Meiotic Chromosome Number Research Articles

ESTUDIOS CROMOSÓMICOS EN ESPECIES DE ASPLENIUM (ASPLENIACEAE) DE LA ARGENTINA

Guillen, R. H. & Davina, J. R. 2005. Chromosome studies in species of Asplenium (Aspleniaceae) from Argentina. Darwiniana 43(1-4): 44-51. We documented somatic and meiotic chromosome numbers of 6 species of Asplenium from Argentina. We present for the first time chromosome numbers of A. ulbrichtii var. serrato-dentatum, 2n=2x=72, and A. triquetrum, 2n=4x=144. Previously reported counts of n=72 for A. auritum, 2n=2x=72 for A. claussenii, n=36 for A. formosum, and 2n=8x=288 for A. serratum, were confirmed.

MEIOTIC AND MITOTIC CHROMOSOME NUMBERS FOR MENTZELIA LEUCOPHYLLA BRANDEGEE (LOASACEAE)

ABSTRACT Meiotic and mitotic chromosome numbers for Mentzelia leucophylla Brandegee (Loasaceae) are reported. The numbers of n = 11 and 2n=22 fit with the aneuploid series that exists in other taxa of Mentzelia section Bartonia, but differ from a chromosome number of n = 18 reported in 1973 by Reveal & Styer. Although additional work should be done on the species, it is suggested that the 1973 count may be in error.

Historical Perspectives

Fifty years ago, Professor Paul Polani and colleagues described young women who had Turner syndrome and were found to have apparently male “chromosomal sex.” (1) At that time, the generally accepted number of chromosomes in humans was 48. Five years earlier, Barr and Bertram described the presence of a prominent mass of chromatin lying close to the nucleolar membrane in neurons of some female cats. (2) This “sex-chromatin” was not found in the males. These “Barr bodies” later were detected in cells grown from skin biopsies. (3) Then, in 1956, Tjio and Levan reported that the number of diploid chromosomes was 46, (4) which rapidly was confirmed by others. (5) From this ripple, a wave soon developed. Three years later, the first association of a clinical syndrome with an abnormal number of chromosomes was reported from France (6) and quickly confirmed in Scotland. (7) This was the association of Down syndrome (mongolism) with an extra chromosome number 21 (trisomy 21), although this was called chromosome number 22 at the time. Not long afterward, translocation was noted in a girl who had Down syndrome born to a 21-year-old mother, (8) and translocation was described as a cause of familial mongolism. (9) Other trisomies soon were described. (10)(11) Based on the realization that the number of sex-chromatin bodies was one less than the number of X chromosomes present, the chromosomes of women who had Turner syndrome and appeared to be chromosomally “male” were investigated. They were found to have 45 chromosomes, with the sex chromosomes being XO. (12) Many of these exciting chromosomal discoveries were made by Professor Polani and his colleagues. Elsewhere, Professor Polani (now 90 years old) has described in detail the origins and evolution of clinical cytogenetics. (13) In this issue of NeoReviews , …

Chromosome contribution to Andean Polyploid Species of Senecio (Asteraceae), from Argentina

Abstract Meiotic chromosome numbers were determined and observations of meiotic behavior were made in six species and two hybrid specimens of Senecio L. (Asteraceae). Two different numbers were found: 2n=4x=40 in S. pogonias Cabr., S. ragonesei Cabr., S. sectilis Griseb. and S. viridis Phil. var. radiatus R. E. Fr. and 2n=8x=80 in S. subulatus D. Don. var. subulatus and in S. uspallatensis Hook. et Arn.; the latter showed the same chromosome number previously reported. The chromosome number of the hybrid individuals was 2n=4x=40, being their putative parents S. ragonesei and S. sectilis. B chromosomes were found in some individuals of S. pogonias, S. sectilis, S. subulatus var. subulatus and S. uspallatensis. Many meiotic irregularities such as bridges, fragments, laggard chromosomes, micronuclei and cellular fusion were observed. The results are analyzed in relation to the persistence and success of these polyploids, and the speciation mechanisms operating within this group are discussed.

Morphometric Analysis of Escobaria sneedii Var. sneedii, E. sneedii Var. leei, and E. guadalupensis (Cactaceae)

We used discriminant analysis to assess taxonomic status of three closely related, rare taxa within the cactus genus Escobaria (E. guadalupensis, E. sneedii var. sneedii, and E. sneedii var. leei). These three taxa consist of nine isolated populations; six of these populations consist of morphologically typical specimens (i.e., similar to the type specimen), while three populations are of questionable taxonomic status. We used the six morphologically typical populations (referred to as assigned populations) to derive predictive dis- criminant functions for each taxon. These discriminant functions were then applied to assigned populations to determine the status and taxonomic boundaries of each taxon, and to the three questionable populations (referred to as unassigned populations) to interpret their taxonomic status. Our model included four predictor variables: number of immature stems, mature stem diameter, number of radial spines, and length of the innermost central spines. Discriminant analysis correctly classified .93% of 186 individuals from the six assigned populations, suggesting a distinct status for each taxon. Applying the predictive discriminant func- tions to unassigned populations resulted in classifying a large percentage of individuals from each unas- signed population into each of two taxa. This suggests that the unassigned populations consist of morpho- logical intermediates, possibly as the result of hybridization. Meiotic chromosome numbers of n 5 11 were determined for E. guadalupensis, E. sneedii var. leei, and the three unassigned populations.

Interspecific variation of nuclear DNA and structural changes in meiotic and mitotic chromosome in some species of Mammillaria (Cactaceae)

Mitotic and meiotic chromosome number, karyotype, chiasma frequency in pollen mother cells, Interphase Nuclear Volume (INV) and nuclear DNA amounts in 12 species of Mammillaria revealed significant...

Estudios cariológicos en Asteraceae. VIII

Meiotic and/or mitotic chromosome numbers were determined and observations on meiotic behavior were made in 14 accessions belonging to 14 especies concerning 8 genera distributed in 4 tribes of the Asteraceae. Five species are investigated chromosomally for the first time. These are as follows, tribe Mutisieae: Brachyclados cespitosus (Phil.) Speg. (n = 23), Nassauvia pygmaea (Cass.) Hooker (n = 22); tribe Cichorieae: Hypochoeris acaulis (Remy) Britton (n = 4,2 n= 8), Hieracium glaucifolium Poepp. ex Froelich in DC. (2n = 18) and Hieracium aff. palezieuxii Zahn (2n = 18). Different chromosome number to those previously reported in the literature were found for Hypochoeris chondrilloides (A. Gray) Cabrera (n = 8), Baccharis ulicina Hook. Am. (2n = 18+3B), Conyza aff. bonariensis (L.) Cronquist (2n = 18). The karyotypes of Brachyclados lycioides Don, Hypochoeris acaulis (Rerny) Britton, Hieracium aff. palezieuxii Zahn and Senecio chilensis Less. are described for the first time. Meanwhile, the karyotypes of Hypochoeris microcephala (Sch. Bip.) Cabrera var. albiflora (Kuntze) Cabrera, H. chillensis (Kunth) Hieron and H. megapotamica Cabrera showed to be slightly different with those described in previous publications. The significance of some of the results in relation to taxonomical and evolutionary problems is discussed.

Chromosome Numbers of Species of Atriplex Section Obione (Chenopodiaceae) and Their Relation to Taxonomy.

The meiotic chromosome numbers for 18 species of Atriplex section Obione (Chenopodiaceae) are presented. This is the first report for Atriplex abata, A. elegans, A. linifolia, A. minuscula, A. parishii, A. pueblensis, A. tampicensis, A. texana and A. thornberi. Photographs of the meiotic figures of 12 species are presented. All the species are diploid with 2n = 18, except for Atriplex argentea, A. cordulata, A. coronata and A. leucophylla tetraploids with 2n = 36. The basic chromosome number (x = 9) for the section is confirmed. Atriplex argentea, with the broadest geographic distribution, has at least two ploidy levels. All the tetraploid species occur in southwestern United States, the area of greatest diversity of the section Obione. Chromosome numbers appear to have taxonomic value and allopolyploidy might have played an important role in the evolution of the section.

Taxonomic studies in the Fuirena pubescens complex (Cyperaceae) in Kenya

Muasya. A. M. & Baauar, S. R. 1995. Taxonomic studies in the Fuirena pubescens complex (Cyperaceae) in Kenya. — Nord. J. Bot. 15: 407–410. Copenhagen. ISSN 0107–055X.Three taxa in the Fuirena pubescens complex were investigated morphologically, palynologically, and cytologically in order to determine their taxonomic identity and appropriate rank. The taxa differ in both morphology and chromosome number. The three former varieties, F. pubescens var. pubescens, var. major, and var. buchananii, are here recognised as distinct species, with var. major and var. buchananii being reinstated as F. pachyrrhiza and F. welwitschii, respectively. Fuirena pubescens and F. pachyrrhiza have terete spikelets and leaf blades more than 5 mm wide, but the former has a meiotic chromosome number of n=21 and white entire nutlets, while the latter has a chromosome number of n=24 and dark‐greenish tuberculate nutlets. Fuirena welwitschii is distinguished by having a 5‐angular spikelets, chromosome number n=40, and brownish tuberculate nutlets.

Interactions between the scs and Vi genes in alloplasmic durum wheat

Two nuclear genes, vitality (Vi) on an A- or B-genome chromosome and species cytoplasm specific (scs) on a 1DL telosome from Triticum aestivum L. or a telosome from Aegilops uniaristata Vis. (un telosome), improved compatibility between the nucleus of Triticum turgidum L. var. durum and the cytoplasm of Ae. longissima S. &M. or Ae. uniaristata. To study interactions between Vi and scs and to determine the chromosomal location of Vi, 29-chromosome fertile plants were crossed with 13 D-genome disomic-substitution (d-sub) lines [except 5D(5A)] of 'Langdon' durum. F1 and backcross progenies were examined for meiotic chromosome number and pairing, fertility, and plant vigor. In 11 crosses, Vi restored seed viability but produced double-monosomics (d-monos) with greatly reduced growth and vigor. In contrast, crosses involving 1D(1A) and 1D(1B) d-sub lines produced d-monos with normal vigor and anthesis but nonfunctional pollen. A backcross of 1D + 1A d-mono F1 and 1D(1A) d-sub lines produced 11 male steriles; 3 had 13 II + 1 II 1D + 1 I 1A, 2 had 13 II + 2 I, 1 had 13 II + 1 II 1D(1A), and 5 were not examined. Crosses of 1D + 1A d-mono F1 with control durum, lo durum (with 1DL), and un durum (with un telosome) lines produced 16 male-sterile d-monos and 14 fertiles with 14 II + 1 I 1D, showing that 15-chromosome female gametes transmitted monosomes 1A and 1D. However, BC2F1's from 1D + 1B d-mono x fertile line with un telosome included 20 male-sterile d-monos, 6 fertile triple monosomics (13 II + 1 I 1D + 1 I 1B + t I un telosome), and 1 fertile plant with a 1B/1D translocation. Unlike d-mono 1A + 1D, d-mono 1B + 1D did not transmit 15-chromosome female gametes with monosomes 1D and 1B. Additional backcrosses also indicated that homozygous scs caused male sterility in 1D(1A) and 1D(1B) d-subs and that the procedure used was not suitable for the chromosomal location of Vi.

Chromosome Numbers of New World Acanthaceae

Meiotic chromosome numbers were determined for 36 species representing 15 genera of Acanthaceae from Jamaica, Mexico, and Panama. Chromosome numbers of 21 species are reported for the first time including the initial reports for two genera, Oplonia (n = 21) and Streblacanthus (n = 18). Based on chromosome numbers and morphological characters, three distinctive groups of New World Justicieae: Odontoneminae are delimited. A primitive basic number of x = 7 is probable for the family. The Acanthaceae are a large, pantropical fam- ily that has only recently begun to receive con- centrated systematic analyses at both floristic and monographic levels. The proportionally large number of acanthaceous genera, includ- ing an abundance of unispecific genera, with respect to the number of species in the family is well documented (Gentry 1973, table 1; Wal- ters 1961). Previous studies of chromosome numbers in American Acanthaceae have been useful both in understanding relationships among genera and in reassessing the status of some of the unispecific genera. This paper is the third in a series of contri- butions on chromosome numbers of New World Acanthaceae. In the previous two papers (Dan- iel et al. 1984, 1990) chromosome numbers were determined for 80 species in 26 genera. Al- though we report chromosome numbers for species from Panama and Jamaica in this paper, our geographic emphasis has been, and contin- ues to be, concentrated on species occurring in Mexico. With more than 350 native and natu- ralized species in some 50 genera representing each of the four subfamilies (Acanthoideae, Mendoncioideae, Nelsonioideae, and Thunber- gioideae) traditionally recognized within the Acanthaceae, Mexico is the major center of di- versity for this family in North and Central America (Daniel, in press a).

Chromosome Numbers of Neotropical Castilleja (Scrophulariaceae: Tribe Pediculareae) and Their Taxonomic Implications

Meiotic chromosome numbers in Castilleja are reported for 105 collections representing 34 species, mostly from Mexico, with a few from Central America and South America. Chromosome numbers of the following 19 species are reported here for the first time: C. bryantii, C. ecuadorensis, C. fissifolia, C. fruticosa, C. gracilis, C. hirsuta, C. integrifolia, C. irazuensis, C. linifolia, C. nubigena, C. ornata, C. ortegae, C. purpusii, C. roei, C. scorzonerifolia, C. stenophylla, C. talamancensis, C. tenuifolia, and C. virgata. Of the 34 species, 24 are exclusively diploid (n = 12); five are tetraploid (n = 24) only; two are octoploid (n = 48) only; three have two or more levels of ploidy (n = 12, 24, and 72)

Morphology and cytology of Cicer canariense, a wild relative of chickpea

The short note describes the morphology and chromosome number of Cicer canariense Santos Guerra & Lewis. This taxon has been found to have a meiotic chromosome number of 2n<16 and not 2n<24, as reported earlier. At ICRISAT Center, while other perennial Cicers did not perform well, Cicer canariense flowered and produced seeds. The species grew vigorously and had multi-podded peduncles and multi-seeded pods. Such traits of Cicer canariense can be very useful in the genetic improvement of chickpeas.

Cytology and Evolution of Jasmines.

Cytological investigations on thirty three taxa of South Indian Jasminum have been carried out. Mitotic, meiotic and gametic chromosome numbers of these are determined by particulary suitable staining techniques. The somatic numbers given in the table are ascertained by comparison with meiotic and gametic numbers. A tentative scheme of cytological evolution is also given in a chart.

Chromosome Numbers in Argentinean Acanthaceae

Mitotic and meiotic chromosome numbers are reported for 22 species representing eight genera of Argentinean Acanthaceae. Counts for 18 of these species are published for the first time (including the first count for the genus Chaetothylax, 2n = 28). In Siphonoglossa, 2n = 36 is a newly reported chromosome number and n = 13 is a new number for Stenandrium. Polyploidy and aneuploidy have been important in chromosomal evolution of Acanthaceae and diploids are ap- parently not very common. The basic number x = 7 seems to be primitive for the family, from which the widespread x = 14 would have been derived.

Karyological studies of Duchesnea (Rosaceae).

The present investigation on the chromosomes of Duchesnea confirmed previous reports indicating that D. chrysantha f. chrysantha has 2n=14 chromosomes and D. indica has 2n=84 chromosomes. The chromosome number of D. chrysantha f. leucocephala, 2n=14, was also ascertained, together with the meiotic chromosome numbers. The two taxa of D. chrysantha had very similar complements consisting of 5 pairs of metacentrics, one pair of metacentric SAT-chromosomes and one pair of submetacentrics. Duchesnea indica had subtelocentric SAT-chromosomes and many subtelocentric chromosomes in addition to metacentric and submetacentric chromosomes. The genome of D. indica contains a genome set involving subtelocentric chromosomes, which were not detected in D. chrysantha. This finding seems to be of importance in considering the course of evolution in D. indica.

Chromosome Numbers of American Acanthaceae

A total of 72 meiotic chromosome numbers were determined for 58 taxa representing 23 genera of Acanthaceae from the United States, Mexico, Panama, and Peru. Chromosome numbers of 41 of these taxa are reported for the first time. Chromosome numbers obtained in Aphanosperma (n = 18), Chalarothyrsus (n = 18), Gypsacanthus (n = 18), Ixtlania (n = 14), Razisea (n = 18), and Teliostachya (n = 9) are the first for these genera. Our counts for Dicliptera resupinata (n = 40), Elytraria imbricata (n = 12), Justicia pectoralis (n = 11), and Yeatesia mabryi (n = 18) differ from previously published numbers for these species. Constancy of chromosome number appears to be characteristic of certain genera of Acanthaceae whereas variation due to polyploidy and aneuploidy occurs in others. Various generic relationships are discussed with respect to the chromosome numbers now known for neotropical Acanthaceae.

Chromosome Numbers in Bromeliaceae

Eighty-three chromosome counts are reported for 72 taxa of the Bromeliaceae. Fifty-eight of these counts are the first known chromosome number reports for their respective taxa. A model of chromosomal evolution in the Bromeliaceae (n = 25) is presented. The model is parsimonious and consistent with existing data on meiotic chromosome numbers within the family and in the closely related Velloziaceae (n = 9). Two hypothesized paleodiploids (n = 8 and n = 9) hybridized to form a tetraploid that in turn hybridized with the n = 8 lineage. The resultant n = 25 is the extant base number for the family. Two alternative hypotheses could explain the unique extant base number (n = 17) for Cryptanthus: 1) Cryptanthus represents the paleotetraploid level, i.e., prior to the second round of hybridization, or 2) the lower number represents the result of a more recent series of aneuploid reductions from n = 25. Given the existence of intergeneric hybrids involving Cryptanthus, aneuploid reduction is the more likely interpretation. RECENT RESEARCH concerning Bromeliaceae systematics and evolution (e.g., Brown and Gilmartin, 1984, 1986; Gilmartin and Brown, 1985, 1986b) has sparked renewed interest in the study of Bromeliaceae chromosomes and chromosome evolution. Past chromosome number surveys in the family (i.e., Lindschau, 1933; Gauthe, 1965; Weiss, 1965; Sharma and Ghosh, 1971; Till, 1984) have relied mostly on mitotic material. The only major exception to this was Marchant (1967) who utilized meiotically active microsporocytes. There is great variability in reported mitotic chromosome numbers (Brown and Gilmartin, 1986), and lack of concordance between mitotic and meiotic numbers for some taxa within the family. This variability in mitotic number is reflected in the variable interpretations of chromosome base numbers for the family. Brown and Gilmartin (1986) summarized the previous controversy over base number determination for Bromeliaceae, and discussed the current level of knowledge concerning poly' Received for publication 13 October 1987; revision accepted 28 October 1988. We thank a dedicated group of field collaborators, without whom this project would not have been possible: James Ackerman, Puerto Rico; Stephan Beck, Bolivia; Olga Benavides, Colombia; Elizabeth Bravo, Ecuador; David Brunner, Paraguay; I. Chacon, Costa Rica; Hermes Cuadros, Colombia; Linda Escobar, Colombia; Gert Hatschbach, Brazil; Stephen Koch, Mexico; Gustavo Martinelli, Brazil; Fernando Ortiz, Ecuador; Isidoro Sanchez Vega, Peru; and Rosa Subils, Argentina. Expert technical help was supplied by Carol Annable. We thank Ron Hartman, Don Hauber, and two anonymous reviewers for their comments. This work was supported by collaborative research grants BSR-8607 187 (GKB) and BSR-8407573 (AJG) from the National Science Foundation. 3 Deceased 10 February 1989. ploidy, chromosome size bimodality, and the correlation of nonconcordance in meiotic and mitotic chromosome numbers with the epiphytic mode of growth. The purpose of this paper is to describe results of an ongoing meiotic chromosome number survey within the Bromeliaceae, and especially subfamily Tillandsioideae. We also present a model for chromosome base number evolution for the family that is consistent and parsimonious with existing data. METHODS AND MATERIALSFloral buds were collected in the field, or obtained from cultivated material at Marie Selby Botanical Gardens, Sarasota, Florida (SEL). Buds were fixed in field-mixed Farmer's solution (100% EtOH: glacial acetic acid; 3: l/v:v) to which a drop of saturated aqueous ferric chloride (FeCl3-6H20) had been added. The latter enhances chromosome stainability. After a minimum of 24 hr, fixed buds are transferred to 70% EtOH. See Gilmartin and Brown (1986a) for a complete description of the field collaborator network and its operation. For chromosome squash preparations, individual anthers were removed from the bud in 70% EtOH and transferred to a pool of 1% acetic carmine on a microscope slide. While in the stain, the anther is cut transversely in half. Using ultrafine-tipped needle and forceps, the sporogenous masses are squeezed from each microsporangium through the median transverse cut. The sporogenous masses are positioned toward the center of the stain pool and a coverslip and gentle finger pressure are applied. The preparation is further flattened by passing the slide through an alcohol flame sev-

CHROMOSOME NUMBERS IN BROMELIACEAE

Eighty‐three chromosome counts are reported for 72 taxa of the Bromeliaceae. Fifty‐eight of these counts are the first known chromosome number reports for their respective taxa. A model of chromosomal evolution in the Bromeliaceae (n = 25) is presented. The model is parsimonious and consistent with existing data on meiotic chromosome numbers within the family and in the closely related Velloziaceae (n = 9). Two hypothesized paleodiploids (n = 8 and n = 9) hybridized to form a tetraploid that in turn hybridized with the n = 8 lineage. The resultant n = 25 is the extant base number for the family. Two alternative hypotheses could explain the unique extant base number (n = 17) for Cryptanthus: 1) Cryptanthus represents the paleotetraploid level, i.e., prior to the second round of hybridization, or 2) the lower number represents the result of a more recent series of aneuploid reductions from n = 25. Given the existence of intergeneric hybrids involving Cryptanthus, aneuploid reduction is the more likely interpretation.

Cytomorphological studies in some taxa of Phaseolus Linn. and Vigna Savi.

Somatic and meiotic study in the different taxa of Phaseolus and Vigna shows the chromosome number to be 2n=22 and n=11 respectively. The size of somatic chromosome ranges from 15.81μm to 25.43 4μm. TF% value in some of the taxa studied is between 35% and 41% with asymmetrical karyotype, whereas in the other taxa it ranges between 42% to 48% with symmetrical karyotype. S% ranges from 36.36% to 66.66%. Meiotic study shows regular formation of eleven bivalents. Variation in meiotic chromosome number have been noted in some of taxa ranging from n=7 to n=12. Laggards and late separating chromosomes are some of the meiotic irregularities observed.Pollen morphology study in the different taxa show the pollen grains to be oblate radiosymmetric and isopolar. All the species of the two genera showed reticulate surface ornamentation except for P. vulgaris surface appeared to be finely rugulate.