Morpho-anatomical characterization, DNA barcoding, and phylogenetic analysis of Solanum argentinum Bitter & Lillo: an addition to the alien Flora of Egypt

Abstract Background Solanum argentinum Bitter & Lillo, a woody species native to South America (Argentina, Bolivia, and Paraguay), is documented as an addition to the alien flora of Egypt. This study presents the species’ first published record in Egypt, based on specimens collected from the Giza Zoological Garden, where it has persisted for over 60 years. Results Morphological and microscopic characterization of the Egyptian material revealed key diagnostic features, including an unarmed woody habit, dendritic non-glandular trichomes, white stellate corollas, and globose yellowish-orange berries (3.5–6 mm in height and diameter) with 4–8 reniform, minutely pitted seeds. Scanning electron microscopy (SEM) showed small, tricolporate, prolate pollen grains (20–25 × 12–16 μm) with scabrate ornamentation. Foliar epidermal analysis showed hypostomatic, anisocytic stomata (rarely anomocytic) on the abaxial surface with an average stomatal density of 186 per mm 2 , and a stomatal index of 26.4%. Anatomical sections of vegetative organs confirmed diagnostic family- and genus-level traits, including bicollateral vascular bundles and sand crystals. Multi-locus phylogenetic analyses of a single Egyptian specimen (voucher ASTU-MA1001), using DNA sequence data from the nuclear internal transcribed spacer (ITS2) and chloroplast ( rbcL and trnL) barcoding markers, placed the Egyptian specimen firmly within the Geminata clade, with close affinity to reference S. argentinum sequences. Re-evaluation of CAI and Kew historical sheets (Mohamed El Mahdi s.n., collected in December 1963) confirmed its continuous casual persistence inside the zoo. Conclusion This study provides the first published record of S. argentinum in Egypt. Because the species remains restricted to a single locality, we classified it as an introduced casual alien. The comprehensive morphological, anatomical, and molecular dataset presented here provides essential diagnostic tools to differentiate this taxon from other native and cultivated Solanum species in Egypt, establishing a robust baseline for long-term monitoring to track potential escape or naturalization.