FISH Karyotype Analysis of Four Wild Cucurbitaceae Species Using 5S and 45S rDNA Probes and the Emergence of New Polyploids in Trichosanthes kirilowii Maxim.

Abstract

Wild relative species of domesticated crops are useful genetic resources for improving agronomic traits. Cytogenetic investigations based on chromosome composition provide insight into basic genetic and genomic characteristics of a species that can be exploited in a breeding program. Here, we used FISH analysis to characterize the ploidy level, chromosome constitution, and genomic distribution of 5S and 45S ribosomal DNA (rDNA) in four wild Cucurbitaceae species, namely, Citrullus lanatus All species were diploids, except for T. kirilowii, which included hexa-, octa-, and decaploid cytotypes (2n = 6x = 66, 8x = 88, and 10x = 110). All species have small metaphase chromosomes in the range of 2-5 µm. The 45S rDNA signals were localized distally compared to the 5S rDNA. C. lanatus var. citroides and M. japonica showed one and two loci of 45S and 5S rDNA, respectively, with co-localization of rDNA signals in one M. japonica chromosome. S. angulatus showed two co-localized signals of 5S and 45S rDNA loci. The hexaploid T. kirilowii cytotype showed five signals each for 45S and 5S rDNA, with three being co-localized. This is the first report of hexaploid and decaploid cytotypes in T. kirilowii. These results will be useful in future Cucurbitaceae breeding programs.

Karyotypes of Three Exotic Cucurbit Species Based on Triple-Color FISH Analysis

“…The family Cucurbitaceae has the most common basic chromosome number of 11 or 12 (Whitaker, 1933;Beevy and Kuriachan, 1996;Schaefer and Renner, 2010;Waminal and Kim, 2015). The three cucurbits, investigated in this study, also verify this chromosome number.…”

“…Most cucurbit species have small chromosomes that are difficult to distinguish (Waminal and Kim, 2012), however, fluorescence in situ hybridization (FISH) has revealed the identity of chromosome pairs and provided information that can be used in breeding programs (Huang et al, 2009;Waminal et al, 2011;Waminal and Kim, 2012). We have carried out triple-color FISH karyotype analysis with Korean wild or crop cucurbit species that will be useful for phylogenetic comparative studies and breeding programs focusing on Korean Cucurbitaceae family (Waminal et al, 2011;Waminal and Kim, 2012;Waminal and Kim, 2015). Here, we determined chromosome composition and distribution patterns of rDNA and telomeric DNA, employing triple-color FISH analysis, in three exotic cucurbit species of C. melo var.…”

Differences in Karyotype and Fluorochrome Banding Patterns among Variations of <i>Trichosanthes cucumerina</i> with Different Fruit Size

“…The mechanism of whether and how these processes may lead to certain chromosomal changes is not known in this case. The cultivar Anguina share same chromosome numbers with TCSF unlike many cultivated cucurbits with higher ploidy (Waminal and Kim 2015). A detailed investigation of chromosome morphology and fluorochrome banding pattern clarified the difference between the T. cucumerina and its cultivar Anguina.…”

Induction of Polyploidy in Cucumis melo ‘Chammel’ and Evaluation of Morphological and Cytogenetic Changes

“…FISH is a molecular cytogenetic technique that uses fluorescently labeled probes to determine the presences of a particular DNA sequence in the nuclei (Speicher and Carter, 2005;Hwang et al, 2020). FISH analysis was used for the accurate confirmation of ploidy in a previous study (Islam et al, 2020;Waminal and Kim, 2015). The 5S rDNA and 18S rDNA loci are usually located at different sites on different chromosomes, and their transcription is carried out by rRNA polymerases.…”