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1.
Summary Crosses between a wild species C. chacoense and three cultivated species of chili pepper viz. C. annuum, C. frutescens and C. chinense yielded hybrids when C. chacoense was the seed parent but the reciprocal crosses were unsuccessful. C. chacoense × C. annuum F1 hybrids were partly fertile and therefore an F2 population could be raised; the other two F1 hybrids were totally sterile. Chromosome pairing in the F1 plants resulted largely in bivalents and a few multivalents and univalents. The genomes of the four species share large homologies and the role of chromosome structural changes in genome differentiation is suggested. Hybrid sterility is the major reproductive isolation mechanism. 相似文献
2.
The F1 hybrids of seven diploid Alstroemeria species (2n=2x=16) were investigated for the production of numerically unreduced (2n) gametes and their mode of origin. Based on a survey of 17 interspecific hybrid combinations,consisting of 119 genotypes,
it was found that the F1 hybrids of Chilean-Brazilian species mostly produced first division restitution (FDR) 2n gametes. These F1 hybrids were self-pollinated in order to obtain F2 seeds, which was an indication that the F1 plants also
produced 2neggs simultaneously. All the F2 progeny plants were typical allotetraploids, most of which formed 16 bivalents and a small
proportion formed multivalents during metaphase I stages of meiosis. Through genomic in situ hybridisation (GISH) it was proved that multivalent formation in F2plants, derived from A. inodora ×A. pelegrina hybrid, was due to homoeologous recombination but not from reciprocal translocations. In order to test the segregation pattern
of the recombinant chromosomes, an F3 population from one genotype, P6C49-6, was investigated. The recombinant chromosomes
assorted independently from each other supporting the hypothesis that the segregation of chromosomes in ring quadrivalents
did not behave like those in translocation heterozygotes. It was concluded that in allopolyploids of Alstroemeria,bilateral sexual polyploidisation could accomplish genetic recombination by both homoeologous crossing-over as well as through
the assortment of chromosomes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Nuclear DNA content in 84 Hosta cultivars was measuredby flow cytometry. As an internal standard we used the closely related Agave americana, the latter was calibrated against other reference species. Propidium iodide values were 20%higher than DAPI values, indicating a lower AT/GC ratio for Hosta. Ten new tetraploid plants were found in addition to the only tetraploid known so far; H. ventricosa.Small forms of the tetraploid H. ventricosa turned out tobe triploid hybrids. Three other triploids were discovered. Threesupposed tetraploids turned out to be diploid. In five plantsthe ploidy levels of the germ layers L1 and L3 appeared to be different. In these cases thick leaves coincides with a tetraploid DNA content. The DNA contents as measured in theseploidy chimeras coincide with differences in leaf colour, thusgiving an opportunity to analyze the build-up of Hosta plants.In general, analysis of the nuclear DNA content can be used as a simple means to increase the possibilities for creating new cultivars in this economically important perennial. 相似文献
4.
Summary 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. 相似文献
5.
Summary Introgression of germplasm from diploid wild Arachis species to A. hypogaea has great potential for improving pest resistance in cultivated peanuts. This investigation evaluated methods for incorporating exotic germplasm into cultivated peanuts, especially for Cercospora arachidicola
Hori resistance. Interspecific hybrids between A. hypogaea (cvs. NC 2 and NC 5) and the wild species A. cardenasii
Krap. et Greg.
nom. nud. and A. chacoense
Krap. et Greg.
nom. nud. were analyzed cytologically and for leafspot resistance. All F1 hybrids were sterile, had irregular meiosis, and very few multivalents. They were highly resistant to C. arachidicola in field tests and had a 10-fold reduction of conidia per lesion in the greenhouse as compared to A. hypogaea cultivars. After colchicine treatments of F1 hybrids, hexaploids (2n=60) and aneuploids (2n=54, 56, 63) were observed. The hexaploids had up to 18 univalents per pollen mother cell and very few multivalents, indicating a low frequency of intergenomic chromosome pairing. For C. arachidicola resistance, significant differences were not found among wild species parents, F1 hybrids and two generations of hexaploids. Most hexaploids were stable at 2n=60 and embryos aborted when backcrosses with the respective wild species were attempted. However, when hexaploids were backcrossed to A. hypogaea, several fertile pentaploid (2n=50) offspring were obtained. Use of self-pollinating pentaploids is believed to be the quickest method to recover 40-chromosome hybrid derivatives in these hybrids. 相似文献
6.
The first success at interspecific hybridization between cultivated sunflower(H. annuus) and a diploid perennial species, H. simulans is reported. The F1s from both direct and reciprocal directions exhibited dominance of the wild species phenotype and were pollen sterile. Meiosis
was irregular in the F1 hybrids and both univalents and multivalents were observed. Multiplication of the interspecific hybrids was achieved through
in vitro culture of nodal sections on Murashige & Skoog medium supplemented with 0.5 mg l-1 benzyladenine. Fertility of the interspecific hybrids was improved by subjecting the in vitro proliferating shoots to 0.001% colchicine incorporated in the shoot multiplication medium. The amphiploids serve as fertile
bridges and facilitate interspecific gene transfer through conventional breeding.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Accessions of Beta macrocarpa Guss., collected on the Canary Islands, were tetraploid (2n = 36). Three of these accessions were studied in detail. The plants were rather uniform in their morphological appearance, both within and between accessions, and were annual and fully self-compatible. Meiosis was completely diploidised, suggesting an alloploid nature of the tetraploid species. Crosses with diploid B. vulgaris yielded triploid hybrids which were sterile or nearly so; a few descendants of such hybrids were highly aneuploid. Crosses between tetraploid B. macrocarpa and autotetraploid cytotypes of B. vulgaris showed variable results, only part of these crosses yielded tetraploid hybrids. The tetraploid hybrids exhibited somewhat higher fertility than the triploids. An F2 generation showed partial hybrid dwarfness, partial fertility and segregation for carliness and coloration of the hypocotyl. All hybrids had multivalents at meiosis (averages: 2.5—5.4 multivalents per pollen mother cell), indicating suppression of the diploidised meiosis. The possibilities of application of the diploidised meiosis in breeding sugar beet are discussed. 相似文献
8.
Cytology and reproductive behavior of diploid, tetraploid and hexaploid germplasm accessions of a wild forage grass: Paspalum compressifolium 总被引：4，自引：0，他引：4
Summary Fourteen germplasm accessions of Paspalum compressifolium native from southern Brazil were cytologically and embryologically analysed. The study revealed that one accession was diploid (2n=20), twelve were tetraploid (2n=40) and one was hexaploid (2n=60). This is the first report of diploid and hexaploid cytotypes for this species. Studies on microsporogenesis, megasporogenesis, and embryo sac development indicated that the diploid cytotype had regular meiotic behavior and reproduces sexually. Tetraploid cytotype usually had an important proportion of chromosomes that associated as quadrivalents during meiosis and reproduced by mean of aposporous apomixis. The hexaploid cytotype showed irregular meiotic behavior with about one third of the chromosomes associated as multivalents and reproduced by aposporous apomixis. Thus, P. compressifolium could be an agamic complex. Breeding in this complex is possible due to the presence of diploid sexuals which can be treated by colchicine and pollinated by apomicts. 相似文献
9.
The wild non-tuberous species Solanumetuberosum is resistant to biotic andabiotic stresses, but is very difficult tocross with cultivated potato. Therefore,interspecific somatic hybrids between adihaploid clone of potato S.tuberosum (2n=2x=24, AA genome) and thediploid species S. etuberosum(2n=2x=24, EE genome) were produced byprotoplast fusion. Among the 7 fertilefusion hybrids analysed by genomic insitu hybridisation (GISH), three groups ofplants were found with the genomicconstitution of AAEE, AAEEEE and AAAAEE.Four fusion hybrids had exactly theexpected chromosome composition, while eachof the three aneuploid hybrids had lost twochromosomes of S. etuberosum. Twobackcross progenies were developed, andGISH analysis was applied to analysetransmission of the parental chromosomesinto the sexual generations. BC1hybrids derived from the crosses of thehexaploid somatic hybrids with tetraploidpotato were pentaploid with thetheoretically expected genomic compositionor with slight deviation from thisexpectation. In the three BC2 hybridsanalysed by GISH seven to 12 chromosomes ofS. etuberosum were detected in thepredominant S. tuberosum background.No recombinant chromosomes in the hybridswere detected. Genome dosage affects tuberformation in hybrids and their progenies,but has less effect on resistance to potatovirus Y (PVY) in fusion hybrids. Severalgenotypes of the fusion hybrids andBC1 progeny did not show viralinfection even in the graftingexperiments. 相似文献
10.
Cytogenetical and molecular investigations on somatic hybrids of Sinapis alba and Brassica juncea and their backcross progeny 总被引：3，自引：0，他引：3
Somatic hybrids of Sinapis alba+Brassica juncea (Sal Sal AABB) were synthesized by protoplast electrofusion. They were true genomic allopolyploids since they possessed 60 chromosomes, i.e. the sum of S. alba (2n= 24) and B. juncea (2n= 36) chromosomes. Chromosome pairing was predominantly bivalent with the occasional occurrence of multivalents in the pollen mother cells at diakinesis and metaphase I. Hybrids were completely pollen-sterile, but produced seeds on back-crossing with B. juncea and B. campestris. A total of 37 BC1 plants were raised from two somatic hybrids (JS-1 and JS-2) and 24 of these were analysed cytologically. The 22 plants originating from the pollinations of somatic hybrids with B. juncea showed a chromosome configuration of 18II+12I and had 42–86% pollen fertility. Two plants from the backcrosses of the somatic hybrid with B. campestris formed 10II +20I, and had 0–4% fertile pollen. Total DNA analysis by probing with pTA71 carrying a full-length 18S–25S rDNA fragment of the wheat nuclear genome revealed that the two somatic hybrids possessed all the characteristic bands of both the species, confirming their hybridity. Probing with the mitochondrial coxI and atp9 genes indicated mitochondrial genome recombination in the hybrids. Hybridization with chloroplast-specific psbD indicated that both the somatic hybrids possessed the cp genome of S. alba origin. 相似文献
11.
Summary An interspecific hybridization program designed to transfer gene(s) controlling apomixis from Pennisetum squamulatum Fresen. (2n=6x=54) to induced tetraploid (2n=4x=28) cultivated pearl millet, Pennisetum americanum (L.) Leeke resulted in four offtype plants, two with 27 chromosomes and two with 28 chromosomes. These plants were found among 217 spaced plants established from open-pollinated seed of an apomictic 21-chromosome polyhaploid (2n=21) plant derived from an apomictic interspecific hybrid (2n=41) between tetraploid pearl millet and Pennisetum squamulatum. It appeared that a 21- (or 20-) chromosome unreduced egg from the apomictic polyhaploid united with a 7-chromosome pearl millet (2n=2x=14) gamete to produce a 28- (or 27-) chromosome offspring. Meiotic chromosome behavior was irregular averaging from 3.60 to 4.05 bivalents per microsporocyte in the 27- and 28-chromosome hybrids. The 27- or 28-chromosome hybrids, like the 21-chromosome female parent, shed no pollen, but set from 1.8 to 28 seed per panicle when allowed to outcross with pearl millet. Progeny of the 28-chromosome hybrids were uniform and identical to their respective female parents, indicating that apomixis had been effectively transferred through the egg. In addition, a 56-chromosome plant resulting from chromosome doubling of a 28-chromosome hybrid was identified. Pollen was 68 per cent stainable and the plant averaged 2.3 selfed seeds per panicle. Chromosomes of the 56-chromosome plant paired as bivalents (x=10.67) or associated in multivalents. Three to nine chromosomes remained unpaired at metaphase I. Multiple four-nucleate embryo sacs indicated the 56-chromosome hybrid was an obligate apomict. The production of 27-, 28-, and 56-chromosome hybrid derivatives were the results of interspecific hybridization, haploidization, fertilization of unreduced apomictic eggs, and spontaneous chromosome doubling. These mechanisms resulted in new unique genome combinations between x=7 and x=9 Pennisetum species. 相似文献
12.
I. H. McNaughton 《Euphytica》1973,22(2):301-309
Summary The synthesis of leafy, forage forms of Brassica napocampestris (2n=58, aaaacc) by colchicine treatment of hybrids between B. napus (2n=38, aacc) and B. campestris (2n=20, aa) is described.The cytology of both triploid and hexaploid hybrids was studied. B. napocampestris proved fairly stable meiotically although multivalents were formed and some aneuploids detected in later generations. Seed fertility proved adequate for commercial production.The variation within the parental species and their easy crossability suggests that several distinct forms of B. napocampestris could be created, some of which may have agronomic potential. B. napocampestris may be used as a stepping stone in elaborating the range of variability within B. napus. 相似文献
13.
Yoshito Asano 《Euphytica》1982,31(1):121-128
Summary Meiotic observations in PMCs were made in eight kinds of interspecific hybrids in Lilium. Three hybrids, 6134-S × L. cernuum. L. regale × L. leichtlinii maximowiczii and L. auratum platyphyllum × L. henryi showed respectively the mean chromosome association frequencies of 1.4II, 0.8II and 1.5II per cell at MI which were the lowest values hitherto reported in Lilium hybrids. In L. longiflorum × L. henryi, 33.3° of the cells had 1 or 2 multivalents of three to five chromosomes in addition to uni- and bivalents. 12° bivalents and 12 univalents were invariably observed in the triploid hybrid L. longiflorum × L. cernuum. The hybrids between the species belonging to the different sections of the genus generally showed high pollen sterility, with some exceptions. A more or less remote genomic homology was found between the different sections in Lilium. 相似文献
14.
Meiosis and Pollen Viability in Helianthus tuberosus L. and its Hybrids with Cultivated Sunflower 总被引：1，自引：0，他引：1
The hexaploid species of Helianthus tuberosus is a potential source of resistance to several sunflower pathogens. But crossed with cultivated sunflower, it produces F, hybrids which have low values of fertility or even full sterility. Pollen viability and meiotic features were studied in 17 populations of the species H. tuberosus and in F1 hybrids. Significant differences in pollen viability existed between populations (47.1–98.8%). In the 15 FI hybrids, plant fertility ranged from 0 to 100 per combination, while pollen viability ranged from 12.4 to 57.1. Meiosis was almost normal in the analyzed species, and irregular in the F, hybrids. The highest percentage of meiocytes was with bivalents (85.9), but univalents (0.3) and multivalents (13.8) occurred as well. In metaphase and anaphase, the percentage of meiocytes with fast and lagging chromosomes was high. In anaphase, chromosome bridges were detected in 9.9 of the meiocytes. 相似文献
15.
Summary The meiotic behaviour of five tetraploid wheat strains x Elytricum fertile (2n=42 chromosomes, AABBD(SH) genomes) F1 hybrids has been analysed. Multivalent associations were observed in the hybrids which could be attributed to Elymus sibiricus L. gene (s) somewhat suppressing the activity of the wheat homoelogous pairing control system. This interaction depends on the wheat genotype. The effect was particularly notable when Triticum turgidum var. salomonis was the wheat parent. The possibility of gene transfer from Elymus to wheat is discussed. 相似文献
16.
Summary Seeds from open-pollinated flowers collected from hybrids of several Coffea species were analysed for caffeine content. The caffeine content was not always intermediary to that of the parents; higher and lower values were found. Diploid F1 hybrids between accessions of C. eugenioides and C. salvatrix showed the lowest seed caffeine content. Seeds of the tetraploid hybrids C. arabica × C. salvatrix or C. arabica × C. eugenioides hybrids presented low caffeine content. The possibility of breeding coffee to reduce the caffeine content in the seeds by interspecific hybridization of C. arabica with other Coffea species is discussed. 相似文献
17.
Summary
Melilotus alba differs by a reciprocal translocation from 7 other species which are categorized into M. officinalis and M. dentata groups. The two species groups, however, remained to be studied in relation to their cytological relations because of early degeneration of hybrid embryo. Interspecific triple crosses were successfully made in order to examine whether or not the reciprocal translocations observed were of the same origin. When F1 hybrids between M. alba and M. officinalis group were crossed with M. dentata group, about a half of hybrids plants were heterozygous for a reciprocal translocation while the remaining plants were normal chromosome pairing, showing a segregation ratio of 1:1. This result indicates that reciprocal translocations observed among the three groups are of the same origin. Accordingly, it is expected that M. officinalis group and M. dentata group have the same chromosomal constitutions. 相似文献
18.
Fingerprinting of alfalfa meiotic mutants using RAPD markers 总被引：5，自引：0，他引：5
Summary A calendar of female sporogenesis and gametogenesis was made for both apomictic tetraploid (2n=4x=36) Brachiaria brizantha and Brachiaria decumbens and their apomictic F1 hybrids with sexual tetraploid (2n=4x=36) Brachiaria ruziziensis. Microgametogenesis was used as a reference. Apospory was facultative in both species and hybrids. Environmental conditions had variable effects on the level of apomixis according to each genotype. Ratios of segregation into sexuals and apomicts in the interspecific hybrids suggest an oligogenic determinism with dominant apomixis in the genus Brachiaria. Highly apomictic and partially male fertile hybrids were identified and will be used in an improvement program to transfer genes for apomixis into the sexual species B. ruziziensis. 相似文献
19.
Summary Hybrids between T. ambiguum and T. repens were successfully established after ovule culture. The hybrids were male sterile but one of the hybrids produced a single seed when backcrossed to T. repens, while the other produced a significantly greater number of seeds. The majority of the backcross hybrids from the latter had 48 chromosomes, being produced from the fertilisation of unreduced gametes of the F1 hybrid by T. repens pollen. Regular meiosis in the BC1 hybrid resulted in the production of balanced gametes containing the full complement of T. repens chromosomes and the polyhaploid set of T. ambiguum chromosomes. There was no difficulty in establishing a substantial population of BC2 hybrids. The meiotic behaviour of the BC1 hybrid indicated that it should be possible to transfer genes from T. ambiguum into white clover T. repens. The significance of the results in terms of the use of alien variation in the improvement of white clover is discussed. 相似文献
20.
Summary Three non-tuberous Solanum species of series Etuberosa-S. brevidens (brd), S. etuberosum (etb) and S. fernandezianum (frn)-upon selfing displayed compatible berry set but seed set varied and on an average was below normal. Also in crosses between species berry set was unhampered (apart from the crosses with short-styled frn as pollen plant), but the interspecific hybrid plants showed various degrees of sterility and a low average seed set upon selfing. Cytological investigations revealed that in pure species-plants semi-sterility regularly occurred and was invariably associated with multivalent associations (up to decavalents). This may account for the decreased seed set found after selfing and intercrossing. Meiosis in F1-hybrids was even more irregular, 75% of the pmc's showing multivalents involving from 4 to as many as 22 chromosomes in various complicated configurations in which even numbers of chromosomes were predominant. However, anaphase I separation was numerically balanced in more than 75% of the cells. Pollen stainability was very low in the hybrids.It is concluded that heterozygous translocations occur within each species and that the genomes of the species are differentiated by means of gross structural changes. In view of this and of the high chromosome pairing affinity the genome symbols E
1, E
2 and E
3 are proposed for etb, brd and frn, respectively.Crossability of the Etuberosa species with tuberous S. pinnatisectum (pnt) was slightly more successful (average 2.7 seeds/berry) than that of Etuberosa species hybrids with S. pinnatisectum (average 1.7 seed/berry). In the hybrids studied-etb × pnt, frn × pnt and (brd × etb) × pnt-a high frequency of univalents was the rule (range 6–16 per cell). In addition rod bivalents (4–8 per cell) and a low frequency of trivalents occurred (0–3 in the biparental hybrids and 1–4 in the trispecific hybrid).Utilization of the valuable characters of Etuberosa for potato breeding is dependent on the degree of gene exchange between Etuberosa chromosomes and chromosomes of tuberous species. In the diploid hybrids such exchange, though limited, may take place through bivalents and trivalents. As shown in this article such diploid hybrids are non-crossable because of complete male and female sterility. Only after doubling the number of chromosomes the hybrids are fertile and can be used for further crosses. 相似文献