A biosystematic analysis of Solanum acaule

J.P. Kardolus

Research output: Thesisinternal PhD, WU

Abstract

<p>This thesis describes a biosysternatic analysis of the allotetraploid species <em>Solanum acaule</em> . <em>Solanum acaule</em> is one of the circa 200 tuber-bearing Solanum species ( <em>Solanum</em> sect. <em>Petota</em> , Solanaceae) and often used in plant breeding programs for its disease resistances and frost tolerance. This species has the widest distribution of all wild potato species, from Ecuador into Argentina, and occurs at altitudes up to 4500 meter in the Andes. Together with the hexaplold <em>S. albicans</em> it forms the polyploid taxonomic series <em>Acaulia</em> . This study focuses on the hybrid speciation of series <em>Acaulia</em> . <em>Solanum acaule</em> shows morphological similarities with species of series <em>Megristacroloba</em> and <em>Tuberosa</em> , which have been hypothesized as possible ancestors. A phylogenetic study is conducted to unravel evolutionary relationships of <em>Solanum acaule</em> and its putative progenitors. Several morphological aspects of series <em>Acaulia</em> and related species are examined, and combined with a study of molecular markers. The thesis is completed with the proposal of a new subspecies of Solanum acaule.<p>In a multivariate morphological analysis the boundaries of series <em>Acaulia</em> are determined and variation within the series is reconsidered. Inflorescence architectural traits, such as the dimensions of pedicels and corollas, are discussed in relation to the taxonomy of Solanum sect. Petota species, their habitat and breeding behavior. An unrecorded inflorescence type, which can be characterized as a monochasium with a strongly reduced peduncle and one or two 'extra' flowers in the axil of the subtending leaf, is described in series Acaulia. The taxonomy of <em>Solanum</em> sect. <em>Petota</em> often depends on quantitative characters. These are often variable, causing difficulties in species classification. However, series <em>Acaulia</em> is characterized by a qualitative character, i.e. a modified or even completely absent pedicel articulation. Normally, unfertilized flowers separate at the floral abscission zone which is located at this articulation. In an anatomical study this zone is proven to be absent in non- articulated pedicels of Solanum acaule. In <em>S. albicans</em> this <em></em> zone is modified. These special features of pedicel articulation in series Acaulia are discussed in relation to the 'jointless'-mutations in tomato. The AFLP <sup>TM</SUP>molecular marker-technique is for the first time applied in <em>Solanum</em> taxonomy. Highly informative DNA fingerprints are produced with the AFLP-technique. Classifications based on AFLPs are generally in agreement with current taxonomic opinions, but also new evolutionary insights are revealed. The results of the present AFLP study casts doubt on the status of certain taxonomic series, and the classification of particular species into these series. Based on the neighbor-joining analysis of the AFLP data it is concluded that the hexaploid <em>Solanum demissum</em> (from Mexico) is likely to be closely related to both the South American series <em>Acaulia</em> and the Central American polyploid series <em>Longipedicellata,</em> and <em></em> feasibly a hybrid descendant of these series. Series <em>Acaulia</em> itself is a monophyletic group in the cladistic analyses, and it is most advanced in the cladograms. In addition to the AFLP study, an isozyme analysis has been conducted on series <em>Acaulia</em> and its closest relatives. Based on both AFLP and isozyme data, it is concluded that series Acaulia is indeed most closely related to series <em>Tuberosa</em> and <em>Megistacroloba.</em> However, <em></em> it is not a simple derivative of a hybridization event of species of these two series, but more probably one of its ancestors could have belonged to the series <em>Megistacroloba / T uberosa</em> affiliation. The second ancestor that provided the unique characters to series <em>Acaulia</em> is still unknown, and possibly extinct.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
Supervisors/Advisors
  • van der Maesen, L.J.G., Promotor
  • van den Berg, R.G., Promotor
Award date11 Feb 1998
Place of PublicationS.l.
Publisher
Print ISBNs9789054858294
Publication statusPublished - 1998

Keywords

  • solanum acaule
  • solanaceae
  • botany
  • taxonomy
  • classification
  • biological nomenclature

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