene flow between crops and troublesome weeds.

Новые генетические источники для селекции видов Prunus L. на полиплоидном уровне

This research is aimed at studying of the chromosomal number distribution within the new, in vitro cultured, amitotic
 clonal lines of Prunus species, at comparing of the fertility and size of pollen for triploid and hexaploid amitotic clones and
 at identifying of new genetic sources and their subsequent use in breeding. Methods. The standard cytological and statistical
 methods were used in this scientific work. Results. The regularities of induced polyploids output both from the initial number
 of chromosomes and from the origin and individual characteristics of the original genotypes were established. For amitotic
 hexaploid genotypes of hybrid cherry, high pollen quality was discovered at the level of 81,8–92,6 % of fertility (in triploids
 the 4,6–18,8 % of such pollen was found), therefore, the studied 4 clonal cherry genotypes (12-1-1Т2, 12-1-1Т6, 12-1-2Т3,
 12-1-2Тv) are recommended for breeding of resistant to fungal diseases varieties. No significant differences were found in the
 diameter of fertile pollen (46.3–47.8 μm) between cherry amitotic triploids and hexaploids. Therefore, in all likelihood, fertile
 pollen in triploids carries an unreduced triploid set of chromosomes. Prime scientific novelty. A completely new and original
 selection material for the genus Prunus L. – polyploid hybrids of P. fruricosa Pall. with rare East-Asiatic cherry species P. serrulata Lindl., P. canescens Bois., P. incisa. Thoub. were studied. The arguments in favor of a positive breeding prospect for the
 transfer of new cherries varieties to the hexaploid level (2n = 48), including an in vitro culture method of chromosome number
 doubling for the sterile triploid interspecific hybrids, have been obtained. The first created tetraploid (2n = 32) amitotic clonal
 lines of microcherry P. pumila L. must be tested in crosses with thorns and hybrids of thorns.

An extracted tetraploid wheat harbouring the BBAA component of common wheat shows anomalous shikimate and sucrose metabolism

BackgroundThe BBAA subgenomes of hexaploid common wheat are structurally intact, which makes it possible to extract the BBAA subgenomes to constitute a novel plant type, namely, extracted tetraploid wheat (ETW). ETW displays multiple abnormal phenotypes such as massively reduced biomass and abnormal spike development, compared to extant tetraploid wheat with a BBAA genome. The genetic, biochemical and physiological basis underlying the phenotypic abnormality of ETW remains unknown.ResultsTo explore the biochemical basis of these phenotypic abnormalities, we analysed the metabolomic and proteomic profiles and quantified 46 physiological traits of ETW in comparison with its common wheat donor (genome BBAADD), and a durum tetraploid wheat cultivar (genome BBAA). Among these three types of wheat, ETW showed a saliently different pattern of nutrient accumulation and seed quality, markedly lower concentrations of many metabolites involved in carbohydrate metabolism, and higher concentrations of many metabolites related to amino acids. Among the metabolites, changes in shikimate and sucrose were the most conspicuous. Higher levels of shikimate and lower levels of sucrose influence many metabolic processes including carbohydrate and amino acid metabolism, which may contribute to the phenotypic abnormalities. Gene expression assay showed downregulation of a shikimate degradation enzyme (5-enolpyruvylshikimate-3-phosphate synthase) coding gene and upregulation of several genes coding for the sucrose hydrolysis enzyme, which could explain the higher levels of shikimate and lower levels of sucrose, respectively.ConclusionsOur results suggest that significant and irreversible biochemical changes have occurred in the BBAA subgenomes of common wheat during the course of its co-evolution with the DD subgenome at the hexaploid level.

Evaluation of triticale accessions for resistance to wheat bacterial leaf streak caused by Xanthomonas translucens pv. undulosa

The bacterium Xanthomonas translucens pv. undulosa (Xtu) causes bacterial leaf streak (BLS) on wheat and other small grains. Several triticale accessions were reported to possess high levels of resistance to wheat Xtu strains. In this study, a worldwide collection of triticale accessions as well as the major North Dakota hard red spring and durum wheat cultivars were evaluated for reaction to two local Xtu strains. All wheat cultivars showed a susceptible reaction but a wide range of reactions was observed among triticale accessions. Out of the 502 accessions tested, 45 and 10 accessions were resistant to the two virulent strains BLS‐LB10 and BLS‐P3, respectively, with five accessions, PI 428736, PI 428854, PI 428913, PI 542545 and PI 587229, being highly resistant to both strains. Statistical analysis showed significant difference among the accessions, strains, and the accession by strain interaction (P < 0.001). Bacterial population growth in resistant triticale was significantly slower than that in susceptible triticale. Molecular cytogenetic characterization in four representative triticale accessions confirmed the hexaploid level of the species and the presence of 12 or 14 rye chromosomes. The triticale accessions identified are valuable materials for developing wheat germplasm with high levels of BLS resistance.

Artemisia estesii (Asteraceae), a new diploid species of the Artemisia ludoviciana complex in the Pacific Northwest (U.S.A.)

The new species described here, Artemisia estesii, belongs to the Artemisia ludoviciana Nutt. species’ group in the Pacific Northwest. It was shown by J.R. Estes (1968a, 1969) to be a diploid member of an otherwise polyploid hybrid complex, with most of its related species and subspecies occurring at the tetraploid and hexaploid levels. Artemisia estesii is recognized by its underground and emergent, over-wintering, basal shoots, which are homologs of the elongate, underground rhizomes found in other herbaceous Artemisia species. Its regularly lobed leaf blades, with usually a broad rachis, differ from subspecies of A. ludoviciana in eastern Oregon. It occupies a narrow zone of streambank vegetation along the central Deschutes River and extends eastward along the lower Crooked River. Disjunct populations are known from Wheeler County and Lake County.

Revisiting meiotic pairing in wheat synthetics in relation to the evolution of the meiotic system in wheat

A large panel of hexaploid wheat synthetics was developed. Their tetraploid parents consisted of either four extracted wheat tetraploids (ETWs) or four natural present-day tetraploids, and their diploid parents consisted of twenty accessions of Aegilops tauschii. Analysis of meiotic behaviour of the synthetics showed that chromosome pairing is highly variable and depends on the progenitor. The meiotic behaviour in the four ETWs was compared to that of the natural tetraploid wheats. It appears there was no evolution at the hexaploid level of the meiotic genes carried by the A and B genomes. We also reach the conclusion that the neo-allohexaploids at the origin of present-day wheat had a meiotic behaviour close to that of the present-day hexaploid wheat. It is likely that other neo-hexaploids with an impaired meiosis were formed, but they had no future due to their more or less rapid disappearance due to increasing aneuploidy level and structural changes, mainly Robertsonian translocations.

Utilizing Wild Species for Peanut Improvement

The cultivated peanut (Arachis hypogaeaL.) is an allotetraploid species with a very large and complex genome. This species is susceptible to numerous foliar and soil‐borne diseases for which only moderate levels of resistance have been identified in the germplasm collection, but several of the 81 wild species are extremely resistant to many destructive peanut diseases. Peanut species were grouped into nine sections, but only taxa in sectionArachiswill hybridize withA. hypogaea. Most of these species are diploid, but two aneuploids and two tetraploids also exist in the section. The first peanut cultivars released after interspecific hybridization were ‘Spancross’ and ‘Tamnut 74’ during the 1970s from a cross betweenA. hypogaeaand its tetraploid progenitor. However, introgression of useful genes from diploids has been difficult due to sterility barriers resulting from genomic and ploidy differences. To utilize diploids in sectionArachis, direct hybrids have been made betweenA. hypogaeaand diploid species, the chromosome number doubled to the hexaploid level, and then tetraploids recovered with resistances to nematodes, leaf spots, rust, and numerous insect pests. ‘Bailey’, a widely grown Virginia‐type peanut, was released from these materials, and other cultivars are gown in Asia and South America. Alternatively, hybrids between diploid A and B genome species have been made, the chromosome number doubled, and cultivars released with nematode resistance derived fromArachisspecies. Introgression fromArachisspecies toA. hypogaeaappears to be in large blocks rather than as single genes, and new genotyping strategies should enhance utilization of wild peanut genetic resources.

Genome size and ploidy levels of creeping phlox and related germplasm of mat-forming taxa from eastern and western North America

The eastern North American creeping phlox (Phlox subulata L.) is a widely cultivated flowering groundcover with a history of breeding and selection. Little is known about genome size variation and ploidy of P. subulata and related taxa. Mean holoploid (2C) and monoploid (1Cx) genome sizes and ploidy were analyzed with flow cytometry for a germplasm collection (n=53) of 11 morphologically similar creeping phlox taxa from natural plant populations, cultivars and hybrids obtained from nursery sources, and the related Microsteris gracilis. Holoploid genome sizes of accessions from natural populations were more variable than cultivated taxa and ranged from 7.47 to 22.86pg and corresponded to diploid (2n=2x=14) tetraploid (2n=4x=28), and hexaploid (2n=6x=42) levels, but most accessions were diploid and genome size ranged from 7.60 to 8.47pg. Two tetraploid accessions were discovered, but hexaploids were limited to one population of P. subulata. Most accessions consisted of a single cytotype, but intrapopulation differences in holoploid genome size were found among P. subulata and P. nivalis. The monoploid genome size of M. gracilis differed significantly from all Phlox, supporting separation of the genera. All cultivar accessions were diploid with genome sizes similar to wild diploid P. subulata, however Phlox×procumbens had a mean genome size (8.73pg) intermediate to parental taxa, P. stolonifera×P. subulata, supporting hybrid origin. Knowledge of cytotype variation in Phlox germplasm will be useful for plant breeders, systematists, and conservationists.

Genetic and epigenetic modifications to the BBAA component of common wheat during its evolutionary history at the hexaploid level.

The formation and evolution of common wheat (Triticum aestivum L., genome BBAADD) involves allopolyploidization events at two ploidy levels. Whether the two ploidy levels (tetraploidy and hexaploidy) have impacted the BBAA subgenomes differentially remains largely unknown. We have reported recently that extensive and distinct modifications of transcriptome expression occurred to the BBAA component of common wheat relative to the evolution of gene expression at the tetraploid level in Triticum turgidum. As a step further, here we analyzed the genetic and cytosine DNA methylation differences between an extracted tetraploid wheat (ETW) harboring genome BBAA that is highly similar to the BBAA subgenomes of common wheat, and a set of diverse T. turgidum collections, including both wild and cultivated genotypes. We found that while ETW had no significantly altered karyotype from T. turgidum, it diverged substantially from the later at both the nucleotide sequence level and in DNA methylation based on molecular marker assay of randomly sampled loci across the genome. In particular, ETW is globally less cytosine-methylated than T. turgidum, consistent with earlier observations of a generally higher transcriptome expression level in ETW than in T. turgidum. Together, our results suggest that genome evolution at the allohexaploid level has caused extensive genetic and DNA methylation modifications to the BBAA subgenomes of common wheat, which are distinctive from those accumulated at the tetraploid level in both wild and cultivated T. turgidum genotypes.

Development and validation of molecular markers linked with stem rust resistance gene Sr13 in durum wheat

Stem rust resistance gene Sr13, found frequently in tetraploid wheats, was tested effective against Puccinia graminis f. sp. tritici pathotype Ug99 (TTKSK) and its derivatives. It remains a candidate for developing new cultivars with diverse combinations of stem rust resistance genes. To combine Sr13 with other genes that produce a similar phenotype, linked markers would be required. We used the AFLP approach to identify markers linked closely with Sr13. The STS marker AFSr13, derived from an AFLP fragment, mapped at 3.4–6.0 cM proximal to Sr13 across three mapping populations. Marker dupw167, previously reported to be linked with Sr13, mapped 2.3–5.7 cM distal to Sr13 in four F3 populations. Marker gwm427 mapped proximal to AFSr13 in two populations, and these markers were monomorphic on one population each. The map order dupw167–Sr13–AFSr13–gwm427 was deduced from the recombination data. Markers dupw167 and AFSr13 were validated on 21 durum wheat genotypes. Combination of dupw167 and AFSr13 would facilitate marker-assisted selection of Sr13 in segregating populations. At the hexaploid level, only gwm427 showed polymorphism and differentiated the presence of Sr13 in 10 of the 15 backcross derivatives carrying Sr13 from their Sr13-lacking recurrent parents.

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.