Hexaploid Cultivars Research Articles

A study to incorporate high protein content from tetraploid wheat (T. turgidum dicoccoides) to hexaploid wheat (T. aestivum vulgare)

Grain protein content of wheat is important for bread making and pasta quality. Wild tetraploid wheat (Triticum turgidum L. var. dicoccoides) has some genes for high protein content as a promising source. Three winter wheat cultivars of Colorado (Halt, Yuma, Akron) and one experimental line (CO99508) and one accession of T. dicoccoides were crossed to obtain backcrosses. The objective of this study was to determine higher protein content, SDSsedimentation and hardiness values in backcrosses T. aestivum x T. dicoccoides. Analysis of variance showed that highly significant differences were found among parents and backcrosses. The minimum and maximum values of grain protein content of all backcross populations changed from low protein parents (bread wheat cultivars) to high protein parent (T. dicoccoides). This increase in grain protein content of backcrosses is most likely due to the transferring of the high protein genes from the T. dicoccoides to the hexaploid cultivars. Although T. dicoccoides has high grain protein content, bread making quality of T. dicoccoides has lower than bread wheat cultivars. This situation has also been observed in all backcross populations. However, based on the results of this study, it could be concluded that high protein genes in the wild tetraploid wheat (T. dicoccoides) could possibly be transferred to the bread wheat cultivars.

Characterization of Total, Free and Esterified Phytosterols in Tetraploid and Hexaploid Wheats

Dietary plant sterols have received increasing attention in recent years due to their favorable health benefits. The present research focused on quantification of phytosterols as free, esterified and total forms in different tetraploid (5 cultivars of Triticum durum Desf., 9 cultivars of Triticum dicoccon Schrank) and hexaploid (5 cultivars of T. aestivum L., 12 cultivars of Triticum spelta L.) wheats. Tetraploid wheats showed the highest content of total sterol (79.4 and 79.5 mg of sterols /100 g dry weight for T. durum and T. dicoccon, respectively). Hexaploid cultivars were the best source of esterified sterols (40.7% and 37.3% of total sterols for Triticum aestivum and T. spelta, respectively). Significant amounts of free sterols (65.5% and 60.7% of total sterols for T. durum and T. dicoccon, respectively) were found in the tetraploid cultivars. The most abundant phytosterol in all wheat samples was sitosterol accounting for 45.1-59.1, 46.6-57.4 and 38.6-59.5% of total, free and esterified sterol fraction, respectively. These results demonstrate that although the sterol profile present in tetraploid and hexaploid wheat species is the same, differences in their relative amounts and distribution allow statistical differentiation between hexaploids and tetraploids, and between soft and durum wheats.

Influence of Extreme Temperatures During Grain Filling on Protein Fractions, and Its Relationship to Some Quality Characteristics in Bread, Biscuit, and Durum Wheat

ABSTRACTExtreme temperatures during grain filling have been identified as a major source of variation in wheat quality characteristics. In this study one biscuit, two bread, and one durum wheat cultivars were evaluated in two consecutive seasons for reaction to extreme high and low temperatures during grain filling. In both years, the soft biscuit wheat cultivar showed the largest reaction to low temperature stress, where the monomeric proteins were significantly increased and the polymeric proteins significantly decreased. The effect of temperature stress was more pronounced in the second year, with an earlier planting date. The durum wheat reacted to both heat and cold stress in the second year, where the small polymeric proteins were significantly reduced, and the small and large monomeric proteins were increased with stress. The effect of wheat type was much more pronounced than the effect of temperature treatments on the protein fractions. The protein fractions of the tetraploid durum wheat were very different from the hexaploid cultivars, with much less polymeric proteins, and more monomeric proteins. The soft biscuit wheat had significantly less large polymeric proteins and more large monomeric proteins than the bread wheat cultivars for both years.

Genome organisation and retrotransposon driven molecular evolution of the endosperm Hardness (Ha) locus in Triticum aestivum cv Glenlea

Wheat endosperm texture is controlled primarily by a locus (Ha), which comprises Gsp-1, Pina and Pinb genes encoding the so-called grain softness protein, puroindoline-a and puroindoline-b, respectively. Pina and Pinb were detected only on the D-genome of hexaploid wheat and its diploid progenitors while Gsp-1 was on all three homoeologous loci. Hexaploid cultivar Glenlea has a hard phenotype due to a null Pina genotype (D-genome) but the sequence organization is not reported. This study aimed at understanding the evolution of homoeologous Ha loci. Sequencing of three BAC clones from cv Glenlea was performed and sequence analyses delimited the Ha loci which spanned 3,925, 5,330 and 31,607 bp in the A-, B- and D-genomes, respectively. A solo LTR of Angela retroelement, downstream to Gsp-A1 and a fragment of Sabrina retroelement, downstream of Gsp-B1, were discovered. We propose that the insertion of these elements into the intergenic regions have driven the deletions of genomic segments harbouring Pina and Pinb genes in the A- and B-genomes of hexaploid wheat. Similarly, fragments of Romani and Vagabond retroelements were identified between truncated Pina and Pinb genes, indicating their role in the deletion of Pina in Glenlea, leading to its hard texture. Structural differences of the Ha locus region of the A-genome between two hexaploid wheat varieties namely Glenlea and Renan (CR626929), suggested the presence of more than one tetraploid ancestor in the origin of hexaploid wheat.

Introgression of crown rust resistance from diploid oat Avena strigosa into hexaploid cultivated oat A. sativa by two methods: direct crosses and through an initial 2x·4x synthetic hexaploid

New sources of resistance to crown rust, Puccinia coronata f. sp. avenae (Eriks.), the major fungal disease of cultivated oat, Avena sativa L. (2n = 6x = 42), are constantly needed due to frequent, rapid shifts in the virulence pattern of the pathogen. Crown rust resistance identified in the diploid oat A. strigosa (Schreb.) (2n = 2x = 14) accession CI6954SP was transferred into cultivated oat using two methods: direct cross of the diploid to a hexaploid cultivar facilitated by embryo rescue, and initial cross of the diploid to a wild tetraploid oat to make a synthetic hexaploid for subsequent crossing to a hexaploid cultivar. Two tetraploids, a crown rust resistant A. murphyi (Ladiz.) accession P12 and a susceptible A. insularis (Ladiz.) accession INS-1, were used in the 2x·4x crosses. Resistant backcross-derived lines were recovered by both methods. Although the 2x·4x synthetic method did not require the laborious discovery and rescue of an infrequent initial hybrid embryo of the direct cross, the direct cross method provided more rapid backcross recovery of plants with high fertility, full transmission of resistance, and desired plant and seed phenotypes. A suppressor effect, present initially but segregating in backcrosses, appeared to come from the CI6954SP donor and is the same as, or analogous to, suppression by an oat line with the crown rust resistance gene Pc38. No resistance from A. murphyi P12 was detected in advanced generations when it was introduced either as a component of a synthetic hexaploid or in direct crosses to A. sativa, indicating suppression of its resistance in interploidy combinations. That the dominant resistance gene transferred from CI6954SP and a gene Pc94 introgressed earlier from a different A. strigosa accession may be the same or quite similar to one another is indicated by their in-common specificity to suppression of resistance expression, susceptibility to a newly recovered rust isolate, and close linkage to the molecular marker SCAR94-2. The introgressed resistance genes from the different sources, even if the same, may have different cultivar genomic introgression sites, which would allow tests of dosage effects on resistance expression.

Transferring a Gene Expression Cassette Lacking the Vector Backbone Sequences of the 1Ax1 High Molecular Weight Glutenin Subunit into Two Chinese Hexaploid Wheat Genotypes

lAxl high molecular weight glutenin subunit (HMW-GS) gene expression cassette (GEC) lacking vector backbone sequences together with selectable marker Bar GEC were co-transformed into Chinese hexaploid cultivars Een 1 and Emai 12 to test the feasibility and the efficiency of explant regeneration, transformation frequency and transgene expression comparing with whole vector transformation by the approaches of plasmid extraction and excision, immature embryo isolation, particle co-bombardment, tissue culture, DNA extraction, PCR amplification, southern hybridization, leaf-painting test and SDS-PAGE etc. No significant difference was shown in tissue culture response of the proportion of embryogenic calli, somatic embryogenesis and regeneration frequency between GEC and whole plasmid bombarded embryos, but both regenerated less well than non-bombarded control. Total 56 plantlets that survived PPT selection had insertion of at least the Bar gene, 18 were from the GEC treatment and 38 from the whole plasmid treatment, the escape ratio averaged 0.23. Six independent transplants f230 - f235 with GEC transformation from genotype Emai 12 presented clear PCR amplification bands of Bar and lAxl gene. The transformation and co-transformation frequency were 3.51 and 100% respectively. PCR amplification using a primer-pair specific for ampicillin resistant gene indicated the existence of Amp R gene in whole vectors but the removal in GECs and transplants. Southern blot of total DNA and PCR products from transgenic plants of lAxl GEC confirmed the integration of the transgene lAxl and the absence of the EcoR I recognition site at both ends of the lAxl GEC when integrated. SDS-PAGE showed the expression of lAxl GEC and un-expression of whole plasmid. The length of integrated fragment, the proportion of the gene of interest (GOI) and the selectable marker (MG), bombardment pressure and genotypes are vital for the expression of a transformed GEC.

Genomic constitution of Festulolium cultivars released in the Czech Republic

AbstractGenomic in situ hybridization (GISH) was used to characterize the chromosome constitutions of individual plants from a set of tetraploid and hexaploid cultivars of Festulolium developed and released in the Czech Republic from hybrids of Lolium multiflorum with Festuca pratensis and F. arundinacea. A simplified GISH protocol readily discriminated parental genomes in the hybrids and facilitated the screening of large numbers of plants per accession. The contribution of parental genomes in the cultivars tested ranged from predominance of chromatin from one of the parents to a more balanced contribution from both parents. However, in none of the cultivars were equal proportions of chromatin from both parents present. The parental contribution to the hybrids was both in the form of complete chromosomes or as chromosome translocations. In hexaploid cultivars from (L. multiflorum × F. arundinacea) × F. arundinacea hybrids the average numbers of complete L. multiflorum chromosomes ranged from 4.95 to 7.5 and the numbers of translocations from 6.33 to 10.21. Two tetraploid cultivars from (L. multiflorum × F. arundinacea) × L. multiflorum hybrids showed a strong prevalence of L. multiflorum chromatin and intergeneric translocations were rare. In the tetraploid cultivar ‘Perun’ of the L. multiflorum × F. pratensis hybrid there were 11.7 chromosomes of L. multiflorum and 14.7 recombined chromosomes on average. Reasons for the domination of one of the parental genomes in hybrid cultivars are not clear and are only partially explained by breeding history. Recombination rates of individual genomes in hybrids involving F. arundinacea were evaluated in double hybridization experiments. The results indicated a strong affinity of the L. multiflorum genome for the F. pratensis genome present in F. arundinacea and little affinity for the F. glaucescens genome. This suggests that introgressions from F. arundinacea into L. multiflorum are primarily limited to the F. pratensis genome which can be more readily accessed in L. multiflorum × F. pratensis hybrids.

Partial sequences of nitrogen metabolism genes in hexaploid wheat

Our objective was to partially sequence genes controlling nitrogen metabolism in wheat species in order to find sequence polymorphism that would enable their mapping. Primers were designed for nitrate reductase, nitrite reductase, glutamate dehydrogenase and glutamate synthase (GOGAT), and gene fragments were amplified on Triticum aestivum, T. durum, T. monococcum, T. speltoides and T. tauschii. We obtained more than 8 kb of gene sequences, mainly as coding regions (60%). Polymorphism was quantified by comparing two-by-two the three genomes of the hexaploid cultivar Arche and genomes of diploid wheat species. On average, the polymorphism rate was higher for non-coding regions, where it ranged from 1/60 to 1/23, than for coding regions (range: 1/110-1/40) except when the hexaploid D genome was compared to that of T. tauschii (1/800 and 1/816, respectively). Genome-specific primers were devised for the ferredoxin-dependent (Fd)-GOGAT gene, and they enabled the mapping of this gene on homoeologous chromosomes of group 2 using Chinese Spring deletion lines. A single nucleotide polymorphism (SNP) detected between the two hexaploid wheat cultivars Arche and Recital was used to genetically map Fd-GOGAT on chromosome 2D using a population of dihaploid lines. Fd-GOGAT-specific primers were used to estimate the SNP rate on a set of 11 hexaploid and nine Durum wheat genotypes leading to the estimate of 1 SNP/515 bp. We demonstrate that polymorphism detection enables heterologous, homeologous and even paralogous copies to be assigned, even if the elaboration of specific primer pairs is time-consuming and expensive because of the sequencing.

Characteristics of F1 Progenies Obtained by Crossing a Small-flowered Tetraploid Garden Chrysanthemum, 'YS' (2n=36), with Hexaploid Chrysanthemum Cultivars (2n=54)

To elucidate the usefulness of the small-flowered chrysanthemum, 'YS', which has the smallest chromosome number (2n=36) among parental breeding materials, the characteristics of progenies derived from 'YS' crosses with hexaploid (2n=54) cultivars were investigated. Our histological observations on the developmental process of the anther showed that the tapetum did not dehisce at the mature pollen stage. Therefore, we regard 'YS' as one example of male sterility. Cross pollinations between 'YS' or its polyploid (2n=72) with three hexaploid cultivars (2n=54) yielded a number of seeds per inflorescence, but their percentage of germination differed with cross combinations. Examinations of the F1 progenies revealed that most progenies grew vigorously, and their mean height exceeded the intermediate value of their parents. Flower types that were classified according to the morphology of the capitulum showed that the progenies between 'YS' (petaloidy-type) × three cultivars (nonpetaloidy-type) were characteristic of the male parent type. The diameters of inflorescences in the progenies derived from 'YS' (small-type) × three cultivars (medium-type) were about 10% smaller than the intermediate value of their parents, whereas their pollen fertilities were: 'YS' (5.3%), its polyploid (43%), and the three cultivars (78.6- 83.1%), similar to their male parents. The progenies derived from 'YS' (male-sterile) × three cultivars (male-fertile) were all male-fertile. The chromosome numbers in the progenies between 'YS' (2n=36) × three cultivars (2n=54) were most frequently pentaploid (2n=45), intermediate between the parents. The stability of the heritable characteristics of progenies over four years showed that although it differed between years and crosses, variable characteristics were plant height, plant form and flowering times, whereas the stable characteristics were their growth appearance, diameter of inflorescence and flower types. The most stable characteristic was flower color. From this study, we considered that 'YS' poses no problem to use as a female parent in crosses between cultivars whose chromosome numbers differ significantly.

Superoxide Dismutase Activity of Hexaploid and Tetraploid Wheat Cultivars Subjected to Heat and Chilling Stress

Effect of heat (37°C, 24 hours) and chilling (4°C, 24 hours) stress on SOD activity was investigated in shoots and roots of hexaploid and tetraploid wheat cultivars. In order to analyse the changes of SOD isozymes against heat and chilling stress, shoot and root extracts were subjected to native PAGE. Extracts of both tissues revealed the presence of Mn and Cu/Zn isozymes of SOD. Cu/ZnSOD activity comprised 90% of total SOD activity in both tissues. Heat stress caused a significant increase in SOD activity both in root and shoot tissues of the hexaploid cultivars whereas a decrease was observed in the tetraploid cultivar. Under cold stress no significant change in SOD activity was observed in shoot tissues of all cultivars. On the contrary, SOD activities in the roots of the hexaploid cultivars were significantly enhanced while a decrease was observed in the roots of tetraploid cultivar. Our data suggest that enhanced SOD activity might be one of the reasons of relatively greater stress tolerance of bread wheat cultiars over durum cultivars under heat and chilling stress conditions.

Diversity of seven glutenin and secalin loci within triticale cultivars grown in Europe

Analysis by SDS-PAGE of the majority of hexapoid triticales (× Triticosecale) (134 cultivars) grown in Europe allowed to identify 40 alleles at seven loci: Glu-A1, Glu-B1, Glu-R1, Gli-R2, Glu-B2, Glu-A3 and Glu-B3. Glu-B1 and Glu-B3 loci were the most polymorphic with 9 alleles at each locus. 95 allelic combinations were observed including 71 specific for one cultivar each. On the basis of allelic frequencies at the seven loci, genetic distances between hexapoid triticales grouped according to their origins revealed two clusters: winter triticales mostly originating from European germplasm and spring triticales essentially of CIMMYT origin. Comparison of allele frequencies between hexaploid triticale cultivars and a world collection of bread (Triticum aestivum) and durum (Triticum durum) wheat was investigated at Glu-A1 and Glu-B1: only a significant association was found for Glu-A1 alleles (γ2=2.26, p=0.36) between triticale and bread wheat.

Ploidy variation in the cultivated yams (Dioscorea cayenensis-dioscorea rotundata complex) from Cameroon as determined by flow cytometry

The ploidy levels of the twenty-two yam (Dioscorea cayenensis-D. rotundata complex) cultivars within germplasm Cameroon Guinea yam were determined by flow cytometry. Three different ploidy levels (4x,6x, 8x) were detected within the samples analysed. Fifteen cultivars were tetraploids, five were hexaploids, and two were octoploids. The cultivar group EKOTO showed a high level of ploidy variation with tetraploid, hexaploid and octoploid cultivars. The hexaploid nature of cultivars Dobnawo and Bilougnou supported the hypothesis that they are hybrids between cultivars of the EKOTO group and either the KPE or BAKOKAE groups.

Phenetic Characterization of Plum Cultivars by High Multiplex Ratio Markers: Amplified Fragment Length Polymorphisms and Inter-simple Sequence Repeats

Variability of commercial plum (Prunus L. sp.) cultivars is unknown since breeding often involves intercrossing hybrids with several species but has been based on a low number of parents. Molecular markers like amplified fragment length polymorphisms (AFLP) and inter-simple sequence repeats (ISSR), which sample multiple loci simultaneously, have become increasingly popular, and were used to characterize 24 diploid and four hexaploid cultivars of plum. Seven AFLP and six ISSR primers were used, and resulted in amplification of 379 and 270 products, respectively. Unweighted pair-group method with arithmetic averages (UPGMA) dendrograms, based on similarity coefficients, reflected a clear separation between diploid and hexaploid plums. Among diploid plums, two pairs of cultivars were relatively distinct from the rest, namely `Golden Japan' and `Methley' and `Ozark Premier' and `Songold'. Furthermore, several cultivars were grouped together both with AFLP and ISSR analysis: 1) `Ambra', `Red Beaut', and `Black Beaut', 2) `Black Diamond' and `Royal Diamond', 3) `June Rose', `Santa Rosa', and `Royal Red', and iv) `Freedom', `Larry Ann', and `Queen Rosa'. Although the phenetic classification obtained by the two methods were similar (r = 0.73, for the diploid group), ISSR had a higher reproducibility and percentage of polymorphisms (87.4% vs. 62.8%) than AFLP. Methodological aspects of both markers systems are discussed. Results obtained suggest that the AFLP and ISSR approaches are valuable tools for identification of specific genotypes and analysis of phenetic relationships in plum.

Production of Nonaploid (2n = 9x) Japanese Persimmons (Diospyros kaki) by Pollination with Unreduced (2n = 6x) Pollen and Embryo Rescue Culture

To produce nonaploid Japanese persimmon (Diospyros kaki L.f.) by artificial hybridization, we surveyed the natural occurrence of unreduced (2n) pollen among hexaploid cultivars and sorted them from normal reduced (n) pollen. The sorted 2n pollen was crossed with a hexaploid female cultivar and the resultant embryos were rescued by in vitro culture techniques to obtain plantlets. Three out of six male-flower-bearing cultivars (2n = 6x = 90) produced 2n pollen at rates of 4.8% to 15.5% varying with the cultivar, which was estimated by both pollen size and flow cytometry. After sorting giant (2n) from normal pollen grains by using nylon mesh, they were crossed with a hexaploid female cultivar. The seeds obtained from pollination with normal pollen were perfect, but those obtained from pollination with giant pollen were mostly imperfect, with embryo growth being suspended at the globular stage. Although the rate of survival was very low, some embryos at the globular stage were rescued successfully and grown in vitro. Both flow cytometric analysis and chromosome counting proved that the plantlets obtained were nonaploid.

Identification of RFLP markers for resistance to wheat spindle streak mosaic bymovirus (WSSMV) disease

Wheat spindle streak mosaic bymovirus (WSSMV) causes an economically important disease of winter wheat in Europe and North America. Artificial inoculation with this virus to identify resistant wheat genotypes is difficult. This study was conducted to identify restriction fragment length polymorphism (RFLP) markers associated with resistance to this disease. A population, consisting of 104 F5 recombinant inbred lines from a cross between hexaploid Triticum aestivum cultivars 'Geneva' (resistant) and 'Augusta' (susceptible), was evaluated for WSSMV symptoms under field conditions for four years. Two linked markers on the long arm of chromosome 2D, Xbcd1095 and Xcdo373, were determined to be associated with WSSMV resistance by bulked segregant analysis of the 10 most resistant and 10 most susceptible lines. Marker Xcdo373 accounted for 79% and Xbcd1095 for 73% of the phenotypic variation. Our results suggest that resistance to WSSMV in this population is qualitative in nature and is controlled by few genes. These markers should be useful in the development of wheat cultivars resistant to WSSMV and perhaps also to wheat yellow mosaic bymovirus (WYMV).Key words: wheat, wheat spindle streak mosaic virus (WSSMV), RFLP markers, resistance, bymovirus, wheat yellow mosaic virus, barley yellow mosaic virus.

Development of PCR‐Based Markers for a High Grain Protein Content Gene from Triticum turgidum ssp. dicoccoides Transferred to Bread Wheat

Grain Protein Content (GPC) of wheat (Triticum aestivum L. and T. turgidum L.) is important for improved nutritional value and is also one of the major factors affecting breadmaking and pasta quality. A quantitative trait locus (QTL) for high GPC was detected a few years ago in the short arm of chromosome 6B from accession FA15‐3 of Triticum turgidum L. var. dicoccoides New molecular markers are presented here to facilitate the transfer of this high GPC gene into tetraploid and hexaploid wheat cultivars. Two sets of PCR (polymerase chain reaction) primers were designed to amplify regions of the non‐transcribed spacer of the XNor‐B2 locus. This locus was selected because it mapped on the peak of the QTL for GPC. The first pair of allele‐specific primers produced an amplification product only when the T. turgidum var. dicoccoides XNor‐B2 allele was present. The second pair of primers amplified fragment(s) of similar length in the different genotypes that after digestion with the restriction enzyme BamHI allowed differentiation of the T. turgidum var. dicoccoides allele. Four microsatellites markers were mapped on the short arm of chromosome 6B at both sides of the QTL peak and two on the long arm. Five additional amplified fragment length polymorphism (AFLP) markers were mapped into the QTL region on 6BS. These PCR markers together with 10 restriction fragment length polymorphism (RFLP) markers showed that the hexaploid cultivar Glupro, selected for high GPC, carries a distal segment of chromosome 6BL and a proximal segment of 6BS from dicoccoides accession FA15‐3 encompassing the segment with highest LOD score for the GPC QTL.

Identification of RFLP markers for resistance to wheat spindle streak mosaic bymovirus (WSSMV) disease

Wheat spindle streak mosaic bymovirus (WSSMV) causes an economically important disease of winter wheat in Europe and North America. Artificial inoculation with this virus to identify resistant wheat genotypes is difficult. This study was conducted to identify restriction fragment length polymorphism (RFLP) markers associated with resistance to this disease. A population, consisting of 104 F5 recombinant inbred lines from a cross between hexaploid Triticum aestivum cultivars 'Geneva' (resistant) and 'Augusta' (susceptible), was evaluated for WSSMV symptoms under field conditions for four years. Two linked markers on the long arm of chromosome 2D, Xbcd1095 and Xcdo373, were determined to be associated with WSSMV resistance by bulked segregant analysis of the 10 most resistant and 10 most susceptible lines. Marker Xcdo373 accounted for 79% and Xbcd1095 for 73% of the phenotypic variation. Our results suggest that resistance to WSSMV in this population is qualitative in nature and is controlled by few genes. These markers should be useful in the development of wheat cultivars resistant to WSSMV and perhaps also to wheat yellow mosaic bymovirus (WYMV).

Cytological Study of Euploid and Monosomic Wheat-Rye Hybrids

The influence of male and female genotypes, the effects of their interactions, the influence of ID, 3D, 4D and 5B chromosomes and the effects of their interaction were studied in 30 F1 wheat - rye euploid and aneuploid hybrids / 2n =28, 27, A B D R / concerning 7 morphological characters: heading date, common tillering productive tillering, culm length, last internode length, ear length and spikelet number per ear. F1 hybrids were obtained by crosses between four hexaploid cultivars Triticum aestivum L.2n=42: Chinese Spring /CS/, Mironovka 808 /M 808 /, Zlatka /Z1 /, Novostepnyachka / N /, as well as their monosomic lines by 1D, 3D, 4D and 5B chromosomes with two inbred lines Secale cereale L. 2n = 14 [Bulgarian Low Stem Rye /BLSR/ and Lozen 14 / L 14 / The morphological characters of the parental genotypes were as well studied. It was established that the parental genotypes influence all of the studied characters, while the effect of their interaction was observed in 14.3 % of the characters (ear length). The group of the monosomic hybrids on 3D chromosomes shows an influence different from the other hybrids for 42.9% of the characters ( heading date, ear length, spikelet number per ear); the hybrids group on 5B chromosome - 71.4 % from the characters (heading date, common and productive tillering, last internode length, ear length); the group of the euploid hybrids - 85.7% of the characters (do not show a difference on culm length).

Differences in Zinc Efficiency among and within Diploid, Tetraploid and Hexaploid Wheats

Greenhouse experiments were carried out with six diploid, nine tetraploid and seven hexaploid wheats, including wild and primitive genotypes, to study the influence of varied zinc (Zn) supply on the severity of Zn deficiency symptoms, shoot dry matter production and shoot Zn concentrations. In addition to wild and primitive genotypes, one modern tetraploid cultivar with high sensitivity to Zn deficiency and two modern hexaploid cultivars, one highly sensitive to and one resistant to Zn deficiency, were included for comparison. Plants were grown for 44 d in a severely Zn-deficient calcareous soil, with (+Zn; 5 mg Zn kg−1soil) and without (−Zn) Zn fertilization. Visible Zn deficiency symptoms, including whitish-brown necrotic patches on leaf blades, appeared very rapidly and severely in all tetraploid wheat genotypes. Compared with tetraploid wheats, diploid and hexaploid wheats were less sensitive to Zn deficiency. With additional Zn, shoot dry matter production was higher in tetraploid than diploid and hexaploid wheats. However, under Zn-deficient conditions tetraploid wheats had the lowest shoot dry matter production, indicating the very high sensitivity of tetraploid wheats to Zn deficiency. Consequently, Zn efficiency expressed as the ratio of shoot dry matter produced under Zn deficiency to Zn fertilization, was much lower in tetraploid wheats than in diploid and hexaploid wheats. On average, Zn efficiency ratios were 36% for tetraploid, 60% for diploid and 64% for hexaploid wheats. Differences in Zn efficiency among and within diploid, tetraploid and hexaploid wheats were positively related to the amount of Zn per shoot of the genotypes, but not to the amount of Zn per unit dry weight of shoots or seeds used in the experiments. The seeds of the accessions of tetraploid wild wheats contained up to 120 mg Zn kg−1, but the resulting plants showed very high sensitivity to Zn deficiency. By contrast, hexaploid wheats and primitive diploid wheats with much lower Zn concentrations in seeds had higher Zn efficiencies. It is suggested that not only enhanced Zn uptake capacity but also enhanced internal Zn utilization capacity of genotypes play important roles in differential expression of Zn efficiency. The results of this study also suggest the importance of the A and D genomes as the possible source of genes determining Zn efficiency in wheat.

Genetic analysis of water-extractable arabinoxylans in bread wheat endosperm

Two mapping populations were used for the analysis of the water-extractable arabinoxylans. One originated from a cross between the hexaploid cultivars ‘Courtot’ and ‘Chinese Spring’ and the other from a cross between an amphiploid (Synthetic) and cv ‘Opata’. Arabinose (Ara), and xylose (Xyl) contents were quantified for the 91 and 76 lines obtained from the two crosses, respectively. Relative viscosity (ηrel) of the wheat flour aqueous extract was evaluated by capillary viscometry. Both crosses gave similar correlation coefficients between sugar contents and relative viscosity. There were strong positive relationships between arabinose, xylose and arabinoxylan contents. The relative viscosity was strongly and positively related to the arabinoxylan content and strongly and negatively related to the Ara/Xyl ratio (arabinose content to xylose content). For one of the two crosses two measurements of relative viscosity were generated from 2 years of consecutive harvesting. As a strong correlation was observed between these two measurements, an important genotypic effect can be deduced for the relative viscosity of water-extractable arabinoxylans. QTL (quantitative trait locus) research did not reveal any chromosomal segments that were strongly implicated in variations in sugar content. However, a QTL was found for relative viscosity values and the Ara/Xyl ratio on the long arm of the 1B chromosome for the two crosses considered. This QTL explained 32–37% of the variations in relative viscosity and 35–42% of the variations in the Ara/Xyl ratio. Genes located at this QTL controlled relative viscosity through modifying the Ara/Xyl ratio. Variations in the Ara/Xyl ratio were supposedly related to differences in the molecular structure of water-extractable arabinoxylans. Minor QTLs were also obtained for relative viscosity and Ara/Xyl ratio, but the chromosomes concerned were different for the two populations evaluated.