Species of the genus Solanum usually possess pedicels with a floral abscission zone, which is designated the "articulation" or "joint." A distinct group of tuber-bearing wild potatoes, series Acaulia, is characterized by an indistinct or completely absent articulation. The anatomy of pedicels without articulation is compared with that of articulated pedicels. No abscission zone is observed in pedicels without an articulation, a situation found in the tetraploids Solanum acaule Bitter ssp. acaule and S. acaule ssp. punae (Juz.) Hawkes & Hjert. The hexaploids Solanum albicans (Ochoa) Ochoa and S. acaule ssp. palmirense Kardolus of series Acaulia have an anatomically incompletely differentiated abscission zone. Solanum acaule ssp. aemulans (Bitter & Wittm.) Hawkes & Hjert. (2n = 48) has articulated pedicels and a floral abscission zone. The absence of a floral abscission zone is presumably a recessive trait. The special features of pedicel articulation in series Acaulia are discussed in relation to the "jointless" mutations in tomato. The position of the articulation on the pedicel is concluded to be less significant for taxonomy than generally considered.Key words: Solanaceae, Solanum acaule, anatomy, "jointless" mutation, pedicel articulation, taxonomy.
Analyses of 202 plastid genomes elucidate the phylogeny of Solanum section Petota
