Genome analysis of Elytrigia pycnantha and Thinopyrum junceiforme and of their putative natural hybrid using the GISH technique.

Genomic in situ hybridization (GISH), using genomic DNA probes from Thinopyrum elongatum (Host) D.R. Dewey (E genome, 2n = 14), Th. bessarabicum (Savul. & Rayss) A. Love (J genome, 2n = 14), Pseudoroegneria stipifolia (Czern. ex Nevski) Love (S genome, 2n = 14), and Agropyron cristatum (L.) Gaertner (P genome, 2n = 14), was used to characterize the genome constitution of the polyploid species Elytrigia pycnantha (2n = 6x = 42) and Thinopyrum junceiforme (2n = 4x = 28) and of one hybrid population (2n = 5x = 35). GISH results indicated that E. pycnantha contains S, E, and P genomes; the first of these was closely related to the S genome of Ps. stipifolia, the second was closely related to to the E genome of Th. elongatum, and the third was specifically related to A. cristatum. The E and P genomes included 2 and 10 chromosomes, respectively, with S genome DNA sequences in the centromeric region. GISH analysis of Th. junceiforme showed the presence of two sets of the E genome, except for fewer than 10 chromosomes for which the telomeric regions were not identified. Based on these results, the genome formula SSPsPsEsEs is proposed for E. pycnantha and that of EEEE is proposed for Th. junceiforme. The genomic constitution of the pentaploid hybrid comprised one S genome (seven chromosomes), one P genome (seven chromosomes), and three E genomes (21 chromosomes). The E and P genomes both included mosaic chromosomes (chromosomes 1 and 5, respectively) with the centromere region closely related to S-genome DNA. On the basis of these data, the genome formula SPSESEE is suggested for this hybrid and it is also suggested that the two species E. pycnantha and Th. junceiforme are the parents of the pentaploid hybrid.     

Genome discrimination by in situ hybridization in Icelandic species of Elymus and Elytrigia (Poaceae: Triticeae).

The genome constitution of Icelandic Elymus caninus, E. alaskanus, and Elytrigia repens was examined by fluorescence in situ hybridization using genomic DNA and selected cloned sequences as probes. Genomic in situ hybridization (GISH) of Hordeum brachyantherum ssp. californicum (diploid, H genome) probe confirmed the presence of an H genome in the two tetraploid Elymus species and identified its presence in the hexaploid Elytrigia repens. The H chromosomes were painted uniformly except for some chromosomes of Elytrigia repens which showed extended unlabelled pericentromeric and subterminal regions. A mixture of genomic DNA from H. marinum ssp. marinum (diploid, Xa genome) and H. murinum ssp. leporinum (tetraploid, Xu genome) did not hybridize to chromosomes of the Elymus species or Elytrigia repens, confirming that these genomes were different from the H genome. The St genomic probe from Pseudoroegneria spicata (diploid) did not discriminate between the genomes of the Elymus species, whereas it produced dispersed and spotty hybridization signals most likely on the two St genomes of Elytrigia repens. Chromosomes of the two genera Elymus and Elytrigia showed different patterns of hybridization with clones pTa71 and pAes41, while clones pTa1 and pSc119.2 hybridized only to Elytrigia chromosomes. Based on FISH with these genomic and cloned probes, the two Elymus species are genomically similar, but they are evidently different from Elytrigia repens. Therefore the genomes of Icelandic Elymus caninus and E. alaskanus remain as StH, whereas the genomes of Elytrigia repens are proposed as XXH.     

Genomic in situ hybridization in Avena sativa.

Genomic fluorescent in situ hybridization was employed in the study of the genome organization and evolution of hexaploid oat (Avena sativa L. cv. Sun II, AACCDD, 2n = 6x = 42). Genomic DNAs from two diploid oat species, Avena strigosa (genomic constitution AsAs, 2n = 14) and Avena pilosa (genomic constitution CpCp, 2n = 14), were used as probes in the study. The DNA from A. strigosa labelled 28 of the 42 (2/3) chromosomes of the hexaploid oat, while 14 of the 42 (1/3) chromosomes were labelled with A. pilosa DNA, indicating a close relationship between the A and D genomes. Results also suggested that at least 18 chromosomes (9 pairs) were involved in intergenomic interchanges between the A and C genomes.     

Genome Analysis of a Natural Hybrid with 2n= 63 Chromosomes in the Genus Elytrigia Desv. (Poaceae) Using the GISH Technique

Abstract: Genomic in situ hybridization (GISH), using genomic DNA probes from Thinopyrum elongatum (E genome, 2 n = 14), Th. bessarabicum (J genome, 2 n = 14), Pseudoroegneria stipifolia (S genome, 2 n = 14), Agropyron cristatum (P genome, 2 n = 28) and Critesion californicum (H genome, 2 n = 14), was used to identify the genome constitution of a natural hybrid population morphologically close to Elytrigia pycnantha and with somatic chromosome number of 2 n = 63. The GISH results indicated the presence of a chromosomal set more or less closely related to the E, P, S and H genomes. In particular, two sets of 14 chromosomes each showed close affinity to the E genome of Th. elongatum and to the P genome of A. cristatum. However, they included 2 and 10 mosaic chromosomes, respectively, with S genome specific sequences at their centromeric regions. Two additional sets (28 chromosomes) appeared to be very closely related to the S genome of Ps. stipifolia. The last genome involved (7 chromosomes) is related to the H genome of C. californicum but includes one chromosome with S genome-specific sequences around the centromere and two other chromosomes with a short interstitial segment also containing S genome related sequences. On a basis of GISH analysis and literature data, it is hypothesized that the natural 9-ploid hybrid belongs to the genus Elytrigia and results from fertilization of an unreduced gamete (n = 42) of E. pycnantha and a reduced gamete (n = 21) of E. repens. The genomic formula SSSSP^SP^SE^SE^SH^S is proposed to describe its particular genomic and chromosomal composition.     

The genomic composition of Tricepiro, a synthetic forage crop.

Chromosome in situ hybridization (FISH and GISH) is a powerful tool for determining the chromosomal location of specific sequences and for analysing genome organization and evolution. Tricepiro (2n = 6x = 42) is a synthetic cereal obtained by G. Covas in Argentina (1972), which crosses hexaploid triticale (2n = 6x = 42) and octoploid Trigopiro (2n = 8x = 56). Several years of breeding produced a forage crop with valuable characteristics from Secale, Triticum, and Thinopyrum. The aim of this work is to analyse the real genomic constitution of this important synthetic crop. In situ hybridization using total DNA of Secale, Triticum, and Thinopyrum as a probe (GISH) labelled with biotin and (or) digoxigenin showed that tricepiro is composed of 14 rye chromosomes and 28 wheat chromosomes. Small zones of introgression of Thinopyrum on wheat chromosomes were detected. The FISH using the rye repetitive DNA probe pSc 119.2 labelled with biotin let us characterize the seven pairs of rye chromosomes. Moreover, several wheat chromosomes belonging to A and B genomes were distinguished. Therefore, tricepiro is a synthetic hexaploid (2n = 6x = 42) being AABBRR in its genomic composition, with zones of introgression of Thinopyrum in the A genome of wheat.     

Identification of mitotic chromosomes of tuberous and non-tuberous solanum species (Solanum tuberosum and Solanum brevidens) by GISH in their interspecific hybrids.

GISH (genomic in situ hybridization) was applied for the analysis of mitotic chromosome constitutions of somatic hybrids and their derivatives between dihaploid clones of cultivated potato (Solanum tuberosum L.) (2n = 2x = 24, AA genome) and the diploid, non-tuberous, wild species Solanum brevidens Phil. (2n = 2x = 24, EE genome). Of the primary somatic hybrids, both tetraploid (2n = 4x) and hexaploid (2n = 6x) plants were found with the genomic constitutions of AAEE and AAEEEE, respectively. Androgenic haploids (somatohaploids) derived from the tetraploid somatic hybrids had the genomic constitutions of AE (2n = 2x = 24) and haploids originating from the hexaploid hybrids were triploid AEE (2n = 3x = 33 and 2n = 3x = 36). As a result of subsequent somatic hybridization from a fusion between dihaploid S. tuberosum (2n = 2x = 24, genome AA) and a triploid somatohaploid (2n = 3x = 33, genome AEE), second-generation somatic hybrids were obtained. These somatic hybrids were pentaploids (2n = 5x, genome AAAEE), but had variable chromosome numbers. GISH analysis revealed that both primary and second-generation somatic hybrids had lost more chromosomes of S. brevidens than of S. tuberosum.     

海岛棉原位杂交及核型比较

采用Ａ染色体组（Ａ genome)棉种亚洲基因组ＤＮＡ（gDNA)为探针,对海岛棉体细胞染色体进行荧光原位杂交（ＦＩＳＨ）,结果发现５２条染色体中有杂交信号与否的刚好各一半,从而直观地证实了海岛棉异源双二倍体起源的理论,但是,染色体的长度Ａ亚组的并非全部大于Ｄ亚组的。海岛棉基于ＦＩＳＨ图像的核型公式为：２n=4x=52=38m 14sm(sat)。３对随体染色体序号分别是Ａ亚组第１１、Ｄ亚组第２２和２５,均属于近中部着丝点（sm)类型,随体均在各自杂色体的短臂上,而且与所有染色体无关晨同一亚组起源。Ａ亚组第５、６和９对染色体长臂发生长了片段的易位,易位的片段较大,占所在染色体和蔗的百分率依次为１９．２１％、１７．６９％和１２．８８％,在Ｄ亚组１３对染色体中,最少５对的着丝点区域多或少地显示出与亚洲棉gDNA探针杂交的红色荧光信号,意味着有Ａ亚组染色体的交换。     

Molecular cytogenetic analysis of Aegilops cylindrica host.

The genomic constitution of Aegilops cylindrica Host (2n = 4x = 28, DcDcCcCc) was analyzed by C-banding, genomic in situ hybridization (GISH), and fluorescence in situ hybridization (FISH) using the DNA clones pSc119, pAs1, pTa71, and pTA794. The C-banding patterns of the Dc- and Cc-genome chromosomes of Ae. cylindrica are similar to those of D-and C-genome chromosomes of the diploid progenitor species Ae. tauschii Coss. and Ae. caudata L., respectively. These similarities permitted the genome allocation and identification of the homoeologous relationships of the Ae. cylindrica chromosomes. FISH analysis detected one major 18S-5.8S-25S rDNA locus in the short arm of chromosome 1Cc. Minor 18S-5.8S-25S rDNA loci were mapped in the short arms of 5Dc and 5Cc. 5S rDNA loci were identified in the short arm of chromosomes 1Cc, 5Dc, 5Cc, and 1Dc. GISH analysis detected intergenomic translocation in three of the five Ae. cylindrica accessions. The breakpoints in all translocations were non-centromeric with similar-sized segment exchanges.     

Evaluation of BC2 progenies derived from 3x-2x and 3x-4x crosses of Lilium hybrids: a GISH analysis

An allotriploid (ALA, 2n=3 x=36) BC(1) plant was obtained by backcrossing a diploid F(1) interspecific hybrid (LA, 2n=2 x=24), derived from a Lilium longiflorum (L genome) and an Asiatic hybrid (A genome), to the latter parent. This allotriploid was backcrossed to a diploid Asiatic hybrid (2n=2 x=24) and to an allotetraploid (LLAA, 2n=4 x=48) LA hybrid. A total of 25 plants of these crosses were examined for ploidy level, and 12 individuals were analyzed for their genome constitution through genomic in situ hybridization (GISH). In most cases the progenies from the triploid-diploid (3 x-2 x) crosses consisted of aneuploids. Further more, there was evidence for the formation of near-haploid (x=12+2) to triploid (3 x=36) gametes in the allotriploid BC(1) plant. The progenies of triploid-tetraploid (3 x-4 x) cross also consisted of mostly aneuploids but in this case the triploid female parent had contributed predominantly near-triploid (2n) gametes for the origin of BC(2) progenies. The different ploidy levels observed between 3 x-2 x and 3 x-4 x crosses are possibly caused by preferential fertilization or survival resulting in a different ratio of chromosome numbers between the embryo and endosperm. Though Lilium has a tetrasporic, eight-nucleate type of embryo sac formation (Fritillaria type), the observed difference between the progeny types in 3 x-2 x and 3 x-4 x crosses is comparable to that of observed in monosporic eight nucleate types (Polygonum type) that predominate in most genera of Angiosperms. An important feature of the genome constitution of the progenies was that the homoeologous recombinant chromosomes were transmitted intact from BC(1) to BC(2) progenies in variable numbers. In addition, there was evidence for the occurrence of new homoeologous recombinations in the triploid BC(1). Of the two euploid BC(2) plants one had originated through the parthenogenetic development of a 2n egg and the other had originated through indeterminate meiotic restitution (IMR).     

Genomic relationships between Medicago murex Willd. and Medicago lesinsii E. Small. investigated by in situ hybridization

Medicago murex Willd. is an annual species (2n = 14) widespread in the wild and of remarkable interest for pastures in regions with a mediterranean climate. It is considered closely related to Medicago lesinsii E. Small (2n = 16) but, up to now, there is no evidence demonstrating their genetic affinity. This research was undertaken to investigate the genomic relationships between M. murex and M. lesinsii by using genomic in situ hybridization (GISH). In this study GISH experiments were performed using both species as sources of chromosomes and genomic probes. To better evaluate the results of the hybridization, the labelled DNA of each species was hybridized to chromosomes of the same species and to chromosomes of the diploid Medicago littoralis (2n = 16). Strong hybridization signals were found on chromosomes of M. murex and M. lesinsii after GISH. Differences in the hybridization strength were not observed when slides from interspecific hybridization were compared with the control preparations. These results suggest that consistent divergences of the DNA sequences did not occur after the separation of the two species. Instead very reduced cross hybridization was found on chromosome spreads of M. littoralis hybridized with the DNA of M. lesinsii or M. murex. The distribution of the ribosomal genes (rDNA) investigated by fluorescent in situ hybridization (FISH) appeared similar in both M. murex and M. lesinsii. The GISH technique may be a valuable approach to obtain information on evolution of the 2n = 14 species and on the origin of the polyploids Medicago rugosa (2n = 30) and Medicago scutellata (2n = 30). The first attempt to investigate the genomic composition of M. scutellata using a genomic probe is reported in this paper.     

Molecular cytogenetic analysis of durum wheat x tritordeum hybrids.

Southern and in situ hybridization were used to examine the chromosome constitution, genomic relationships, repetitive DNA sequences, and nuclear architecture in durum wheat x tritordeum hybrids (2n = 5x = 35), where tritordeum is the fertile amphiploid (2n = 6x = 42) between Hordeum chilense and durum wheat. Using in situ hybridization, H. chilense total genomic DNA hybridized strongly to the H. chilense chromosomes and weakly to the wheat chromosomes, which showed some strongly labelled bands. pHcKB6, a cloned repetitive sequence isolated from H. chilense, enabled the unequivocal identification of each H. chilense chromosome at metaphase. Analysis of chromosome disposition in prophase nuclei, using the same probes, showed that the chromosomes of H. chilense origin were in individual domains with only limited intermixing with chromosomes of wheat origin. Six major sites of 18S-26S rDNA genes were detected on the chromosomes of the hybrids. Hybridization to Southern transfers of restriction enzyme digests using genomic DNA showed some variants of tandem repeats, perhaps owing to methylation. Both techniques gave complementary information, extending that available from phenotypic, chromosome morphology, or isozyme analysis, and perhaps are useful for following chromosomes or chromosome segments during further crossing of the lines in plant breeding programs.     

Identification of the Genomic Constitution ofMusaL. Lines (Bananas, Plantains and Hybrids) Using Molecular Cytogenetics

The genomic constitutions of someMusaL. lines (bananas, plantainsand artificial hybrids) were identified using molecular cytogenetictechniques. Double targetin situDNA:DNA hybridization to chromosomespreads using as probes, total genomic DNA isolated from diploidMusalinesof known AA (labelled with biotin-11-dUTP) and BB (labelledwith digoxigenin-11-dUTP) genome constitution was carried out.The use of 60% acetic acid combined with heating over a flamegave high quality chromosome spreads free of cytoplasm forinsituhybridization. Total genomic A DNA labelled broad centromericregions of all 22 chromosomes of the diploid line, Calcutta4 (M. acuminataColla. ssp.burmanniccoides; A genome) with somechromosomes showing stronger hybridization. Labelled DNA fromthe B genome hybridized strongly to the centromeric regionsof all 22 chromosomes of Butohan 2 (M. balbisianaColla; B genome).The two satellited chromosomes of genome B labelled stronglywith genomic A DNA.In situhybridization of labelled A and Bgenomic DNA to metaphase chromosomes of triploid AAB and ABBcultivars discriminated between A and B genome chromosomes.The plantains Agbagba, Obino l'Ewai and Mbi Egome showed 22genome A and 11 genome B chromosomes while the cooking bananasBluggoe and Fougamou showed 11 genome A and 22 genome B chromosomes.Hybridization of labelled A and B genomic DNA to chromosomesof the hybrids showed that TMP2x 2829-62 has all 22 genome Achromosomes while TMPx 4698-1 has 33 genome A and 11 genomeB chromosomes.In situhybridization of labelled total genomicDNA to chromosomes has immense potential for identificationof chromosome origin and can be used to characterize cultivarsand hybrids produced inMusabreeding.Copyright 1997 Annals ofBotany Company Genomicin situhybridization; banana; plantain; hybrids; plant breeding; genome organization; biodiversity     

中间偃麦草的GISH分析

以染色体组为E^eE^e的二倍体长穗偃麦草（Thinopyrum elongatum,2n=2x=14)、染色体组为E^bE^b的二倍体比萨偃麦草（Th.bessarabicum,2n=2x=14）、染色体组为StStStSt的四倍体拟鹅冠草（Pseudoroegneiria strigosa,2n=4x=28)的总基因组DNA为探针,对中间偃麦草（Th.intermedium)进行GISH分析。结果表明,中间偃麦草是由2个亲缘关系较近的染色体组、1个亲缘关系较远的染色体组构成;中间偃麦草所含的亲缘关系较近的染色体组分别与二倍长穗偃麦草染色体组E^e、比萨偃麦草染色体组E^b、以及1个亲缘关系较远的染色体组与拟鹅冠草染色体组St基本相似,但不完全一样,因此,中间偃麦草的染色体组用E^etE^etE^btStSt表示。     

Genome plasticity in Festuca arundinacea: direct response to temperature changes by redundancy modulation of interspersed DNA repeats

The response of the genome of Festuca arundinacea seedlings to changes in the temperature at which they were grown was investigated. Fifteen repeated sequences in the nuclear DNA were isolated and hybridized to the genomic DNA of seedlings grown at 10 degrees C or 30 degrees C. The redundancies of sequences recognized by four probes ( FaA5, FaH8, FaH13 and FaH14), were found to differ significantly in the two DNAs. DNA sequences recognized by FaH8, FaH13 and FaH14 were more represented in the genome of the 30 degrees C-raised seedlings than in the genome of the 10 degrees C-raised seedlings (76.5 x 10(3), 1.9 x 10(3), and 111.8 x 10(3) copies per haploid, 1C genome vs 62.7 x 10(3), 1.3 x 10(3), and 80.8 x 10(3) copies, respectively). In contrast, FaA5-related sequences were more represented in the genome of seedlings grown at the lower temperature (15.5 x 10(3) vs 10.2 x 10(3) copies, respectively). Southern-blot hybridization of these repeats to digested genomic DNA produced patterns which indicated that the probe sequences were part of longer repeated sequences having a limited degree of structural heterogeneity. These patterns were partly different when the probes were hybridized to the DNA from seedlings grown at 10 degrees C or 30 degrees C. In situ hybridization showed that the DNA sequences recognized by each probe were scattered along the length of all the chromosomes, with preferential location of FaA5- and FaH13-related sequences at given, mainly centromeric, regions of certain chromosomes. These findings suggest that redundancy modulations of interspersed repeated sequences allow direct responses of the genome of F. arundinacea to changes in environmental temperature.     

Evidence for integrity of parental genomes in the diploid hybridogenetic water frog Pelophylax esculentus by genomic in situ hybridization

The Western Palearctic water frogs Pelophylax ridibundus and P. lessonae were identified as parental (sexual) species and P. esculentus as their interspecific, hybridogenetically reproducing hybrid with hemiclonal heredity. We used genomic in situ hybridization (GISH) to identify parental chromosomes of P.lessonae and P.ridibundus in diploid P. esculentus karyotypes (2n = 26). GISH probes were made by fluorochrome labeling of total genomic DNA extracted from the sexual progenitors. The labeled probe from one species was hybridized to chromosomes of P. esculentus in the presence of excess of unlabeled genomic DNA from the other species. Thus, the P. lessonae probe was blocked by P. ridibundus unlabeled DNA, and vice versa. We successfully discriminated each of the 13 respective parental chromosomes in metaphase complements of the hybrids according to species-specific hybridization signals. GISH enabled us to confirm additional differences between parental chromosomes in size (smaller chromosomes belong to P. lessonae) and in the presence of DAPI-positive centromeric heterochromatin (detected in chromosomes of P. ridibundus, but not in P. lessonae). The fact that no visible intergenomic exchanges were found in metaphase chromosomes of diploid P. esculentus provides important information on the genomic integrity of hemiclonal transmission and supports hybridogenesis as a reproductive mode at the chromosome level for the specimens examined.     

Alignment of the genomes of Brachypodium distachyon and temperate cereals and grasses using bacterial artificial chromosome landing with fluorescence in situ hybridization

As part of an initiative to develop Brachypodium distachyon as a genomic "bridge" species between rice and the temperate cereals and grasses, a BAC library has been constructed for the two diploid (2n = 2x = 10) genotypes, ABR1 and ABR5. The library consists of 9100 clones, with an approximate average insert size of 88 kb, representing 2.22 genome equivalents. To validate the usefulness of this species for comparative genomics and gene discovery in its larger genome relatives, the library was screened by PCR using primers designed on previously mapped rice and Poaceae sequences. Screening indicated a degree of synteny between these species and B. distachyon, which was confirmed by fluorescent in situ hybridization of the marker-selected BACs (BAC landing) to the 10 chromosome arms of the karyotype, with most of the BACs hybridizing as single loci on known chromosomes. Contiguous BACs colocalized on individual chromosomes, thereby confirming the conservation of genome synteny and proving that B. distachyon has utility as a temperate grass model species alternative to rice.     

A fertile amphiploid between durum wheat (Triticum turgidum) and the x Agroticum amphiploid (Agropyron cristatum x T. tauschii)

Agropyron (Gaertn) is a genus of Triticeae which includes the crested wheatgrass complex, i.e. A. cristatum (L.) as representative species containing the P genome. This species is an important source for increase the genetic variability of both durum and bread wheat. Among the possible interesting features to be introgressed into wheat are resistance to wheat streak mosaic virus, rust diseases, and tolerance to drought, cold and moderate salinity. By crossing tetraploid wheat (Triticum turgidum conv durum, 2n = 4x = 28; AABB) with a fertile allotetraploid (2n = 4x = 28; DDPP) between diploid wheat (T. tauschii) and crested wheatgrass (A. cristatum L.), amphiploid plants were obtained. Fluorescence in situ hybridization (FISH) using both genomic DNA from A. cristatum and the repetitive probe pAs1, proved that the plants were true amphiploids with a chromosome number 2n = 8x = 56 and genomic constitution AABBDDPP. Using total genomic in situ hybridization (GISH) to study meiotic metaphase I, data on allosyndetic and autosyndetic chromosome pairing were obtained. The amphiploids were perennial like the male parent but their morphology was close to that of the wheat parent. They were resistant to wheat leaf rust and powdery mildew under field conditions.     

Identification of genome constitution of Oryza malampuzhaensis, O. minuta,and O. punctata by multicolor genomic in situ hybridization

Multicolor genomic in situ hybridization (McGISH) was applied to identify the genomic constitution of three tetraploid species (2n = 4x = 48) in the Oryza officinalis complex of the genus Oryza, i.e. Oryza malam-puzhaensis, Oryza minuta, and Oryza punctata. The genomic probes used were from three diploids, i.e. Oryza officinalis (CC), Oryza eichingeri (CC) and Oryza punctata (BB), respectively. The results indicated that all three tetraploids are allotetraploid with the genomic constitution of BBCC, and among them the genome constitution of O. malampuzhaensis was verified for the first time. Restoration of the independent taxonomic status of O. malampuzhaensis is suggested. One pair of satellite chromosomes belonging to the B genome was identified in O. malampuzhaensis, but no such satellite chromosomes were found in either O. minuta or the tetraploid O. punctata. The average chromosome length of the C genome was found to be slightly larger than that of the B-genome chromosomes of O. minuta, but not in the tetraploids O. punctata and O. malampuzhaensis. McGISH also revealed that the B genome of O. minuta and the B genome of diploid O. punctata showed clear differentiation from each other. Therefore, the suggestion was proposed that the B genome in diploid O. punctata was not the source of the B genome of O. minuta. The present results proved that multicolor GISH had high resolution in identifying the genomic constitution of polyploid Oryza species. Received: 14 February 2000 / Accepted: 13 November 2000     

Identification of individual chromosomes and parental genomes in Brassica juncea using GISH and FISH

The three diploid (B. nigra, B. oleracea, B. campestris) and three allotetraploid (B. carinata, B. juncea, B. napus) species of Brassica, known as the "U-triangle" are one of the best model systems for the study of polyploidy. Numerous molecular investigations have provided a wealth of new insights into the polyploid origin and changes during the evolution of Brassica, but there are still many controversial aspects of their relationship and evolution. Interpretation of genome changes during evolution requires individual chromosome identification within the genome and clear distinction of genomes within the allotetraploid. The aim of this study was to identify individual chromosomes of B. juncea (genome AABB; 2n = 4x = 36) and to determine their genomic origin. Fluorescence in situ hybridization with 5S and 45S rDNA probes enabled discrimination of a substantial number of chromosomes, providing chromosomal landmarks for 20 out of 36 chromosomes of B. juncea. Additionally, along with double target genomic in situ hybridization, it allowed assignment of all chromosomes to either the A or B genomes.