Aneuploid Series Research Articles

Coreopsis Nuecensis (Compositae) and a Related New Species from Southern Texas

An aneuploid chromosome series ofn = 6, 7, 8, 9, and 10 inCoreopsis nuecensis Heller was analyzed for morphological, distributional, and genetic correlations with the chromosome number classes. The results show that two sets of basic chromosome numbers occur within what has been treated asC. nuecensis: n = 6, 7 andn = 9, 10. Then = 7 class frequently carries a pair of B chromosomes, forming then = 8 class. The base chromosome numbers are correlated with some minor but consistent morphological differences, with distributional differences, and with strong sterility barriers in the F1 hybrids. It is proposed that then = 9, 10 segment be recognized as a new species,Coreopsis nuecensoides.

Production of aneuploids in Avena sativa L.

Oat plants were treated with nitrous oxide shortly after pollination. A high frequency of aneuploids in the progenies of treated plants indicates that this technique may be a useful tool for the production of aneuploid series in oats. Several 12-ploid, or nearly 12-ploid, oat plants were also obtained.

Chromosome Numbers in Compositae VIII: Heliantheae

One hundred and ninety-three new counts are reported for the tribe Heliantheae of Compositae, mostly based on determinations of meiotic material, including first counts for the genera Adenothamnus, Chrysogonum, Enceliopsis, Guardiola, Isocarpha, Lipochaeta, Otopappus, and Oyedaea, as well as first counts for 66 species. The original counts are discussed in relation to those previously reported for the tribe, by genera and subtribe. Two-thirds of the approximately 150 genera and more than a third of the roughly 1500 species have now been examined. The incomplete knowledge of generic relationships in the tribe often make the interpretation of these chromosome numbers difficult. Three observations are documented and discussed: (1) genera with low chromosome numbers are few; (2) genera with aneuploid series are abundant; and (3) the original basic chromosome number in the tribe is probably in the range of x = 8 to x = 12.

CHROMOSOME NUMBERS IN COMPOSITAE VIII: HELIANTHEAE

One hundred and ninety‐three new counts are reported for the tribe Heliantheae of Compositae, mostly based on determinations of meiotic material, including first counts for the genera Adenothamnus, Chrysogonum, Enceliopsis, Guardiola, Isocarpha, Lipochaeta, Otopappus, and Oyedaea, as well as first counts for 66 species. The original counts are discussed in relation to those previously reported for the tribe, by genera and subtribe. Two‐thirds of the approximately 150 genera and more than a third of the roughly 1500 species have now been examined. The incomplete knowledge of generic relationships in the tribe often make the interpretation of these chromosome numbers difficult. Three observations are documented and discussed: (1) genera with low chromosome numbers are few; (2) genera with aneuploid series are abundant; and (3) the original basic chromosome number in the tribe is probably in the range of x = 8 to x = 12.

ANTHOCYANIDINS OF SOMEIMPATIENSSPECIES

The genus Impatiens (Balsaminaceae) is mainly tropical with a few members native to temperate regions. The chromosome numbers thus far reported form an aneuploid series of n = 6, 7, 8, 9, 10, and 12 and a polyploid series of n = 16, 17, 20, 24, and 33 (Jones and Smith, 1966). Over one thousand species have been described, but possibly only half of these should be recognized as valid. Both woody and herbaceous habits are present in the genus. variety of morphological characteristics gives the impression that the genus might easily be subdivided, but Hooker and Thomson (1860, p. 106) observed: A little further examination of these seemingly objective groups sufficed to dispel the illusion. Since Impatiens is so rich in subtlely varying taxa which include many endemics (Chatterjee, 1962), it appears to be ideal for the study of evolutionary trends within a genus. Members of this group are pollinated by birds, bees, beetles, moths, and butterflies, and show the expected correlation between principal pollinator and the shape and color of the flower (Vogel, 1954). It is well documented that bees fly readily to blue and yellow flowers, and birds to red (Meeuse, 1961). However, this distribution does not seem to be as clear cut as once thought. Since many insect eyes are sensitive to ultra-violet light but not to red light, some flowers appearing red in

Notes on technic. Reducing breakage of metaphase plates in Feulgen-stained root tips of wheat; ice-water storage before squashing.

Cytogenetic studies with aneuploid series in wheat usually involve a large number of chromosome counts. The reliability of results and the speed of this work are limited by several factors: (1) method of pretreatment for contraction and spreading of chromosomes, (2) the staining procedure, (3) the method of maceration, and (4) the technique of squashing. These determine the final quality of squash preparations.

CHROMOSOME NUMBERS IN THE MALVALES. II. NEW OR OTHERWISE NOTEWORTHY COUNTS RELEVANT TO CLASSIFICATION IN THE MALVACEAE, TRIBE MALVEAE

Forty‐six chromosome counts from 29 species in 15 genera of Malvaceae, tribe Malveae are reported. Counts from 28 species and four genera, Bakeridesia Hochr., Hoheria A. Cunn., Plagianthus J. R. and G. Forster, and Robinsonella Rose and Baker, are new. These counts provide a basis for modifying a generic classification of the Malveae proposed by Bates in 1968. The identificaton of a heretofore unsuspected base chromosome number of x = 15, perhaps of ancient polyploid origin, has resulted in the realignment of Anoda Cav., Bakeridesia, Callirhoë Nutt., Napaea L., Periptera DC., and Sidalcea A. Gray. The data also support the thesis that the base chromosome number of the Malveae, or at least of the Abutilon alliance, is x = 8; that the genera of the New Zealand and Australian Plagianthus alliance were probably derived from abutiloid ancestors; that the generic boundaries of Pseudoabutilon R. E. Fries and Wissadula Medic. require redefinition; and that the Chilean Malacothamnus chilensis (Gay) Krapov. is generically distinct from the North American species of that genus. Callirhoë may be cytologically the most complex genus of Malveae. It includes both euploid and aneuploid series, probably supernumerary chromosomes, and perhaps structural rearrangements in the form of reciprocal trans‐locations between non‐homologous chromosomes.

Chromosome Numbers of Some Saccharum Species Hybrids and Their Cell Suspension Cultures

Chromosome numbers of five Saccharum species hybrids and their cell suspension cultures were determined. The chromosome number was stable in four parental clones (2n = 122, 114, 114, and 112), but was variable in another (2n = 108-128). The cell suspension cultures have been maintained in a yeast extract-enriched nutrient medium for more than 6 years. These cultures were variable in chromosome number for all clones, with a partial aneuploid series at the haploid and/or polyploid level. Each clone had different chromosomal population modes after 6 years of culture. The loss of chromosomes over a period of time would have an effect on the genetic makeup of a cell population. This has implications in the use and interpretation of data from pathological, cytogenetical, biochemical, and physiological studies using cell cultures and is probably a partial explanation for the loss of totipotency in 6-year-old sugarcane tissue and suspension cultures.

CHROMOSOME NUMBERS OF SOME SACCHARUM SPECIES HYBRIDS AND THEIR CELL SUSPENSION CULTURES

Chromosome numbers of five Saccharum species hybrids and their cell suspension cultures were determined. The chromosome number was stable in four parental clones (2n = 122, 114, 114, and 112), but was variable in another (2n = 108‐128). The cell suspension cultures have been maintained in a yeast extract‐enriched nutrient medium for more than 6 years. These cultures were variable in chromosome number for all clones, with a partial aneuploid series at the haploid and/or polyploid level. Each clone had different chromosomal population modes after 6 years of culture. The loss of chromosomes over a period of time would have an effect on the genetic makeup of a cell population. This has implications in the use and interpretation of data from pathological, cytogenetical, biochemical, and physiological studies using cell cultures and is probably a partial explanation for the loss of totipotency in 6‐year‐old sugarcane tissue and suspension cultures.

QUANTITATIVE GENETIC ANALYSIS OF CHARACTERS IN WHEAT USING CROSSES OF CHROMOSOME SUBSTITUTION LINES (THEORETICAL CONSIDERATIONS)

COMPARED to studies based on ordinary homozygous varieties, the use of chromosome substitution lines obtained by means of aneuploid series in Triticum uestiuum L. (SEARS 1944, 1953; UNRAU, PERSON and KUSPIRA 1956; PERSON 1956) permits a more complete, detailed and reliable analysis of the genetic structure of hexaploid wheats (KUSPIRA and UNRAU 1957; SEARS, LOEGERING and RODENHISER 1957; LOEGERING and SEARS 1966). The present paper attempts to show the development of a quantitative genetic analysis of characters in common wheat using triparental groups consisting of three parents, of which one or two are disomic substitution lines, and of the corresponding crosses and some of the backcrosses. The analysis basically follows the scaling test pattern (MATHER 1949) , the obtained genotypic values representing the interaction effects of sets of genes at the level of homologous and/or nonhomologous chromosomes. A preliminary section under the heading Definitions and Concepts is intended to provide the formulation of the simple theoretical foundations underlying the analyses. The symbols of set theory are used in this section, and partly in the subsequent sections (e.g. see KEMENY, SNELL and THOMPSON 1957; LIPSCHUTZ 1964; HALMOS 1965). 1. Definitions und Concepts The genotype of an individual (a zygote) is the set of nuclear genes controlling the manifestation and the inheritance of its characters. The individual in the present case is a common wheat plant, and the character considered is one of its metrical, presumably polygenically controlled, characters. Let G denote the set of nuclear genes constituting the genotype of the wheat plant in question, and C one of its subsets. If it is assumed that C contains all the genes constituting the homozygous loci of the genotype, then its relative complement with respect to G, denoted as CO in this case, must contain all the genes (if any) constituting its heterozygous loci. Note that G = C U E, and, as such, represents a genotype in general. In the case of a quantitative character, the set G, as a whole, most likely in

Chromosome Numbers in Compositae. XI. Peruvian Species

Chromosome counts are reported for 60 collections of Peruvian Compositae representing 59 species in 31 genera. Most of these are first reports for a taxon concerned, including the genera Ascidiogyne (n - 10), Diplostephium (n - 9), Oriotrophium (n - 9), Achyrocline (n = ca 14), Gynoxys (n = 40), Loricaria (n = ca 14), Monopholis (n - ca 30) and Pappobolus (n - 17). Supernumerary or B chromosomes have been found in Baccharis and Monopholis, and an unusual aneuploid series has been detected in Liabum (x = 9, 12, 14, and ca 18). Chromosome counts for 60 collections of Peruvian Compositae are presented in Table 1. Bud material was collected in the field by Dr. John Wurdack and airmailed to the senior author in Austin, Texas, where the counts were made by the usual squash techniques (Turner & Johnston, 1959). Since most of these collections were from remote areas, it was often several weeks before the fixed material could be mailed. These delays and the high temperatures to which the meiotic material was exposed probably account for the numerous approximate counts reported in this paper. (Label-data on the voucher specimens-deposited TEX, US-give approximate counts, plus or minus 1 or 2 chromosomes; in Table 1 we have listed all such counts as approximations only.) Identifications were made by J. Cuatrecasas except for those of Bidens and Coreopsis (by the late E. E. Sherff), Hypochaeris (by A. L. Cabrera) and Liabum rugosum (by R. Ferreyra); chromosome counts were made by Powell and Turner, either singly or in combination.

CHROMOSOME NUMBERS IN POPULATIONS OF CLAYTONIA VIRGINICA FROM THE NEW YORK METROPOLITAN AREA

Buds of Claytonia virginica were examined from 9 locations in the metropolitan New York area. A large amount of meiotic irregularity was characteristic of the populations studied. Chromosome counts on pollen mother cells were higher than any reported previously for the taxon, which contains an extensive aneuploid series including at least 40 different numbers ranging from 2n = 12 to ca. 190. In one New Jersey population, plants having approximately 90 chromosomes were associated with those having only 16. All the observations indicated that Claytonia virginica is an unusual species with an ability to tolerate fluctuations in chromosome material without apparent effects on fertility and morphology.

Chromosome Numbers in Populations of Claytonia Virginica from the New York Metropolitan Area

Buds of Claytonia virginica were examined from 9 locations in the metropolitan New York area. A large amount of meiotic irregularity was characteristic of the populations studied. Chromosome counts on pollen mother cells were higher than any reported previously for the taxon, which contains an extensive aneuploid series including at least 40 different numbers ranging from 2n = 12 to ca. 190. In one New Jersey population, plants having approximately 90 chromosomes were associated with those having only 16. All the observations indicated that Claytonia virginica is an unusual species with an ability to tolerate fluctuations in chromosome material without apparent effects on fertility and morphology.

BIOSYSTEMATIC STUDIES IN THE BOUTELOUA CURTIPENDULA COMPLEX. III. POLLEN SIZE AS RELATED TO CHROMOSOME NUMBERS

Pollen size statistics are presented for 10 closely related species of Bouteloua and relationships between pollen size and chromosome numbers are presented for 13 populations of 5 species and 3 varieties. With 1 exception, all populations of all taxa conformed to a general pattern of pollen size dependent upon chromosome number. Chromosome numbers varied from 2n = 20 to 2n = ca. 103, with several independent aneuploid series. Statistical analyses were made of pollen size as related to chromosome number in the 3 varieties of B. curtipendula. These data showed that tetraploids (2n = 40) of var. tenuis had significantly greater pollen size and coefficient of variation than diploids (2n = 20) of the same variety. Similarly, aneuploids of var. curtipendula with 2n = 45 to 2n = 64 chromosomes had significantly larger and more variable pollen than tetraploids (2n = 40) of the same variety. Highly significant positive regression coefficients were obtained from analyses of chromosome numbers and mean pollen size, and chromosome numbers and coefficient of variation, for var. curtipendula. Regression coefficients for var. caespitosa populations with chromosome numbers over the hexaploid (2n = 60) level were not significant.

Biosystematic Studies in the Bouteloua curtipendula Complex. III. Pollen Size as Related to Chromosome Numbers

Pollen size statistics are presented for 10 closely related species of Bouteloua and relationships between pollen size and chromosome numbers are presented for 13 populations of 5 species and 3 varieties. With 1 exception, all populations of all taxa conformed to a general pattern of pollen size dependent upon chromosome number. Chromosome numbers varied from 2n = 20 to 2n = ca. 103, with several independent aneuploid series. Statistical analyses were made of pollen size as related to chromosome number in the 3 varieties of B. curtipendula. These data showed that tetraploids (2n = 40) of var. tenuis had significantly greater pollen size and coefficient of variation than diploids (2n = 20) of the same variety. Similarly, aneuploids of var. curtipendula with 2n = 45 to 2n = 64 chromosomes had significantly larger and more variable pollen than tetraploids (2n = 40) of the same variety. Highly significant positive regression coefficients were obtained from analyses of chromosome numbers and mean pollen size, and chromosome numbers and coefficient of variation, for var. curtipendula. Regression coefficients for var. caespitosa populations with chromosome numbers over the hexaploid (2n = 60) level were not significant.

BIOSYSTEMATIC STUDIES IN THE BOUTELOUA CURTIPENDULA COMPLEX. I. THE ANEUPLOID RHIZOMATOUS B. CURTIPENDULA OF TEXAS

Gould, F. W., and Z. J. Kapadia. (A. & M. College of Texas, College Station.) Biosystematic studies in the Bouteloua curtipendula complex. I. The aneuploid rhizomatous B. curtipendula of Texas. Amer. Jour. Bot. 49(8): 887–891. Illus. 1962.—Widespread throughout central U.S. is a rhizomatous form of B. curtipendula that basically is tetraploid (2n = 40). In the southwest the predominant type is a caespitose aneuploid with a high chromosome number (2n = ca. 80 to 2n = ca. 102). The present study has shown the presence of an extensive series of rhizomatous aneuploids in central Texas, with chromosome numbers ranging from 2n = 41 to 2n = 64. The distribution of these plants is centered about the region of overlap in the ranges of the 2 previously mentioned types. Available evidence indicates that the rhizomatous aneuploids have arisen through hybridization of the caespitose aneuploids and the rhizomatous tetraploids.

Chromosome-mosaics Observed in a Variety of Wheat, “Shirahada”

1) A variety of wheat, “Shirahada”, showed an abnormal meiotic behavior, “chromosome-mosaics”. In every plant selected at random there were to be seen aneuploid PMC's such as “hypo-” or “hyper-” cells mixed together with euploid ones in the same anther-loculus. Especially the “hypo-” cells with less than 2n chromosome number were frequently noticed. Such aberrant PMC's are usually characterized by a relatively large number of unpaired chromosomes.2) In euploid PMC's there were often observed one or two pairs of univalents while multivalent chromosomes such as trivalent or tetravalent were rarely discovered. On an average about 18% of aneuploid PMC's observed had such irregularities. Laggards and bridges were also frequently observed in both 1st and 2nd anaphase, especially so in 1st division.3) An upset in mitosis which was induced by gene-controlled spindle abnormalities just before meiosis seems to be the probable cause of the origin of these hypo- and hyper-cells.4) As a result of such irregularities in the meiotic division, there appeared frequently in the progenies various types of aneuploids, especially monosomics (2n=41). In the self-pollinated progenies of a plant with the lowest seed fertility, a series of aneuploids having 2n=39, 40 and 41 chromosome numbers were found together with euploids (2n=42).

Developmental sequence of chromosome number in a cytologically unstable Rubus hybrid

1. Serial cytological observations were made on one abnormal seedling from the thornless segregants of the F2 progeny from crossing two tetraploid (2n = 28) Rubus species. The number of root-tip chromosomes was found to vary between 9 and 46 per cell, with the mode always at 35. The wide variation in chromosome number decreased with time, until there was almost stability at 2n = 35. A vegetative (stipule) cell was 2n = 39. The numbers lower than 35 were not due to terminal fusion.2. Evidence from the number of satellites per cell suggests that not always were the same chromosomes being eliminated, although there is a general increase in satellite number with increased numbers of chromosomes per cell.3. There was a correlation between the chromosome numbers and corresponding cell sizes within the aneuploid series. This may be associated with the incremental change of DNA following the addition or subtraction of individual chromosomes, which are highly similar in Rubus.4. The cause of the instability was not definitely established. Its initiation is probably attributable to the egg mother cell, as Rubus pollen reacts sensitively to chromosome unbalance. No abnormalities were observed in the mitoses, and virus infection was not responsible for the instability.5. Chromosome number instability of this plant is discussed in relation to other examples from the same and different genera: it is suggested that the changes in chromosome number known in various Rubi may have arisen somatically.

Chromosome Numbers in Umbelliferae. II.

Bell, C. Ritchie (U. of North Carolina, Chapel Hill.), and Lincoln Constance. Chromosome Numbers in Umbelliferae. II. Amer. Jour. Bot. 47(1) : 24-32. Illus. 1960.–Chromosome numbers are reported for plants representing an additional 100 taxa of Umbelliferae. Chromosome numbers for 77 of these taxa are published here for the first time, previously published chromosome numbers of 19 taxa are verified, and numbers differing from those previously published are reported in 4 instances. Ten of the genera included here have been previously unknown cytologically. Polyploidy has been discovered in Bowlesia and confirmed in Pimpinella. Aneuploid series appear to occur in Eremocharis, Eryngium, Oenanthe, Perideridia, and Ptilimnium. Every chromosome count is referable to a cited herbarium specimen.

ANEUPLOIDY IN CLAYTONIA VIRGINICA

Rothwell, Norman V. (Long Island U., Brooklyn, N. Y.) Aneuploidy in Claytonia virginica. Amer. Jour. Bot. 46(5): 353–360. Illus. 1959.—Within the taxon, Claytonia virginica L., an extensive aneuploid series has been found including the following chromosome numbers: 2n = 12, 14, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 48, and 72. Studies revealed that a population could be composed of individuals differing in chromosome number. Pollen fertility appears to be high in natural populations and in plants showing meiotic irregularities. Different karyotypes were found within the taxon; plants having the same chromosome number may have different karyotypes. Hybrids have been obtained as the result of crossing plants differing both in number and karyotype. From all the evidence, C. virginica appears to be able to tolerate transitions from one cytological type to another. The hypothesis is proposed that most of the various numbers have been derived from a haploid complement of 8 chromosomes possessing median centromeres. The following factors are suggested to account for the origin of the different numbers: nondisjunction, univalent lagging, misdivision of univalents, polyploidy, and fertile triploids.