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.

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 x 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.     

Meiotic configuration and chromosome number in some Iranian species of Ely mus L. and Agropyron Gaertner (Poaceae: Triticeae)

Chromosome numbers and analyses of meiotic metaphase I are reported for the following taxa: Agropyron cristatum subsp. incanum (2 n = 42), A. cristatum subsp. pecttnatum (2 n =28 – 33), Elymus elongatus subsp. ponticus (2 n = 69, 70), E. hispidus var. hispidus (2 n = 41 43), var. podperae (2 n = 42) and var. villosus (2 n = 41, 42), E. libanoticus (2 n = 14), E. pertenuis (2 n = 28, 28+1B), E. repens (2 n = 42), E. transhyrcanus (2 n = 40–42), E. hispidus var. villosus x E. cf. repens (2 n = 42). Chromosome numbers only are reported for the following taxa: E. gentri (2 n = 41, 42), E. nodosus subsp. dorudicus (2 n = 28), and E. elongatiformis (2 n = 56, 57). The haploid genomic constitution SP is reported for Elymus pertenuis. Variable chromosome numbers (2 n = 28–32) were observed in the meiotic metaphase I within single anthers of Agropyron cristatum subsp. pectinatum , and the supernumerary chromosomes in this taxon are assumed to have originated from crosses with hexaploids. Partial elimination of these supernumerary chromosomes probably occurs during archesporial mitotic divisions or at an early stage in the meiotic cycle. A hybrid, morphologically intermediate between E. hispidus and E. repens , was obtained from a seed of E. hispidus collected in the field. The meiotic metaphase I configuration in this E. hispidus hybrid suggests that the pollen parent may itself be a hybrid or hybrid derivative of E. repens x E. hispidus.     

Trisomics and aneuploids of ryegrass

Summary Primary trisomics (2 n + 1 = 15), double trisomics (2 n + 1 + 1 = 16) and aneuploids with 24 to 30 chromosomes, as well as a diploid and tetraploids, were found in the progeny of a hypertriploid (2 n = 22) plant of perennial ryegrass, Lolium perenne L. Trisomics and double trisomics differed in their mean chromosome association, chiasma number and spike morphology. A few aneuploids and tetraploids had reciprocal translocations. The diploid, primary trisomics and tetraploids were more fertile than the double trisomics and aneuploids. Most trisomics and aneuploids were probably produced through female transmission. One double trisomic had a high univalent number, a low chiasma number and loose chromosome coiling. Both the extra chromosomes carried secondary constrictions. The gene for desynapsis might be located on one of these chromosomes.     

TRISOMICS IN SOLANUM CHACOENSE: FERTILITY AND CYTOLOGY

Twenty trisomic plants found in the progeny 3x x 2x crosses in Solatium chacoense and their F₁ trisomies obtained by 2x + 1 X 2x crosses were studied with respect to their fertility and cytology. The female transmission of the extra chromosome in the trisomics varied from 2 to 60 %. The transmission frequencies of F₁ trisomies were similar to their parent trisomies in most of the lines. The transmission through the pollen ranged from 0 to 20 %. Female and male fertility of the parent trisomies was high. They produced an average of 37 seeds per pollination as the female or as the male parent. The F₁ trisomies produced about half the seed set of their parent trisomies. The extra chromosomes of six trisomies were identified by pachytene analysis. They were isochromosomes for the long arms of chromosomes I, IV and IX and the short arms of IV, IX and XII. Chromosome morphology of the extra chromosomes in pachytene stage was described. A chromosome association of 12 II + 1 I was found in 66 % of the cells at MI. About 29 % of the cells had one trivalent and 5 % had three or five univalents. The frequency of trivalent formation was not affected by the length of the extra chromosome. The possibility of univalent shift in secondary trisomies was discussed.     

Cytological identification of some trisomics of Russian wildrye (Psathyrostachys juncea).

Russian wildrye, Psathyrostachys juncea (Fisch.) Nevski (2n = 2x = 14; NsNs), is an important forage grass and a potential source of germplasm for cereal crop improvement. Because of genetic heterogeneity as a result of its self-incompatibility, it is difficult to identify trisomics of this diploid species based on morphological characters alone. Putative trisomies (2n = 2x + 1 = 15), derived from open pollination of a triploid plant by pollen grains of diploid plants, were characterized by Giemsa C-banding. Based on both karyotypic criteria and C-banding patterns, four of the seven possible primary trisomics, a double-deletion trisomic, and two tertiary trisomics were identified.     

Production of n + 1 plants and tetrasomics by means of anther culture of trisomic plants in rice (Oryza sativa L.)

Summary Eleven primary trisomics of rice, variety Nipponbare, were subjected to anther culture. The 12th trisomic did not produce normal anthers. A total of 3,734 plants were obtained, which were examined morphologically at the seedling stage in the greenhouse. A number of plants appeared in the progenies of ten trisomics which had unique morphological features. The frequency of these variant types differed among different progenies. Cytological observations revealed that 43 variant plants in the progenies of nine trisomics had 13 chromosomes (n + 1), and 56 were tetrasomics (2n = 26). The tetrasomic plants in the progeny of a trisomic were morphologically identical. Similarly, n + 1 plants in the progeny of a trisomic were also identical. Plants with 23, 25, 36, 39, and 73 chromosomes were also obtained. Results show that valuable aneuploids such as n + 1 and 2n + 2 can be obtained in the anther-culture-derived progenies of trisomics.     

Assignment of molecular linkage groups to soybean chromosomes by primary trisomics

Gene-linkage groups (classical linkage groups, CLGs; molecular linkage groups, MLGs) and chromosome relationship in soybean [ Glycine max (L.) Merr., 2n = 40] is not yet established. However, primary trisomics provide an invaluable cytogenetic tool to associate genes and linkage groups to specific chromosomes. We have assigned 11 MLGs to soybean chromosomes by using primary trisomics (2 x + 1 = 41) and SSR markers. Primary trisomics were hybridized with Glycine soja Sieb. and Zucc. (2n = 40) in the greenhouse, F(1) plants with 2n = 40 and 41 were identified cytologically and 41 chromosome plants were selfed. A deviation from the 1:2:1 ratio in the F(2) population suggests a marker is associated with a chromosome. Of the possible 220 combinations involving 20 MLGs and 11 primary trisomics, 151 combinations were examined. The relationships between soybean chromosomes and MLGs are: 1 = D1a+q, 3 = N, 5 = A1, 8 = A2, 9 = K, 13 = F, 14 = C1, 17 = D2, 18 = G, 19 = L and 20 = I. This study sets the stage to establish relationship between nine remaining MLGs with the other genetically unidentified nine primary trisomics. The association of CLGs with the soybean chromosomes will be discussed.     

Trisomics from triploid-diploid crosses in self-incompatible Lycopersicum peruvianum

Summary The transmission rate of trisomy was determined for two primary trisomic types, triplo-1 and triplo-3, of the self-incompatible species Lycopersicum peruvianum. Chromosome counts in somatic metaphases of root-tip squashes from 112 progeny plants showed that 8 individuals (7.2 %) were trisomic and 104 (92.8%) were diploid. The average frequency of transmission approximated 2.6% in triplo-1 and 8.6% in triplo-3. Data are presented on the karyotype and the morphological features of the 8 trisomics detected in the progenies of triplo-1 and triplo-3 and the various factors affecting the transmission rate of trisomy are discussed.The transmission rate of trisomy was also determined for the trisomic plant 269 which displayed a complete deletion of the satellited part of chromosome 2 and was characterized by ovate fruits. Out of 18 progeny plants analysed, 8 (44.4%) were trisomic and 10 (55.6%) were diploid. Cytological and morphological analyses of the 8 trisomic individuals revealed that only two of them (11.1 %) resembled the parental trisomic. A number of diploid and trisomic progenies exhibited a partial or a complete deletion of the satellited segment of chromosome 2.This work has been supported by a contract between the European Communities and the CNEN. This publication is contribution n ° 484 from The Division Applicazioni delle Radiazioni del CNEN and contribution n ° 1482 from the Biology Radioprotection Medical Research programme of the Directorate General XII of the European communities     

Genome analysis of Elytrigia pycnantha and Thinopyrum junceiforme and of their putative natural hybrid using the GISH technique.

Genomic in situ hybridization (GISH), using genomic DNA probes from Thinopyrum elongatum (Host) D.R. Dewey (E genome, 2n = 14), Th. bessarabicum (Savul. & Rayss) A. Love (J genome, 2n = 14), Pseudoroegneria stipifolia (Czern. ex Nevski) Love (S genome, 2n = 14), and Agropyron cristatum (L.) Gaertner (P genome, 2n = 14), was used to characterize the genome constitution of the polyploid species Elytrigia pycnantha (2n = 6x = 42) and Thinopyrum junceiforme (2n = 4x = 28) and of one hybrid population (2n = 5x = 35). GISH results indicated that E. pycnantha contains S, E, and P genomes; the first of these was closely related to the S genome of Ps. stipifolia, the second was closely related to to the E genome of Th. elongatum, and the third was specifically related to A. cristatum. The E and P genomes included 2 and 10 chromosomes, respectively, with S genome DNA sequences in the centromeric region. GISH analysis of Th. junceiforme showed the presence of two sets of the E genome, except for fewer than 10 chromosomes for which the telomeric regions were not identified. Based on these results, the genome formula SSPsPsEsEs is proposed for E. pycnantha and that of EEEE is proposed for Th. junceiforme. The genomic constitution of the pentaploid hybrid comprised one S genome (seven chromosomes), one P genome (seven chromosomes), and three E genomes (21 chromosomes). The E and P genomes both included mosaic chromosomes (chromosomes 1 and 5, respectively) with the centromere region closely related to S-genome DNA. On the basis of these data, the genome formula SPSESEE is suggested for this hybrid and it is also suggested that the two species E. pycnantha and Th. junceiforme are the parents of the pentaploid hybrid.     

Ring chromosomes in barley (Hordeum vulgare L.)

A plant with 2n = 14 + 1 ring chromosomes was obtained in the progeny of a primary trisomie for chromosome 7 of a two-rowed cultivar, Shin Ebisu 16. The morphological characteristics of the trisomic plants with an extra ring chromosome were similar to the primary trisomic for chromosome 7 (Semierect), which suggests that it originated from this chromosome. The ring chromosomes were not completely stable in mitotic cells because of abnormal behavior. Chromosome complements varied in different plants and in different roots within a plant. Root tip cells and spikes with 2n = 14 and 14 + 2 ring chromosomes were observed on plants with 14 + 1 ring chromosomes. Breakage-fusion-bridge cycle was inferred. The ring chromosome was associated with two normal homologues forming a trivalent in 17.6% sporocytes at metaphase I. The transmission of the extra ring chromosome was 23.1% in the progeny of the plant with 14 + 1 ring chromosomes. Trivalent formation may have been much higher at early prophase stages which were difficult to analyze in barley; only 4 of 120 sporocytes analyzed showed an isolated ring at pachytene. The ring chromosome moved to one pole without separation in 24.7% of the sporocytes at AI, and divided in 27.1% sporocytes giving rise to 8-8 separation. Only 10% of the sporocytes showed bridge formation at AI.     

Meiotic studies on a Brassica campestris-alboglabra monosomic addition line and derived B. campestris primary trisomics.

Diakinesis chromosomes were studied in pollen mother cells of Brassica campestris (2n = 20, genome AA), B. alboglabra (2n = 18, genome CC), a B. campestris-alboglabra monosomic addition line (AA + 1 chromosome from the C genome), and four derived B. campestris primary trisomics. The nucleolar chromosomes of B. campestris were distinguishable by their morphology at diakinesis. The alien C-genome chromosome in the addition line paired preferentially with the nucleolar chromosome of the A genome. Very rarely, it paired with another pair of the A genome. Thus, it was concluded that the alien C-genome chromosome of the addition line is primarily homoeologous to the nucleolar chromosome and secondarily to another chromosome of the A genome. Three of the four derived B. campestris trisomic plants were identified as B campestris nucleolar trisomics. Trisomy in the fourth plant involved another chromosome. The cytological mechanism underlying the origin of trisomics in the addition line and chromosome homoeology relationships between B. campestris and B. alboglabra are envisaged.     

Tertiary trisomics in the garden pea as a model of B chromosome evolution in plants

It is hypothesized that, in plants, genetically empty B chromosomes may originate from the extra chromosome (E) of tertiary trisomics if (i) the region of basic chromosomes homologous to the E (H-region) harbors a sporophytic lethal covered by the wild-type allele in E, and (ii) crossing-over between E and the H-region is suppressed. Under these conditions, most loss-of-function mutations occurring in the H-region are deleterious for haploid gametophytes, whereas those occurring in E are neutral or advantageous for hyperploid (n+1) gametophytes. As a result, natural selection at the gametophyte level can lead to the degeneration of E, leaving the H-region intact. Using Hammarlund translocation T(3-6)a, we synthesized two trisomic lines of the garden pea (Pisum sativum L.), where E was composed of the short arms of chromosomes 3 and 6 and the H-region carried recessive markers. In the trisomic line TRIS, we found few crossovers between E and the H-region. In the trisomic line TRUST, obtained after a change of basic chromosome constitution, recombination in this region was completely suppressed. After induction in the H-region of TRUST of a recessive sporophytic mutation rmv, two 15-chromosome lines of stable trisomics were established. One of them passed 11 generations, having produced more than 6000 individuals, all of them trisomic, and E remained present as a single element with no pairing partners. No tetrasomics were detected in these lines. If such trisomics occurred in nature, their extra chromosomes are likely to become a B chromosome.     

Genome Analysis of a Natural Hybrid with 2n= 63 Chromosomes in the Genus Elytrigia Desv. (Poaceae) Using the GISH Technique

Abstract: Genomic in situ hybridization (GISH), using genomic DNA probes from Thinopyrum elongatum (E genome, 2 n = 14), Th. bessarabicum (J genome, 2 n = 14), Pseudoroegneria stipifolia (S genome, 2 n = 14), Agropyron cristatum (P genome, 2 n = 28) and Critesion californicum (H genome, 2 n = 14), was used to identify the genome constitution of a natural hybrid population morphologically close to Elytrigia pycnantha and with somatic chromosome number of 2 n = 63. The GISH results indicated the presence of a chromosomal set more or less closely related to the E, P, S and H genomes. In particular, two sets of 14 chromosomes each showed close affinity to the E genome of Th. elongatum and to the P genome of A. cristatum. However, they included 2 and 10 mosaic chromosomes, respectively, with S genome specific sequences at their centromeric regions. Two additional sets (28 chromosomes) appeared to be very closely related to the S genome of Ps. stipifolia. The last genome involved (7 chromosomes) is related to the H genome of C. californicum but includes one chromosome with S genome-specific sequences around the centromere and two other chromosomes with a short interstitial segment also containing S genome related sequences. On a basis of GISH analysis and literature data, it is hypothesized that the natural 9-ploid hybrid belongs to the genus Elytrigia and results from fertilization of an unreduced gamete (n = 42) of E. pycnantha and a reduced gamete (n = 21) of E. repens. The genomic formula SSSSP^SP^SE^SE^SH^S is proposed to describe its particular genomic and chromosomal composition.     

Identification of five new primary simple trisomies in soybean based on pachytene chromosome analysis.

Primary trisomics are ideal cytogenetic tools for associating genes and linkage groups to known chromosomes and testing their independence. In the cultivated soybean, only 8 of the possible 20 primary simple trisomics are known. In this report cytological evidence for the identification of five more new primary simple trisomics, corresponding to chromosomes 6, 8, 12, 16, and 19, is presented for the first time. The precise identification was based on trivalent configuration of chromosomes at the pachynema stage of meiosis, where the chromosomes were identified by their characteristic total length, arm ratio, and distribution of heterochromatin and euchromatin. Cytological observation of chromosome pairing in the 2n = 42 chromosome F1 plants, obtained from eight crosses between known primary trisomics, also supported the identification of primary trisomics in soybean based on pachytene chromosome analysis. Together with the eight primary trisomics identified previously, 13 of the possible 20 primary simple trisomics have been successfully identified, which accounts for about 76% of the total nuclear euchromatin in soybean.     

Secondary Trisomics and Telotrisomics of Rice: Origin, Characterization, and Use in Determining the Orientation of Chromosome Map

Secondary trisomics and telotrisomics representing the 12 chromosomes of rice were isolated from the progenies of primary trisomics. A large population of each primary trisomic was grown. Plants showing variation in gross morphology compared to the primary trisomics and disomic sibs were selected and analyzed cytologically at diakinesis and pachytene. Secondary trisomics for both arms of chromosomes 1, 2, 6, 7 and 11 and for one arm of chromosomes 4, 5, 8, 9 and 12 were identified. Telotrisomics for short arm of chromosomes 1, 8, 9 and 10 and for long arms of chromosomes 2, 3 and 5 were isolated. These secondary and telotrisomics were characterized morphologically and for breeding behavior. Secondary trisomics 2n + 1S.1S, 2n + 1L.1L, 2n + 2S.2S, 2n + 2L.2L, 2n + 6S.6S, 2n + 6L.6L and 2n + 7L.7L are highly sterile, and 2n + 1L.1L, 2n + 2L.2L and 2n + 7L.7L do not set any seed even upon backcrossing. Telotrisomics are fertile and vigorous. Genetic segregation of 43 marker genes was studied in the F(2) or backcross progenies. On the basis of segregation data, these genes were delimited to specific chromosome arms. Correct orientation of 10 linkage groups was determined and centromere positions on nine linkage groups were approximated. A revised linkage map of rice is presented.     

Effect of genetic background on trisomy in ryegrass

Six primary trisomics of ryegrass, Lolium perenne L., were studied in perennial and perennial x annual hybrid backgrounds. Chromosome association at meiotic metaphase I and chiasma number per cell of the individual trisomes did not differ in the two genetic backgrounds. Hybrid trisomies showed wider variation in morphology, and had higher pollen fertility than the perennial trisomics and disomics. — It is concluded that the transfer of perennial ryegrass chromosomes and segments into annual ryegrass can be accomplished without any serious consequence on the cytological stability of the reconstituted genome.     

Meiotic disjunction and embryonic lethality in trisomies derived from an X-linked translocation in the onion fly,Hylemya antiqua (Meigen)

Translocation- and tertiary trisomies (for the X-chromosomes) were obtained after testcrossing translocation heterozygous females of an X-linked “simple” translocation stock. Meiotic disjunction as judged from segregations at M II (males) and in young eggs of testcrosses (males and females) in translocation trisomics was studied. No progeny of tertiary trisomic males and females was found, but male M II could be studied. Six different orientation types appeared in translocation trisomie (2n + 1) males and these were present in equal frequencies. No adjacent II configurations were found. The small X- and Y-chromosomes and the large translocated X-chromosome of the translocation complex disjoin at random (n and n + 1 gametes) in both translocation- and tertiary trisomic males. In translocation trisomic females four different orientation types appeared. From the high frequency of two of these (together, 94.5%) it is concluded that the two normal X-chromosomes show preferential pairing and disjunction, while the translocated X-chromosome moves to either one of the two poles at random. Primary trisomic (for the X-chromosome) males (XXY) and females (XXX) were obtained from testerossed translocation trisomics. Cytological analysis of adult male progeny of testerossed XXY males showed that no random orientation for the X-, X- and Y-chromosomes occurred because half of the sons was disomic (XY) and half of them trisomic (XXY). A possible mechanism is discussed. Analysis of young eggs of testerossed XXX females indicated a segregation of 2X∶1X=1∶1. The level of “semi”-sterility as scored from testcrosses of translocation trisomies appeared to be as in translocation heterozygotes. Here again a close relation exists between “semi”-sterility and deficiencies in eggs for a large chromosomal segment. The possible use of this translocation for genetic control of insect pests is discussed.     

谷子雄性不育系1066A不育基因和黄苗基因的染色体定位

以谷子(Setaria italica (L.) Beauv.)雄性不育系1066A为母本,豫谷1号三体(1～7)及四体8和四体9作父本进行杂交,应用初级三体分析法,进行了谷子雄性不育基因和黄苗基因的染色体定位研究.通过配置大量杂交组合和反复授粉,利用豫谷1号三体的极少量花粉,获得了三体2～9的F1代杂种,各杂种三体的形态与豫谷1号三体基本相似,略有差异,苗色呈绿色且可育.杂种F2植株的苗色和育性都产生分离.结果是三体3、5、7、8、9的F2代分离出的可育株与不育株之比为3∶1,三体6的可育株与不育株之比为14∶1 (χ2=0.012,P=0.01).杂种F2分离出的绿苗与黄苗之比只有三体7为12∶1 (χ2=0.36, P=0.01),其他均为3∶1.因此,可以确定1066A的不育基因为隐性单基因,位于第6号染色体上,该品系的黄苗基因也是隐性单基因,位于第7号染色体上.     

The use of primary trisomics for the localization of genes on the seven different chromosomes ofPetunia hybrida. I. Triplo V

Data on 3n×2n and 2n×3n crosses as a source of trisomics inPetunia are given. The delayed germination and retarded growth ofPetunia trisomics, in comparison with diploids, is mentioned. The application of recent fluorescence staining techniques to enzymatically macerated roottips made it possible to distinguish the seven chromosome pairs ofPetunia hybrida. With the aid of the standard karyogram, a number of primary trisomics could be identified. The origin of two primary trisomics is discussed. With these trisomics, some genetic factors, placed in linkage groups, have been localized on one of the chromosomes. This first localization concerns the linkage group, containing the geneUn (=Undulata) for flower shape. In a primary trisomic with the undulate flower shape, chromosome V proved to be present in triplicate. From the deviating ratios for the undulata character in crosses with this trisomic, it was concluded that the location of the linkage group containing the geneUn is on chromosome V.     

TRIVALENT FORMATION IN MULTIPLE TRISOMICS OF CLARKIA UNGUICULATA

Vasek, F. C. (U. California, Riverside.) Trivalent formation in multiple trisomics of Clarkia unguiculata. Amer. Jour. Bot. 50(3): 244–247. 1963.—A series of multiple trisomics, ranging from 2n + 1 to 2m + 7, was scored for univalents and trivalents at first metaphase. The mean number of trivalents per cell per extra chromosome was 0.43, 0.46, 0.46, 0.56, 0.54, 0.55 and 0.59 for plants with 1, 2, 3, 4, 5, 6 and 7 extra chromosomes respectively. These trivalent frequencies are interpreted to fall into 2 classes, indicating that the cytological differences between triploids and single trisomies may be based on a threshold effect. The results are compared with available data from other genera, and it is suggested that the observed increase in trivalent formation per extra chromosome may be associated with an increase in chiasma frequency.