Production and identification of primary trisomics in diploid Agropyron cristatum (crested wheatgrass).

Six of the seven possible primary trisomics in Agropyron cristatum were produced. Based on morphology, arm length ratios, and C-banding patterns, they were identified as primary trisomics for chromosomes A, B, C, D, E, and G. Agropyron cristatum is one of several species constituting the crested wheatgrass complex. All species in this complex contain one basic genome (P). A study was conducted to produce and identify a primary trisomic series that will be used to map genes to individual chromosomes. A population of 157 plants were generated by crossing autotriploids (PPP) with diploid (PP) A. cristatum: 58 were diploid (2n = 14), 76 were primary trisomies (2n = 15), 17 were double trisomic (2n = 16), 4 were triple trisomics (2n = 14 + 3), 1 was telocentric trisomic (2n = 14 + 1 telo), and 1 was tetratrisomic (2n = 14 + 4). Karyotype analysis of acetoorcein-stained chromosomes was carried out using the CHROMPAC III computer program; for analysis of C-banded karyotypes, the computer imaging analysis program PCAS (Plant Chromosome Analysis System) was used to identify the primary trisomics. Of the 47 primary trisomics analyzed, 21 plants had one extra satellited chromosome E, 18 with the satellited D chromosome, 3 each for chromosomes B and G, and 1 each for chromosomes C and A. Chromosome pairing was studied in trisomies B, D, E, and G. Trisomics for chromosomes B and G were similar in their mieotic behavior. Each had a trivalent frequency of about 60% and pollen stainability of less than 40%. Trisomics for chromosomes D and E had a trivalent frequency of about 30% and pollen stainability of over 70%.     

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.     

TRISOMIC TRANSMISSION IN CLARKIA UNGUICULATA

Vasek , F. C. (U. California, Riverside.) Trisomic transmission in Clarkia unguiculata. Amer. Jour. Bot. 48(9): 829–833. 1961.—Seven primary trisomic plants derived from a triploid-diploid cross were self-pollinated. The 7 progenies included diploids and trisomics, the latter varying in frequency from 16 to 30%. In addition, 2 of the progenies included tetrasomic plants. Crosses were made between diploids and either trisomics or tetrasomics. The extra chromosome of 1 progeny was readily transmitted through the pollen of trisomic and tetrasomic plants. When a trisomic of the same progeny was used as a seed parent, only diploids and tetrasomics were found among the offspring, indicating a duplication of the extra chromosome. The extra chromosomes of other progenies were not transmitted through either pollen or eggs in controlled diploid-trisomic crosses but trisomics of these progenies were recovered after self-pollination. It is suggested that differential pollen-tube growth precluded transmission to diploid-trisomic hybrids and that under conditions of reduced pollen competition the extra chromosome normally would be transmitted through pollen. The extra chromosomes generally occur as univalents at metaphase and are ordinarily included in telophase nuclei.     

Primary trisomics obtained from autotriploid by diploid reciprocal crosses in cucumber

To promote cytogenetical studies on cucumber (Cucumis sativus L., 2n = 2x = 14), the reciprocal crosses were made between autotriploid and diploid for selecting the primary trisomics. Meanwhile, chromosome behavior during meiosis in autotriploid cucumber was investigated to look for cytological evidences for origin of primary trisomics. Many viable F₁ seeds were obtained from reciprocal crosses between autotriploid and diploid. The number of chromosomes of 56 surviving progenies varied from 14 to 28, with plants having 2n = 15 occurring at the highest frequency (51.8%). Primary trisomics were firstly obtained in this study. Four types of primary trisomics were isolated and they could be distinguished from each other, as well as diploid. Variable chromosome configurations, e.g. univalent, bivalents and trivalents were observed in many pollen mother cells of the autotriploid at metaphase I. Binomial chromosome distribution was observed at anaphase I and frequency of 8/13 was 6.25%. The meiosis of autotriploid, especially the class of gametes with eight chromosomes, gave the cytological evidence of producing 2x + 1 type gamete and could be induced into primary trisomic plants from progeny of autotriploid–diploid crosses. These studies have established a ground work for selecting a series of primary trisomics, and further using them for associating linkage groups with specific chromosomes in cucumber.     

Spontaneous structural rearrangements in Solanum phureja Juz. et Buk. 2. Meiotic behaviour and identification of interchange chromosomes using primary trisomics.

Meiosis was studied in two diploid (2n = 2x = 24) siblings of Solanum phureja Juz. et Buk. and in 11 disomic and 2 trisomic descendants. The diploid siblings carry the same heterozygous interchange and either one or two inversions. The frequency of quadrivalents at diakinesis/metaphase I in these clones was 0.56 and 0.62 per pollen mother cell. In two plants from the first inbred generation (I1) this frequency was about the same but in some other I1 plants and a full sib the frequency was substantially lower, varying from 0.00 to 0.16. Most quadrivalents, 78-83%, were rings. A variety of quadrivalent configurations at diakinesis and metaphase I was observed, giving rise to balanced and unbalanced gametes. The absence of ring quadrivalents in trisomic descendants of one of the siblings implied that tertiary trisomics or primaries being homozygous for the interchange were present in the I1 generation. Regular chromosome distribution (12-12) at anaphase I occurred in 46.5 and 73.2% of the pollen mother cells studied in the two original clones. Irregularities, such as 11-13 distribution, lagging chromosomes, and a bridge and fragment, were detected on average in 2.7, 3.3, and 32.5%, respectively, of the anaphase I cells analysed. In hybrids from crosses between 6 primary trisomics as females with the interchange heterozygote, the involvement in the interchange of chromosomes 3 and 12 was clearly demonstrated.     

Oocyte meiosis in a trisomy 18 fetus. Behavior of the supernumerary chromosome and identification of the 18 bivalent]

Associations of the three n degrees 18 chromosomes were studied in a trisomy 18 fetus (the chromosomal constitution of which had been identified by amniocentesis). The three classes of associations observed were those observed in other trisomic organisms:trivalent, trivalent presenting an important asynaptic region, and bivalent accompanied by a univalent. In addition, the sequence was established of chromomeres, the number of which varied from 18 to 23 depending on the degree of chromosome contraction. In elongated pachytene oocyte bivalents each G-band of mitotic metaphase chromosomes could be subdivided into several sub-bands.     

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.     

Development and applications of a complete set of rice telotrisomics

We previously isolated a complete set of primary trisomics along with many other aneuploids from triploid plants derived from an indica rice variety "Zhongxian 3037." About 30,000 progeny from these trisomic and aneuploid plants were grown each year from 1994 to 1999. The variants that differed morphologically from both the diploids and the original primary trisomics were collected for cytological identification. From these variants, a complete set of telotrisomics covering all 24 rice chromosome arms was obtained. The identities of the extra chromosomes were further confirmed by dosage analysis of the RFLP markers on extra chromosome arms. The telocentric nature of the extra chromosomes in these stocks was verified by fluorescence in situ hybridization (FISH) using a rice centromeric BAC clone as a marker probe. In general, the shorter the extra chromosome arm of a telotrisomic, the stronger the resemblance it bears to the diploid; the longer the extra chromosome arm, the stronger the resemblance to the corresponding primary trisomic. We demonstrated that DNA clones can be rapidly assigned to specific chromosome arms by dosage analysis with the telotrisomics. We also showed that telotrisomics are valuable tools for chromosome microdissection and for developing chromosome-specific DNA markers.     

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.     

Increasing the transmission rate of the extra chromosome in a trisomic Nicotiana sylvestris line by modifying the means of pollination

Summary Trisomies of primary trisomic line B220 of Nicotiana sylvestris, which contain an extra chromosome shown to be a satellite chromosome, can be readily identified by their larger flower and leaf sizes. In seed-propagated species, the low transmission of the extra chromosome has prevented such plants from becoming agriculturally useful cultivars. In line B220, the transfer of the extra chromosome in 2n×2n+1 crosses was very low (13.5%), although n and n + 1 pollen grains were produced in equal quantities, as was confirmed by anther culture. This was due to the delayed development of n + 1 pollen grains, which are not at full maturity at the time of an thesis. The transfer of the extra chromosome in 2n×2n+1 crosses was increased by a 1 day delay in pollination and also by pollination of small pollen grains selected through nylon meshes. The delayed pollination increased the frequency of trisomics by 9%, whereas pollen selected by using 30 and 25 n nylon meshes induced an extremely high transfer of the extra chromosome, namely 51.9% and 70.4%, respectively. The observed frequencies of trisomics and tetrasomics in artificial selfing of 2n+1 plants with selected small pollen grains were lower than those expected from the data of reciprocal crosses between 2n and 2n+1 plants. This discrepancy seems to indicate a disadvantage of the n+1 pollen in fertilization due to the longer style of the trisomics relative to that of the diploids.     

Primary trisomics of rice: origin, morphology, cytology and use in linkage mapping

Twelve primary trisomics of Oryza sativa L. were isolated from the progenies of spontaneous triploids and were transferred by backcrossing to the genetic background of IR36, a widely grown high yielding rice variety. Eleven trisomics can be identified morphologically from one another and from diploids. However, triplo 11 is difficult to distinguish from diploid sibs.—The extra chromosome of each trisomic was identified cytologically at pachytene stage of meiosis, and the chromosomes were numbered according to their length at this stage. The major distinguishing features of each pachytene chromosome were redescribed.—The female transmission rates varied from 15.5% for triplo 1, the longest chromosome, to 43.9% for triplo 12, the shortest chromosome. Seven of the 12 primary trisomics transmitted the extra chromosome through the male. The low level of chromosomal imbalance tolerated by rice and other evidence are interpreted to indicate that this species is a basic diploid.—Genetic segregation for 22 marker genes in the trisomic progenies was studied. Of a possible 264 combinations, involving 22 genes and 12 trisomics, 120 were examined. Marker genes for each of the 12 chromosomes were identified. The results helped establish associations between linkage groups and cytologically identifiable chromosomes of rice for the first time. Relationships between various systems of numbering chromosomes, trisomics, linkage groups and marker genes are described, and a revised linkage map of rice is presented.     

Comparison of the transmission of three trisomies by males and females in the newt Pleurodeles waltlii (author's transl)]

In the newt Pleurodelles waltlii, males and females trisomic for chromosomes 8, 10 and 11 are fertile. Crosses between such trisomics and diploids were carried out. Progeny analysis showed that an extra chromosome is transmitted to half of the gametes of both males and females trisomics. The extra chromosome apparently causes interference in the regular mechanics of meiotic division, so that trisomics throw nonparental aneuploids and polyploids in their progenies. Moreover, some descendants develop chromosome anomalies during embryonic life ; thus, the progeny of trisomics include diploids, parentaltype trisomics, and embryos with new chromosome anomalies. Morphology and chromosome anomalies of the embryos are compared. A possible explanation for the secondarily acquired anomalies are discussed.     

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.     

Chromosome inheritance in triploid Pacific oyster Crassostrea gigas Thunberg

Reproduction and chromosome inheritance in triploid Pacific oyster (Crassostrea gigas Thunberg) were studied in diploid female x triploid male (DT) and reciprocal (TD) crosses. Relative fecundity of triploid females was 13.4% of normal diploids. Cumulative survival from fertilized eggs to spat stage was 0.007% for DT crosses and 0.314% for TD crosses. Chromosome number analysis was conducted on surviving progeny from DT and TD crosses at 1 and 4 years of age. At Year 1, oysters from DT crosses consisted of 15% diploids (2n=20) and 85% aneuploids. In contrast, oysters from TD crosses consisted of 57.2% diploids, 30.9% triploids (3n=30) and only 11.9% aneuploids, suggesting that triploid females produced more euploid gametes and viable progeny than triploid males. Viable aneuploid chromosome numbers included 2n+1, 2n+2, 2n+3, 3n-2 and 3n-1. There was little change over time in the overall frequency of diploids, triploids and aneuploids. Among aneuploids, oysters with 2n+3 and 3n-2 chromosomes were observed at Year 1, but absent at Year 4. Triploid progeny were significantly larger than diploids by 79% in whole body weight and 98% in meat weight at 4 years of age. Aneuploids were significantly smaller than normal diploids. This study suggests that triploid Pacific oyster is not completely sterile and cannot offer complete containment of cultured populations.     

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.     

Trisomy in Aedes aegypti.

A trisomic (2n=6+1) pupa of the yellow fever mosquito Aedes aegypti has been found. The trisomy involved chromosome 3 which is intermediate in size between 1 and 2. The extra chromosome formed a univalent or a trivalent during meiosis.     

PHENOTYPIC VARIATION IN TRISOMICS OF CLARKIA UNGUICULATA

Vasek , F. C. (U. California, Riverside.) Phenotypic variation in trisomics of Clarkia unguiculata. Amer. Jour. Bot. 50(4): 308–314. 1963.—Progenies of 3n × 2n crosses included, in addition to diploids, plants trisomic for 1, 2, 3, 4, 5, 6 or 7 chromosomes. Means and variances were calculated for 15 phenotypic traits, including 3 width/length ratios, in one set of progenies, and for 10 of the traits, including 2 of the ratios, in another set of progenies. In 25 trait comparisons, including 15 different traits, the means for each chromosome number class were heterogeneous in 11 comparisons, which included 8 different traits. Single trisomics differed significantly from diploids in 5 comparisons (4 different traits). Despite these significant differences the variation followed no particular pattern except that sepal length increased and pollen fertility decreased with chromosome number, and trisomics, as a group, sometimes differed from diploids with regard to the width/length ratio of leaves or petals. The variances were heterogeneous in 5 comparisons (4 different traits). Sepal length and pollen fertility were the only traits for which single trisomics were more variable than diploids and for which the entire population was more variable than diploids. In addition, in 4 progenies of self-pollinated trisomics, diploids and trisomics (which within each progeny were trisomic for the same Chromosome) differed significantly in mean value in only 3 traits (out of 60 trait comparisons). Variances were significantly different in 6 comparisons (4 different traits) but, surprisingly, diploids were more variable than trisomics in 3 of these 6 comparisons. Except for sepal length, pollen fertility and some width/length ratios, a wide variety and number of extra chromosomes rarely had a significant effect on the mean or variability of various phenotypic traits, and single specific extra chromosomes had very little effect except sometimes on pollen fertility or an occasional ratio. A large amount of variation, probably caused by the environment and the general genetic background, may obscure possible specific trisomic phenotypes. Morphological identification of specific trisomics is considered impractical in this species.     

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     

The quantitative analysis of chromosome pairing and chiasma formation based on the relative frequencies of M I configurations. II. Primary trisomics

On an earlier occasion the estimation of the “crossing-over potentials” of the two arms of a chromosome from the relative frequencies of the different types of bivalent was discussed. When in normal diploids the bivalents in M I can not be distinguished from each other, primary trisomics may be used to mark particular chromosomes. For the estimation of the “crossingover potentials” of the two arms the only type of configuration available (trivalent) is not sufficient. The required additional information may be obtained from the average probability (b) of the chromosome arms to be bound. Using the satellite chromosome trisomic ofSecale cereale it is shown that the use ofb introduces an excessive error, especially with highb values. Consequently, the primary trisomics can not be recommended for the estimation of the “crossing-over potentials” of the two arms of particular chromosomes. The telocentric trisomics permit the recognition of more configurations and are to be preferred. Partner exchange and nucleolus may both interfere with chiasma formation. The data suggest that the three homologous chromosomes may not be equal in respect to pairing and chiasma formations. There are indications that the initiation of pairing is localized in one locus on each arm.     

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

Summary An attempt was carried out to produce trisomics of the wild tomato L. peruvianum, to define their essential features, and to detect relationships between trisomy and the expression of self-compatibility.Triploid-diploid crosses in L. peruvianum yielded nearly 40% aneuploids. Of these, 18% were single trisomics, and the rest had 2, 3 and 4 extra chromosomes. Almost all the trisomics occurred in crosses where the triploid was used as female parent. Vigour and fertility of trisomics were not much different from those of disomics, and morphologically they were very similar.The extra chromosome was identified in three self-compatible trisomic plants through somatic and pachytene chromosome morphology. One of these plants was trisomic for chromosome 1, while the other two were trisomic for chromosome 3. In these trisomics a positive correlation was found between chromosome length and trivalent formation, but no relationship between chromosome length and frequency of laggards was observed.A series of test-crosses revealed that the capacity of the trisomics to produce seed upon selfing always resulted from alterations of the incompatibility phenotype of the style and not from competitive interaction in the pollen. Progeny analyses showed that the self-compatibility features of the trisomics were not transmitted from one generation to the next. The implications of these findings are discussed.This work has been supported by a contract between the European Communities and the CNEN. This publication is contribution no. 1458 from the Biology Division of the European Communities and contribution no. 472 from the Divisione Applicazioni delle Radiazioni del CNEN.