Assessing diversity of solanum nigrum l grown in Kenya
Rwigi, Susan Wagio
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Solanum nigrum (commonly referred to as black nightshade) are world-wide weeds on arable land, gardens and rubbish pits. Nightshades have been used in the field of medicine in the manufacture of analgesics, ointments and vasodilators. The limited information available on this neglected and underutilized family hinders their development as well as sustainable conservation. Existing knowledge on the genetic potential of these plants is limited and the information regarding the genomic organization of Solanum nigrum complex species found in Kenya is scarce. The objective of this work was to evaluate diversity of S. nigrum populations grown in selected parts of Kenya using morphological and Simple Sequence Repeats (SSR) markers. A total of 120 samples from four populations were assessed. Four aerial characters were used in morphological characterization. Leaf surface (smooth and hairy), Leaf margin (entire and sinuate), Leaf shape (ovat, lanceolate and diamond ), Fruit colour (Red, Purple small and Purple large). Tukeys HSD test revealed significant variation in the characteristics assessed (P≤0.05). Four SSR primers generated 63 polymorphic bands ranging between 14-17 bands per primer set. Polymorphic Information Content ranged from 0.1429 to 0.1855 with a mean of 0.1704. The average heterozygosity He=0.1370 for SSR markers used. Axis 1 and 2 of PCoA accounted for 44.65% of the variance in the population distribution. AMOVA revealed 14% variation among populations and 86% within populations. Variation among regions was not genetically evident. Nei’s genetic distance ranged from 0.010 (Kipkaren and Matanya) to 0.020 (Makuyu and Mauche). Dissimilarity analysis was performed using Unweighted Neighbor Joining with 1000 bootstraps in DARwin 6.0.5 software. The dendogram did not reflect morphological and genetic differences, a good indicator of missing genetic divergence between populations. Variation in the Agro Ecological Zone does not imply variation in the S. nigrum varieties grown. Comparison between morphological and molecular data revealed clustering of leaf surface and fruit colour with genetic data. However, there was no clustering between leaf shape and leaf margin with the same data. Observed morphological differences are mainly as a result of selection by human. Findings from this study show that S. nigrum complex exhibit low genetic diversity but high morphological variability. S. nigrum is a group of closely related plants as shown by low genetic distance and lack of clustering patterns. The output of this study will have far reaching applications in the development of markers linked to important agronomic traits that can be used in future breeding programs of the Solanum complex. The findings will further contribute to changing the taxonomic confusion within the Solanum nigrum.