Karyotype Analysis of Diploid and Autotetraploid Mini-watermelon
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Taking the diploid and autotetraploid mini-watermelon as meterial,the diploid and autotetraploid miniwatermelons' karyotype were analyzed using traditional tabletting method.The results showed that the diploid miniwatermelon karyotype formula was 2n=2x=22=22mwith the index of the As.k(karyotypic asymmetry)of 58.90%,with 11pairs metacentric chromosomes.The karyotype belonged to 1A,with ultimately symmetry karyotype.In addition,the tetraploid mini-watermelon karyotype formula was 2n=4x=44=44m,As.k was 56.45%,same as diploid.The results proved that tetraploid mini-watermelon resulted in the chromosome doubling of diploid.Keywords:
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ABSTRACT In the plant-parasite nematode Heterodera glycines, 2 forms, in addition to the diploid (9 bivalents), have been isolated and analysed: a tetrapioid (18 bivalents) and an aneuploid (14 bivalents, hybrid between the diploid and the tetrapioid). Observations on the formation of their karyotypes indicates normal and non-homologous pairing. Eighteen normal synaptonemal complexes (SC) are present in pachytene nuclei of the tetrapioid. Two of the SCs are enclosed in a large heterochromatin mass that is displaced to one side of the nucleus. Such a mass has not been observed in the diploid or the aneuploid. Another 2 normal SCs of the tetrapioid have each a ‘modified SC region’ (MSC) within which the SC appears disorganized. The aneuploid has 14 SCs that are unattached at either end. Only 25% of the karyotype length is normal in the appearance of the SCs. The rest can be traced by the presence of disorganized SC material and condensed chromatin. Four MSCs are present in the hybrid nuclei. The possible role of the MSCs in the sex determination system is discussed.
Heterodera
Soybean cyst nematode
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Triploid-diploid crosses yielded nearly 75% aneuploid progeny. Of these, 60% were trisomics (2n = 25) and the rest ranged from 2n = 26 to 2n = 29. The most productive parents were those involving triploid S. maglia and diploid S. berthaultii. The initial trisomics often were not morphologically distinguishable from diploid sibs. Distinctive characteristics – such as slow growth; small, compact habit; lack of interstitial leaflets; and a bilobed stigma — were apparent in the backcross progenies. Most of the trisomics were fertile enough to be used in further genetic studies. Transmission of the extra chromosome through the female for three trisomics was 20–24%. Only primary trisomics were expected but meiotic study of seven clones indicated that all were secondary trisomics. The isochromosome may have originated from the tetraploids involved in the formation of the triploid clones or have been produced during meiosis of the triploid parent.
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Platycodon grandiflorus is an important medicinal plant in China. Induction of polyploidy was successfully attempted in this medicinal plant using 0.05% colchicine semi-solid under 72 h by apical shoot tip treatment of young seedlings, and then 50% mutant plants were obtained. It was testified by the chromosome number in mitosis and its karyotype analysis for diploid control and obtained mutants. The results showed that the chromosome number of the diploid plant was 2n=2x=18, whereas the chromosome number of the obtained mutants was 2n=4x=36. The karyotype formula of mutant plant and diploid control were K=2n=4X=36=24m+12sm (4SAT) and K=2n=2X=18=12m+6sm (2SAT), respectively by karyotype analysis and they belonged to 2B and 2A karyotype. It was confirmed that the obtained mutant plants were tetraploid. Key words: Platycodon grandiflorus, Obtained mutants, karyotype analysis.
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Morpho-criteria and karyotype analysis of two mulberry verities, namely, Kollegal and Morus cathyana were selected. Morpho-criteria, stomatal frequency, somatic chromosome number, ploidy level, karyotype analysis, arm ratio and total haploid chromatin length were studied. Kollegal is diploid with 2n=28 and Morus cathyana is tetraploid with 2n=56. Somatic chromosome length ranges from 1.26 m to 3.22 m where as arm ratio ranges from 0.62 to 0.97 m. Stomatal frequency is lesser in diploid when compared to tetraploid variety. In both the varieties 3 to 4 types of chromosomes have been observed. Chromosomes are small sized with a narrow range of variation in length.
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1. The tetraploid plant of giant variety of Petunia was selfed. Among 31 plants of the F1 progeny 29 were tetraploid, one 4n-1 and one 4n-3. No significant morphological differences were noticed among them.2. The tetraploid plants of the giant variety and the diploid plants of small variety were crossed reciprocally. Among the populations of F1 progenies two gave a high percent of triploids besides each one plant of heteroploids and a diploid. The third gave no triploid but respectively one plant of 2n, 3n+2 and 4n. Among these three diploid plants, one was completely different from both the parents, while the other two were complete replicas of the diploid parent. The triploid plants showed approximately intermediate characters more or less tending toward the tetraploid parent.3. The triploid progeny was cytologically studied. In the heterotypic metaphase 7 sets of trivalent were not infrequentiy found. Almost all the trivalent configurations possible in auto-triploids were observed excepting one. Besides these the ring of three or triangle, and the multivalents were sometimes met with. These may be interpreted by the segmental interchange hypothesis.4. The 2n×4n crossing gave only the diploid progeny in one Gase. These progeny exhibited exactly the same characters morphologically as well as physiologically as the diploid parent. Another mating resulted in three tetraploids and one 4n-1 plant.5. The triploid hybrids selfed gave 26, 27, 28 and 29 chromosome plants in the F, progeny among which 27 chromosome plants were of the highest fequency. The majority of these progenies had one or two fragments of chromosomes. A trabant derived from the diploid ancestor is identified at one end of one of the chromosomes.6. The triploid hybrid was back crossed to the diploid parent. Three plants were obtained with the somatic number respectively of 19, 20 and 21. This shows that the gametes of the triploid with the chromosome numbers of 12, 13 and 14 function.7. The tetraploid-triploid crossings gave the F1 progenies of 24, 26, 27, 28 and 29 chromosomes with respective frequencies of 1, 6, 17 and 29.8. The reciprocals of the above crossings gave one 29 chromosome plant and twenty 28 chromosome plants.9. The appearance of diploid progenies in the crossings between 2n and 4n plants may be explained by the diploid parthenogenesis.10. As to the appearance of diploid progenies in 4n×2n crossings, two different Gases must be distinguished: (1) diploid parthenogenesis and (2) merogony. Both of these are supposed to occur.11. The occurrence of tetraploid plants among the F1 progeny of 4n×2n crossings probably was induced by the fertilization of an egg nucleus by a generative nucleus with double number of chromosomes.12. The tetraploid and triploid plants of Petunia must be autotetraploid and auto-triploid.
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SUMMARYThe karyotype and microsporogenesis of triploid Crocus sativus were studied. The high percentage of trivalents observed at metaphase I (on average, 7.3 trivalents per cell) together with the karyotype configuration confirm autotriploidy. Some considerations about the presence of one unique chromosome in the karyotype and about the origin of triploidy are presented.
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Secale
Plant biochemistry
Chromosome morphology
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