Morphological and cytomolecular assessment of intraspecific variability in scarlet eggplant (Solanum aethiopicum L.)

Authors: Sakhanokho, Hamidou; ISLAM-FARIDI, M - Us Forest Service (FS); BLYTHE, EUGENE - Mississippi State Extension Service; Smith, Barbara; Rajasekaran, Kanniah - Rajah; MAJID, MA - Us Forest Service (FS)

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2014
Publication Date: 7/14/2014
Publication URL: http://handle.nal.usda.gov/10113/59408
Citation: Sakhanokho, H.F., Islam-Faridi, M.N., Blythe, E., Smith, B.J., Rajasekaran, K., Majid, M. 2014. Morphological and cytomolecular assessment of intraspecific variability in scarlet eggplant (Solanum aethiopicum L.). Journal of Crop Improvement. 28:437-4453.

Interpretive Summary: Solanum aethiopicum L., which is also known as scarlet eggplant, Ethiopian eggplant, “pumpkin on a stick”, or “mock tomato”, is native to Sub-Saharan Africa, and can now be found in many parts of the world including tropical Africa, South and North America, Asia, and southern Europe. The specific use of this crop depends on the geographic area and/or plant type. Fruit, leaves, shoots, and roots are used for both food and medicinal purposes. Also, some varieties are used as ornamentals. Scarlet eggplant belongs to the same family (Solanaceae or nightshades) as the common eggplant, tomato, and potato. Because some scarlet eggplant varieties show resistance to certain fungal and bacterial diseases, S. aethiopicum has been used in hybridization studies or as a rootstock to transfer resistance genes for these pathogens to common eggplant or tomato plants. Despite these attributes, very little is known about S. aethiopicum genetics as not much investment has been made towards understanding its genome structure. Therefore, the purpose of this work was to contribute to our understanding of variability among S. aethiopicum varieties using morphological and genetic means. Our results showed both similarities and differences among the varieties of scarlet eggplant. Most of the variability among the varieties was due to flower- and fruit-related traits. The results presented in this study contribute to a better understanding of variability in scarlet eggplant, which can be very important for both basic research and the breeding and varietal selection of this crop.

Technical Abstract: Solanum aethiopicum L. (scarlet eggplant), native to Sub-Saharan Africa, can now be found grown as a crop in many parts of the world including tropical Africa, South and North America, Asia, and southern Europe. The specific use of this crop depends on the geographic area and/or plant type. Fruit, leaves, shoots, and roots are used for both food and medicinal purposes. S. aethiopicum is sometimes used as an ornamental and as a rootstock for tomato and common eggplant because of its resistance to certain pathogens. Despite these attributes, very little is known about S. aethiopicum genetics as not much investment has been made towards elucidating its genome. Therefore, the purpose of this work was to contribute to the understanding of intraspecific variability in S. aethiopicum via morphological and cytomolecular characterization of 12 scarlet eggplant accessions. Cluster analysis (Ward's method) was used for grouping the 12 accessions using means of 27 variables. Four separate groups were found, with two each consisting of five accessions and two other each consisting of only one accession. Variability of flower- and fruit-associated descriptors was high among the 12 accessions. Flow cytometry was used to analyze the ploidy of the accessions, and chromosome root tip spread was performed on selected accessions to confirm the ploidy (2n = 2x = 24). Monoploid genome sizes (Cx-value), average chromosome sizes (C/n-value), and guanine + cytosine (GC) content were determined for the 12 accessions. Haploid genome size of S. aethiopicum ranged from 1.312 pg/1C to 1.538 pg/1C, which is very close to the genome size (1.2 pg/1C) of S. melongena L., the common eggplant. GC content of S. aethiopicum accessions was about 40%. Finally, 18S-28S rDNA and 5S rDNA probes were used to study the distribution and physical position of these ribosomal genes in S. aethiopicum, accession Tourimé. One each of 18S-28S and 5S rDNA sites has been identified in this accession. These results contribute to a better understanding of intraspecific variability in S. aethiopicum and can be important for the breeding and varietal selection of this crop.