Confirmation of Ancient Polyploidy in Dahlia (Asteraceae) Species using Genomic In Situ Hybridization

The successful production of interspecific hybrids between membersof the dysploid chromosome series inDahlia offers a unique opportunityto investigate chromosome evolution. Analysis of meiotic metaphaseI in these hybrids using genomic in situ hybridization (GISH)has shown that pairing occurs both between and within parentalgenomes. These results have provided clear evidence for theallotetraploid origin of Dahlia species with 2n=32 and suggeststhat species with 2n=34 and 2n=36 have also arisen via allopolyploidy.A bivalent promoting mechanism proposed for species with 2n=32also appears to be present in Dahlia species with 2n=34 and2n=36 .Copyright 1999 Annals of Botany Company Dahlia , GISH, dysploidy, chromosome pairing, karyotype analysis, polyploidy.     

CHROMOSOME NUMBER IN TWO PHENOTYPICALLY DISTINCT POPULATIONS OF LITTORINA SAXATILIS OLIVI, AND IN SPECIMENS OF THE LITTORINA OBTUSATA (L.) SPECIES-COMPLEX

Chromosome numbers counted from embryo cells of the marine gastropodLittorina saxatilis (=L. rudis), were the same, 2n = 34, inpopulations of two different phenotypes from a small area inSweden. Chromosome number in the related species-complex, Littorinaobtusata, could not be determined definitely, but the most adequatefigure seemed to be 2n = 34. (Received 9 September 1982;     

Somatic hybridisation of Daucus carota and D. capillifolius by protoplast fusion

Summary Protoplasts isolated from cultured cells of albino carrot (Daucus carota) and normal green D. capillifolius were fused by polyethylene glycol. Selection of somatic hybrid plants was based on the restoration of photosynthetic function in hybrids. Green plantlets selected from embryo cultures were characterized on the basis of leaf morphology. The interspecific protoplast fusion resulted in green plants with leaves which were intermediate between those of the parents. The somatic hybrids between orange rooted carrot variety and D. capillifolius with long white roots produced long, white and fleshy roots. The cytological analysis of parasexual hybrids revealed that the chromosome number ranged from 34 to 54. The most frequent chromosome number was 2n = 36. Hybrids were also found with 34 and 35 chromosomes. The somatic hybrid showed the same isoenzyme pattern of leaf peroxidase as D. carota.     

Production and cytogenetics of the intergeneric hybrids Brassica juncea×Orychophragmus violaceus and B. carinata×O. violaceus

 Intergeneric hybrids between Brassica juncea (2n=36), B. carinata (2n=34) and Orychophragmus violaceus (2n=24) were produced when B. juncea and B. carinata cultivars were used as female parents. The hybrids between B. juncea and O. violaceus had an intermediate morphology except for petal colour and were partially fertile. The hybrids between B. carinata and O. violaceus had a matroclinous morphology and were nearly fertile. Cytological analysis of the hybrids and their progenies gave the following results. (1) In the hybrids between B. juncea and O. violaceus, the somatic tissues of the roots, leaves and styles were mixoploid (2n=12–42), and cells with 24, 30 or 36 chromosomes were the most frequent. Based on the recorded numbers and behaviour of the mitotic and meiotic chromosomes, complete and partial separation of the parental genomes was proposed to have occurred during mitosis. This resulted in the occurrence of cells with possibly complete and incomplete complements of the parental species and cells with parental complements and some additional chromosomes from the other parent. (2)  Pollen mother cells (PMCs) possibly with both parental chromosome complements, only B. juncea chromosomes or a complete B. juncea complement with additional O. violaceus chromosomes were more competitive in entering meiosis. The majority of fertile gametes were deduced to have been produced by PMCs with a B. juncea complement with or without additional O. violaceus chromosomes. (3) The progeny plants from selfed hybrids between B. juncea and O. violaceus were morphologically either of a B. juncea, hybrid or variable type. Cytologically they were grouped into six types according to the frequencies of cells with various chromosome numbers. All of the plants except 2 which constituted two types, were mixoploids, composed of cells with various chromosome numbers, mainly in a certain serial range. (4) The hybrid plants between B. carinata and O. violaceus were mixoploids with chromosome numbers in the range of 12–34, and cells with 2n=34 were the most frequent. The main categories of PMCs with 17 bivalents at metaphase I and 17 : 17 segregations at anaphase I contributed to the high fertility of the hybrids and the fact that their progeny after selfing were mainly plants with 2n=34. Somatic and meiotic separation of the parental genomes was proposed to have occurred in the hybrids between B. carinata and O. violaceus. (5) Mitotic and meiotic elimination of what could be O. violaceus chromosomes might also have contributed to the observed mitotic and meiotic cell types in the two kinds of hybrids studied. Finally, the possible mechanisms behind these cytological observations and their potential in the production of Brassica aneuploids were discussed. Received: 4 February 1997/Accepted: 29 July 1997     

Karyotype evolution in South American subterranean rodents Ctenomys magellanicus (Rodentia: Octodontidae): chromosome rearrangements and (TTAGGG)n telomeric sequence localization in 2n=34 and 2n=36 chromosomal forms

Ctenomys is the most numerous genus of South American subterranean rodents and one of the most karyotypically diverse clades of mammals known. Ctenomys magellanicus is the southernmost species of the group and the only one living in Isla Grande de Tierra del Fuego (Argentina). This species presents two chromosomal forms, i.e. 2n=34, and 2n=36 (FN=68). Recent studies suggest that genetic divergence between both karyotypic forms resulted from a chromosomal speciation process. In order to identify the chromosomal rearrangement involved in the process of karyotype evolution in this species, we used chromosome banding techniques and fluorescence in situ hybridization with a telomeric probe to metaphase chromosomes of the two chromosomal forms of Ctenomys magellanicus. Chromosome analysis of Giemsa-stained and G-banding preparations showed that Cm34 and Cm36 karyotypes differ in one rearrangement involving chromosomes A9 from Cm34 and B12 and B17 from Cm36. In addition FISH analysis showed that all of the chromosomes from both chromosomal forms exhibit a telomeric-only distribution pattern of the (TTAGGG)n sequence, indicating that none of the chromosomal forms of Ctenomys magellanicus has true telocentric chromosomes. Our results suggest that a chromosome fission event would have occurred during the process of karyotype evolution in this species.     

KARYOTYPES OF FIVE SUBANTARCTIC BIVALVE SPECIES

Chromosomes of five subantarctic species were studied from mitoticmetaphases using cell suspension techniques. Among the Protobranchia,Malletiagigan-lea has a diploid chromosome number of 2n = 38with five metacentric, seven submetacentric, five sub-telocentricand one telocentric pairs, and Yoldia (Aequiyoldia) woodwardialso shows 2n = 38 but with ten metacentric, six submetacentricand three sub-telocentric pairs. Among the Lamellibranchia,the pterioidan Limatula pygmaea has 2n = 38 with six metacentric,eleven submetacentric and two sub-telocentric pairs, the veneroidanCyclocardia astar-toides has 2n = 30 with five metacentric andten telocentric pairs and the anomalodesmatan Laternula ellipticahas 2n = 40 with two metacentric, one submetacentric, two subtelocentricand fifteen telocentric pairs. Our results indicate that in all the Nuculoidea studied so far,a diploid number of 2n = 38 has been found. In addition, thekaryotypes show a close overall appearance in relative lengthswith a majority of meta-centric-submetacentric chromosomes.The species differ in the proportion of the different morphologicaltypes of chromosomes. In the Lamellibranchia, each species correspondsto a particular case within their respective orders (Pterioida,Veneroida, Anomalodesmata). (Received 22 January 1990; accepted 28 March 1990)     

A cytological study ofPelargonium sect.Eumorpha (Geraniaceae)

The chromosome numbers of seven species ofPelargonium sect.Eumorpha have been determined from material of known wild origin, and karyotypic comparisons have been made. Within the section there is variation in basic chromosome number (x = 4, 8, 9, 11), variation in chromosome size, and two species have polyploid races. The three species with chromosome numbers based on x = 11 have the smallest chromosomes (1.0–1.5 µm); chromosomes are larger (1.0–3.0 µm) in the other species.P. elongatum has the lowest chromosome number in the genus (2n = 8).P. alchemilloides is exceptional in that it has four cytotypes, 2n = 16, 18, 34 and 36, and the form with 2n = 36 has large chromosomes (2.0–5.0 µm). Evidence from a synthesized hybrid suggests thatP. alchemilloides with 2n = 16 may be of polyploid origin. The three species based on x = 11 appear to be more closely related to species from other sections ofPelargonium that have the same basic chromosome number and small chromosome size, rather than to other species of sect.Eumorpha.     

苍耳X anthium strumarium L.染色体数目和核型的观察

苍耳Xanthium strumarium L. (X. sibiricum Patr. ex Widder, X. iaponicum Widder) 为菊科苍耳属的一年生草本,广布于欧亚大陆和北美洲;我国各地也均有分布。苍耳为常用中药,其果实入药,能发汗通窍、祛风湿,解表镇痛,用于治风湿性关节痛及鼻炎等症。     

苍耳Xanthium strumarium L. 染色体数目和核型的观察

苍耳Xanthium strumarium L.(X. sibiricum Patr. ex Widder, X. iaponicum Widder)为菊科苍耳属的一年生草本,广布于欧亚大陆和北美洲;我国各地也均有分布。苍耳为常用中药,其果实入药,能发汗通窍、祛风湿,解表镇痛,用于治风湿性关节痛及鼻炎等症。     

Photosynthetic and genetic differentiation in sun and shade populations of Holcus mollis L.

Three Holcus mollis L. populations, one with 2n = 28 chromosomes living in a forest and two with 2n = 35 chromosomes, the first living in a forest, the second in open land, are compared for photosynthesis.Simultaneous measurements of oxygen and carbon dioxide, either in high light, low light, or dark experiments indicate that the 2n = 28 chromosomes population is photosynthetically well adapted to shade, while 2n = 35 chromosomes forest population, is not.The 2n = 35 chromosomes plants growing in the forest does not automatically acquire the photosynthetic character of a shade plant, the genome must show an evolution for this. In our study, only the plants with 2n = 28 chromosomes demonstrated the shade adaptation.     

Parental genome separation and elimination of cells and chromosomes revealed by AFLP and GISH analyses in a Brassica carinata x Orychophragmus violaceus cross

BACKGROUND AND AIMS: The phenomenon of parental genome separation during the mitotic divisions of hybrid cells was proposed to occur under genetic control in intergeneric hybrids between cultivated Brassica species and Orychophragmus violaceus (2n = 24). To elucidate further the cytological and molecular mechanisms behind parental genome separation, Brassica carinata (2n = 34) x O. violaceus hybrids were resynthesized and their chromosome/genomic complements analysed. METHODS: F(1) hybrids of the cross were obtained following embryo rescue, and were investigated for their cytological behaviour and subjected to genomic in situ hybridization (GISH) and amplified fragment length polymorphism (AFLP) to determine the contribution of parental genomes. KEY RESULTS: All the F(1) plants with high fertility closely resembled B. carinata in morphological attributes. These were mixoploids with 2n chromosome numbers ranging from 17 to 35; however, 34, the same number as in B. carinata, was the most frequent number of chromosomes in ovary and pollen mother cells (PMCs). GISH clearly identified 16 chromosomes of B. nigra in ovary cells and PMCs with 2n = 34 and 35. However, no O. violaceus chromosome was detected, indicating the presence of the intact B. carinata genome and elimination of the entire O. violaceus genome. However, some AFLP bands specific for O. violaceus and novel for the two parents were detected in the leaves. Cells with fewer than 34 chromosomes had lost some B. oleracea chromosomes. F(2) plants were predominantly like B. carinata, but some contained O. violaceus characters. CONCLUSIONS: The cytological mechanism for the results involves complete and partial genome separation at mitosis in embryos of F(1) plants followed by chromosome doubling, elimination of cells with O. violaceus chromosomes and some introgression of O. violaceus genetic information.     

Chromosome evolution in the genus Mikania (Compositae)

Karyotypic analysis of ten species of the genus Mikania was carried out using Feulgen staining. Species belonging to the following sections were analyzed: Section Thyrsigerae containing M. additicia (2n = 34), M. hemisphaerica, M. lanuginosa, and M. punctata (2n = 36), and Mikania sericea (2n = 42), which adds a new basic chromosome number (x = 21) to the genus and to the tribe Eupatorieae; Section Corymbosae with M. hastato-cordata (2n = 34) and M. involucrata and M. microptera with 2n = 36 chromosomes; Section Spicato-Racemosae with M. sessilifolia, with 2n = 108 chromosomes. One unidentified species with 2n = 34 chromosomes was also analyzed. All the species studied show one large pair of chromosomes with a secondary constriction in the middle region of the long arm. The morphology of this chromosome suggests that it can be considered as a cytological marker for the genus. Because of the distinctive inflorescence types found in the genus Mikania and the high frequency of species with x = 18, a correlation between morphological and chromosomal evolution is discussed. The present study suggests that the basic original chromosome number for the genus is x = 18, from which the others (x = 17, 19, 20, 21) have been derived by aneuploidy to form the observed aneuploid series.     

Cytogenetic studies on natural intergeneric hybridization inAster alliances

The karyotype and meiosis of the 12-ploid plants—one of the offspring of the natural F₁ hybrid (Aster ageratoides subsp.ovatus (2n=36) ×Kalimeris incisa (2n=72), 2n=72)—were examined. The 2n=108 chromosomes of the 12-ploids were found to consist of 18 large chromosomes and 90 small chromosomes. In meiosis of the PMCs of the 12-ploid, chromosome configurations of 3_III+46_II+7_I, 2_III+48_II+6_I and 3_III+47_II+5_I were observed. All the univalents and trivalents were small, and among the 46–48 bivalents nine were large and the remaining 37–39 were comparatively small. The large bivalents were found to represent autosyndetic pairings, and the small bivalents and trivalents were probably formed by autosyndetic pairings. The large chromosomes of the 12-ploids were found to coincide with the large chromosomes ofovatus, and the 90 small chromosomes to correspond to small chromosomes ofovatus andK. incisa. The 12-ploids were concluded to have been produced by a fusion of an unreduced gamete of the F₁ plant and a reduced gamete ofK. incisa which was growing in proximity to the F₁s. Thus the 12-ploids were regarded to be an amphidiploid having 36 chromosomes ofovatus and 72 chromosomes ofK. incisa.     

Cytotaxonomical Studies on Liliaceae (s.l.): (2) Report on Chromosome Numbers and Karyotypes of 8 Species of 8 Genera from Zhejiang,China

Eight species in eight genera of Liliaceae from Zhejiang were cytotaxonomically studied in this work. The karyotypes of Chinese materials of these species are mostly reported for the first time. The results are shown as follows (see Table 2-4 for chromosome parameters of them): 1. Disporum sessile D. Don Sixteen chromosomes are counted at metaphase of roottip cells.The Karyotype formula is 2n=16=2lm+2sm+4st+2sm+3sm+ 1sm(SAT)+2st (Plate 1: 2-3, see Fig. 1:1 for its idiogram). The Karyotype belongs to 3B in Stebbins’ (1971) karyotype classification, and consists of four pairs of larger chromosomes (1-4) and four pairs of smaller chromosomes (5-8). One SAT-chromosome is situated at the sixth pair. The chromosomes range between 4.85-16.63μm. The karyotypic constitution is similar to that of Japanese material reported by Noguchi (1974). Chang and Hsu (1974) reported 2n=14=13st+1sm and 2n= 16=2m + 13st + 1sm for the material from Taiwan under the name of D. shimadai Hay. (=D. sessile D. Don). Compared with our result of D. sessile, the differences are obvious. 2. Polygonatum odoratum (Mill.) Druce PMCs diakinesis shows eleven bivalents, n = 11, 5 large and 6 small (Plate 2:5). The meiosis is normal. The majority of reports of this species are 2n=20, with a few 2n=22 and 30 (see Table 1). The materials from southen Siberia and the Far East in USSR are all of 2n= 20. Our result is the same as recorded by Jinno (1966) in the Japanese material and by Li (1980) from Beijing. Ge (1987) reported 2n=20 in the cultivated individuals of Shandong, China, showing that both 2n=20 and 22 exist in China. 3. Scilla scilloides (Lindl.) Druce This species has the somatic chromosome number 2n=18 (Plate 1: 4-6, see Fig. 1:2 for its idiogram), of which two groups of chromosomes can be recognized, i.e. the 1 st -5 th pairs of large and the 6 th-9th pairs of small chromosomes. A distinct character of the karyotype is that two satellites are attached to the short arms of the 1st pair of chromosomes. The degree of asymmetry is of 3C. The karyotype formula is 2n = 18 = 2sm (SAT) + 6st + 2t+ 6m + 2sm. The chromosomes range from 2.02 to 11.93 μm. The Previous counts on the species are 2n = 16, 18, 26, 34, 35, 36 and 43 (see Table 1). The present investigation confirms Noda’s and Haga’s results. The species is considered to be of two genomes, namely A(x = 8) and B(x = 9). Our result shows a genome composition of BB, having a pair of large SAT-chromosomes. Chang and Hsu (1974) reported 2n = 34 from a population of Taiwan, an amphidiploid (AABB), Karyotypes of other Chinese populations are worth further researches. 4. Tricyrtis macropoda Miq. The chromosome number of somatic cells is 2n= 26, and PMCs MII shows 13 bivalents (n= 13) (Plate 3:1-3, see Fig. 1:3 for its idiogram). The karyotype formula is 2n= 26= 6m + 10sm + 6st + 4st (or t), which is composed of chromosomes: 4L + 22S in size. The degree of asymmetry is of 3B. No centromeres of the 12th and 13th pairs of chromosomes were observed at metaphase, and the chromosomes may be of st or t. Nakamura (1968) reported 2n= 26(4L+ 22S)= 2sm+ 2sm-st+ 14st-sm+ 8st for T. macropoda Miq. and 2n= 26(4L+ 22S)= 8m+ 2sm+2sm-st+ 2st-sm+ 12st for its ssp. affinis, both from Japan. It is clear that the major character of their karyotypes, i. e. 4L + 22S, is consistent with that reported here. Based on the previous and present reports, all Tricyrtis species studied are remarkably uniform in the basic karyotype, i. e. 4L + 22S. 5. Allium macrostemon Bunge. The present observation on the root-tip cells of the species shows 2n = 32 (Plate 3: 4-5, see Fig. 1:4 for its idiogram). The karyotype formula is 2n (4x)= 32= 26m + 6sm, which belongs to 2B, being of high symmetry. Except the 6th, 10th and 13th pairs of chromosomes all the are metacentric. Chromosomes of this species are large, ranging from 5.94 to 18.06 μm. Our result agrees with Kawano’s (1975) report under the name of A. grayi Regel ( = A. macrostemon, Wang and Tang 1980). 6. Asparagus cochinchinensis (Lour.) Merr. Ten bivalents were observed in PMCs MI, n=10 (Plate 1: 1). The present result confirms the number of a population of Taiwan recorded by Hsu (1971). 7. Ophiopogon japonicus (L. f.) Ker-Gawl. The species from Mt. Taogui, Hangzhou, is found to have 2n (2x)=36=22m + 14sm (Plate 2: 1,5, see Fig. 1:5 for its idiogram) which belongs to 2B. The karyotype is composed of 2 medium-sized chromosomes with metacentric centromeres and 34 small chromosomes, ranging from 1.34 to 4.92 μm. The populations from Mt. Tianzhu and Mt. Yuling, Zhejiang, are found to be aneuploids at tetraploid level (2n=64-70). It is interesting that Nagamatsu (1971) found the karyotypes of Japanese materials to be 2n= 67 and 68, also showing unsteady 4x karyotypes of this species. In the previous. reports (see Table 1), the chromosome numbers of this species are mainly 2n = 72, besides 2n = 36 recorded by Sato (1942) from Japan. 8. Liriope platyphylla Wang et Tang The somatic complement of the species collected from Mt. Tianzhu, Hangzhou, is 2n = 36 (Plate 2: 3-4, see Fig. 1:6 for its idiogram). The karyotype is 2n(2x) = 36 = 16m + 20sm, belonging to 2B type. The chromosomes are small except the medium-sized, 1st pair and the range is from 1.27 to 5.19μm. The material from Mt. Yuling, Zhejiang, is found to have a variety of chromosome numbers (2n= 60-71), as observed in Ophiopogon japonicus. Hasegawa (1968) reported the karyotype of 2n = 72 (4x) from Japan The 2x karyotype is first recorded. This genus is closely related to Ophiopogon. Based on the Hasegawa’s and present studies, all the species in these two genera are remarkably uniform in karyo-type. Therefore, the taxonomy of the two genera is worth further researches.     

Low glucosinolate Brassica juncea breeding line revealed to be nullisomic.

The low glucosinolate Brassica juncea breeding line 1058 was derived from a BC1F3 plant of an interspecific cross between high glucosinolate Indian B. juncea (genome AABB, 2n = 36) line 60143 and B. rapa (genome AA, 2n = 20) canola strain CZY. Line 60143 had 2n = 36 chromosomes (18 bivalents at metaphase I) and strain CZY had 2n = 20 chromosomes (10 bivalents). Line 1058 was nullisomic, with 2n - 2 = 34 chromosomes, with 17 bivalents formed at metaphase I and an even chromosomal segregation of 17:17 at anaphase I. In F1 hybrid plants of the cross 1058 x CZY, 98.3% of the pollen mother cells had 10 bivalents and seven univalents. This is evidence that plants of line 1058 are nullisomic, missing one pair of B-genome chromosomes.     

Chromosome markers and alterations in mitotic cells from interspecific Citrus somatic hybrids analysed by fluorochrome staining

Mitotic cells from Rough lemon (Citrus jambhiri Lush.), Ohta ponkan (C. reticulata Blanco) and two somatic hybrid plants obtained from protoplast fusion were analysed by double staining with chromomycin A₃ (CMA) and 4′-6-diamidino-2-phenylindole. Only CMA-positive bands were observed in metaphasic chromosomes. The two parental karyotypes (2n=2x=18) were heteromorphic, yielding some marker chromosomes that could be identified in the somatic hybrids. One of the somatic hybrids had 2n=37 chromosomes, and the possible extra chromosome was distinguishable. The second somatic hybrid was tetraploid (2n=4x=36), with one of the chromosomes bearing a putative structural alteration. Furthermore, aneusomaty and some mitotic abnormalities were also observed in this latter plant. Such irregularities are reported for the first time for citrus somatic hybrids, and their possible causes and implications are discussed. Received: 23 December 1996 / Revision received: 21 May 1997 / Accepted: 16 June 1997     

High efficiency production and genomic in situ hybridization analysis of Brassica aneuploids and homozygous plants

Inplantbreedingandgeneticresearch,karyotypicallystablecrosseswhichproducehybridplantshavebeenextensivelyusedtointroduceintocropsthetargettraitsandgenesfromrelatedwildorcultivatedspeciesortoconstructstocksforgeneticanalysis(alienchromosomeadditions,substitutionsandtranslocations)[1—3].Uniparentalgenomeeliminationinkaryotypicallyunstablehybridshasbeenutilizedforhaploidproduction[2,4].Becausetheartificiallysynthesizedallopoly-ploidscannotbeusedascropsformanyreasons,onepurposeofwidehybridizations…     

High efficiency production and genomic<Emphasis Type="Italic">in situ</Emphasis> hybridization analysis of<Emphasis Type="Italic">Brassica</Emphasis> aneuploids and homozygous plants

Interspecific and intergeneric hybridizations have been widely used in plant genetics and breeding to construct stocks for genetic analysis and to introduce into crops the desirable traits and genes from their relatives. The intergeneric crosses between Brassica juncea (L.) Czern. & Coss., B. carinata A. Braun and Orychophragmus violaceus (L.) O. E. Schulz were made and the plants produced were subjected to genomic in situ hybridization analysis. The mixoploids from the cross with B. juncea were divided into three groups. The partially fertile mixoploids in the first group (2n = 36-42) mainly contained the somatic cells and pollen mother cells (PMCs) with the 36 chromosomes of B. juncea and additional chromosomes of O. violaceus. The mixoploids (2n = 30-36) in the second and third groups were morphologically quite similar to the mother plants B. juncea and showed nearly normal fertility. The plants in the second group produced the majority of PMCs (2n = 36) with their chromosomes paired and segregated normally, but 1-4 pairs of the O. violaceus chromosomes were included in some PMCs. The plants in the third group produced only PMCs with the 36 B. juncea chromosomes, which were paired and segregated normally. The mixoploids (2n = 29-34) from the cross with B. carinata produced the majority of PMCs (2n = 34) with normal chromosome pairing and segregation, but some plants had some PMCs with 1-3 pairs of chromosomes from O. violaceus and other plants had only PMCs with the B. carinata chromosomes. The Brassica homozygous plants and aneuploids with complete or partial chromosome complements of Brassica parents and various numbers of O. violaceus chromosomes were derived from these progeny plants. The results in this study provided the molecular cytogenetic evidence for the separation of parental genomes which was previously proposed to occur in the hybridizations of these two genera.     

COMPARATIVE KARYOLOGICAL ANALYSIS OF FIVE SPECIES OF VIVIPARUS (GASTROPODA: PROSOBRANCHIA)

Karyological analysis was performed on Viviparus ater (Cristofori& Jan, 1832), V. acerosus Bourguignat, 1862, V. mamillatus (Kuster),V. viviparus (Linnaeus, 1758) and V. contectus (Millet, 1813),collected from different freshwater bodies of Switzerland, Hungary,Albania, Italy and Lithuania. The karyotypes of V. acerosusand V. mamillatus are described for the first time. The diploidnumber of chromosomes in V. contectus equals 14, whereas indiploid sets of other studied species, 18 chromosomes are present.The karyotype formula is in V. contectus (5m + 2sm, NF = 28,in V. ater, 7m + 1sm-m + 1 sm, in V. acerosus and V. viviparus,8m + 1sm, NF = 36, in V. mamillatus, 6m + 1m-sm + 1sm-m + 1sm,NF = 36. In females of V. ater, V. mamillatus and V. acerosus,the heteromorphism of chromosome pair no. 8 was observed, witha sex-determining mechanism — ZW female /ZZ male. Although,Z and W chromosomes are metacentric, significant differences(P > 0.05, or P > 0.001) in their size were determined.The interspecific significant differences (P > 0.05) in karyotypesof V. ater, V. mamillatus, V. acerosus and V. viviparus weredetected by using one-way ANOVA and Bonferronis Multiple Comparisontests. Only chromosomes of the pair no. 5 were of similar shapein all of these species. The smallest interspecific differencewas between V. viviparus and V. acerosus. The intraspecifickaryological differences in relative chromosome length and centromericindex of V. contectus from lakes Garda (Italy), Olauka andAsveja (Lithuania) were observed in the chromosome pair no.5. (Received 29 March 1999; accepted 19 October 1999)     

Accessory Chromosomes in a tree--Ficus krishnae

Accessory chromosomes in a tree, Ficus krishnae are reportedfor the first time. Besides the normal complement of 2n = 26;1–2 small euchromatic accessory chromosomes were encountered.The frequency of accessory chromosomes in somatic cells was30 per cent. In meiotic cells one accessory chromosome was presentin 54 per cent of cells while two were observed in 9 per centof the pollen mother cells.