Diploid Cytotypes Research Articles

Cytogenetic analyses in Paspalum L. reveal new diploid species and accessions

Chromosome numbers were counted in 126 new accessions of 50 Paspalum species from Brazil, Argentina, Paraguay and Bolivia. The chromosome numbers 2n=12, 20, 24, 30, 40, 50, 60, 80 were confirmed. Chromosome numbers for P. arenarium (2n=20), P. barretoi (2n=20), P. aff. ceresia (2n=40), P. corcovadense (2n=20), P. crispulum (2n=20), P. flaccidum (2n=40), P. nummularium (2n=20), P. scalare (2n=20), P. vescum (2n=20) and P. rectum (2n=20) and a diploid cytotype of P. malacophyllum are reported for the first time. The predominance of tetraploid accessions (43.6%) was confirmed, but an unusually high number of diploid species (44%) and accessions (35.7%) was found. These results open new perspectives for breeding programs, phylogenetic studies, and for research on apomixis control, since diploids of Paspalum are typically sexual.

Revision of the Solanum medians Complex (Solanum section Petota)

Solanum medians is a widely distributed species of wild potato (Solanum sect. Petota), growing along the coastal lomas and up the western slopes of the Andes Mountains from central Peru and northern Chile, from 200–3800 m elevation. Fertile diploid and sterile triploid cytotypes are common, are believed to be associated with morphological variants, and are formally named as subspecies. A morphometric study based on principal components and canonical discriminate analyses of characters obtained from herbarium specimens tests the circumscription of these subspecies and other currently recognized species that are very similar to S. medians. The results show so much overlap of these taxa that it is impractical to use morphology to define species or to provide reliable keys or identifications. We synonymize ten names under S. medians: S. medians var. angustifoliolum, S. medians var. majorifrons subvar. majorifrons, S. medians var. majorifrons subvar. protohypoleucum, S. medians var. autumnale, S. sandemannii, S. tacnaense, S. weberbaueri var. decurrentialatum, S. tacnaense f. decurrentialatum, S. weberbaueri, S. weberbaueri var. poscoanum. We also treat S. neoweberbaueri as a closely related species to S. medians. We consider the synonymy in S. medians to be part of a much larger need for reduction of names in sect. Petota.

Morphometric and genetic differentiation of diploid and hexaploid populations of Aster amellus agg. in a contact zone

The aim of this study is to determine the origin, genetic relationships and morphological differences between diploid and hexaploid cytotypes of Aster amellus aggregate (Asteraceae) at their contact zone in the Czech Republic. We collected data on morphological and isozyme variation in a range of populations of the two cytotypes. We also studied the plasticity of the morphological traits in a common garden. The results suggest that hexaploid individuals of Aster amellus aggregate are of autopolyploid origin. The isozyme data indicate that diploids and hexaploids have different evolutionary histories. This, together with previous detailed cytological and ecological analyses, suggests that there is a secondary contact zone between the two cytotypes in the Czech Republic. The results of multivariate morphometric analyses and data on plasticity of the morphological traits indicate that it is not possible to distinguish the two cytotypes morphologically. The previously published morphological distinction between the cytotypes is thus not supported.

Cytogenetics, geographical distribution, and pollen fertility of diploid and tetraploid cytotypes of Santolina pectinata Lag. (Asteraceae: Anthemideae)

A cytogenetic study of 62 populations of Santolina pectinata in Spain shows the existence of two ploidy levels. The diploid cytotypes with 2n = 18 occupy the eastern Betic mountains, and the tetraploid cytotypes with 2n = 36 are located on the spurs of the Iberian System. The former show a much wider ecological spectrum than the latter. Mixed cytotypes were observed in two diploid populations, with one tetraploid in each, showing different karyotypes. Three trisomic individuals were detected, one in a diploid population and the other two in a tetraploid population. Also, three hypotetraploid individuals were detected in a tetraploid population. Polyploidy is shown to be spontaneous and recurrent, promoting partial sterility in the pollen. Structural chromosomal changes, principally translocations, and local speciation through autopolyploidy are the principal factors in the evolution and diversification of this species. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 657–667.

Structure des infrutescences et capacité fructifère de deux cytotypes de Lygeum spartum L. de l’ouest algérien

Lygeum spartum, the only species of the genus Lygeum, is present in Algeria either as a diploid (2n = 16) or a polyploid (2n = 40) cytotype. Our results show that the two cytotypes differ in spikelet morphology and reproductive capacity. The diploid cytotype has more vigorous fructifications with lemmas characterized by shorter distal parts, a character which can be used for an easy recognition of the cytotype in the field. It is present only in isolated stations of the high plateaus (e. g. at Kheiter and at Aïn Benkhellil, stations 100 km apart). The polyploid cytotype, in spite of a higher number of defective fructifications (between 12 and 17%) and a higher percentage of aborted flowers (21.94% against 9.01%), can be found in stations localized either in the littoral, saline region or on the semi-arid high plateaus. Thus, the two cytotypes differ by morphological, biological characters as well as by their geographical location. Further in situ observations based on the present results would lead to a better understanding of the extension potential of both cytotypes in view of better management, protection and regeneration of Lygeum spartum communities.

Meiotic Studies in Species from the Cold Deserts of Lahaul-Spiti and Adjoining Areas (Northwest Himalaya)

Meiotic investigations were carried out on 29 species of 13 Polypetalae families from the cold deserts of Lahaul-Spiti and adjoining areas of north-west Himalaya. Additional/varied cytotypes have been reported for two species for the first time. The present chromosome count of 2n=18 in Hypericum elodeoides adds a new cytotype to the existing diploid (2n=2x=16) chromosome number. The meiotic count of 2n=2x=14 in Potentilla fruticosa var. rigida adds a new diploid cytotype to the already existing tetraploid (2n=4x=28) cytotype. The chromosome numbers of 10 species viz. Aquilegia fragrans (n=7), Silene vulgaris (n=12), Astragalus bicuspis (n=8), Cicer microphyllum (n=8), Potentilla fruticosa var. rigida (n=7), Melilotus officinalis (n=8), Rosa webbiana (n=7), Bergenia stracheyi (n=17), Sedum ewersii (n=11) and Datisca cannabina (n=11) are new records for India. The cytomixis involving the inter pollen mother cell transfer of chromatin is observed in Caltha palustris, Astragalus bicuspis, Meconopsis aculeata, Melilotus officinalis, Potentilla fruticosa var. rigida and Trifolium pratens. In Caltha palustris the cytomixis (20–28%) results into various meiotic abnormalities and heterogeneous sized pollen grains. In other species the frequency of PMCs (pollen mother cells) involved in chromatin transfer is very low (0.1–1%) without affecting the pollen fertility.

A systems study of lotus's leaf area

PurposeA systematic study of a lotus's leaf area is described through the genetic improvement of Lotus glaber, an induced tetraploid population known as, Leonel, was obtained. Initial assessment showed an increase in dry material in comparison with a diploid population. The aim was to evaluate whether the increased production of forage found in the tetraploid population Leonel was due to increased foliolae sizes.Design/methodology/approachThree populations were studied L. glaber: diploid cytotype: seeds from a naturalised population of La Pampa Deprimida (Azul, Argentina); Tetraploid cytotype C1 seeds from the Leonel population, and Lotus corniculatus (Italia) seeds from Italy. Analysis of variance was carried out with a random design using a single factor, for the variables of area, length and width of the central foliolae. Linear and non‐linear model families were determined to estimate the area of the central foliolae. The selection criteria applied were: the best R2, good efficiency, the greatest simplicity of the model and its stability.FindingsThe widths of the L. glaber diploid foliolae were less than those of L. corniculatus tetraploide and these were longer. The areas of the L. glaber foliolae were greater than those of the tetraploid L. corniculatus, and the areas of the foliolae of the diploid cytotype were slightly superior to the induced tetraploid cytotype L. Leoner. The best model was that which estimated the area of the central foliolae according to their width.Practical implicationsNon‐destructive estimates of foliar area were obtained for different species of the Lotus genus. The methodology chose provides a useful example of a systemic approach.Originality/valueThe variables studied are significant morphophysiological characteristics that can be used in programmes for the genetic improvement of L. glaber and L. corniculatus.

Hieracium × grofae — a rediscovered diploid hybrid from the Ukrainian Carpathians

Diploid hybrid plants (2n = 18) between sexual diploid cytotypes of Hieracium alpinum and H. umbellatum were found in the Ukrainian Eastern Carpathians. They were identified with H. × grofae Wol., originally used for the combination H. decipiens × H. umbellatum var. lactaris. As H. decipiens sensu Wol. (non Tausch) does not produce viable pollen grains and is most probably a polyploid apomict, it is unlikely to produce diploid hybrid plants with diploid H. umbellatum. Both parent species, Hieracium alpinum and H. umbellatum are also given by Woloszczak from the original locality. Thus we conclude that H. × grofae is result of hybridization between H. alpinum and high mountain form of H. umbellatum. Hybrid plants are morphologically intermediate between the parent species, and moreover resemble closely or they are identical with the experimental hybrids of the same parent combination. Hybrids produce rather high amount of homogeneously sized pollen grains (values of standard deviation and coefficient of variation lower then upper limits for diploids — 3μm or 7.5%, respectively), and might probably serve as male parents in further crosses; on the other hand, they are fully seed-sterile. A lectotype of H. × grofae, a second proved nothotaxon in the genus Hieracium s.str., is designated. Localities of H. × grofae are located in subalpine belt of the Marmarosh Mts, the Svydovets’ Mts and the Horhany Mts (all in the Ukrainian Eastern Carpathians). Biotopes of hybrid plants usually represent secondary formed and disturbed pastures allowing close contact of altitudinally vicariant parent taxa.

Identification of an EcoRI restriction site for a rapid and precise determination of β-asarone-free Acorus calamus cytotypes

Calamus ( Acorus calamus L., Araceae) is an aromatic herb, indigenous to Central Asia and Eastern Europe. The fragrant oils obtained by alcoholic extraction of the rhizome are mainly used in the pharmaceutical and oenological industries. Nevertheless, the occurrence of β-asarone [( Z)-1,2,4-trimethoxy-5-prop-1-enyl-benzene] limits the possibility of its use due to the carcinogenic properties of this compound. The aim of this work was to identify a diploid β-asarone-free A. calamus by using chemical and molecular approaches. For these purposes alcoholic extracts of both diploid and triploid A. calamus were analyzed by gas chromatography–mass spectrometry (GC–MS) and comparison of the 700 bp sequence of the non-transcribed spacer (NTS) in the 5S-rRNA gene was also performed. Alcoholic extracts of the triploid A. calamus were characterized by a higher percentage of β-asarone (11%), which was the main compound, followed by higher percentages of camphene (2.27%), E-β-ocimene (3.28%), camphor (1.54%), calarene (1.42%), α-selinene (5.02%) and τ-cadinol (2.00%), when compared to the diploid A. calamus. The latter had higher percentages of iso-shyobunone (8.62%), β-sesquiphellandrene (3.28%), pre iso calamendiol (22.81%) and acorone (26.33%), and completely lacked of β-asarone. The 5S-rRNA spacer region of both diploid and triploid A. calamus were amplified by PCR using a pair of primers located at the 3′ and 5′ ends of the coding sequence of 5S-rRNA gene. The resulting PCR products (about 700 bp) were gel purified, subcloned into pGEM®-T Easy vector and sequenced. By aligning the isolated nucleotide sequences of the two varieties and the sequences from different A. calamus chemotypes present in Genbank, sequence diversities were found in the spacer region. Furthermore, the PCR products were digested by using EcoRI. The restriction profile of the spacer domain resulted different for the two cytotypes. Along with chemical analysis of alcoholic extracts, sequence analysis coupled to restriction mapping was demonstrated to represent a powerful tool to distinguish the A. calamus diploid cytotype from the others. The security and effective usage of the diploid β-asarone-free A. calamus was also discussed.

Karyological observations onArtemisia albaTurra (Asteraceae)

Abstract Artemisia alba Turra from Calabria is karyologically studied (2n = 18). From the analysis of literature it results that this species shows three cytotypes, with a rather distinct geographical distribution: 1) diploids with 2n = 18, previously identified as A. alba subsp. chitachensis Maire (name which is here typified) or A. alba subsp. glabrescens (Willk.) Valdes-Bermejo. This diploid cytotype, known from Spain, Morocco and Bosnia-Hercegovina, occurs also in S Italy (Timpa di S. Lorenzo, Calabria). 2) Tetraploids with 2n = 36, generally identified with the typus subspecies. This cytotype appears the most widespread in northern part of the species range. 3) hexaploids with 2n = 54, known only from Abruzzo and Apulia. This cytotype seems of more recent origin, and is here considered of probable hybridogen origin between the 2n = 36 and 2n = 18 cytotypes. This unit can possibly be identified with A. columnae Ten. (= A. camphorata var. garganica Ten.). These latter names are lectotypified. We tested...

Triploid bridge and role of parthenogenesis in the evolution of autopolyploidy.

Autopolyploidization is considered to play an important role in plant evolution. In polyploidization, the polyploid evolves from the original diploid cytotype, in which the triploid state is considered to mediate the process (triploid bridge). Nevertheless, the fitness of triploid individuals seems to be too low to facilitate the polyploidization process (triploid block). The evolutionary condition of autopolyploidy was analyzed using a mathematical model focusing on the role of parthenogenesis in triploid and tetraploid individuals. In addition, offspring were assumed to arise by sexual reproduction by conjugations between haploid, diploid, and triploid gametes produced by diploid, tetraploid, and triploid individuals. According to the analysis, even if triploid block suppresses the fitness of sexually produced triploids, the polyploidization process can proceed when parthenogenesis occurs frequently. If only triploids frequently reproduce parthenogenetically, the evolutionary consequences tend to depend on the fitness of the tetraploid individuals. On the basis of a predetermined parameter set, if tetraploid fitness is relatively low, all three ploidies can coexist. Otherwise, tetraploidization occurs. In this case, triploid parthenogenesis promotes not only triploidization but also tetraploidization. However, if both triploids and tetraploids frequently reproduce parthenogenetically, the ploidy levels with the highest fitness are likely to dominate in the population through direct competition among cytotypes.

Karyo-taxonomic study of the genusPseudolysimachion (Scrophulariaceae) in the Czech Republic and Slovakia

Flow cytometry was used to determine ploidy levels in the Czech and Slovak taxa of the genusPseudolysimachion (W.D.J. Koch)Opiz (=Veronica auct. p.p.,Scrophulariaceae). In total, 123 populations from the Czech Republic, Slovakia, Ukraine (one locality), Austria (one locality) and Hungary (one locality) were analyzed. InP. maritimum (L.)A. Love etD. Love andP. spicatum (L.)Opiz, two cytotypes were found: diploid (2n=2x=34) and tetraploid (2n=4x=68). In both species the tetraploid cytotype predominated (P. maritimum: 41 tetraploid populations out of 45;P. spicatum: 57 tetraploid populations out of 58). The two cytotypes ofP. maritimum have no taxonomic significance because ploidy level is not obviously correlated with morphology, distribution pattern or ecology. Tetraploid populations ofP. spicatum belong to two morphologically different subspecies, subsp.spicatum and subsp.fischeri Travnicek. The diploid cytotype (one population only) should be provisionally classified as a third subspecies ofP. spicatum, which is morphologically similar to the Asian subsp.porphyrianum (Pavlov)Travnicek. Only diploid plants (2n=2x=34) ofP. orchideum (Crantz)Wraber were found; all 13 populations that were analyzed belong toP. orchideum s.str. One diploid population sample ofP. spurium subsp.foliosum (Waldst. etKit.)Holub (2n=2x=34) and one tetraploid sample ofP. incanum subsp.pallens (Host)Travnicek (2n=4x=68) were also analyzed. In addition, three tetraploid populations of hybrid origin were investigated:P. maritimum ×P. spicatum subsp.spicatum (one population) andP. maritimum ×P. spurium subsp.foliosum (two populations). While hybrid plants ofP. maritimum ×P. spicatum arose from tetraploid parental species, plants ofP. maritimum ×P. spurium probably resulted from a cross between tetraploidP. maritimum and diploidP. spurium. The putative origin and evolutionary importance of polyploids in thePseudolysimachion are discussed.

Extended genetic resources of Dactylis glomerata subsp. izcoi in Galicia (northwest Spain)

Dactylis glomerata subsp. izcoi, endemic to Galicia (NW Spain), includes diploid and tetraploid cytotypes. The present paper results from ongoing research on the distribution of Dactylis in Galicia. Tetraploids dominate all kind of habitats, but diploids do occur in restricted areas. After intensive exploration carried out by the Mision Biologica de Galicia, dealing with diploid populations of subspecies izcoi, 13 new diploid localities were recently detected along the ridge called “Macizo Galaico Duriense” three on the west side of the ridge and the remainder on the east, persisting in ancient habitats in the following communities: Quercetea robori-petrea, Erico-Ulicetalia, Ericion australis and Ulicion nanae. Two diploid populations have been detected for the first time in Coruna Province. However, no diploids were found on the west side (near the coast) of Coruna and Pontevedra Provinces, probably due to Atlantic influence.

Giemsa C-Banded Karyotypes of two Cytotypes (2x, 4x) of Psathyrostachys Lanuginosa (Poaceae; Triticeae)

The karyotypes of the diploid (2n = 2x = 14) and tetraploid (2n = 4x = 28) cytotypes of the outbreeding P. lanuginosa collected from one population in China were investigated by Giemsa C- and N-banding and AgNO3 staining. The complement of the diploid consisted of 14 large chromosomes: 8 metacentrics and 6 SAT-chromosomes, one metacentric and 2 submetacentric pairs, with small to minute, polymorphic, completely heterochromatic satellites. Except that only eight SAT-chromosomes were observed, the complement of the tetraploid matched a doubling of that of the diploid and indicated an autoploid origin. The existence of 12 chromosomes with nucleolus organizers was established through AgNO3 staining demonstrating nucleoli. C-banding patterns comprised from zero to three (2x), or four (4x) small bands per chromosome giving a low content of constitutive heterochromatin (< 3 percnt;). The level of banding pattern polymorphism was low. N-banding produced no bands. Variation in the size of nucleoli demonstrated a differential nucleolus forming capacity of nucleolus organizers among SAT-chromosomes. The basic karyotype was similar to those of P. fragilis, P. juncea and P. stoloniformis, indicating a close relationship and the presence of genome N. Meiotic analysis suggested the presence of a chromosomal rearrangement in the diploid. The frequency of interstitial chiasmata was high. Differences in pollen diameters differentiated the two cytotypes.

Genome relationships in the genus Dasypyrum (Gramineae).

To elucidate the genome relationships in the genus Dasypyrum and the ancestry of tetraploid D. breviaristatum, two cytotypes of D. breviaristatum and D. villosum were reciprocally crossed with one another. Chromosome pairing at the first metaphase of meiosis and fertility were examined in the F1 hybrids and the parental plants. The mean pairing configuration and mean arm pairing frequency in D. villosum-D. breviaristatum (2x) hybrids were 11.12I + 1.44II per cell and 0.107, respectively, and they were almost completely sterile. In D. breviaristatum (4x)-D. breviaristatum (2x) hybrid, up to seven trivalents were formed, and the mean pairing configuration was 3.38I + 3.20II + 3.74III + 0.005IV per cell. The mean arm pairing frequency and relative affinity calculated in that F1 hybrid were 0.915 and 0.641, respectively. Seven bivalents and seven univalents were characteristically formed in D. villosum-D. breviaristatum (4x) hybrids. Based on the present results, we clearly concluded that the genome of diploid D. breviaristatum is distantly related to the genome V of D. villosum, and that these two species have different basic genomes. We, therefore, proposed the symbol Vb for the haploid genome of diploid cytotype of D. breviaristatum. Moreover, we concluded that tetraploid D. breviaristatum is an autotetraploid with doubled sets of the genomes homologous with that of diploid D. breviaristatum, and we proposed the genome constitution VbVb for the haploid genome set of tetraploid cytotype of D. breviaristatum. Furthermore, from the chromosome pairing in the F1 hybrids involving Moroccan and Greek accessions, it was suggested that complicated rearrangements of chromosome structure have occurred in tetraploid D. breviaristatum in its natural populations across the entire distribution area.

Banding techniques on tardigrade chromosomes: the karyotype of Macrobiotus richtersi (Eutardigrada, Macrobiotidae).

This work represents the first attempt to define tardigrade chromosomes using banding techniques. Macrobiotus richtersi, a eutardigrade morphospecies with amphimictic diploid and thelytokous triploid cytotypes, was used as a model. Prime consideration was given to oocyte chromosomes because they are larger than those of spermatocytes and of mitotic chromosomes. With Giemsa staining, the chromatids of the 6 bivalents of the diploid cytotypes and those of the 17-18 univalents of the triploid cytotypes were very similar to each other and appeared rod- or flame-shaped. In the amphimictic strain, a chiasma was generally present in each bivalent at diplotene, whereas there were no chiasmata in the oocyte prophase chromosomes of the triploid strain. Both in diploid and triploid cytotypes, C-banding and fluorescence showed a heterochromatic centromeric band on the telomere of each chromosome oriented towards the spindle pole, indicating that all of them were acrocentric. Silver staining showed the presence of a NOR in only a pair of chromosomes, close to the centromeric C-banded site. NOR was particularly evident in the oocyte prophases. Other silver positive regions, corresponding to the kinetochore, were located on all other chromosomes on the telomeres towards the spindle pole.

Speciation in Chenopodium in West Bengal, India

Two diploid cytotypes of Chenopodiumalbum have earlier been proposed as the probable ancestors ofhexaploid C. album in Gangetic Plainof West Bengal on the basis of cytomorphological data. The present study withthe diploid cytotypes of C. album (onebroad leaved, another narrow leaved), one wild species, C.murale and the hexaploid C.album utilizing parameters like seed protein, isozyme,RAPD, tissue culture along with conventional cytomorphological data supports ourearlier hypothesis of allopolyploid origin of hexaploid C.album. The results indicate that all the three diploidprogenitors have contributed for the evolution of present day semi-cultivatedhexaploid C. album. This study furthersuggests that the diploid cytotypes had been evolved sympatrically.

Rediscovery of a diploid cytotype of Dasypyrum breviaristatum in Morocco

The chromosome numbers of a total of 273 Dasypyrumbreviaristatum plants sampled from 20 Moroccan and one Greek naturalpopulations were examined. 270 plants from all of the populations weretetraploids. Among them, 223 were eu-tetraploids with 28 chromosomes and 47 wereaneuploids with 25, 27 and 29 chromosomes. Besides, three plants were found tobe diploids among 16 plants from a population in the Moyen Atlas Mountains ofMorocco. This is the second report of a diploid cytotype ofD. breviaristatum since the firstcommunication in 1957. Morphologically, the diploids were similar to but smallerthan the tetraploids in plant height, spike length, spikelet number and leafepidermis cell size. However, it was not possible to distinguish between the twocytotypes based on those morphological characteristics alone. A distinctdifference was found between the two cytotypes only in the number of trichomeson the leaf surfaces. The karyotype of the diploid cytotype consisted of a pairof SAT-chromosomes, five pairs of metacentric and a pair of submetacentricchromosomes. Based on the similarity in karyotype and in plant morphologybetween the two cytotypes of D.breviaristatum, we suggest that the diploid cytotype is themost probable candidate for the ancestral form of the tetraploid cytotype.

Non-adaptive hypothesis of allopatric cytotype distribution inMyosotis lamottiana (Boraginaceae)

In order to provide insight into the possible differentiation withinMyosotis lamottiana, which is a classical example of a species with a disjunct distribution area, a morphological analysis of 12 populations and a chromosome number analysis of 15 populations were made. Conspicuous chromosomal differentiation was observed comprising diploids (2n=22) and tetraploids (2n=44). The diploid chromosome number is reported for the first time for this species. Diploid and tetraploid cytotypes differ in geographical distributions; diploids are restricted to the Massif Central and tetraploids to the Pyrenees, Mt. Picos de Europa and the Cantabrian Mountains. A detailed morphometric analysis, however, revealed no clear-cut differences in the morphology of diploids and tetraploids except for pollen size, which is a character obviously correlated with ploidy level. No obvious ecological differences were observed between the cytotypes. It was concluded that the current disjunct distribution of diploids and tetraploids ofM. lamottiana may be explained by non-adaptive processes rather than by adaptive ones. A morphological description and notes on the nomenclature ofM. lamottiana are presented as well. A lectotype is chosen and designated for the nameMyosotis lamottianaBraun-Blanq.

Karyotype analysis of some Paullinieae species (Sapindaceae)

Abstract The karyotypes of four species of South American Paullinieae-Sapindaceae are analized for the first time: Paullinia coriacea, 2n= 24= 16m + 6sm + 2st; Serjania cissoides, 2n= 24= 18m + 2sm + 4st ; S. suborbicularis, 2n= 24= 12m + 8sm + 4st and the diploid cytotype of U. ulmacea 2n= 2x= 22= 16m + 6sm. The significance of the results are discussed in relation to previous information for these genera and also in regard to the systematics treatment of this tribe.