Meiotic studies on a Brassica campestris-alboglabra monosomic addition line and derived B. campestris primary trisomics.

Diakinesis chromosomes were studied in pollen mother cells of Brassica campestris (2n = 20, genome AA), B. alboglabra (2n = 18, genome CC), a B. campestris-alboglabra monosomic addition line (AA + 1 chromosome from the C genome), and four derived B. campestris primary trisomics. The nucleolar chromosomes of B. campestris were distinguishable by their morphology at diakinesis. The alien C-genome chromosome in the addition line paired preferentially with the nucleolar chromosome of the A genome. Very rarely, it paired with another pair of the A genome. Thus, it was concluded that the alien C-genome chromosome of the addition line is primarily homoeologous to the nucleolar chromosome and secondarily to another chromosome of the A genome. Three of the four derived B. campestris trisomic plants were identified as B campestris nucleolar trisomics. Trisomy in the fourth plant involved another chromosome. The cytological mechanism underlying the origin of trisomics in the addition line and chromosome homoeology relationships between B. campestris and B. alboglabra are envisaged.     

Cytology, RAPD, and seed colour of progeny plants from Brassica rapa-alboglabra aneuploids and development of monosomic addition lines.

Progeny plants from Brassica rapa-alboglabra aneuploids were characterized genetically by scoring random amplified polymorphic DNA (RAPD) markers and seed colour and cytologically as to chromosome number and pairing. Sets of RAPD markers specific for each of the encountered eight alien Brassica alboglabra chromosomes were defined. The finding of subsets of markers associated with the presence or absence of alien chromosomes inferred the frequent occurrence of intergenomic genetic recombination and introgression. The chromosome numbers were in the range 2n = 20-28, with a maximum of seven alien B. alboglabra chromosomes and one trisomic B. rapa chromosome. Five types of monosomic addition lines were obtained, two of which have not been developed before. Differences in chromatin condensation patterns made it possible to differentiate between the B. rapa and B. alboglabra chromosomes at diakinesis, and to detect intergenomic homoeological pairing. In addition to the frequent formation of trivalents by homoeologous pairing of an alien B. alboglabra chromosome and a background B. rapa pair, occasional heteromorphic intergenomic bivalents and B. rapa univalents were encountered. Homoeological intergenomic pairing occurred between chromosomes with similar centromeric and karyotypic positions. Plants with structurally changed alien chromosomes were found. The RAPD and cytological data substantiated each other. Observations of the colour of sown and harvested seeds indicated that B. alboglabra chromosome 4 carries a gene for brown seed colour. It exerts its control embryonically, and thus it differs from chromosome 1 which controls seed colour maternally.     

Studies on the Karyotypes and C-Banding Patterns of Chinese Kale (Brassica alboglabra ) and Cabbage ( B. oleraca var.eapitata)

The karyotypes of B. alboglabra and B. oleracea var. capitata were analyzed by an improved technique. The diploids of the two species consist of 4 pairs of metacentric and 5 pairs of submetacentric chromosomes (1 pair of satellites). The karyotype formula is summarized as 2n =18=8m+10sm (2 SAT). But the relative positions of some similar chromosomes are different in the genomes. Four kinds of satellites were observed in B. oleracea var. capitata. C-banding patterns were obtained by BSG C-banding. The C-banding formula is: 2n= 18=CITS pattern = 10C+2CI+ +4CT+ +2CS for B. alboglabra, and 2n= 18=CITS pattern = 8C+2CI +6CT+ + 2CS for B. oleracea var. capitata. The relationship between B. alboglabra and B. oleracea was discussed based on the chromosomal characteristics.     

Molecular cytogenetic analysis of Brassica rapa-Brassica oleracea var. alboglabra monosomic addition lines

Interspecific alien chromosome addition lines can be very useful for gene mapping and studying chromosome homoeology between closely related species. In this study we demonstrate a simple but robust manner of identifying individual C-genome chromosomes (C5, C8 and C9) in the A-genome background through the simultaneous use of 5S and 25S ribosomal probes on mitotic and meiotic chromosomes of three different Brassica rapa-B. oleracea var. alboglabra monosomic addition lines. Sequential silver staining and fluorescence in situ hybridisation indicated that 18S-5.8S-25S rRNA genes on the additional chromosome C9 are expressed in the A-genome background. Meiotic behaviour of the additional chromosomes was studied in pollen mother cells at diakinesis and metaphase I. In all of the addition lines the alien chromosome was most frequently observed as a univalent. The alien chromosome C5, which carries an intercalary 5S rDNA locus, occasionally formed trivalents that involved either rDNA- or non rDNA-carrying chromosomes from the A genome. In the case of chromosomes C8 and C9, the most frequently observed intergenomic associations involved the regions occupied by 18S-5.8S-25S ribosomal RNA genes. It is possible that not all such associations represent true pairing but are remnants of nucleolar associations from the preceding interphase. Variations in the numbers and distribution of 5S and 25S rDNA sites between cultivars of B. oleracea, B. oleracea var. alboglabra and B. rapa are discussed.This revised version was published online in April 2005 with corrections to Fig. 2.     

A Brassica campestris-alboglabra addition line and its use for gene mapping,intergenomic gene transfer and generation of trisomics

Summary Brassica campestris-alboglabra monosomic addition lines were developed from a trigenomic Brassica hybrid (2 n=3 x=29, AAC) obtained by backcrossing a resynthesized B. napus (2 n=4 x=38, AACC) line to its parental B. campestris (2 n=2 x=20, AA) line. One addition line was characterized genetically with three loci specific for the alien chromosome and cytologically by meiotic analysis. The following results were obtained. (1) The same chromosome in the B. alboglabra (2 n= 2 x=18, CC) genome carried the three loci, E _c, W _c and Lap-1 C ^c, which control the biosynthesis of erucic acid, white flower colour and the faster migrating band of leucine aminopeptidase, respectively. The linear order and possible positions of the three loci were inferred. The meiotic behaviour of the alien chromosome was documented and its transmission frequency was assessed. (2) Intergenomic recombination frequently occurred in the monosomic addition line, resulting in the introgression of one or two loci from the alien chromosome into the B. campestris genome. (3) B. campestris trisomics were found in the progeny of the monosomic addition line. (4) The removal of the other eight C-genome chromosomes from the trigenomic Brassica hybrid led to a dramatic increase in the erucic acid content of the monosomic addition line. (5) No offspring of the trigenomic Brassica hybrid showed evidence of intergenomic recombination and introgression of the W _c locus into the B. campestris genome. It is questioned whether such a difference might be due to a possible regulating mechanism for homoeologous chromosome pairing.     

Studies on the Karyotypes and Pollen Morphology of Brassica oleracea L.and B. alboglabra Bailey

The karyotypes and pollen morphology of Brassica oleracea L. and B. alboglabra Bailey were studied by preparing mitotic chromosome specimens and scanning electron microscope. The results are as follows: 1. the karyotypes of the 4 varieties in B. oleracea L. and of B. alboglabra Bailey are similar, all with the same chromosome number (2n=18) satellite number (one pair) and a type of karyotype, but different in respect to satellite position and karyotype symmetry 2. The pollengrains of 2 varieties of B. oleracea L. are 3-colporate and reticulate, distinctly different from those in B. alboglabra, which are pantoporate with smaller lumina. Based on the results we tend to regard that B. alboglabra Bailey is an independent species.     

Production and cytogenetics of Brassica campestris-alboglabra chromosome addition lines

 Four different Brassica campestris-alboglabra monosomic addition lines (AA+1 chromosome from C, 2n=21) were obtained after consecutive backcrosses between resynthesized B. napus (AACC, 2n=38) and the parental B. campestris (AA, 2n=20) accession. The alien chromosomes of B. alboglabra (CC, 2n=18) in the addition lines were distinguished by random amplified polymorphic DNA (RAPD) marker analysis and morphology of mitotic chromosomes. Four RAPD marker synteny groups were established, which represented the four different alien chromosomes of B. alboglabra in the four addition lines. Three of the four addition lines were identified to harbour chromosomes 4, 8 or 9 of B. alboglabra. Studies on meiotic pairing in the addition lines revealed intergenomic homoeology relationships among specific chromosome arms between the A- and C-genomes. The long arm of B. campestris chromosome 9 was homoeologous with the long arm of B. alboglabra chromosome 4, while its short arm with the short arms of B. alboglabra chromosomes 8 and 9. Such an intergenomic homoeology relationship supports the hypothesis that B. campestris and B. alboglabra share a common ancestor but that chromosomal rearrangements have occurred during the evolution of the two species. Intergenomic introgression was observed in the progenies of the addition lines. The introgression of an entire B. alboglabra marker synteny group into the B. campestris genome implied the possible occurrence of interspecific chromosomal substitution. Received: 30 May 1996 / Accepted: 18 October 1996     

Report on Karyotypes of 10 Species of Liliaceae (s. l.) From Qinling Range

The karyotypes of 10 species of the Liliaceae from the Qinling Range are reported as follows. I. Polygonatum Mill. (1) P. odoratum ( Mill. ) Druce was found to have the karyotype 2n=20=12m+8sm ( Plate 3, Fig. I), which belongs to Stebbins’ (1971) karyotype classification 2B. The chromosomes range from 3.88 to 11.26μm in size. Table 2 shows the karyotypes and number fundamentals (N.F.) of 13 materials from 12 different localities. The N. F. of these materials can be classified into two groups: N.F. =36 and N.F.=40, besides one (N.F. =38) from Beijing. N. F. =36 covers all the materials with 2n= 18 which have relatively symmetrical karyotypes ( all consisting of m and sm chromosomes), one with 2n=20 (10m+6sm+4st) and one with 2n=22 (14m+8st). N.F. =40 include four materials with 2n= 20 (all of m and sm chromosomes ) and 3 with 2n= 22 (10m+ 8sm+ 4st). ￥ It is considered that there are two original karyotypes, 2n= 18 with N. F. = 36 and 2n= 20 with N.F. =40, which are relatively symmetrical. All the more asymmetrical karyotypes with some st chromosomes have probably evolved from the symmetrical karyotypes without st chromosomes by centric fission. (2) P. zanlanscianense Pamp. has the karyotype 2n=30=18m(2SAT) + 4sm+ 6st+ 2t (Plate 1, Fig. 1) which belongs to 2C. The chromosomes range from 2.16 to 9.76μm. ￥ II. Asparagus filicinus Buch.-Ham. ex D.Don. The karyotype of this species is 2n = 16= 8m(2SAT )+ 6sm + 2st (Plate 1, Fig. 1 and Table 3 ) , which belongs to 2B. The chromosomes range from 2.33 to 5.30μm. Most species in Asparagus, including A.Filicinus, are reported to have basic number x= 10, and therefore 2n= 16 is a new chromosome number for A.filicinus. EL-Saded et.al.(1972) gave a report of n=8 for A. stipularis from Egypt, while Delay (1947) reported 2n = 24 for A. trichophyllus and A. verticillatus, Sinla(1972 ) gave a report of 2n=48 for A.racemosus. It is certain that there are two basic numbers in the genus Asparagus. III. Cardiocrinum giganteum (Wall.) Makino was found to have the karyotype 2n=24=4m+8st+12t (Plate 1, Fig. 1 ), which belongs to 3B. The chromosomes range from 8.71 to 20.24μm. IV. Smilax discotis Warb. was shown to have the karyotype 2n=32=4m+22sm+4st (2SAT)+2t (Plate 1, Fig. 1 and Table 3), which belongs to 3C. The first pair is much longer than others. The chromosomes range from 1.79 to 9.21μm. The chromosome number and karyotype of S. discotis are both reported for the first time. V. Reineckia carnea (Andr.) Kunth is of the karyotype 2n=38=28m+10sm (Plate 2, Fig. 1 ), which belongs to 2B. The chromosomes range from 5.65 to 12.75μm. VI. Tupistra chinensis Baker was found to have the karyotype 2n=38=25m+ 13sm (Plate 2, Fig. 1), which belongs to 2B. The chromosomes range from 8.11 to 23.82μm. A pair of heterozygous chromosomes is arranged at the end of the idiogram. The eighth pair possesses an intercalary satellite. Huang et al. (1989) reported the karyotype of T. chinensis from Yunnan as 2n = 38 = 24m+ 14sm without any intercalary satellite. Nagamatsu and Noda (1970) gave a report on the karyotype of T. nutans from Bhutan, which consists of 18 pairs of median to submedian chromosomes and one pair of subterminal chromosomes. And one pair of submedian chromosomes possess intercalary satellites on their short arms. VII. Rohdea japonica (Thunb) Roth. was found to have the karyotype 2n=38=30m+6sm+2st ( Plate 2, Fig. 1), which belongs to 2B. The chromosomes range from 7.94 to 18.29μm. Nagamatsu and Noda (1970) reported that the karyotype of R.japonica from Japan was the same as that of Tupistra nutans from Bhutan. But we have not discov ered any chromosome with an intercalary satellite. VIII. Hosta Tratt. (1) H. plantaginea (Lam.) Aschers was shown to have 2n=60. The 60 chromosomes are in 30 pairs,which can be classified into 4 pairs of large chromosomes (7.32- 8.72μm ), 3 pairs of medium-sized ones (4.72-5.60μm), and 23 pairs of small ones (1.40-3.64μm), (Plate 3 ,Table 4 ). The karyotype of H. plantaginea is reported for the first time. (2) H. ventricosa (Salisb.) Stearn was counted to have 2n=120, The 120 chromosomes are in 60 pairs, which can be classified into 8 pairs of large chromosomes (7.00- 8.40μm ), 6 pairs of medium-sized ones(4.40- 6.15um ), 46 pairs of small ones (1.20- 3.85μm), (Plate 3, Table 4). Based on the karyotypes of H. plantaginea and H. ventricosa, the latter is probably a tetraploid in the genus Hosta. Kaneko (1968b) gave a report on the karyotype of H. ventricosa, which is of8 pairs of large chromosomes, 4 pairs of medium-sized and 48 pairs of small ones.     

大白菜-结球甘蓝5号和8号单体异附加系的筛选和鉴定

为建立成套的大白菜-结球甘蓝异附加系,以大白菜-结球甘蓝异源三倍体（AAC,2n=3x=29）与二倍体大白菜（AA,2n=2x=20）回交世代BC1为材料,对其进行细胞学观察并从中筛选单体异附加系。结果表明,BC1群体植株发生了染色体数目变异,变异范围为2n=20～29,其中以2n=23～24的非整倍体植株居多,占总观察株数的51．44％;对2个2n=21的植株进行核型分析,初步鉴定为大白菜-结球甘蓝5号和8号单体异附加系,分别命名为CO-5—1和CO-8—2。     

Physical mapping of rDNA loci in Brassica species.

The number of major rDNA loci (the genes coding for 18S-5.8S-26S rRNA) was investigated in the economically important Brassica species and their wild relatives by in situ hybridization of an rDNA probe to metaphase chromosomes and interphase nuclei. The diploid species B. nigra (B genome) has two major pairs of rDNA loci, B. oleracea (C genome) has two major pairs and one minor pair of loci, while B. campestris (A genome) has five pairs of loci. Among the three tetraploid species arising from these three diploid ancestors, B. carinata (BBCC genomes) has four loci, B. juncea (AABB genomes) has five major pairs and one minor pair of loci, and B. napus (AACC genomes) has six pairs of loci, indicating that the number of loci has been reduced during evolution. The complexity of the known rDNA restriction fragment length polymorphism patterns gave little indication of number of rDNA loci. It is probable that chromosome rearrangements have occurred during evolution of the amphidiploid species. The data will be useful for physical mapping of genes relative to rDNA loci, micro- and macro-evolutionary studies and analysis of aneuploids including addition and substitution lines used in Brassica breeding programs.     

Karyotype Analysis of Speirantha gardenii (Hook.) Baill.

This paper reports the chromosome numbers and karyotype analysis of Speirantha gardenii, which is endemic to China. The material was collected from Huang Shan, Anhui. It is a diploid species. Its somatic chromosome is 2n=38=22m+6sm+10st. The 9th pair is submedian centromere chromosomes, but it has two constrictions. The secondary constriction is on the short arm near centromere. Of the 19 chromosome pairs,secondary constriction is present only in this pair.     

Assigning Brassica microsatellite markers to the nine C-genome chromosomes using Brassica rapa var. trilocularis–B. oleracea var. alboglabra monosomic alien addition lines

Brassica rapa var. trilocularis-B. oleracea var. alboglabra monosomic alien addition lines (MAALs) were used to assign simple sequence repeat (SSR) markers to the nine C-genome chromosomes. A total of 64 SSR markers specific to single C-chromosomes were identified. The number of specific markers for each chromosome varied from two (C3) to ten (C4, C7 and C9), where the designation of the chromosomes was according to Cheng et al. (Genome 38:313-319, 1995). Seventeen additional SSRs, which were duplicated on 2-5 C-chromosomes, were also identified. Using the SSR markers assigned to the previously developed eight MAALs and recently obtained aneuploid plants, a new Brassica rapa-B. oleracea var. alboglabra MAAL carrying the alien chromosome C7 was identified and developed. The application of reported genetically mapped SSR markers on the nine MAALs contributed to the determination of the correspondence between numerical C-genome cytological (Cheng et al. in Genome 38:313-319, 1995) and linkage group designations. This correspondence facilitates the integration of C-genome genetic information that has been generated based on the two designation systems and accordingly increases our knowledge about each chromosome. The present study is a significant contribution to genetic linkage analysis of SSR markers and important agronomic traits in B. oleracea and to the potential use of the MAALs in plant breeding.     

四种金花茶的核型比较

<正> 金花茶是山茶属的珍稀植物,目前在我国广西南部已发现20个种和变种,但做过染色体核型研究的仅有5个种。本文首次报道凹脉金花茶(Comellia impressinervis)的核型,并结合显脉金花茶(C. euphlebia),金花茶(C. chrysantha),小金花茶(C. microcarpa)的核型作了分析比较,意在为研究金花茶的来源、分类和杂交育种提供     

白菜rDNA及C0t-1DNA的荧光原位杂交及其核型分析

以早熟白菜苔为实验材料,从其基因组DNA中分离出C0t-1DNA并用生物素标记作探针,25SrDNA用地高辛标记作探针,对有丝分裂中期相染色体进行双色荧光原位杂交。每对染色体上均显示出了特定的C0t-1DNA荧光原位杂交带型,5对染色体上显示出了25SrDNA荧光原位杂交带型。双色荧光原位杂交证实了C0t-1DNA与25SrDNA二者具有一致的染色体位置特征,表明基于rDNA及C0t-1 DNA的荧光原位杂交核型分析技术,优于目前普遍采用的只基于rDNA的荧光原位杂交核型分析方法。结合C0t-1 DNA与25SrDNA的荧光原位杂交带型和传统的染色体的形态学标记分析方法及白菜已公布的基于rDNA分布的核型分析结果,创建了一个精确的白菜核型。     

A Chromosomal Study on 7 Species of Smilax L.

The chromosome numbers and karyotypes of 7 species of Smilax L. in Liliaceae (s. 1.) are cytotaxonomically studied in this work. Their karyotypic characters, distinction between the species and the chromosomal basis of sexual differentiation are discussed. The karyotypes of most species are first reported. The results are shown as follows (see Tables 1-4 for the chromosome parameters and the karyotype constitution; Fig. 1 for their idiograms): 1. Smilax nipponica Miq. The species is one of the herbaceous species distributed in East Asia. Two karyotypes, 2n = 26(type A) and 2n = 32 (type B), are found in the species (Plate 1: 1-7). The karyotype of No. 88032 (uncertain of -L--M--S- sexuality) is 2n = 26 = 2m + 6st + 6m + 4sm + 6sm + 2st. The karyotype has 4 pairs of L chromosomes, of which the first three pairs are subterminal, and the 4th is median. The karyotype belongs to 3B. No. 88045 (the male) and No. 88046 (the female) have 2n = 32. Their karyotypes are basically uniform, and both are -L--M-- S 2n=32= 2m+4sm+ 2st+ 2m+4sm+ 6m+ 10sm + 2st, also with 4 pairs of L chromosomes, but the 2nd pair is median, and thus different from the type A. The karyotype belongs to 3B. The first pair of chromosomes of the male are distinctly unequal in length, with the D. V. (0.93) of relative length between them obviously greater than that of the female (0.1). The pair seems to be of sex-chromosomes. Sixteen bivalents (n= 16) were observed at PMCs MI of No. 88045 (Plate 1: 4). The major difference between the karyotypes A and B are greater relative length of L chromosomes in the type A than in the type B, and the increase of chromosome number in the karyotype B mainly due to the increase of st chromosomes. Nakajima (1937)reports 2n= 30 for S. hederacea var. nipponica (=S. nipponica, Wang and Tang, 1980). 2. S. riparia A. DC. This species is also herbaceous, distributed in East Asia. Thirty chromosomes were found in root-tip cells (uncertain of sexuality). The kar -L--M--S-yotype is 2n = 30 = 8st + 6sm + 2st + 6m + 6sm + 2st (Plate 3: 1, 5), consisting mainly of sm and st chromosomes. There are 4 pairs of L chromosomes which are all subterminal and the m chromosomes appear to fall all into S category. Though the karyotype belongs to 3B, it is less symmetrical than that of S. nipponica. The species is karyologically rather different from S. nipponica, therefore. The first pair of chromosomes of this material are unequal in length, and it may be a male. The karyotype of this species is first reported. 3. S. sieboldii Miq. The species is a thorny climbing shrub, distributed in East Asia. At PMCs All, 16 chromosomes (n= 16) were found (Plate 2: 6), in accordance with Nakajima's (1933) report for a Japanese material. 4. S. china L. This species, a thorny climbing shrub, is of a wide distribution range mainly in East Asia and Southeast Asia. Two karyotypes were observed in different populations. (1) The population from Xikou has 2n = 96(6x) = 20st+L- -M- 6t + 6sm + 12st + 52(S) (Plate 3:7), of which the first three pairs of chromosomes are terminal, different from those in the other species. The arm ratios of both L and M chromosomes are larger than 2.0, which resembles those of S. davidiana. (2) PMCs MI of the population from Shangyu shew 15 chromosomes (n 15). The hexaploid of the species is recorded for the first time. Hsu (1967,1971) reported 2n = 30 from Taiwai and Nakajima (1937) recorded n = 30 from Japan, which indicates that the karyotype of the species varies not only in ploidy, but also in number. 5. S. davidiana A. DC. The somatic cells were found to have 32 chromosomes, and PMCs MI shew 16 bivalents (Plate 2: 1-5). The karyotype is 2n = 32=-L- -M- -S 8st + 4sm + 4st + 8sm + 8st. The karyotype belongs to 3B, and is less symmetrical than those in herbaceous species. The D. V. (0.20) of relative length between the two homologues of the first pair is slightly larger in the male than in the female (0.14), and it is thus difficult to determine whether they are sexual chromosomes or not. 6. S. glabra Roxb. The species is a non-thorny climbing shrub, distributed in East Asia and Southeast Asia. 32 chromosomes were found in somatic cells. The -L- -M- - Skaryotype is 2n= 32= 8st + 10st+6sm+8st (Plate 3: 2, 6),with only 3 pairs of sm chromosomes (12, 13 and 16th). The karyotype is more asymmetric than that of S. davidiana, although it is also of 3B (Table 1). The karyotype is first reported for the species. 7. S. nervo-marginata Hay. var. liukiuensis (Hay.) Wang et Tang The variety has a relatively narrow distribution range, mainly occurring in eastern China. The chromosomal number of somatic cells is 2n= 32 (Plate 3: 3-4). The karyotype is -L- -M- -S 2n = 32 = 2sm + 6st + 2sm + 2st + 2m + 6sm + 12st, evidently different from that of S. glabra. The first pair of chromosomes are submedian, and much longer than the 2nd to 4th pairs. The ratio in length of the largest chromosome to the smallest one is 4.3. The symmetric degree is of 3C, a unique type. The karyotype of the species is reported for the first time. In Smilax, the known basic numbers are 13, 15, 16 and 17. The two herbaceous species distributed in East Asia have three basic numbers: 13, 15 and 16, while the woody species studied mainly have 16, with no 13 recorded. Mangaly (1968) studied 8 herbaceous species in North America and reported 2n=26 for them except S. pseudo-china with 2n=30. Mangaly considered that a probably ancestral home of Smilax, both the herbaceous and woody, is in Southeast Asia and the eastern Himalayas, and speculated that the ancestral type of Sect. Coprosmanthus is possibly an Asian species, S. riparia. The karyotypes of the two herbaceous species in East Asia consist mostly of sm and m chromosomes, whereas those for the North American species are all of st chromosomes. Based on the general rule of karyotypic evolution, i.e. from symmetry to asymmetry, his speculation seems reasonable. Researches on sex-chromosomes of Smilax have been carried out since 1930 (Lindsay, 1930; Jensen, 1937; Nakajima, 1937; Mangaly, 1968), and they are generally considered to be the largest pair, but there is still no adequate evidence. The result of our observation on S. nipponica may confirm that the first pair of chromosomes of this species is XY type of sex-chromosomes. Chromosomes of the genus are small and medium-sized, varying between 1-6 μm, slightly larger in herbaceous species than in woody ones, larger in the karyotype of 2n=26 than in that of 2n=32. Based on karyotype constitution of the above 5 species, the karyotype in the genus is characterized by 4 pairs of L chromosomes and 2-5 pairs of M chromosomes, and mostly st and sm chromosomes, and by rather asymmetrical 3B type. The degree of symmetry in the above 5 species is from Sect. Coprosmanthus to Sect. Coilanthus, and herbaceous species towoody ones.     

四福花染色体核型的分析

四福花[Tetradoxa ometensis (Hara)C.Y.Wu]体细胞具有36个染色体。其核型组成为2n=36=6m+14sm+4st+12t,即具有3对中部着丝点染色体,7对亚中部着丝点染色体,2对亚端部着丝点染色体和6对端部着丝点染色体。 四福花染色体核型分析表明,与传统对五福花科植物染色体具9基数的认识不同,其基数应为X=18。与Noguchi所发现的具18基数的三倍体五福花的核型相比较,二者在核型组成及染色体结构上都有明显差异。     

Comparative genomic in situ hybridization (cGISH) analysis of the genomic relationships among Sinapis arvensis, Brassica rapa and Brassica nigra

To further understand the relationships between the SS genome of Sinapis arvensis and the AA, BB genomes in Brassica, genomic DNA of Sinapis arvensis was hybridized to the metaphase chromosomes of Brassica nigra (BB genome), and the metaphase chromosomes and interphase nucleus of Brassica rapa (AA genome) by comparative genomic in situ hybridization (cGISH). As a result, every chromosome of B. nigra had signals along the whole chromosomal length. However, only half of the condensed heterochromatic areas in the interphase nucleus and the chromosomes showed rich signals in Brassica rapa. Interphase nucleus and the metaphase chromosomes of S. arvensis were simultaneously hybridized with digoxigenin-labeled genomic DNA of B. nigra and biotin-labeled genomic DNA of B. rapa. Signals of genomic DNA of B. nigra hybridized throughout the length of all chromosomes and all the condensed heterochromatic areas in the interphase nucleus, except chromosome 4, of which signals were weak in centromeric regions. Signals of the genomic DNA of B. rapa patterned the most areas of ten chromosomes and ten condensed heterochromatic areas, others had less signals. The results showed that the SS genome had homology with AA and BB genomes, but the homology between SS genome and AA genome was clearly lower than that between the SS genome and BB genome.     

加拿大一枝黄花的核型分析及B染色体初报

对安徽蚌埠地区外来植物加拿大一枝黄花的染色体核型进行了分析。结果如下:该入侵种的染色体数为2n=50,各染色体间形态差异不明显,均为中着丝粒或近中着丝粒染色体,最长与最短染色体相对长度比为1.72,全套染色体未见随体,核型公式为2 n=50=38 m 12 sm 6 B s,核型类型为较对称的2A型。首次报道了存在于体细胞中的异于常染色体的6个B染色体,这些B染色体在不同细胞中保持恒定的数目,并讨论了B染色体的存在与加拿大一枝黄花在新生境中具有入侵性之间的关系。     

Karyomorphology of the genusLycopodium sensu stricto and relationships among species

Karyomorphological comparisons were made of six species of JapaneseLycopodium sensu stricto. There were no marked differences at interphase and prophase among the six species.Lycopodium annotinum had 2n=68 and the formula of its metaphase karyotype was 18m(median centromeric chromosomes)+12sm(submedian)+12st(subterminal)+26t(terminal).Lycopodium casuarinoides had 2n=68=16m+10sm+18st+24t,L. clavatum 2n=68=22m+12sm+18st+16t, andL. obscurum 2n=68=10m+22sm+20st+16t. Each of these species, which belong to different sections, displayed several karyomorphological differences. Among themL. casuarinoides differs largely from the others in its mean chromosome length, ratio of the longest chromosome to the shortest, and frequency of m+sm chromosomes. BothLycopodium complanatum andL. nikoense, belonging to sectionComplanata, had a common karyotype 2n=46=10m+12sm+18st+6t. This section displayed a low differentiation in its karyotype. In the wholeLycopodium s.s., the ratios of m+sm in a complement varied from 38 to 50%, being higher among pteridophytes.