The cytotaxonomy and origin ofRanunculus yaegatakensis,an endemic taxon of Yakushima Island

Ranunculus yaegatakensis, a close relative of the widespreadR. silerifolius, is endemic to the alpine region (ca. 1,600 m alt.) of Yakushima Island. This species differs morphologically fromRanunculus silerifolius mainly due to its dwarfism and leaf shape, but has an identical karyotype with one (Karatsu-type) of the four cytotype ofR. silerifolius. Ranunculus yaegatakensis is highly cross-compatible with the Karatsu-type plants ofR. silerifolius. Their F₁ hybrids show regular meiotic behaviors and set seeds successfully. In addition, the Karatsu-type ofRanunculus silerifolius is found in individuals that are collected not only from the lowland of Yakushima Island but from its neighboring islands. It is supposed to be more specialized than other cytotypes. This evidence suggests thatRanunculus yaegatakensis has been derived from the Karatsu-type plants ofR. silerifolius. We suggest thatRanunculus yaegatakensis be reduced to a variety ofR. silerifolius.     

Intergeneric hybridization between Hordeum and Hordelymus (Poaceae)

Intergeneric hybridization between the monotypic Eurasian genus Hordelymus and species of Hordeum was performed. Hybrids were obtained in nine combinations and the meiotic pairing was analyzed in four combinations (6 families). Hordelymus europaeus is probably an alloploid with two different genomes. The very low pairing in the hybrids with H. jubatum, H. brachyantherum , and H. pusillum indicates that these species do not have any genomes in common with Hordelymus. The hybrids with H. depressum have an intermediate pairing which suggests that there is a certain homoeology in one genome.     

Isozyme Variation and Ploidy Levels within the Apomictic Ranunculus auricomus Complex: Evidence for a Sexual Progenitor Species in Southeastern Austria

Abstract: Allozyme variation of 11 enzymes in each of three populations of the diploid species Ranunculus notabilis and the tetraploid R. variabilis of the predominantly apomictic R. auricomus complex has been studied by horizontal starch gel electrophoresis. Genetic interpretation of electrophoretic patterns is supported by chromosome counts and densitometric ploidy level determination. R. notabilis is confirmed as diploid (2 n = 16), and R. variabilis as tetraploid (2 n = 32). Two triploids and one tetraploid individual were sorted out as putative hybrids. Genetic variability measures based on both allelic frequencies and genotype frequencies were calculated for 13 polymorphic loci. Allelic and genotypic variation in R. notabilis is similar to other sexual plants, and the species is shown to be an outbreeder and not a dihaploid apomict. Corresponding values in R. variabilis confirm a previously assumed clonal population structure. A higher frequency of observed heterozygotes in R. variabilis indicates its hybridogenous origin and the lack of meiosis. Putative hybrids showed combinations of morphological phenotype and electrophoretic patterns of both species. Genetic identity is high among species (0.905), but still lower than within species ( R. notabilis : 0.965, R. variabilis : 0.940); corresponding distance values allow a clear separation of the two species in a dendrogram. Genetic identity and distance values between R. notabilis and R. variabilis resemble those of other progenitor-derivative species pairs. The results favour the hypothesis that R. notabilis is an ancient sexual species of the R. auricomus complex and also one progenitor of the presumably allopolyploid R. variabilis.     

EXPERIMENTAL HYBRIDS IN EPILOBIUM (INCLUDING SECT. ZAUSCHNERIA) SPECIES WITH N = 15 (ONAGRACEAE)

Experimental hybrids involving the three diploid subspecies of Epilobium sect. Zauschneria formed 15 bivalents at meiotic metaphase I, as did experimental hybrids between the three other species of Epilobium (comprising sect. Cordylophorum) with n = 15. The gametic chromosome number of E. suffruticosum Nutt., n = 15, and its relationship to the other two species are reported for the first time. Although we have not obtained hybrids between the species of these two sections, their morphological similarities are impressive and they are surely closely related.     

Cytogenetical changes of offsprings from the induced tetraploid hybrid betweenRanunculus silerifolius (2n = 16) andR. chinensis (2n = 16) (Ranunculaceae)

Cytogenetical studies were carried out on the successive generations of offsprings from the induced tetraploid hybrid (2n = 32) betweenRanunculus silerifolius (2n = 16) andR. chinensis (2n = 16). Aneuploids, 2n = 30 to 35, frequently occurred. In latter subsequent generations the deviation of aneuploids increased, but the proportion of euploids decreased, accompanied by the reduction of fertility of pollen grains and seed sets. F₂ and F₄ PMCs constantly exhibited meiotic abnormality, i.e. formation of quadrivalents and univalents. The speciation process ofR. cantoniensis (2n = 32), which was presumed to arise from tetraploid hybrids between the above two species, is discussed on the basis of the above evidences.Former contributions of this series areOkada & Tamura (1977) andOkada (1984).     

Genome analysis of Elytrigia caespitosa, Lophopyrum nodosum, Pseudoroegneria geniculata ssp. scythica, and Thinopyrum intermedium (Triticeae: Gramineae).

To elucidate the genome constitutions of the tetraploid (2n = 4x = 28) species Elytrigia caespitosa, Lophopyrum nodosum, and Pseudoroegneria geniculata ssp. scythica and the hexaploid (2n = 6x = 42) Thinopyrum intermedium, meiotic pairing was studied in these species as well as 10 hybrids. Karyotype analysis with aceto-orcein stained root-tip cells was performed for the four species and the hybrids of T. bessarabicum with E. caespitosa, P. geniculata ssp. scythica, and T. intermedium. Karyotype analysis by Giemsa C-banding was carried out with the three tetraploid species and the two triploid hybrids involving T. bessarabicum. The species behaved as strict allopolyploids. All hybrids were male sterile with few stainable pollen grains. It is concluded from the results that the three tetraploid species have the genome formula JeJeSS and T. intermedium has the formula JeJeJeJeSS. The chromosomes of the Je and S genomes in these species had C-banding patterns differing from each other and from those of the extant diploid species. Based on these findings, the four species investigated should be placed in the same genus or the same section of a genus. However, new combinations are not proposed at this time pending future taxonomic investigation of the genome constitution of Elytrigia repens (L.) Nevski.     

Frequency of spontaneous amphiploids in Gilia (Polemoniaceae) hybrids

This paper reports the frequency of spontaneous amphiploids or neopolyploids in experimental interspecific hybrids in two annual sections of Gilia (Polemoniaceae, sects. Arachnion and Gilia, x = 9). In each section the species were intercrossed in numerous hybrid combinations to obtain an array of F1 hybrid types; seven of the hybrid types spontaneously produced new amphiploid progeny in F2. In sect. Arachnion the parental species and F1s were all diploids and the amphiploids were tetraploid; in sect. Gilia the parental species were diploids or tetraploids and the amphiploids were tetraploid or hexaploid. Two measures were used to express the frequency of spontaneous amphiploid formation. The first is the proportion of the F1 hybrid combinations that yielded any amphiploid progeny at all. In sect. Arachnion this proportion is 3/39 or 7.7%; in sect. Gilia it is 4/16 or 25%. A second measure is needed to express the variation in productivity among the seven amphiploid-producing hybrid types. The measure adopted is the mean number of new amphiploids per single F1 hybrid plant. The productivity numbers for the three hybrid combinations in sect. Arachnion are 0.25, 0.67, and 2.0; and those for four hybrid combinations in sect. Gilia are 0.15, 0.62, 2.25, and 12.62. There are large differences from one hybrid combination to another in rate of amphiploid formation, and the rate is quite high in some hybrids. The factors affecting these differences are discussed.     

Cytoplasmic and genomic effects on meiotic pairing in brassica hybrids and allotetraploids from pair crosses of three cultivated diploids

Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and "fixed heterosis" in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids.     

Genome size variation and species relationships in Hieracium sub-genus Pilosella (Asteraceae) as inferred by flow cytometry

BACKGROUND AND AIMS: Hieracium sub-genus Pilosella (hawkweeds) is a taxonomically complicated group of vascular plants, the structure of which is substantially influenced by frequent interspecific hybridization and polyploidization. Two kinds of species, 'basic' and 'intermediate' (i.e. hybridogenous), are usually recognized. In this study, genome size variation was investigated in a representative set of Central European hawkweeds in order to assess the value of such a data set for species delineation and inference of evolutionary relationships. METHODS: Holoploid and monoploid genome sizes (C- and Cx-values) were determined using propidium iodide flow cytometry for 376 homogeneously cultivated individuals of Hieracium sub-genus Pilosella, including 24 species (271 individuals), five recent natural hybrids (seven individuals) and experimental F(1) hybrids from four parental combinations (98 individuals). Chromosome counts were available for more than half of the plant accessions. Base composition (proportion of AT/GC bases) was cytometrically estimated in 73 individuals. KEY RESULTS: Seven different ploidy levels (2x-8x) were detected, with intraspecific ploidy polymorphism (up to four different cytotypes) occurring in 11 wild species. Mean 2C-values varied approx. 4.3-fold from 3.53 pg in diploid H. hoppeanum to 15.30 pg in octoploid H. brachiatum. 1Cx-values ranged from 1.72 pg in H. pilosella to 2.16 pg in H. echioides (1.26-fold). The DNA content of (high) polyploids was usually proportional to the DNA values of their diploid/low polyploid counterparts, indicating lack of processes altering genome size (i.e. genome down-sizing). Most species showed constant nuclear DNA amounts, exceptions being three hybridogenous taxa, in which introgressive hybridization was suggested as a presumable trigger for genome size variation. Monoploid genome sizes of hybridogenous species were always between the corresponding values of their putative parents. In addition, there was a good congruency between actual DNA estimates and theoretical values inferred from putative parental combinations and between DNA values of experimental F(1) hybrids and corresponding established hybridogenous taxa. CONCLUSIONS: Significant differences in genome size between hawkweed species from hybridogenous lineages involving the small-genome H. pilosella document the usefulness of nuclear DNA content as a supportive marker for reliable delineation of several of the most problematic taxa in Hieracium sub-genus Pilosella (including classification of borderline morphotypes). In addition, genome size data were shown to have a good predictive value for inferring evolutionary relationships and genome constitution (i.e. putative parental combinations) in hybridogenous species.     

ARTIFICIAL HYBRIDIZATIONS IN THE SUBTRIBE PERITYLANAE (COMPOSITAE–HELENIEAE)

Artificial hybridizations were conducted with 37 species of four genera of the subtribe Peritylanae (Compositae). Crossability, pollen stainability, and meiotic behavior were examined for most of the resulting 61 F₁ hybrid combinations. Intergeneric hybrids involving Amauria, Eutetras, Pericome, and Perityle, and infrageneric hybrids involving Perityle were readily obtained. Lower crossability and hybrid fertility were displayed by intergeneric crosses. The infrageneric crosses of Perityle were organized into two categories, intersectional and infrasectional, based upon the taxonomic sections that are recognized for the genus; sect. Pappothrix, sect. Laphamia, and sect. Perityle. In general, the crossability and hybrid fertility of intersectional crosses was markedly higher than that of intergeneric crosses. The results suggest a closer relationship between the three taxonomic sections of Perityle than between Perityle and other genera of the subtribe.     

A Biosystematic Study on Hybrids Between Psathyrostachys huashanica and Two Species of Roegneria

Intergeneric crosses were made betweem Psathyrostachys huashanica (2n=14, NN)and two Roegneria species, namely, R. ciliaris (2n=28, SSYY), and R. tsukushiensis (2n=42, SSHHYY). Two combinations of P. huashanica crossed with R. ciliaris and R. tsukushiensis produced adult hybrid plants. Although completely sterile, the hybrid plants developed rather vigorously, and were morphologically intermediate between the two parents.Two spikelets per node in part were observed in hybrids, which evidently came from P. huashanica. The chromosome configurations of R. ciliaris × P. huashanica and R. tsukushiensis × P. huashanica were 20.73 I+0.318 II, 24.80 I+1.578 II+0. 012 III, respectively. Polypolar division was found at anaphase I in meiosis of two hybrids. Abnormal meiosis in two hybrids was observed. The chromosome pairing indicates that there is only a little chromosome homoeology between “N” genome of P. huashanicaand “S”, “Y” or “H” genomes of R. ciliaris and R. tsukushiensis.     

Investigations on the artificial synthesis of amphidiploids of Brassica tournefortii Gouan with the other elementary species of Brassica. I. Genomic relationships

With the object of studying the genomic relationships of Brassica tournefortii Gouan with the other elementary species of Brassica viz. B. campestris (2n=20, A genome), B. oleracea (2n=18, C genome) and B. nigra (2n=16, B genome), it has been hybridized with them. The percentage of F₁ hybrids formed, their morphology and meiotic behaviour have been described. Based upon crossability relationships and meiotic pairing in the F₁ hybrids, it is inferred that the D genome of B. tournefortii is more closely related to the A genome than to the B and C genomes. It may have been derived from the A genome which likewise shows a strong genetic isolation from B and C. The species has developed a strong genetic barrier in the course of its evolution and shows little crossability, high hybrid sterility and no gene flow with any of the other elementary species. The fact that it has not formed any natural amphidiploids with the elementary species which otherwise are formed in all combinations, is more evidence that it originated more recently than the A genome. It is presumed that B. tournefortii, being more distantly related to B. nigra than to other elementary species, may form stable artificial aphid resistant amphidiploids with the former.     

Behaviour of rye univalents in hybrids of 6x-triticale with Triticum turgidum (L.) ssp. turgidum conv. durum (Desf.)

In a cytological analysis of the meiotic behaviour in PMCs of five hybrids between hexaploid triticale and durum wheat, Triticum turgidum L., chromosome association at meiotic first metaphase and the behaviour of rye univalents at first anaphase were analyzed. The chromosomes of the B genome, chromosomes 4A and 7A (disomic condition), and the seven rye chromosomes, could be distinguished by their C-banding pattern. No wheat-rye paring was detected at metaphase I. Rye univalents were observed as laggards which disjoined either predominantly equationaly (2R, 3R, 4R, 5R and 7R) or predominantly reductionaly (1R and 6R). Misdivision occurred in up to 3% of rye univalents.     

Genomic relationships between species of theElymus semicostatus group andElymus sensu lato (Poaceae)

Meiotic pairing behaviour in 19 interspecificElymus hybrids is reported and discussed. The hybrids were made between four species belonging to theE. semicostatus group of sect.Goulardia, viz.,E. semicostatus, E. abolinii, E. fedtschenkoi, andE. panormitanus (all 2n = 28), andElymus species of seven different sections, viz., sect.Clinelymiopsis:E. caucasicus (2n = 28); sect.Elymus:E. sibiricus (2n = 28); sect.Goulardia:E. caninus (2n = 28),E. trachycaulus (2n = 28), andE. tsukushiensis (2n = 42); sect.Hyalolepis:E. batalinii (2n = 42); sect.Hystrix:E. hystrix (2n = 28); sect.Macrolepis:E. canadensis (2n = 28); and sect.Turczaninovia:E. dahuricus (2n = 42). Chromosomal pairing at meiotic metaphase I indicated that the species of theE. semicostatus group are genomically closer to the tetraploidE. caucasicus and the hexaploid species, regardless of sectional origin, than to the other tetraploid species of sectionGoulardia. Highest meiotic pairing was found in hybrids involvingE. caucasicus, E. tsukushiensis, andE. dahuricus. The presence of pairing regulating genes inE. abolinii is suspected.     

Polyphyletic allopolyploid origin ofRanunculus cantoniensis (4x) fromR. silerifolius (2x) ×R. chinensis (2x)

Both diploid and tetraploid experimental interspecific hybrids betweenRanunculus silerifolius (2x) andR. chinensis (2x) exhibit normal bivalent pairing. However, microspores of diploid hybrids do not undergo mitosis and their pollen grains are highly sterile, whereas tetraploid hybrids form good pollen grains after microspore division. Evidence is forwarded for the assumption thatR. cantoniensis (4x) has originated by hybridization between these two diploid parental species and by polyploidization of the diploid hybrids. Parallelisms between the different karyotypes ofR. cantoniensis (4x) andR. silerifolius (2x) suggest that the former is a species of polyphyletic origin.     

Morphology,fertility and cytogenetics of intergeneric hybrid between Roegneria kamoji Ohwi and Dasypyrum villosum (L.) Candargy (Poaceae: Triticeae)

The intergeneric hybrids between Roegneria kamoji Ohwi and Dasypyrum villosum (L.)Candargy were successfully obtained by means of embryo culture in vitro. Studies on morphology, fertility and chromosome pairing behavior in meiosis of the parents and their hybrid F_l were carried out in the present work. The results showed that: (1) there were ob vious morphological differences between R. kamoji and D. villosum, and spikes of F_l plants were morphologically intermediate between the two parental species; (2) the seed set of the cross was 11.63%; the hybrid plant was infertile, which indicated that strong repro ductive isolation existed between the parents and R. kamoji and D. villosum were inde pendent biological species; (3) The somatic chromosome number in root-tips of F_l hybrids was 28. Chromosome pairing at MI of PMCs in F_l hybrids was quite low. The meiotic con figuration was 26.72 Ⅰ + 0.62 Ⅱ + 0.02 Ⅲ, which indicated that very low homoeology was detected between the St, H, Y genomes of R. kamoji and the V genome of D. villo- sum, and the relationship between the parental species was remote.     

Inheritance of plant height in hexaploid triticales with R/D substitution

Inheritance of plant height has been studied in combinations of R/D-substituted forms of hexaploid triticale and varieties that have a complete chromosome set of rye and carry various genes determining dwarfism. Analysis of F₁-F₃ hybrids has demonstrated an additive effect of the dwarfism genes and the genetic component of chromosome D affecting the plant height. Deviations in the segregation with respect to plant height found in F₂ combinations involving R/D-substituted forms and varieties with a complete chromosomal set of the R genome may be caused by meiotic disturbances resulting from the R/D substitution and an increased frequency of the transmission of the heterologous chromosome in the monosomic substituted form.     

披碱草属与大麦属系统关系的研究

禾本科中,披碱草属Elymus L.为多倍体属,约含150余种;大麦属Hordeum L.具二倍体和多倍体,约有40余种,该两属均广泛地分布于全球温带地区。该两属,尤其是披碱草属的系统分类较为困难。基于形态学的传统研究认为这两个属的系统关系较远,而细胞学研究的资料却表明,披碱草属的H染色体组起源于大麦属。笔者对来源不同的披碱草属和大麦属的物种进行了远缘杂交,并对其属间杂种F1的减数分裂中期I染色体配对行为进行了分析。结果表明,若以披碱草属作母本,该两属有相对较高的杂交亲合力,通过对杂种幼胚进行分割和离体培养,也能获得杂种F1植株。属间杂种植株的形态介于双亲之间,但更接近于披碱草属,杂种的生殖器官发育不健全,而且所有的杂种F1均完全不育。细胞学的观察结果表明,这两个属间的杂种F1通常具有较低的减数分裂中期I染色体配对数,但有较大的变异。通过笔者的工作及掌握的形态学和细胞学的资料分析认为：披碱草属和大麦属的亲缘关系较为复杂,不能一概而论。含H染色体组的披碱草属和大麦属物种有着较近的亲缘关系,但这两个属中所含的H染色体组已产生了程度不同的分化;不含H染色体组的披碱草属及大麦属的物种具有较远的亲缘关系。     

Somatic cell hybridization of ’oxy’ CMS Brassica juncea (AABB) with B. oleracea (CC) for correction of chlorosis and transfer of novel organelle combinations to allotetraploid brassicas

Alloplasmic lines of cultivated Brassica species with B. oxyrrhina cytoplasm are male-sterile and suffer from severe chlorosis. We developed male-sterile lines corrected for chlorosis by fusing protoplasts of CMS B. juncea (AABB) with ’oxy’ cytoplasm and normal B. oleracea (CC). A large number of male-sterile AABBCC somatic hybrids with desirable organelle combinations, i.e. chloroplasts of B. oleracea and mitochondria with recombinant genomes, were recovered. While no recombination was observed in the chloroplast genome, the mitochondrial genome showed extensive recombination that resulted in the appearance of totally novel banding patterns in some of the hybrids. Hybrids with a parental-type mitochondrial genome as well as recombinant patterns close to either of the parental types were also obtained. Using AABBCC somatic hybrids as bridging material, we transferred the desirable organelle combinations to B. juncea (AABB), B. napus (AACC), and B. carinata (BBCC). Many of these lines are now at advanced stages of backcrossing and show stable inheritance of the CMS character and do not suffer from chlorosis. Received: 9 August 1999 / Accepted: 14 September 1999     

Inheritance of plant height in hexaploid triticales with R/D substitution

Inheritance of plant height has been studied in combinations of R/D-substituted forms of hexaploid triticale and specimens that have a complete chromosome set of rye and carry various genes determining dwarfism. Analysis of F1-F3 hybrids has demonstrated an additive effect of the dwarfism genes and the genetic component of chromosome D affecting the plant height. Deviations in the segregation with respect to plant height found in F2 combinations involving R/D-substituted forms and specimens with a complete chromosomal set of the R genome may be caused by meiotic disturbances resulting from the R/D substitution and an increase frequency of the transmission of the heterologous chromosome in the monosomically substituted form.