Hexaploid Forms Research Articles

Cytogenetic study of Helianthus laevigatus and its F1 and BC1F1 hybrids with cultivated sunflower, Helianthus annuus

AbstractAlthough the wild sunflower species Helianthus laevigatus has not been extensively studied it may be considered for sunflower breeding as a potential source of desirable genes for Sclerotinia stalk rot resistance and high contents of proteins and linoleic acid in the seed.A set of six H. laevigatus populations was crossed to cultivated sun~ower lines and produced nine F1 (2‐14 plants) and 66 BC1F1 hybrid combinations (1‐13 plants). Male sterility occurred in F1 and BC1F1 hybrid combinations and pollen viability was lower in the progenies than in the parents (51.6‐77.2%in F1 and in F1 and 4.8‐34.0% in BC1F1). Meiosis was normal in the H. laevigatus populations It was found that this tetraploid species also occurred in a hexaploid form Numerous irregularities were observed in the meiosis of the F1 interspecific hybrids During diakinesis, quadrivalents and hexavalents were recorded in addition to bivalents Dislocated chromosomes and chromosome bridges were present in the other phases The chromosome number in F1 was 68 (tetraploid). Irregularities in chromosome pairing were observed in the interspecific hybrids at BC1F1. There were many univalents, and trivalents quadrivalents and hexavalents were also present The chromosome number in the BC1F1 generation ranged from 34 to 60. The occurrence of meiotic irregularities in the F1 and BC1F1 interspecific hybrids indicates that H. laevigatus and the cultivated sunflower differ in genome constitution.

Variation in Populations of Tribulus terrestris (Zygophyllaceae) .2. Chromosome Numbers

Variation in chromosome number was investigated as part of a study to identify the origins of the widespread weed and potential biological control target Tribulus terrestris L. s.1. (Zygophyllaceae). Three ploidy levels, tetraploid 2n = 24, hexaploid 2n = 36 and octoploid 2n = 48, were detected in 24 Australian and 24 overseas collections. Northern Territory and Queensland collections, possibly representing a native species of Tribulus, had counts of 2n = c. 24. The majority of collections of T. terrestris in southern and north-western regions of Australia had counts of 2n = c. 36, but two collections had counts of 2n = c. 24. Collections from South Africa and Namibia also had a mixture of tetraploid and hexaploid forms. The USA, Mediterranean and West Asian samples (except for three Kuwait samples) were all hexaploid. All Indian and three Kuwait samples were the only octoploid collections observed. These ploidy levels agree with those previously reported for T. terrestris. It was concluded that the polyploid complex has an allopolyploid origin. The predominantly hexaploid collections in Australia indicate an overseas origin, and the presence of two tetraploid collections points to two or more separate introductions of T. terrestris into Australia. Counts for T. micrococcus and T. occidentalis were 2n = c. 48, which provide further evidence for a base number of x = 6 or 12 for the genus.

Slower Moving to the Anode Malate Dehydrogenase Isozymes of Rye, Wheat and Triticale Seeds

Summary The author's own modification of Davis' method (1964) for protein electrophoretic separation was used in an analysis of protein extracts from seeds of tetraploid and hexaploid forms of triticale, diploid and tetraploid rye, T. aestivum, T. durum . Results substantiated the conclusion that the slower moving to the anode isozymes were dimers. This corresponded to data from the dissociation — recombinant analysis of the mixture of T. durum and rye extracts. It was found that the two groups of isozymes separated specially on the gel differed in their relation to 2 M urea in the protein extract — those moving fast lost their activity completely, while the ones moving slower remained almost unchanged. This fact is connected with the known reference data that the most anodic isozymes in wheat and barley are from the fraction of cytoplasmic malate dehydrogenase (McDaniel 1969; Newton 1983). It was presumed that malate dehydrogenase isozymes of rye, wheat and triticale seeds moving slower to the anode belong to the mitochondrial fraction. It is pointed out that the reaction of malate dehydrogenase isozymes to urea in suitable concentrations could be used as an easily applied criterion differentiating the two basic types of malate dehydrogenase isozymes in a total protein extract.

Progressive Differentiation of Spikelet Types in Relation to Ploidy in the Genus Avena

AbstractIn the study of interspecific and interploidy hybrids of Avena the order of spikelet types in the recessive < dominance sequence was found to be as follows: N1 (naked type) < C1,2 (cultivated, type) < W1,2 (wild type) < S1,2 (subwild type) < W3 < S3 < C3 < N(1)3, where superscripts 1, 2 and 3 indicate the spikelet type of diploid, tetraploid and hexaploid species, respectively. Nullisomic studies of hexaploid species showed that chromosome MK‐9 of the 3rd genome controlled multiple alleles W3, S3 and C3 types, except N(1)3 type, and synapsis of meiotic chromosomes. Its homoeologous chromosomes of the 1st and 2nd genomes appeared to affect the W type (probably introduction of W1 and W2) as well as meiotic asynapsis. The asynapsis might be induced by deficiency of a synapsis‐gene(s) in a primary hexaploid form or species. The N(1)3 type probably occurred by dominant or epistatic mutation of the W1 type in A. sativa, and the C3 type hidden was present. The maintenance of such a heterozygosity system may be mainly due to diploid‐like pairing of chromosomes on the balance between the synaptic and asynaptic gene functions.

D genome donors for Aegilops crassa (DDMcrMcr, DDD2D2McrMcr) and Ae. vavilovii (DDMcrMcrSpSp) deduced from esterase analysis by isoelectric focusing.

Putative D genome donors to Aegilops crassa (2n=4x=28, DDMcrMcr and 2n=6x=42, DDD2D2McrMcr) and Ae. Vavilovii (2n=6x=42, DDMcrMcrSpSp) were studied for esterase isozyme similarities. Esterase isozymes examined by gel isoelectrofocusing reveal no inter- or intraspecific variation in Ae. crassa and Ae. Vavilovii. The putative parents, Ae. Squarrosa (2n=2x=14, DD) and Ae. comosa (2n=2x=14, MM), each exhibit three isozyme phenotypes. The natural tetraploid form of Ae. crassa has an isozyme pattern corresponding to a mixture of esterases from type 2 squarrosa and type 1 comosa. We conclude from this that the D genome donor to Ae. Crassa 4x is type 2 squarrosa. The hexaploid form of Ae. Crassa possesses the same D genome as the tetraploid form, suggesting a duplication of the type 2 squarrosa D genome. Moreover, the D genome of the hexaploid form is the same as the D genome of Triticum aestivum cv. Chinese Spring (bread wheat, 2n=6x=42, AABBDD). It was also found that the putative D genome donor to Ae. Vavilovii corresponds to type 2 squarrosa.

Variation in Populations of Claytonia perfoliata (Portulacaceae)

Variation in Populations of Claytonia perfoliata (Portulacaceae)

Chromosome Pairing in Triploid F1 and Hexaploid F1, F2, and F3 Generations of Gossypium Hirsutum L. ✕ G. Sturtianum Willis1

Chromosome pairing was studied in the triploid F1 and the hexaploid F1, F2, and F3 generations of Gossypium hirsutum L. (AD genome) ✕ G. sturtianum Willis (C genome) hybrid. Pairing in the hexaploid forms in each generation was essentially homogenetic indicating that the transfer of agronomic characters between genomes by conventional breeding methods for cotton improvement would be difficult.

DOĞU ANADOLU'DAN TOPLANAN KAFKAS ÜÇGÜLÜ (Trifolium ambiguum M. Bieb.) ÖRNEKLERİNİN KROMOZOM SAYILARI ve BAZI MORFOLOJİK ÖZELLİKLERİ

Dogu Anadolu'dan toplanan kafkas ucgulu ornekleri, poliploid formlarin tesbiti icin, kok uclarinda kromazam sayimi yapilmak uzere saksilarda koklendirildi. Koklendirilen bitkilerden alinan kok udannin doymus poradichlorobenzene eriyiginde S-lO°C sicaklikta 3 saat beklettikten sonra aseto-orsem-hidroklorik asit ile boyanmasindan iyi sonuc alinmistir. Kromozom sayimi sonunda kafkas ucgulunun diploid (2n=16), tetraploid ve hekzaploid formlarinin Dogu Anadolu'da dogalolarak yetistigi ilk defa tesbit edilmistir. Morfolojik karakter/er bakimindan bitkilerin kromozom sayisi arttikca ortalama deger/erde de bir arti§ olmustur. Ancak degerlerin dagilisinda formlar arasinda genellikle bir gecis giirulmektedir. Bu durumda adi gecen karektedere gore poliploid formlari kesin olarak ayirt etmek mumkun gorUimemektedir. CHROMOSOME COUNTS IN THE ROOT TIPS AND SOME OF THE MORPHOLOGICAL CHARACTERS OF CAUCASIAN CLOVER (Trifolium anibiguum M. Bieb.) COLLECTED FROM EASTERN ANATOLIA Chromosome eounts were made In the i oot tips of Caucasian clover collected from eastem Anatolia, in order to determine ploidy level of the plants. The best and rapid preparation was obtained by keeping root tips in the paradiehlorobenzene solution for 3 hours and staining with aeeto-orceinHCL solution (BaysaL, 1966 and 1968). Root tips obtained from the pla,nts, which were growing in the pots, were put into a saturated paradichlorobenzene saluiion for 3 hours at 8-io°C. Of the Imm, tip of the roots were cut, cleaned and transferred to a mixture of i.5 % ateco-orcein and 0.5 normal HCL solution in the proportion of 10 to I. The root tips were heated over a name up to boiling points (5-10 seconds) and than were left for cooling. The root tips were transferred to one drop 45 % acetic acid and squashed. For practically permenant slide, a smalll drop ori u % glycerine in 45 % acetic acid (Rattenbury, 1956) was placed at the margin ofthe CQverslip and allowed to now undei as the aqueous portions evaporates. If bubbles appeai after a day or two, another drop of the glycerine solution may be added. After the chromosome couting, polyploid series of diploid (2n=16), tetraploid and hexaploid forms of Caucasian clover were established. This was done for the first time among the p1ant materials colleeted from eastem Anato1ia. B. Morphologicat characters 1. Middle leaflet length, width and index (lengthfwidth) and length of stoma and stipu/e: Mean values of these characters increased with p10idy. However an overplapping in· the ranges showed that these characters will not be positive criterion, for establishing the ploidy leve1 of a giyen planL - The mean middle /eaflet legih was 32.9±2.25 in diploids, 40.2±2.-58 in tetraploids and 58.1 +0.94 mm. in hexaploids. The range of this value was from 24.7 to 62.5 mm. in tetraploids. Diploid and hexaploid mean values were within this range. The mean midd/e leaflet ividlh was 18.3±0.88 in diploids, 16.8±O.l4 in tetraploids, and 24. i ±0.51 mm. in hexaploids: Tne mean middle leajlet index was 1.8±0.02 in dipolids, 2.4±0.05 in tetraploids and 2.4±0.33 in hexaploids . MinImum index value (1.3) was in diploids and maxumim (3.4) in tetraploids. The mean stoma /engtli was 21. 8±0.05 microns in diploids, 24.7±0.01 microns in tetraploids, and 33.1 ±O.02 microns i? bexaploids. it migth be possible to identify the bexaploids, from 64 other two forms, wItb greater mean value and range (31.4-34.2 microns). 2. Head length and width and plani heigh/: Varied mean values witb 1'10idyle vels were obtained for these cbaracters. There was an overlap between ploidy levels in the disribution of the values. The mean head length was 29.1 ± 0.46 mm. diploids, 29.±4.021 in tetraploids, and 29.5±0.39 mm. in hexaploids. The mean head width was 25.1 ±0.46 mm. diploids, 23.8±0.10 in tetrapIoids and 29.5±0.39 mm. in bexapIoids. The mean plant height was 12.3± 0.76 cm. in dip10ids, 9.3±0.43 cm. in tetraploids and 28.5±0.64 cm. in hexaploids. There were erect, semi erect and prostrate, pJants in dip10ds and tetrapIoids. All hexaploids were erect. 3. FIOlver and pistil length, ca/yx length and width, calyx teeth /ength and pal/en grain size: VaIues obtaincd for these cabaracters varied with 1'10idy level of plants. The mean f/over length was 12.7± 0.11 mm. in diploids, 12.3±u.04 in tetrap10ids and 16.2±O.15 in hexaploids. Pisti! length and width and calyy: teeth /engt mean values: in diploids mean values of calyx lengtb (5'-1 ±O.OS mm.) and clayx teeth length (2.1 ±O.O1) were greater tban tetraploids (4.3±0.03 and 1.3±0.01 mm. resepc.tIvely); mean calyx width in tctraploids (I-.9±0.01 mm.) was graetar tb an diploids (1.8± 0.05 mm.) Mean calyx length and width, and calyx teeth !ength of hexaploids (6.9±0.09, 2.6±0.03, 2.6±00.2 respectively) were greater then the other two fonns.· These charcateristics can be used to distinguish hexaploids from other two fonn. Average pol/en grain size was 29. 1±0.04 microns in diploids 32.2±0.01 microns in tetraploids and 35.1 ±0.03 microns in hexaploids.

Chromosome numbers in some species ofIschaemum linn- andSehima forsk. In parts of Western India

Somatic and meiotic chromosome numbers in 13 species ofIschaemum and two species ofSehima have been reported. Most of these numbers either constitute new reports or a revision of the earlier reports. Basic chromosome number seemed to be 10 inIschaemum andSehima with incidence of polyploidy ranging from diploid to hexaploid forms inIschaemum and diploid to tetraploid forms inSehima.

CYTOGENETIC RELATIONSHIPS OF KEY DIPLOID MEMBERS OF THE MIMULUS GLABRATUS COMPLEX (SCROPHULARIACEAE).

The Mimulus glabratus complex of related species and varieties exhibits an unusual polyploid series-unusual in that the polyploid levels increase from north to south throughout almost the entire length of the Western Hemisphere. Scattered populations of the diploid forms are found from southern Canada to northeastern Mexico and from eastern California to the Great Plains. The relatively rare tetraploids occur along the southern limit of the distribution of the diploids from southern California to northeastern Mexico. The aneuploid-tetraploids range from northern Mexico to southern Guatemala but are common only in the highlands of central Mexico. Occasional populations of the hexaploid forms are found throughout much of South America from high in the Andes of Columbia to the plains and mountains of southern Patagonia (Vickery, 1966, 1969). This pattern of distribution suggests that the M. glabratus complex spread southward from North America almost to the tip of South America in at least four successive adaptive radiations-first the diploids, next the tetraploids, then the aneuploid-tetraploids, and finally the hexaploids. Each of these adaptive radiations appears to have been initiated by one or more mutations that changed the chromosome number and the climatic tolerance, competitive ability, or other attributes of that member of the complex which allowed it to spread into new areas. All of the various mutations, whether polyploid or aneuploid, appear to involve the diploid forms either directly or indirectly. Therefore, a thorough cytogenetic understanding of the diploid forms ought to provide insight into the pathways by which the tetraploids and hexaploids arose. So, this study was initiated to investigate the cytology and crossing behavior of key diploid forms and thus provide some of the basic information needed for our long-range goal of elucidating the evolutionary relationship of the entire M. glabratus complex.

Meiotic chromosome pairing in Triticale.

CONSIDERABLE attention is currently being paid to the possible use of Triticale as a new crop; indeed, a variety has already been named in Canada1. Triticale is a hybrid genus of synthetic amphiploids which have the full chromosome complements of wheat (Triticum) and rye (Secale). Octoploid forms, of Triticale have fifty-six chromosomes, made up of the forty-two of the hexaploid bread wheat (T. aestivum) and the fourteen of a rye species. Hexaploid forms have forty-two chromosomes, comprising twenty-eight from one of the subspecies of tetraploid wheat (T. turgidum) and fourteen from rye.

Cytogeography of Achillea Millefolium in Western Oregon

A cytogeographic study was made of the tetraploid and hexaploid forms ofAchillea millefolium L. in western Oregon in order to clarify their distributions, to determine whether pentaploid hybrids are present at zones of contact between the two, and to correlate environmental conditions with the presence of the tetraploid in the coastal areas of Coos and Curry Counties, Oregon. The distributional pattern of the two chromosome forms was found to be more complex than previously reported, involving overlapping of ranges, the occurrence of mixed populations, and the presence of disjunct populations of one form in areas occupied by the other. A naturally occurring pentaploid hybrid with meiotic pairing of 18 II’s and 9 I’s was found, which could not be distinguished morphologically from the presumed parents. The coastal tetraploid form in southwestern Oregon is limited to the Siskiyou Mountains. Plants of this area, especially those at its geographical margins, were observed to be producing a large number of viable, unreduced pollen grains. It is suggested that the North American hexaploid form originated by autopolyploidy from earlier existing tetraploids.

Karyotypic Studies in someLoliumandFestucaSpecies

SUMMARY1. Karyological investigations of some twenty-four species in the Lolium-Festuca group were made as a preliminary to meiotic studies of selected species and hybrids. Comparative studies were made on relative length and arm ratio of all the chromosomes in the various species. The chromosomes with secondary constrictions were classified into sixteen types and designated as A.B,C,……J.2. In the Lolium species, which were all diploid, three inbreeding species, L. temulentum, L. remotum, L. loliaceum and four outbreeding species, L. multiflorum, L. westerwoldicum, L. rigidum and L. perenne were studied. (a) These studies confirmed that the basic karyotype was similar in the two groups and all the species had three pairs of satellited chromosomes. However, the two groups could be differentiated clearly on the basis of a difference in the position of the secondary constriction in chromosome 1. (b) Significant differences in relative chromosome length and arm ratio between corresponding chromosomes of different species were found. (c) There appeared to be more variability among the outbreeding species in respect of the various chromosome characters than in the inbreeding species. (d) It is concluded that many chromosome rearrangements have occurred in the differentiation of the various species but gene mutations must also have been involved.3. In Festuca seventeen species and six populations of tall fescue belonging to the sections Ovinae, Bovinae, Scariosae, Montanae, Sub-bulbosae and Variae were studied. (a) All the diploid species differed in their karyotypes both with respect to relative length and arm ratio and the satellited chromosomes were distinct in the different species. (b) Karyotypes of F. arundinacea var. glaucescens (2n = 28) indicated similarities of some of its satellited chromosomes with those of F. pratensis (2n = 14) and F. Mairei (2n = 28). In addition, similarities were also discerned between glaucescens and two other forms of F. arundinacea (2n = 42,70). This indicated the phylogenetic relationship of these forms. (c) The tetraploid form of F. spadicea included some of the satellited chromosomes of its diploid form. Similar relationships were found between satellited chromosomes of the hexaploid forms of F. ampla and F. rubra with their octoploid forms respectively.4. Special attention was given to the karyotypic analysis of one indigenous and six exotic populations of F. arundinacea (2n = 42). There was positive evidence of chromosomal differentiation between the populations. (a) The indigenous population had four satellited pairs whereas introduced ones had five to eight pairs. In addition diversity with regard to the size and shape of the satellites of different populations were also found. This variation was also observed with regard to arm ratio and relative length. (b) Chromosomal repatterning as a result of segmental inter-change, inversion and deletion must have played some significant role in the differentiation of tall fescue.5. Such karyotypic variations were also found in other species including F. Mairei, glaucescens, arundinacea (2n = 70). Apparently chromosomal repatterning is well spread and possibly perpetuated by vegetative reproduction.6. The following general conclusions were also drawn: (a) The separate status accorded to the two genera Lolium-Festuca is supported. (b) In the evolutionary process there was no change in the basic chromosome number for the species in this group and there was evidence to support the view that the two genera had a common origin. Compared with the diploids the polyploids were of relatively recent origin. (c) From a study of chromosome asymmetry in the different species it was possible to evaluate the evolutionary trends in the genus Festuca and to show the significant part played by polyploidy in speciation.

COLCHIPLOIDY AND HISTOLOGICAL IMBALANCE IN TRIPLOID APPLE AND PEAR

Colchicine treatment of the triploid apple varieties ‘Paragon’ and ‘Stayman’ resulted in 6–3–3 and 3–6–6 chimeras, and 6–3–3 chimera in ‘Baldwin.’ Treatment of a triploid pear selection ‘U.S. 44–3–1’ resulted in totally 6x as well as 6–3–3 and 3–6–6 chimeras. As triploid plants are not suitable for breeding, sexually hexaploid forms (totally 6x or chimeral 3–6–6) of high‐quality triploid apples and pears may become very useful as breeding material. The primary purpose of treating the ‘Stayman’ apple was to obtain a 6–3–3 chimera to find out if large cells in the epidermis would reduce or eliminate the severe cracking of fruit of this variety which occurs in some seasons. Chimeral forms in the other plants were to serve as material for comparison with the ‘Stayman’ variety. Observations on the fruit‐cracking problem will have to wait until the chimeral plants fruit. Hexaploid tissue in chimeral shoots of all affected plants has grown more slowly than triploid tissue, causing various degrees of malformation of the leaves. Similar reduction in growth due to restricted ploidization in 4–2–2 or 2–4–4 chimeras has not resulted in many other plants, including apples and pears, but was reported in an 8–4–4 chimera in cranberry. Slower growth of 6x tissue in the apple and pear may be attributed to the presence of multiple homologous genes in the duplicated chromosome forms of these particular triploid plants.

Cytology of tetraploid x hexaploid timothy (Phleum pratense L.)

Ten pentaploids were isolated from seedling populations developed from seed of tetraploid plants grown in association with hexaploid timothy. About 80% of the prophase sporocytes exhibited severe or moderate pycnosis. These pycnotic accumulations appear to arrest the meiotic processes and apparently result in sporocyte lethality. Surviving sporocytes at diakinesis possessed nuclei with configurations that varied from 1 VI+14 II+1 I to 9 II+17 I. It is suggested that the conventional sorts of irregularities (univalents, inversions and translocations) cannot account for the low percentages of stainable pollen. Pairing relations indicated that considerable duplication and/or autosyndesis occurred in the genomes combined, and suggest that even though the tetraploid (2n=28) and hexaploid (2n=42) forms of Phleum pratense are closely related they are not identical. A portion of the sterility observed may be due to nuclear-cytoplasmic interaction.

Biosystematics ofSisymbrium IrioComplex

SUMMARY AND CONCLUSIONSA comparison of habitat preferences, morphological characters and pollen and seed fertilities of the various races within the Sisymbrium irio complex has been made.Pending cytological evidence, it could be concluded from the above comparisons that the various races have not arisen due to the autoploidy of the genome of the diploid. Had it been so, then there would be uniform differences of only quantitative nature among the five races. That these races have genomes completely different from one another, is also ruled out since there do exist some basic resemblances between all of them. However, the complex constitutes a single phylogenetic unit in which the different characters are shared by various races to varying extent. This has caused « reticulation » in relationship. It is clear that morphologically the diploid, triploid and hexaploid form a single group and the tetraploid and octoploid form the other group. There are, however, some differences among the members of each group....

CYTOLOGICAL STUDIES IN THE GENUS AGROPYRON

Eighteen species of the genus Agropyron from Western Canada, Russia, Siberia, and Denmark formed a polyploid series with a basic number of seven chromosomes. Di-, tri-, tetra- and octaploid forms were found among Western Canadian species; di-, tetra-, penta-, hexa- and decaploid forms among the Russian and Siberian species; di-, tetra- and hexaploid forms among the Danish species.The forms collected in Western Canada showed an extremely wide range of morphological variability both within and between the various species. This is probably due to natural hybridization such as has been reported between certain native species in Russia and Denmark. The cytology of these European species and their supposed hybrids has been studied here and has shown that natural crossing has probably taken place between diploid and hexaploid species in some cases and between tetraploid and hexaploid species in others. Some evidence of a similar situation among Western Canadian species has been found. Chromosome doubling, triploidy and aneuploidy occurred in certain of the latter. The relation of these phenomena to hybridization is discussed.