Triploid F1 Hybrids Research Articles

Genetic Diversity of Cynodon transvaalensis Burtt‐Davy and Its Relatedness to Hexaploid C. dactylon (L.) Pers. as Indicated by AFLP Markers

Cynodon transvaalensis Burtt‐Davy (African bermudagrass) is valued as turf and for use in interspecific hybridization with C. dactylon (L.) Pers. var. dactylon to produce turf cultivars. Little information is available regarding the magnitude of genetic variation within the taxon. Accordingly, this study was undertaken to evaluate the genetic diversity among 14 C. transvaalensis accessions and to examine the phylogenetic relatedness of C. transvaalensis, two hexaploid (2n = 6x = 54) C. dactylon var. dactylon accessions, two C. transvaalensis by hexaploid C. dactylon var. dactylon interspecific tetraploid (2n = 4x = 36) F1 hybrids, and one putative tetraploid C. dactylon var. dactylon by C. transvaalensis triploid (2n = 3x = 27) F1 hybrid. Fluorescence‐labeled amplified fragment length polymorphism (AFLP) DNA profiling was used to study the genetic relationships among these accessions. A total of 381 polymorphic AFLP markers were amplified from 13 primer combinations. The 14 C. transvaalensis accessions and the putative triploid F1 hybrid clustered into one group and had genetic dissimilarity coefficients ranging from 0.01 to 0.51. The 14 C. transvaalensis accessions had genetic dissimilarity coefficients ranging from 0.01 to 0.34. The C. dactylon var. dactylon accessions and the two tetraploid F1 hybrids clustered in the second group, with genetic dissimilarity coefficients ranging from 0.17 to 0.33. The tetraploid F1 hybrids were more closely related to C. dactylon var. dactylon than to C. transvaalensis, while the opposite was true for the putative triploid F1 hybrid. The results indicate the presence of genetic diversity in C. transvaalensis that could be exploited in intra‐ and interspecific breeding improvement.

Endosperm balance number manipulation for direct in vivo germplasm introgression to potato from a sexually isolated relative (Solanum commersonii Dun.).

Diploid (2n = 2x = 24) Solanum species with endosperm balance number (EBN) = 1 are sexually isolated from diploid 2EBN species and both tetraploid (2n = 4x = 48, 4EBN) and haploid (2n = 2x = 24, 2EBN) S. tuberosum Group Tuberosum. To sexually overcome these crossing barriers in the diploid species S. commersonii (1EBN), the manipulation of the EBN was accomplished by scaling up and down ploidy levels. Triploid F1 hybrids between an in vitro-doubled clone of S. commersonii (2n = 4x = 48, 2EBN) and diploid 2EBN clones were successfully used in 3x x 4x crosses with S. tuberosum Group Tuberosum, resulting in pentaploid/near pentaploid BC1 progenies. This provided evidence of 2n (3x) egg formation in the triploid female parents. Two selected BC1 pentaploid hybrids were successfully backcrossed both as male and as female parents with S. tuberosum Group Tuberosum. The somatic chromosome number varied greatly among the resulting BC2 progenies, which included hyperaneuploids, but also a number (4.8%) of 48-chromosome plants. The introgression of S. commersonii genomes was confirmed by the presence of S. commersonii-specific randomly amplified polymorphic DNA markers in the BC2 population analyzed. The results clearly demonstrate the feasibility of germplasm introgression from sexually isolated diploid 1EBN species into the 4x (4EBN) gene pool of the cultivated potato using sexual hybridization. Based on the amount and type of genetic variation generated, cumbersomeness, general applicability, costs, and other factors, it would be interesting to compare the approach reported here with other in vitro or in vivo, direct or indirect, approaches previously reported.

Identification of a barley chromosomal interchange using N-banding and in situ hybridization techniques

The combination of N-banding and in situ hybridization was used to illustrate the rapid identification of the chromosomes involved in a newly formed chromosomal interchange (reciprocal translocation) in barley. The plant heterozygous for the interchange was derived from the backcross of 'Su Pie', a two-rowed Chinese winter barley cultivar (2n = 2x = 14), with pollen from a triploid interspecific F1 hybrid (2n = 3x = 21) obtained from the cross of 'Su Pie' × tetraploid Hordeum bulbosum accession GBC141 (2n = 4x = 28). Pollen mother cells of the interchanged plant exhibited one quadrivalent and five bivalents in 97.8% of cells. Partial sterility of florets was observed in spikes obtained from self-pollination and the plants morphologically resembled barley. Barley chromosomes were readily identified by N-banding from root-tip cells with one band missing from the short arm of one of the pair of chromosome 4. N-banding of metaphase I of meiosis revealed that chromosomes 1, 2, and 5 were not involved in the interchange. In situ hybridization with a rDNA probe showed that chromosomes 6 and 7 were paired as bivalents. In conclusion, chromosomes 3 and 4 are involved in the interchange with the breakpoint in the short arm of chromosome 4 between the two proximal N-bands. The use of chromosome-specific DNA probes for chromosome identification using in situ hybridization is proposed.Key words: barley, chromosomal interchange, N-banding, in situ hybridization, rDNA.

The Attempted Transfer of Male Sterility from the Cornerstone Mutant of Tetraploid Wheat to Diploid Wheat

AbstractAn attempt was made to transfer male‐sterility, mslc, from the Cornerstone mutant of tetraploid wheat to diploid wheat. The N‐banding technique revealed that chromosome 4 A of tetraploid wheat does not pair with chromosome 4 of diploid wheat in triploid F1 hybrids: consequtntly the transfer of male‐sterility gene(s) from tetraploid wheat to diploid was not successful. The culchiane induced ampliploids possessing AAAABB in mslc background were fully fertile indicating the complete compensation of mslc by the newly introduced A genome of T. monocaccum. The fertility compensating gene(S) presumably located on chromosome 4 of diploid wheat may be used to produce hybrid wheat by the XYZ system.

Synthesis and evaluation of Triticum durum — T. monococcum amphiploids

Nine Triticum durum — T. monococcum amphiploids (AABBAmAm) were synthesized by chromosome doubling of sterile triploid F1 hybrids involving nine T. durum (AABB) cultivars and a T. monococcum (AmAm) line. The triploid F1 hybrids had a range of 4–7 bivalents and 7–13 univalents per PMC. The synthetic amphiploids, however, showed a high degree of preferential pairing of chromosomes of the A genomes of diploid and tetraploid wheats. The amphiploids were meiotically stable and fully fertile. Superiority of four amphiploids for tiller number per plant, 100-grain weight, protein content and resistance to Karnal bunt demonstrated that these could either be commercially exploited as such after overcoming certain inherent defects or used to introgress desirable genes into durum and bread wheat cultivars. Methods for improvement of these amphiploids are discussed.

Polyploid complexes of Glycine tabacina (Labill.) Benth. and G. tomentella Hayata revealed by cytogenetic analysis

Observations on geographical distribution, cytotypes, crossability, and meiotic chromosome behavior in intra- and interspecific F1 hybrids revealed that the complexes of Glycine tabacina (2n = 40, 80) and G. tomentella (2n = 38, 40, 78, 80) evolved through allopolyploidization. It is apparent from this study that 80-chromosome tabacinas are composed of two distinct morphological complexes having one common genome: with and without adventitious roots. In contrast, the tomentellas are inseparable morphologically. They are composed of accessions with at least three genomic complexes: (i) 2n = 80, accessions from Australia and Taiwan; (ii) 2n = 80, an accession from Papua New Guinea; and (iii) 2n = 78, accessions from Australia and Papua New Guinea. Hybrids within each group showed complete synapsis and set normal seeds; however, hybrids between the groups apparently differed by one genome and were completely sterile. Chromosome pairing in triploid interspecific F1 hybrids (2n = 59, 60) indicated that G. canescens (2n = 40) was probably the donor of the common genome for 80-chromosome tabacinas and tomentellas. Glycine latifolia (2n = 40) appears to have contributed its genome to G. tabacina (2n = 80) but could not have participated in the speciation of 80-chromosome tomentellas. Likewise, the 38-chromosome G. tomentella has no genomic affinity with 80-chromosome tabacinas but has complete affinity with 80-chromosome tomentellas. On the basis of present findings and the results published earlier, the evolution of the genus Glycine will be discussed. Key words: Glycine spp., genome, hybridization (intraspecific), hybridization (interspecific), speciation.

Gene transfer from non-tuberous to tuberous Solanum species: Evidence from meiosis in hybrids

The distant hybrids between non-tuberous Solanum species and tuberous S. pinnatisectum display little or no pairing in F1 and predominantly bivalent formation (preferential pairing) after chromosome doubling. In such a situation the question about the potential and extent of gene transfer from the non-tuberous parent to the tuberous one is relevant to potato breeding. This question was investigated by studying meiosis in triploid and hexaploid hybrids from crosses between diploid TV5 x tetraploid (S. etuberosum x S. pinnatisectum). TV5 is similar to S. verrucosum with cytoplasm of S. tuberosum. The following evidence was found for the desirable transfer of S. etuberosum genes to the tuberous species. The triploid F1 hybrids did not display the configurations 12 II+12 I expected if no gene exchange would take place between S. etuberosum and the tuberous species; however, a considerable number of multivalents per cell was observed in all plants studied. In the hexaploid F1 hybrids, obtained from the triploids through somatic doubling in vitro, 36 bivalents could reasonably be expected. Although bivalents were predominant (an overall average of 24.2 per cell) quite a few chromosomes were associated as multivalents in all plants investigated. It is concluded that in the hybrids studied a considerable amount of pairing and chiasma formation occurs between chromosomes of non-tuberous and those of tuberous Solanum species. This pairing affinity is larger than that found in 2x and 4x hybrids from S. etuberosum x S. pinnatisectum. Some hypotheses are put forward to explain this increased pairing affinity.

Biochemical Genetic Analyses of the Grass Carp ♀ X Bighead Carp ♂ F1Hybrid and the Parental Species

Abstract The patterns of isozyme expression in tissues of the grass carp Ctenopharyngodon idella, bighead carp Hypophthalmichthys nobilis, and F1 hybrid (grass carp ♀ x bighead carp ♂) were analyzed by vertical starch gel electrophoresis and histochemical staining procedures. Both parental species and the F1 hybrid were fixed for electrophoretically indistinguishable alleles at 21 of 30 loci studied. However, the two parental species were fixed for different alleles at the remaining nine loci. Quantitative isozyme determinations were used to calculate the parental gene dosages in individuals of the 1979, 1980, and 1981 broods of F1 hybrids produced in Arkansas. Exclusive of low percentages of gynogenetic grass carp observed, the percentages of triploid F1 hybrids were 100% (1979), 44% (1980), and 100% (1981).

ATTEMPTED GENE TRANSFER FROM TETRAPLOIDS TO DIPLOIDS INTRITICUM

The possibility of introgression from tetraploid (2n = 28) AABB to diploid (2n = 14) AA wheats was investigated. Reciprocal crosses were made between tetraploid Triticum turgidum L. var. durum Desf. and diploids T. monococcum L. var. boeoticum Boiss., or T. urartu Tum.; and between T. turgidum var. carthlicum Nevski and T. monococcum L., or boeoticum, or urartu. The triploid F1hybrids were backcrossed to diploid parents. All backcross derivatives were lethal at BC1or BC2except those of durum × boeoticum which were carried to BC4. However, neither fertile plants nor plants with the diploid chromosome number were obtained up to BC4generation. As backcross generations advanced, backcross seed set, seed development, seed viability and plant vigor decreased. The failure of introgression from tetraploid to diploid wheats may be due to differential selection for unreduced gametes and adverse nucleo-cytoplasmic interactions.

Transfer of resistance to race 2 of Plasmodiophora brassicae from Brassica napus to cabbage (B. Oleracea spp. Capitata). IV. A resistant 18-chromosome B1 plant and its B2 progenies

The somatic karyotype and meiotic chromosome behavior were studied in an 18-chromosome B1 plant derived from backcrossing a triploid (Brassica napus x B. oleracea ssp. capitata) F1 hybrid to cabbage. It is considered that cabbage chromosomes no. 1 and no. 7 were substituted by two shorter B. napus chromosomes. Meiotic disturbances were more apparent during the late stages of second division. Seed fertility of this plant was largely restored in the second backcrosses with both cabbage and broccoli. 18-chromosome B2 plants resistant to race 2 of Plasmodiophora brassicae were recovered among the progenies.

Transfer of resistance to race 2 of Plasmodiophora brassicae from Brassica napus to cabbage (B. oleracea ssp. capitata). III. First backcross and F2 progenies from interspecific hybrids between B. napus and B. oleracea ssp. capitata

The first backcross and F2 progenies from triploid F1 and tetraploid F1 hybrids between B. napus and 2x and 4x B. oleracea ssp. capitata (cabbage) were studied for their general morphology, resistance to race 2 of the clubroot pathogen, chromosome number and meiotic chromosome behavior. No linkage was apparent between resistance and the major morphological characters. Unreduced gametes played a large part in the successful formation of seed of the B1 and F2 progeny. B1 plants with low chromosome numbers were selected for use in recurrent backcrosses. The potential use of anther culture to extract gametic progenies from resistant B1 and F2 plants with higher chromosome numbers was suggested. The presence of homoeologous pairing observed in all the plants is considered advantageous for selecting suitable progeny in later generations.

Fertility of 17 Colchicine‐induced Perennial Triticeae Amphiploids Through Four Generations1

Seed set and pollen stainability were determined for 17 perennial colchicine‐induced amphiploids (2n=42 or 56) derived from sterile triploid and tetraploid F1 hybrids of Agropyron, Elymus, Hordeum, and Sitanion species. Chromosome doubling restored fertility; however, the level of fertility in the originally doubled hybrids (C0 generation) declined in advanced generations. Fertility stabilized in most hexaploids after the C1 generation, whereas fertility of most octoploids continued to decline. Seed set (seeds/spike) of nine hexaploid amphiploids averaged 17.5, 18.9, and 17.4 in the C1, C2, and C3 generations, respectively. Eight octoploid amphiploids averaged 8.1, 9.1, and 4.2 seeds/spike, respectively, over the same three generations. Synthesis of fertile Triticeae grass species appears to be feasible at the hexaploid level but not at the octoploid level.

Meiosis in different F1-hybrids of Solanum acaule Bitt. x S. bulbocastanum Dun. and its bearing on genome relationship, fertility and breeding behaviour

Meiosis was studied in some triploid, tetraploid and hexaploid F1-hybrids from Solanum acaule x S. bulbocastanum and in a triploid F1-hybrid from S. acaule x S. tuberosum-haploid.

GENETIC RELATIONSHIPS BETWEEN DIPLOIDS AND TETRAPLOIDS IN SERIES EUBARBATAE OF AVENA

Diploid (2n = 14) and tetraploid (2n = 28) entities in series Eubarbatae of the genus Avena have been found to be genetically closely linked and are regarded as a single polyploid complex. At both ploidy levels the various morphological types are interfertile. Diploids and tetraploids are largely sympatric in their distribution and converge considerably in their ranges of morphological variation. Contacts between diploids and tetraploids are common and blurred morphological boundaries characterize mixed populations.The possibility of gene flow between diploids and tetraploids has been indicated by the behavior of triploid F1 hybrids. Such hybrids have been found to be partially fertile. In their progeny a conspicuous restoration of fertility is apparent: numerous plants of the F2 generation have been stabilized around the tetraploid level, few around the diploid level. In contact areas, triploids can be regarded as efficient bridges of gene flow between the two ploidy levels.The range of variation found at the tetraploid level is fully explicable by the variation present in the diploid races. Tetraploids are therefore regarded to have had an inter-varietal origin, i.e. have evolved from a single genome. They apparently represent an extreme case of bivalentization, where a full shift from an autotetraploid to an allotetraploid meiotic behavior had occurred. Meiotic behavior of the F2 plants also indicate such origin.

Chromosome mosaics in synthetic amphiploids in the Avenae

1. Chromosome-deficient cells were found at the meiotic stage in synthetic amphiploids derived from various diploid-tetraploid combinations in the Avenae. 2. Chromosome-deficient cells were found to be dependent on the species used as parents to produce the triploid F1 hybrid. 3. Chromosome deficiency in two amphiploid plants Cc 4387/1 and Cc 4435/1 did not follow a Poisson distribution. 4. A study of chromosome pairing revealed that aberrant cells undergo normal meiosis. 5. First (A1) and second (A2) generation amphiploid plants showed that chromosome-deficient gametes were functional. 6. The occurrence of chromosome-deficient cells is attributed to spindle abnormalities at the pre-meiotic divisions.

CYTOTAXONOMIC STUDIES ON RUMEX SECTION AXILLARES

The present investigation covers only the North American species of Rumex subgenus Rumex (Lapathum) section Axillares. A review was made of all the previous taxonomical and cytological work done in this group. All the species of the section Axillares were morphologically studied and their natural distribution plotted on maps. The distributional data were derived from about 3000 herbarium specimens gathered from various herbaria in the United States and Canada. Chromosome numbers of 17 taxa of the section Axillares were determined. The three subsections were found to comprise a polyploid series, the monotypic subsection Venosi with 2n = 40, R. verticillatus of the subsection Verticillati with 2n = 60, and all but two of the species studied in the subsection Salicifolii with 2n = 20; the two exceptions were R. mexicanus and R. utahensis, both with 2n = 40. Meiosis was studied in the species of the subsection Salicifolii only. Both the diploid and the tetraploid species showed essentially normal meiotic behavior. Pollen fertility was also very high in all the species. A number of intra- and inter-specific hybridizations were made between the taxa in the subsection Salicifolii, involving both the diploid and the tetraploid species. The resulting diploid (diploid × diploid), triploid (diploid × tetraploid), and tetraploid (tetraploid × tetraploid) F1 hybrids were both morphologically and cytologically studied. Morphologically almost all the diploid and tetraploid hybrids were intermediate between the two parents. The triploid hybrids showed more similarity to the tetraploid species involved in the cross, Meiosis in all the diploid hybrids was essentially normal with 10 bivalents. However, there was a significant decrease in chiasma frequency as compared with the parent species. This was postulated to be due to cryptic structural hybridity. There were three different categories of pollen fertility, ranging from low to very high, which were not correlated with any meiotic irregularities. All the diploid hybrids were fertile and set abundant seeds. Meiosis in the triploid hybrids was very irregular with mostly 10 bivalents and 10 univalents at metaphase I. Anaphases were also irregular, resulting in numerous micronuclei. All the triploid hybrids were sterile and set only a few undeveloped seeds. Meiosis in the tetraploid hybrid studied was also irregular with mostly 9 bivalents and 22 univalents. It was thus postulated that both the tetraploid species are allotetraploids with one genome in common between them and that this genome is essentially the same one shared by the diploid species so far cytologically studied. The tetraploid hybrids were completely sterile and did not set any seed. From the cytogenetic data, the diploid species studied were shown to be very closely interrelated. However, no taxonomic revision was undertaken owing to lack of more complete data involving all the species comprising the group.

FERTILE HYBRIDS DERIVED FROM A WIDE SPECIES CROSS INASTER

EvolutionVolume 11, Issue 4 p. 482-486 ArticleFree Access FERTILE HYBRIDS DERIVED FROM A WIDE SPECIES CROSS IN ASTER Charlotte J. Avers, Charlotte J. Avers Department of Botany, University of Miami, Coral Gables, FloridaSearch for more papers by this author Charlotte J. Avers, Charlotte J. Avers Department of Botany, University of Miami, Coral Gables, FloridaSearch for more papers by this author First published: December 1957 https://doi.org/10.1111/j.1558-5646.1957.tb02919.xCitations: 7AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume11, Issue4December 1957Pages 482-486 ReferencesRelatedInformation