Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VII. Telotrisomics and a ditelotetrasomic

Genome ◽  
1992 ◽  
Vol 35 (5) ◽  
pp. 849-854 ◽  
Author(s):  
Nam-Soo Kim ◽  
J. Kuspira
Keyword(s):  
Chromosome Segregation ◽  
Seed Set ◽  
Triticum Monococcum ◽  
Intermediate Phenotype ◽  
Telocentric Chromosome ◽  
Primary Trisomics ◽  
A Genome ◽  
Chromosome 5A ◽  
Cytogenetic Analyses ◽  
Growing Conditions

Telotrisomics (2n = 14 + t) were obtained from primary trisomics for chromosome 5A in Triticum monococcum. Subsequently, a ditelotetrasomic (2n = 14 + 2t) plant was obtained from these telotrisomics. C-banding analysis revealed that the extra telocentric chromosome in these aneuploids consisted of the short arm of chromosome 5A (triplo 5AS). Of 78 meiocytes studied at diakinesis and metaphase I in the telotrisomics, 20 (27.0%), 46 (58.9%), and 12 (14.1%) showed 6 II + 1 III,6 II + 3 I, and 7 II + 1 I configurations, respectively. Although the majority of the cells (84%) at anaphase I (AI) in the telotrisomics showed a 7–8 chromosome segregation, chromosome laggards were also observed. Their frequency (16%) was much higher than in primary trisomics. In a ditelotetrasomic plant, 14, 6, 8, and 4 cells of the 42 meiocytes studied showed 6 II + 1 IV, 7 II + 2 I, 6 II + 1 III + 1 I, and 8 II configurations, respectively. Approximately 62% of the meiocytes at AI in this plant showed an 8–8 chromosome segregation. Compared with primary trisomics and diploids, telotrisomics showed an intermediate phenotype for many of the characters studied. The telotrisomics headed earlier than primary trisomics, but later than diploids. The ditelotetrasomic headed much later than the telotrisomics. The ditelotetrasomic plant also showed very deleterious phenotypes such as slow growth and degeneration of tillers during the later stage of growth. An average of 51.7% of the florets of the telotrisomics exhibited seed set under greenhouse growing conditions. Fertility of the ditelotetrasomic plant on the other hand was very low (2.5%) under the same growing conditions.Key words: Triticum monococcum, C-bands, A genome.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VI. Production and identification of primary trisomics using the C-banding technique

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 542-555 ◽  
Author(s):  
B. Friebe ◽  
N.-S. Kim ◽  
J. Kuspira ◽  
B. S. Gill
Keyword(s):  
Nucleolus Organizer ◽  
Triticum Monococcum ◽  
Banding Patterns ◽  
Primary Trisomics ◽  
Nucleolus Organizer Regions ◽  
C Banding ◽  
A Genome ◽  
Chromosome 5A ◽  
Triple Dose

Cytogenetic studies in Triticum monococcum (2n = 2x = 14) are nonexistent. To initiate such investigations in this species, a series of primary trisomics was generated from autotriploids derived from crosses between induced autotetraploids and diploids. All trisomics differed phenotypically from their diploid progenitors. Only two of the seven possible primary trisomic types produced distinct morphological features on the basis of which they could be distinguished. The chromosomes in the karyotype were morphologically very similar and could not be unequivocally identified using standard techniques. Therefore, C-banding was used to identify the chromosomes and trisomics of this species. Ag–NOR staining and in situ hybridization, using rDNA probes, were used to substantiate these identifications. A comparison of the C-banding patterns of the chromosomes of T. monococcum with those of the A genome in Triticum aestivum permitted identification of five of its chromosomes, viz., 1A, 2A, 3A, 5A, and 7A. The two remaining chromosomes possessed C-banding patterns that were not equivalent to those of any of the chromosomes in the A genome of the polyploid wheats. When one of these undesignated chromosomes from T. monococcum var. boeoticum was substituted for chromosome 4A of Triticum turgidum, it compensated well phenotypically and therefore genetically for the loss of this chromosome in the recipient species. Because this T. monococcum chromosome appeared to be homoeologous to the group 4 chromosomes of polyploid wheats, it was designated 4A. By the process of elimination the second undesignated chromosome in T. monococcum must be 6A. Analysis of the trisomics obtained led to the following conclusions. (i) Trisomics for chromosome 3A were not found among the trisomic lines analyzed cytologically. (ii) Primary trisomics for chromosomes 2A, 4A, 6A, and 7A were positively identified. (iii) Trisomics for the SAT chromosomes 1A and 5A were positively identified in some cases and not in others because of polymorphism in the telomeric C-band of the short arm of chromosome 1A. (iv) Trisomics for chromosome 7A were identified on the basis of their distinct phenotype, viz., the small narrow heads and small narrow leaves. Because rRNA hybridizes lightly to nucleolus organizer regions on chromosome 1A and heavily to nucleolus organizer regions on chromosome 5A, our results indicate that trisomics in line 50 carry chromosome 1A in triple dose and trisomics in lines 28 and 51 carry chromosome 5A in triplicate. Variable hybridization of the rDNA probe to nucleolus organizer regions on chromosomes in triple dose in lines 7, 20, and 28 precluded the identification of the extra chromosome in these lines. Cytogenetic methods for unequivocally identifying trisomics for chromosomes 1A and 5A are discussed. Thus six of the series of primary trisomics have been identified. Telotrisomic lines are also being produced.Key words: Triticum monococcum, trisomics, C-banding, Ag-NOR staining, in situ hybridization, rDNA probes, plant morphology.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. IX. Cytological behaviour, phenotypic characteristics, breeding behaviour, and fertility of primary, double, and triple trisomics

Genome ◽  
1993 ◽  
Vol 36 (3) ◽  
pp. 565-579 ◽  
Author(s):  
N.-S. Kim ◽  
J. Kuspira
Keyword(s):  
Meiotic Chromosome ◽  
Triticum Monococcum ◽  
Low Fertility ◽  
Chromosome Behaviour ◽  
Primary Trisomics ◽  
Breeding Behaviour ◽  
Male Gametes ◽  
A Genome ◽  
Cytogenetic Analyses ◽  
Metaphase I

Cytogenetic studies in Triticum monococcum (2n = 2x = 14, AA) were initiated by generating a series of primary as well as double and triple trisomics from autotriploids derived from crosses between induced autotetraploids and a diploid progenitor. Analysis of meiotic chromosome behaviour revealed that, with the exception of primary trisomics for chromosome 7A, the chromosome present in triple dose in all other trisomics formed either a bivalent plus a univalent or a trivalent (always V shaped) at diakinesis – metaphase I in approximately equal proportions. Trisomics for chromosome 7A formed a bivalent plus a univalent or a trivalent in approximately a 1:2 ratio. About 99% of the anaphase I segregations in all the trisomics were seven to one pole and eight to the other, suggesting that primary trisomics in T. monococcum form n and n + 1 meiotic products in equal proportions. The double trisomics and triple trisomics formed 5 II + 2 III and 4 II + 3 III during metaphase I, respectively. A majority of the secondary meiocytes from the double and triple trisomics possessed unbalanced chromosome numbers. All the trisomics differed phenotypically from their diploid progenitors. Single primary trisomics for chromosomes 3A and 7A produced distinct morphological features on the basis of which they could be distinguished. The phenotypes of the double and triple trisomics deviated to a greater extent from that of diploids than those of the single trisomics. Less than 50% of the progeny of all primary trisomics were trisomics themselves. Trisomic progeny were not produced in diploid female × trisomic male crosses, indicating that functional n + 1 male gametes were not generated. Diploid as well as trisomic progeny were produced in the reciprocal crosses and upon self-fertilization of the trisomics. The average frequency of trisomic progeny was 9.9%. The fertility of primary trisomics ranged from 3.8% in trisomics for chromosome 1A to 40.6% in trisomics for chromosome 2A and was significantly less than that of diploids (99.6%). The breeding behaviour and low fertility of these trisomics make their maintenance and use in cytogenetic analyses difficult.Key words: Triticum monococcum, primary trisomics, double trisomics, triple trisomics, meiotic chromosome behaviour, phenotypes, breeding behaviour, fertility.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. IV. Synaptonemal complex formation in autotetraploids

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 309-318 ◽  
Author(s):  
C. B. Gillies ◽  
J. Kuspira ◽  
R. N. Bhambhani
Keyword(s):  
Synaptonemal Complex ◽  
Theoretical Models ◽  
Triticum Monococcum ◽  
Pachytene Nucleus ◽  
Lateral Element ◽  
A Genome ◽  
Cytogenetic Analyses ◽  
The Difference ◽  
Quadrivalent Frequency ◽  
Metaphase I

Electron microscopy of synaptonemal complex spreads from autotetraploid Triticum monococcum (2n = 4x = 28) revealed a minimum mean of 3.59 multivalents per zygotene–pachytene nucleus. The range of values was from 1 to 6 multivalents per nucleus. Most of the multivalents were quadrivalents with single, medially located pairing partner switch points. Lateral element pairing switches, particularly the few multiple switches, were often accompanied by extensive asynapsis around the switch point. The synaptonemal complex multivalent frequency is considerably higher than the metaphase I quadrivalent frequency previously reported for the same material. Calculations of expected pachytene quadrivalent frequency from metaphase I data, using several published theoretical models, gave values that did not agree with the results obtained here. The difference between the multivalent frequencies at pachytene and metaphase I does not appear to be the result of a correction process. Instead, it could be caused by a combination of preferential pairing or crossing-over and the effects of the position of partner switches and asynapsis associated with switches. Key words: autotetraploid, multivalents, synaptonemal complex, pairing effects.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. I. Cytology, breeding behaviour, fertility, and morphology of induced autotetraploids

1985 ◽  
Vol 27 (1) ◽  
pp. 51-63 ◽  
Author(s):  
J. Kuspira ◽  
R. N. Bhambmani ◽  
T. Shimada
Keyword(s):  
Decisive Role ◽  
Leaf Size ◽  
Kernel Weight ◽  
Triticum Monococcum ◽  
Fertility Level ◽  
Breeding Behavior ◽  
Diploid Progenitor ◽  
Artificial Medium ◽  
A Genome ◽  
Cytogenetic Analyses

Autotetraploids were colchicine-induced in Triticum monococcum and, upon comparison to their diploid progenitor, possessed the following characteristics: (i) their cells were on the average 20.8% larger; (ii) plant height was reduced by 15% and tillering by 37.5%; (iii) spikes, 1000-kernel weight, pistil size (length (L)/weight (W), and leaf size (L/W) were 53.9, 51.2, 80/57.1, and 60/26.4% larger, respectively; and (iv) they were 12.4% earlier in heading. Observed mean numbers of univalents, bivalents, trivalents (linear, convergent, and indifferent coorientations), and quadrivalents (convergent and parallel alignments only) per microsporocyte at metaphase I were 0.62, 9.86, 0.23, and 1.74, respectively; 65.4% of all meiocytes possessed bivalents and (or) quadrivalents and produced balanced meiotic products; 34.6% also possessed univalents and (or) trivalents and, therefore, produced balanced and unbalanced meiotic products. The actual 70.9% balanced meiotic products falls within the calculated range of 65.4–81.3%. Our tetraploids breed true. Evidence and reasons for this are discussed. The fertility of our tetraploids was high (79.8%). Irregular chromosome behaviour during meiosis may play a decisive role in determining the fertility level. Genic factors may also be involved. Methods of improving fertility and whether chromosomal factors alone are responsible for tetraploid fertility levels are discussed. Mature seed from reciprocal 2n = 4x × 2n = 2x crosses was shrivelled because of endosperm collapse and did not germinate. Thus, embryo excision and culturing on artificial medium was required to obtain viable autotriploids.Key words: Triticum monococcum, autotetraploid, cytology, breeding behavior, fertility, morphology.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. III. Cytology, breeding behavior, fertility, and morphology of autotriploids

1986 ◽  
Vol 28 (5) ◽  
pp. 867-887 ◽  
Author(s):  
J. Kuspira ◽  
R. N. Bhambhani ◽  
R. S. Sadasivaiah ◽  
D. Hayden
Keyword(s):  
Diploid Species ◽  
Leaf Size ◽  
Kernel Weight ◽  
Triticum Monococcum ◽  
High Fertility ◽  
Breeding Behavior ◽  
Seed Fertility ◽  
A Genome ◽  
Cytogenetic Analyses

Mature triploid seed from reciprocal (2n = 4x × 2n = 2x) crosses in Triticum monococcum was minute and shrivelled because of endosperm collapse and therefore failed to germinate. This necessitated the excision of embryos from successful pollinations and their growth in vitro to ensure subsequent germination so as to obtain viable and vigorous autotriploids. A comparison of these triploids with their diploid and tetraploid progenitors revealed that cell size, kernel weight, and pistil size increased with an increase in ploidy level. However, unlike other species, optimum expression was observed in these triploids for plant height, tillering, size of spikes, number of spikelets/spike, and leaf size. Earliness, althoughenhanced in tetraploids relative to diploids, was delayed in the triploids. Mean numbers of univalents, bivalents, and trivalents per microsporocyte were 2.65, 2.60, and 4.38, respectively. Only chains (93.5%), which formed V-shaped metaphase I (MI) configurations, frying pan (5.0%), and Y-shaped (1.5%) trivalent associations occurred. On the average, two reciprocal exchanges occurred per bivalent and trivalent. Trivalents corriented randomly at MI. At anaphase I, all sets of three homologues segreated randomly to the two poles, lagging univalents always divided equationally, and only meiocytes with such chromosomes formed micronuclei. The reasons for similarities and differences in meiotic behaviour of T. monococcum triploids with those of other species are discussed. Confirmation of the conclusions drawn with respect to the cytology of the triploids was obtained from similar cytological observations with primary single trisomics. These triploids produced euploids, primary single trisomics as well as some double and triple trisomics all of which differed phenotypically from diploids. Triticum monococcum, like most diploid species, is highly intolerant of aneuploidy. Possible reasons for the differences in levels of tolerance of aneuploidy in species like T. monococcum and those like Petunia hybrida, which are highly tolerant of aneuploidy, are discussed. Pollen fertility was high and seed fertility was very low. Reasons for the latter as well as the high fertility in species that are highly tolerant of aneuploidy and allotriploids are discussed.Key words: Triticum monococcum, autotriploid, trisomic, cytology, breeding behavior, fertility, morphology.

Genetic and cytogenetic analyses of the A genome of Triticum monococcum. VIII. Localization of rDNAs and characterization of 5S rRNA genes

Genome ◽  
1993 ◽  
Vol 36 (1) ◽  
pp. 77-86 ◽  
Author(s):  
Nam-Soo Kim ◽  
J. Kuspira ◽  
K. Armstrong ◽  
R. Bhambhani
Keyword(s):  
In Situ Hybridization ◽  
5S Rdna ◽  
Triticum Monococcum ◽  
Rrna Genes ◽  
26S Rdna ◽  
Recognition Sites ◽  
Evolutionary Changes ◽  
A Genome ◽  
Chromosome 5A

In situ hybridization with [3H]dCTP labelled pScT7 (5S rDNA) and pTa80 (18S + 26S rDNA) indicated that both hybridized to the terminal regions of two pairs of chromosomes in Triticum monococcum. When the hybridization was performed with a mixture of both probes, only two pairs of chromosome arms were labelled, which suggested that the loci of both genes were located in juxtaposition to one another. Both probes labelled one pair of sites more heavily than the other. Southern analysis of 5S with BamHI-digested DNA from 12 accessions of T. monococcum (including T. urartu) produced two superimposed ladders of approximate sizes of 500 and 330 bp, which differ from T. aestivum in which 500- and 420-bp ladders were found. The 500-bp ladder is derived from chromosome 5A (5SDna-A2) and the 330-bp ladder from chromosome 1A (5SDna-A1). The recognition site for SstI was present in the long spacer region but absent in the short spacer as in T. aestivum; however, unlike T. aestivum, there were HaeIII (GGCC) and HindIII (AAGCTT) recognition sites in the short spacer region. The TaqI recognition sites (TCGA) in the long and short spacer regions are probably more highly methylated in T. monococcum than in T. aestivum. The results have implications regarding the evolutionary changes that occurred in the A genome of the hexaploid compared with the diploid.Key words: Triticum monococcum, 5S rDNA, 18S + 26S rDNA, in situ hybridization, Southern hybridization, restriction fragments, methylation.

scholarly journals Stripe rust resistance gene Yr34 (synonym Yr48) is located within a distal translocation of Triticum monococcum chromosome 5AmL into common wheat

2021 ◽  
Author(s):  
Shisheng Chen ◽  
Joshua Hegarty ◽  
Tao Shen ◽  
Lei Hua ◽  
Hongna Li ◽  
...  
Keyword(s):  
Resistance Gene ◽  
Common Wheat ◽  
Stripe Rust ◽  
Rust Resistance ◽  
Triticum Monococcum ◽  
Rust Resistance Gene ◽  
Stripe Rust Resistance ◽  
Polyploid Wheat ◽  
Stripe Rust Resistance Gene ◽  
A Genome

AbstractKey messageThe stripe rust resistance geneYr34 was transferred to polyploid wheat chromosome 5AL from T. monococcumand has been used for over two centuries.Wheat stripe (or yellow) rust, caused by Puccinia striiformis f. sp. tritici (Pst), is currently among the most damaging fungal diseases of wheat worldwide. In this study, we report that the stripe rust resistance gene Yr34 (synonym Yr48) is located within a distal segment of the cultivated Triticum monococcum subsp. monococcum chromosome 5AmL translocated to chromosome 5AL in polyploid wheat. The diploid wheat species Triticum monococcum (genome AmAm) is closely related to T. urartu (donor of the A genome to polyploid wheat) and has good levels of resistance against the stripe rust pathogen. When present in hexaploid wheat, the T. monococcum Yr34 resistance gene confers a moderate level of resistance against virulent Pst races present in California and the virulent Chinese race CYR34. In a survey of 1,442 common wheat genotypes, we identified 5AmL translocations of fourteen different lengths in 17.5% of the accessions, with higher frequencies in Europe than in other continents. The old European wheat variety “Mediterranean” was identified as a putative source of this translocation, suggesting that Yr34 has been used for over 200 years. Finally, we designed diagnostic CAPS and sequenced-based markers that will be useful to accelerate the deployment of Yr34 in wheat breeding programs to improve resistance to this devastating pathogen.

Linkage mapping and genome-wide association reveal candidate genes conferring thermotolerance of seed-set in maize

2019 ◽  
Vol 70 (18) ◽  
pp. 4849-4864 ◽  
Author(s):  
Jingyang Gao ◽  
Songfeng Wang ◽  
Zijian Zhou ◽  
Shiwei Wang ◽  
Chaopei Dong ◽  
...  
Keyword(s):  
Candidate Genes ◽  
Linkage Mapping ◽  
Genome Wide Association Study ◽  
Seed Set ◽  
Crop Yields ◽  
Expression Profiles ◽  
Snp Markers ◽  
Genome Wide Association ◽  
Genome Wide ◽  
A Genome

AbstractIt is predicted that high-temperature stress will increasingly affect crop yields worldwide as a result of climate change. In order to determine the genetic basis of thermotolerance of seed-set in maize under field conditions, we performed mapping of quantitative trait loci (QTLs) in a recombinant inbred line (RIL) population using a collection of 8329 specifically developed high-density single-nucleotide polymorphism (SNP) markers, combined with a genome-wide association study (GWAS) of 261 diverse maize lines using 259 973 SNPs. In total, four QTLs and 17 genes associated with 42 SNPs related to thermotolerance of seed-set were identified. Among them, four candidate genes were found in both linkage mapping and GWAS. Thermotolerance of seed-set was increased significantly in near-isogenic lines (NILs) that incorporated the four candidate genes in a susceptible parent background. The expression profiles of two of the four genes showed that they were induced by high temperatures in the maize tassel in a tolerant parent background. Our results indicate that thermotolerance of maize seed-set is regulated by multiple genes each of which has minor effects, with calcium signaling playing a central role. The genes identified may be exploited in breeding programs to improve seed-set and yield of maize under heat stress.

scholarly journals Understanding the Evolution of Reptile Chromosomes through Applications of Combined Cytogenetics and Genomics Approaches

2019 ◽  
Vol 157 (1-2) ◽  
pp. 7-20 ◽  
Author(s):  
Janine E. Deakin ◽  
Tariq Ezaz
Keyword(s):  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Chromosome Analysis ◽  
Evolutionary Significance ◽  
Initial Report ◽  
Genomic Technologies ◽  
A Genome ◽  
Sand Lizard ◽  
Cytogenetic Analyses ◽  
Lacerta Agilis

Studies of reptile (nonavian reptiles) chromosomes began well over a century ago (1897) with the initial report on the description of sand lizard (Lacerta agilis) chromosomes. Since then, chromosome analysis in reptiles has contributed significantly to understanding chromosome evolution in vertebrates. Reptile karyotypes are also unique, as being the only vertebrate group where the majority of the species possess variable numbers of macro- and microchromosomes, which was first reported for iguanids and teiids in 1921. In addition, many reptiles have microchromosomes as sex chromosomes, highlighting their evolutionary significance, yet very little is known about their evolutionary origin and significance in shaping amniote genomes. Advances in genomic technologies in recent years have accelerated our capacity to understand how sequences are arranged within a genome. However, genomic and cytogenetic analyses have been combined for only 3 species to provide a deeper understanding of reptile chromosome evolution and sequence organization. In this review, we highlight how a combined approach of cytogenetic analysis and sequence analysis in reptiles can help us answer fundamental questions of chromosome evolution in reptiles, including evolution of microchromosomes and sex chromosomes.

scholarly journals Maximising seed production potential in white clover: factors influencing seed set per floret

1996 ◽  
Vol 6 ◽  
pp. 41-44
Author(s):  
R.G. Thomas
Keyword(s):  
Seed Production ◽  
White Clover ◽  
Management Practices ◽  
Seed Set ◽  
Head Development ◽  
Light Intensities ◽  
Ovule Sterility ◽  
Growing Conditions ◽  
High Level ◽  
Seed Yields

The causes of low seed set per floret in white clover (Trifolium repens L.) are reviewed. Three stages of flower head development are distinguished as important for a high level of seed set: a pre-fertilisation stage, a stage of anthesis leading to pollination, and a postfertilisation stage in which seed provisioning occurs. In sunny conditions the percentage seed set is limited at the pre-fertilisation stage by up to 20-30% ovule sterility. Relatively low light intensities during the postfertilisation stage can lead to abortion of a high proportion of fertilised ovules and developing seeds. Experimental results suggest that seed yields under optimal growing conditions can be limited solely by the level of pre-fertilisation ovule sterility and probably cannot be bettered, but further understanding of the seed-provisioning requirements for photosynthate could lead to improved management practices for seed production under conditions of lower light intensities. Keywords: abortion, light intensity, ovule, seed provisioning, sterility, white clover

Sign in / Sign up

Export Citation Format

Share Document