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  • Author or Editor: Hamidou F. Sakhanokho x
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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.

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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.

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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.

Open Access

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.

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An efficient primary somatic embryo (SE) and secondary somatic embryo (SSE) production system was developed for the ornamental ginger Hedychium bousigonianum Pierre ex Gagnepain. Addition of two ethylene inhibitors, salicylic acid (SA) and silver nitrate (AgNO3), to the culture media improved the system. Callus was initiated and proliferated on a medium containing Murashige and Skoog (MS) basal salts supplemented with 9.05 μM 2,4-dichlorophenoxyacetic acid and 4.6 μM kinetin. Friable callus was transferred to a liquid medium containing MS basal salts, B5 vitamins, 0.6 μM thidiazuron, and 8.9 μM 6-benzylaminopurine to induce somatic embryogenesis. The effects of various concentrations of SA (0, 25, 50, 75, 100, 125, 150 μM) and AgNO3 (0, 10, 20, 30, 40, 50, 60 μM) on callus growth, SE, and SSE development was further evaluated. The rate of callus growth decreased as the concentrations of SA or AgNO3 increased. AgNO3 and SA at all concentrations stimulated SE and SSE development better than the control although a decrease in embryo production was observed at higher concentrations of both SA and AgNO3. The best concentrations for SA were 75 and 100 μM, whereas for AgNO3, they were 30 to 50 μM for both SE and SSE production.

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Breeding blueberry cultivars with enhanced fruit quality requires simple, accurate, and cost-effective assays to select individuals from segregating populations. In this study, berry diameter, berry weight, firmness, pH, total polyphenol, total acids, D-glucose, D-fructose, total glucose, and total sugar content were quantified in 188 southern highbush blueberry selections and cultivars over 2 years. Significant variation between years, genotype, and year × genotype interaction was detected for all traits. Glucose and fructose were the predominant sugars, and they were in a range of 32.14–64.72 and 28.61–69.63 mg/mL, respectively. Total sugars content ranged from 62.22 to 131.15 mg/mL. Correlation analysis showed a strong positive correlation between total sugar content measured with the discrete analyzer and total soluble solids assessed as Brix (r2 = 0.96). In addition, glucose, fructose, and total glucose showed high and positive correlation between them and with the total sugar content. The titratable acidity was positively correlated with total acids (r2 = 0.60) and strong positive correlation between berry diameter and berry weight (r2 = 0.94) was detected. Principal component analysis (PCA) showed that PC1 explained 44.9% of the variation and the major contributing traits for diversity were D-fructose, D-glucose, total glucose, and total sugars. PC2 accounted for 21.2% of the variation and was mainly attributed to berry weight and diameter. Cluster analysis showed that the blueberry genotypes fell into two major groups. Cluster-I comprised genotypes with the highest amounts of total acids, pH, polyphenol, D-glucose, D-fructose, total glucose, and total sugar, whereas Cluster-II has genotypes with distinctly lower amounts of tested compounds and larger berries. Information obtained from this study is critical to identify superior genotypes for future crosses and advance evaluation. In addition, the firmness tester and discrete analyzer used in this study were invaluable in improving the efficiency and precision of phenotyping.

Open Access