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Journal ArticleDOI

Cytological Studies in Cucumis and Citrullus

25 Dec 1970-Cytologia (Japan Mendel Society, International Society of Cytology)-Vol. 35, Iss: 4, pp 561-569
TL;DR: As regards the phylogenetic relationship between the two taxa, it is suggested that C. vulgaris var.
Abstract: The cytological studies in three species of the genus Cucumis, one species and one cultivar of the genus Citrullus have been carried out The possibility that the base number seven, the lowest in the family, has given rise to the base number 12 by fragmentation or the latter has given rise to the former by reduction in the genus Cucumis, has been analysed and discussed in this paper In the genus Citrullus polynemy has been assumed for the difference in the size of the chromosomes As regards the phylogenetic relationship between the two taxa, it is suggested that C vulgaris var fistulosus should be given a distinct specific rank, because of distinct differences in total chromatin matter, chiasmata frequency and breeding behaviour
Citations
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Book ChapterDOI
01 Jan 1993
TL;DR: The use of this vegetable is highlighted and its cytology, genetics, germplasm resources, and reproductive biology are reviewed and techniques applicable to the improvement of cucumber are described.
Abstract: Publisher Summary Cucumber, Cucumis sativus L., is a member of the Cucurbitaceae, which comprises 90 genera and 750 species. It is one of the oldest cultivated vegetable crops and is cultivated in nearly all countries of temperature zones. It is a thermophilic and frost-susceptible plant species, growing best at temperatures above 20 °C. This chapter highlights the use of this vegetable and reviews its cytology, genetics, germplasm resources, and reproductive biology. The taste and demands of the consumer varies according to country. Special varieties must be bred that set fruit under suboptimal temperature conditions. The demands of the processing industry concerning outer appearance—fruit shape, size, and color—also varies depending on the preservation process and the corresponding country. Therefore, cucumber breeders must consider several different breeding aims. General breeding objectives in cucumber are resistance to diseases and animal pests, maintenance of resistance in existing varieties, fruit quality, and fruit yield. Additionally, breeding aims such as parthenocarpy, constancy of femaleness, germination, and fruit set at suboptimum temperatures may be of importance in special breeding programs. Unlike many other plant species, there are different sex types in cucumber, which are of different value in breeding and concerning yield potential. By using sex inheritance and influencing sex expression, the breeding methods of self-pollinated and open-pollinated plants can be applied to cucumber. Thus, the cucumber breeder needs complete knowledge of sex inheritance and of potential ways of influencing sex expression. The chapter provides an overview of the selection of cucumber breeding methods and these methods. There have been several reports on the possibility of applying in vitro techniques in plant breeding of cucumber. The chapter describes techniques that are applicable to the improvement of cucumber.

128 citations

Book ChapterDOI
01 Jan 1993
TL;DR: This chapter discusses the germplasm resources and reproductive biology of melon, and further reviews the selection of breeding methods for melon and the breeding methods and strategies used formelon.
Abstract: Publisher Summary Melon is a member of the genus Cucumis, subtribe Cucumerinae, tribe Melothrieae, subfamily Cucurbitoideae, and family Cucurbitaceae Immature melons are used fresh in salads, cooked—soup, stew, curry, stir-fry—or pickled Mature fruit is eaten fresh as a dessert fruit or in a canned form or used for syrup or jam; dehydrated slices—lightly processed—for short-term or moderate-term storage can be reconstituted, and the pressed juice may be canned Melon seeds are a dietary source of unsaturated vegetable oil and protein and may be lightly roasted and eaten like nuts Melon has a base chromosome number of 12 and is a diploid species, 2n = 24 Polysomatic cells regularly occur in melon Seven polyploid—allopolyploid and autopolyploid—Cucumis species occur but none appears to be closely related to melon The 96 genes reported in melon can be roughly classified into six categories with different categories and number of genes in each: (1) plant, 24, (2) flower, 16, (3) fruit, 19, (4) disease resistance, 22, (5) insect resistance, 5, and (6) isozyme, 14 Inheritance and dominance relationships of economically important plant and fruit characters of melon are not as simple as their quantitative descriptions and gene symbols imply Sex expression is one of the more challenging genetic problems in front of melon breeders This chapter discusses the germplasm resources and reproductive biology of melon It further reviews the selection of breeding methods for melon and the breeding methods and strategies used for melon It also discusses some objectives of breeding in melon

114 citations

Journal ArticleDOI
TL;DR: A fine-scale understanding of the mechanisms of dysploid chromosome reduction that has not been achieved previously is allowed to be achieved.
Abstract: †These authors contributed equally to this work. SUMMARY In the large Cucurbitaceae genus Cucumis, cucumber (C. sativus) is the only species with 2n = 2x = 14 chromosomes. The majority of the remaining species, including melon (C. melo) and the sister species of cucumber, C. hystrix, have 2n = 2x = 24 chromosomes, implying a reduction from n = 12 to n = 7. To understand the underlying mechanisms, we investigated chromosome synteny among cucumber, C. hystrix and melon using integrated and complementary approaches. We identified 14 inversions and a C. hystrix lineage-specific reciprocal inversion between C. hystrix and melon. The results reveal the location and orientation of 53 C. hystrix syntenic blocks on the seven cucumber chromosomes, and allow us to infer at least 59 chromosome rearrangement events that led to the seven cucumber chromosomes, including five fusions, four translocations, and 50 inversions. The 12 inferred chromosomes (AK1–AK12) of an ancestor similar to melon and C. hystrix had strikingly different evolutionary fates, with cucumber chromosome C1 apparently resulting from insertion of chromosome AK12 into the centromeric region of translocated AK2/AK8, cucumber chromosome C3 originating from a Robertsonian-like translocation between AK4 and AK6, and cucumber chromosome C5 originating from fusion of AK9 and AK10. Chromosomes C2, C4 and C6 were the result of complex reshuffling of syntenic blocks from three (AK3, AK5 and AK11), three (AK5, AK7 and AK8) and five (AK2, AK3, AK5, AK8 and AK11) ancestral chromosomes, respectively, through 33 fusion, translocation and inversion events. Previous results (Huang, S., Li, R., Zhang, Z. et al., 2009, Nat. Genet. 41, 1275‐1281; Li, D., Cuevas, H.E., Yang, L., Li, Y., Garcia-Mas, J., Zalapa, J., Staub, J.E., Luan, F., Reddy, U., He, X., Gong, Z., Weng, Y. 2011a, BMC Genomics, 12, 396) showing that cucumber C7 stayed largely intact during the entire evolution of Cucumis are supported. Results from this study allow a fine-scale understanding of the mechanisms of dysploid chromosome reduction that has not been achieved previously.

83 citations


Cites background from "Cytological Studies in Cucumis and ..."

  • ...The origin of the seven cucumber chromosomes has been a long-standing question, with opposite hypotheses being proposed to explain it: a fragmentation hypothesis that postulated de novo regeneration of centromeres from n = 7 to n = 12 (Kozhukhow, 1930; Whitaker, 1933; Bhaduri and Bose, 1947) and a fusion hypothesis that postulated that n = 7 was derived from n = 12 via unequal translocation or fusion of non-homologous chromosomes (Trivedi and Roy, 1970)....

    [...]

  • ...…that postulated de novo regeneration of centromeres from n = 7 to n = 12 (Kozhukhow, 1930; Whitaker, 1933; Bhaduri and Bose, 1947) and a fusion hypothesis that postulated that n = 7 was derived from n = 12 via unequal translocation or fusion of non-homologous chromosomes (Trivedi and Roy, 1970)....

    [...]

Journal ArticleDOI
TL;DR: Both centromere activation and inactivation in cucurbit species were associated with a gain/loss of a large amount of pericentromeric heterochromatin.
Abstract: The centromere of an eukaryotic chromosome can move to a new position during evolution, which may result in a major alteration of the chromosome morphology and karyotype. This centromere repositioning phenomenon has been extensively documented in mammalian species and was implicated to play an important role in mammalian genome evolution. Here we report a centromere repositioning event in plant species. Comparative fluorescence in situ hybridization mapping using common sets of fosmid clones between two pairs of cucumber (Cucumis sativus L.) and melon (Cucumis melo L.) chromosomes revealed changes in centromere positions during evolution. Pachytene chromosome analysis revealed that the current centromeres of all four cucumber and melon chromosomes are associated with distinct pericentromeric heterochromatin. Interestingly, inactivation of a centromere in the original centromeric region was associated with a loss or erosion of its affixed pericentromeric heterochromatin. Thus, both centromere activation and inactivation in cucurbit species were associated with a gain/loss of a large amount of pericentromeric heterochromatin.

83 citations


Cites background from "Cytological Studies in Cucumis and ..."

  • ...Alternatively, if the ancestor species contained 2n 24 chromosomes (25, 26), Cu6 would be derived from a chromosomal fusion event....

    [...]

Journal ArticleDOI
TL;DR: A Bayesian method was developed for calling genotypes from an F₂ population of bottle gourd to construct a high-density genetic map and it was revealed that the cucumber genome region syntenic to the high FST island on LG7 harbors an ortholog of the tomato fruit shape gene OVATE.
Abstract: Restriction site-associated DNA sequencing (RAD-Seq), a next-generation sequencing-based genome 'complexity reduction' protocol, has been useful in population genomics in species with a reference genome. However, the application of this protocol to natural populations of genomically underinvestigated species, particularly under low-to-medium sequencing depth, has not been well justified. In this study, a Bayesian method was developed for calling genotypes from an F₂ population of bottle gourd [Lagenaria siceraria (Mol.) Standl.] to construct a high-density genetic map. Low-depth genome shotgun sequencing allowed the assembly of scaffolds/contigs comprising approximately 50% of the estimated genome, of which 922 were anchored for identifying syntenic regions between species. RAD-Seq genotyping of a natural population comprising 80 accessions identified 3226 single nuclear polymorphisms (SNPs), based on which two sub-gene pools were suggested for association with fruit shape. The two sub-gene pools were moderately differentiated, as reflected by the Hudson's F(ST) value of 0.14, and they represent regions on LG7 with strikingly elevated F(ST) values. Seven-fold reduction in heterozygosity and two times increase in LD (r²) were observed in the same region for the round-fruited sub-gene pool. Outlier test suggested the locus LX3405 on LG7 to be a candidate site under selection. Comparative genomic analysis revealed that the cucumber genome region syntenic to the high FST island on LG7 harbors an ortholog of the tomato fruit shape gene OVATE. Our results point to a bright future of applying RAD-Seq to population genomic studies for non-model species even under low-to-medium sequencing efforts. The genomic resources provide valuable information for cucurbit genome research.

81 citations

References
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133 citations

Journal ArticleDOI
TL;DR: Are sex chromosomes in higher pl,~nt~ nucleologenic?
Abstract: Introduction . M~t~rial and methods 0 bservations: Cucumis a~giz,u~ . Cucumis Memo Trichoaanth~ diolca Luffa aegyp~i~c,a . Luffa a~u~an~u~a . 6'o~iuia indica Beuincasa cerifera M~,mrdica cllarantia Cucurbita ~r~aarima Polysomaty Discussion (i) Numerica! correlation between m a~m um number ofnucleoli, sat~llltes and secondary constrictions (ii) Maximum number of nucleo]i ,lnd nucleolar constrictions of chromosomes witah reference to polyplcidy and aneuploidy . . . {iii) Variation of chromosome number in Cucm.bitaceac and R~. cytogsnetic interpretation (iv} Are sex chromosomes in higher pl,~nt~ nucleologenic? . Summary P, efsrsnces P A G ~

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Journal ArticleDOI
17 Dec 1955-Nature

52 citations

01 Jan 1967

18 citations