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- Author or Editor: Nurul Islam-Faridi x
Christia obcordata is an intriguing small-sized house plant with unusual and attractive features such as its striped leaves. Because very little is known about the plant, we conducted an investigation of its genome and chromosomes. The number of chromosomes was determined using a protoplast technique to prepare root tip chromosome spread and was found to be 2n = 2x = 20. Flow cytometry was used to determine nuclear DNA content (1C = 0.65 pg = 634.4 Mb) for C. obcordata and AT/GC composition was shown to be AT% = 62.8% ± 0.0% and GC% = 37.2% ± 0.0%. Finally, fluorescent in situ hybridization was used to locate ribosomal RNA gene families in C. obcordata. Ribosomal RNA gene families, viz. 18S-28S and 5S rDNA, are unique cytomolecular landmarks that provide valuable information about the evolutionary organization of a genome. We have identified one locus each of 18S-28S and 5S rDNA. The 18S-28S rDNA is located in the subterminal position on the secondary constriction region [also known as the nucleolus organizer region (NOR)] and the 5S rDNA is located interstitially close to a centromeric position. The basic information gathered in this study on C. obcordata will be helpful in understanding the genetics of this species.
We report for the first time the incidence of spontaneous autotetraploidy in Solanum aethiopicum (PI 636107). Stomatal dimensions and frequency, number of chloroplasts per guard cell, flow cytometry, and chromosome counts were used to differentiate the diploid plants from tetraploids. The impact of increased ploidy on pollen viability as assessed by in vitro germination and on selected morphological traits was evaluated. In vitro pollen germination was reduced in tetraploid plants, but no significant differences were found in fruit production per plant between diploid and tetraploid plants. Compared with the diploids, the tetraploid plants were significantly shorter and had wider leaves and smaller fruits; therefore, tetraploid S. aethiopicum plants can be valuable for future breeding programs, particularly those aiming to develop shorter, more compact plants. Moreover, some S. aethiopicum selections are grown for their edible leaves, so tetraploid plants producing large leaves would be desirable. Additionally, the availability of tetraploid S. aethiopicum could remove hybridization barriers caused by ploidy differences with other tetraploid Solanum species.
Ziziphus mauritiana Lam. is a widespread shrub or tree of the Sahel region, where it grows wild and is used for various purposes, including nutrition, medicine, and firewood. Current domestication programs focus on using the local species as rootstock for the improved imported Asian cultivars to provide tolerance to pests and diseases. The plant plays an increasing economic role in the livelihoods of local Sahelian populations, but despite this there is little genetic information about it. The purpose of our study was to determine the genome size estimate and chromosome numbers of Z. mauritiana germplasm collected from eastern Senegal, West Africa. Genome size estimates were determined using flow cytometry, and chromosome count was achieved using chromosome spreads of actively growing root tips. The mean, median, minimum, and maximum genome size estimates (1Cx-DNA) of Z. mauritiana were 418.74 Mb, 417.45 Mb, 410.72 Mb, and 432.12 Mb, respectively. Plants of the germplasm investigated were found to be octoploid with a chromosome number of 2n = 8x = 96. The genetic information gathered in this study can be useful for phylogenetic studies, sequencing projects, and domestication programs that focus on controlled pollination for the development of improved Z. Mauritania cultivars in the Sahel region.
The ploidy level of H. muluense, a diploid (2n = 2x = 34) and dwarf ornamental ginger species, has been determined and is reported for the first time. Oryzalin and colchicine were successfully used to induce polyploidy in Hedychium muluense in vitro. Embryogenic cell lines were treated with oryzalin (30, 60, or 120 μM) and colchicine (2.5, 5, or 10 mm) for 24, 48, or 72 h. The control contained no antimitotic agent. Flow cytometry, chloroplast count, and stomatal frequency were more effective and reliable than stomatal length as methods for assessing ploidy. Overall, oryzalin was more effective than colchicine in inducing polyploidy. The highest induction frequency (15%) of tetraploidy was achieved when embryogenic callus was exposed to 60 μM oryzalin for 72 h. For colchicine, exposure of embryogenic callus to the 2.5 mm colchicine for 24 h was the most effective in creating tetraploid (13%) plants.
To our knowledge, there has been no published technique to produce consistently high-quality slides of somatic chromosomes of roses (Rosa sp.). Therefore, various pretreatments, fixatives, digestions, stains, and maceration and squashing methods were tested to identify a procedure to produce clear, well-spread chromosomes from shoot tips. The best results were obtained after pretreatment in a mixture of 0.1% colchicine and 0.001 m 8-hydroxyquinoline for 4 h, and fixation in 2 acetone: 1 acetic acid (v/v) with 2% (w/v) polyvinylpyrrolidone. The darkest-stained chromosomes were obtained with carbol-fuchsin staining of air-dried cell suspensions that had been spread in 3 ethanol: 1 acetic acid (v/v).