R.G. van den Berg

THE POTENTIAL OF AFLPS IN BIOSYSTEMATICS : A FIRST APPLICATION IN SOLANUM TAXONOMY (SOLANACEAE)

Using the AFLP technique highly informative DNA fingerprints were generated from 19 taxa ofSolanum sect.Petota (potatoes) and three taxa ofSolanum sect.Lycopersicum (tomatoes). Both phenetic and cladistic analyses were conducted from the individual genotypic level to the species level. An AFLP fingerprint, using a combination of suitable AFLP primers, generated 12 to 71 scorable fragments per genotype which was sufficient for taxonomic interpretation. The classifications based on the molecular markers were generally in agreement with current taxonomic opinions. Unexpectedly,S. microdontum was associated with ser.Megistacroloba rather than with ser.Tuberosa, andS. demissum (ser.Demissa) and species of ser.Acaulia appeared closely affiliated. AFLP is an efficient and reliable technique to generate biosystematic data and therefore a promising tool for evolutionary studies.

Collapse of morphological species in the wild potato Solanum brevicaule complex (Solanaceae: sect. Petota)

The major cultivated potato, Solanum tuberosum, and six other related cultivated species, are hypothesized to have arisen from a group of weedy relatives indigenous to the central Andes of central Peru, Bolivia, and northern Argentina. A major problem hindering investigations of the origins of the cultivated species has been a continuing debate over the species boundaries of their putative progenitors. This study investigated the morphological phenetic species boundaries of these putative progenitors and five cultivated taxa, here collectively referred to as the Solanum brevicaule complex. Two hundred fifteen accessions of 30 taxa in the S. brevicaule complex and 42 accessions of six taxa outside of the complex were assessed for 53 morphological traits in replicate plots in a common garden, resulting in a total of over 81;t3000 data points. Phenetic analyses of these data are unable to support 30 taxa, suggesting instead a single variable complex at best only weakly divided into three widely intergrading sets of populations: (1) Peruvian and geographically adjacent Bolivian accessions (including wild species and all the cultigens), (2) Bolivian and Argentinian accessions and S. verrucosum from Mexico (including only wild species), and (3) the Bolivian and Argentinian wild species S. oplocense. These and other data suggest that Hawkess 1990 treatment (The Potato: Evolution, Biodiversity, and Genetic Resources, Smithsonian Institute Press, Washington, DC.) of 232 morphological species is an overestimate for sect. Petota.

Reduction of species in the wild potato Solanum section Petota series Longipedicellata: AFLP, RAPD and chloroplast SSR data

Abstract.Species boundaries were assessed with three molecular markers [AFLPs, RAPDs and chloroplast simple sequence repeats (cpSSRs)] for all six species of wild potatoes (Solanum section Petota) assigned to ser. Longipedicellata: Solanum fendleri, S. hjertingii, S. matehualae, S. papita, S. polytrichon and S. stoloniferum. These tetraploid (2n = 4x = 48) species grow in the southeastern United States (S. fendleri) and Mexico (all six species), and a recent morphological analysis supported only three species: (1) S. polytrichon, (2) S. hjertingii (including S. matehualae) and (3) S. stoloniferum (including S. fendleri and S. papita). We analyzed all six species of ser. Longipedicellata (tetraploid) and also analyzed diploids in ser. Bulbocastana, ser. Pinnatisecta, ser. Polyadenia and ser. Tuberosa; tetraploids in ser. Acaulia and hexaploids in ser. Demissa. Concordant with morphological data, AFLP and RAPD results support the synonymy of S. hjertingii and S. matehualae, and completely intermix S. papita and S. fendleri. However, accessions of S. stoloniferum have a tendency to cluster but with exceptions, and S. polytrichon is completely intermixed with S. fendleri and S. papita. The cpSSRs fail to distinguish any of the species in ser. Longipedicellata. Combined morphological and molecular data support only two species in ser. Longipedicellata: S. hjertingii and S. stoloniferum.

AFLP markers support separation of Solanum nodiflorum from Solanum americanum sensu stricto (Solanaceae)

This study was aimed at examining the relationships between the African material of Solanum americanum (also designated as S. nodiflorum), accessions of this taxon from other geographical areas, and American S. americanum using AFLP markers. 96 individuals representing 39 accessions of S. americanum sensu lato and related diploid species from the widest possible geographical range, and one accession of S. dulcamara (as outgroup) were used. The AFLP results suggested that American S. americanum differs from S. nodiflorum and that the material investigated in this study can be assigned to three different species: S. americanum sensu stricto, S. nodiflorum and a Solanum species from Brazil. These species can be differentiated based on a combination of floral and fruit characteristics.

A reexamination of infraspecific taxa of a wild potato,Solanum microdontum (Solanum sect.Petota:Solanaceae)

Current taxonomic interpretations ofSolanum microdontumBitter partition the species into two or three infraspecific taxa, variously recognized as subspecies or varieties. The present study reexamines these taxa using morphological data from four individuals each of 69 accessions from most of the range of the species, planted in a common field plot. Our results show that the character states used to recognize infraspecific taxa inS. microdontum often vary within accessions and have no correlation with geography. We conclude that past hypotheses have used typological concepts and that infraspecific taxa are not warranted. This study questions other hypotheses of infraspecific taxa in sect.Petota.

Solanum sect. petota in Guatemala; Taxonomy and genetic resources

There are five wild potato species in Guatemala:Solanum agrimonifolium,S. bulbocastanum,S. clarum,S. demissum, andS. morelliforme. We conducted a collecting expedition there from September 11 to November 5, 1995. The goals of the expedition were to gather field data for taxonomic studies of the five species of Guatemalan wild potatoes and to collect potato germplasm. Our 43 true seed collections nearly quadruple the available wild potato germplasm for Guatemala, provide germplasm from most previously known localities, and add new ones. We provide a systematic treatment of Guatemalan wild potatoes, geographic and logistical data for collecting wild potatoes in Guatemala, statistics on human population growth and deforestation to help explain decline of wild potato populations, recommend areas for future collecting, and suggest two areas as in-situ reserves for wild potatoes

Numerical taxonomic study of some tribes of Brassicaceae from Egypt

Abstract. A systematic study of 45 taxa belonging to 23 genera of tribes Arabideae, Euclidieae, Hesperideae, Lunarieae, Matthioleae and Sisymbrieae of Brassicaceae from Egypt was conducted by means of numerical analysis based on sixty two morphological characters, including vegetative parts, pollen grains and seeds. On the basis of UPGMA clustering and PCO analysis, four main groups are recognised: Lunarieae, Euclidieae, Matthioleae and a mixed group. Representatives of these groups are clustered together based on characters with high factor loading in the PCO analysis. The tribe Euclidieae is the most homogeneous group, and the tribe Arabideae is the most heterogeneous one.

Pollen morphology of some tribes of Brassicaceae from Egypt and its systematic implications

Pollen morphology of 39 species belonging to 23 genera of the tribes Arabideae, Euclidieae, Hes-perideae, Lunarieae, Matthioleae and Sisymbrieae from Brassicaceae from Egypt were studied by using scanning electron microscope (SEM). The pollen grains were tricolpate. Their shape varies from prolate spheroidal, subprolate to prolate. Three pollen types can be distinguished based on the size of the lumina. The ornamentation varies between genera within the tribes and between species within the same genus. The ornamentation was found use-ful to distinguish among closely related genera such as Matthiola, Morettia and Diceratella and among species in the same genus such as Arabis, Morettia, Malcolmia and Neotorularia. Our results suggest that tribes Sisymbrieae, Matthioleae, Hesperideae and Arabideae are heterogeneous because all three types of ornamentation are found among the genera of these tribes. However, the tribes Euclidieae and Lunarieae are homogeneous because we found only one type of ornamentation among the genera. Aus der Flora Agyptens wurde die Pollenmorphologie von 39 Arten aus 23 Gattungen der Tribus Arabideae, Euclidieae, Hesperideae, Lunarieae, Matthioleae und Sisymbrieae (Brassicaceae) mittels Raster-Elektronenmikroskopie (REM) untersucht. Die Ergebnisse zeigen, dass die Pollenkorner tricolpat sind. Ihre Formen variieren von prolat spharoid uber subprolat bis prolat. Drei Pollentypen konnen nach der Grose der Lumina unterschieden werden. Die Skulptur der Exine variiert zwischen den Gattungen, innerhalb von Triben und zwischen den Arten einer Gattung. Die Pollen-Ornamentierung kann zur Unterscheidung nahe verwandter Gattungen wie Matthiola, Morettia und Diceratella herangezogen werden. Auch zur Abgrenzung von Arten der Gattungen Arabis, Morettia, Malcolmia und Neotorularia ist die Ornamentierung der Pollen einsetzbar. Unsere Resultate zeigen, dass die Triben Sisymbrieae, Matthioleae, Hesperideae und Arabideae heterogen sind, da alle drei Typen der Ornamentierung in den Gattungen dieser Triben gefunden wurden. Die Triben Euclidieae und Lunarieae hingegen sind diesbezuglich homogen, da wir nur einen Ornamenttyp innerhalb einer Gattung gefunden haben.

Potato Germplasm Collecting Expedition to Mexico in 1997: Taxonomy and New Germplasm Resources

Wild potato (Solanum sect.Petota) germplasm has been collected in Mexico on nine major expeditions, as determined by 20 collections or more from each expedition currently at the United States potato genebank, the National Research Support Program-6 (NRSP-6). These have resulted in 609 accessions with good collection data. In addition, NRSP-6 has germplasm of approximately 90 other Mexican collections that are unspecific regarding date or place of collection. This expedition was funded to collect those remaining collections with no or little germplasm:Solanum clarum,S. xedinense, S. hintonii, S. hjertingii var.physaloides, S. leptosepalum, S. lesteri, S. macropilosum, S. xmichoacanum, S. xsambucinum, andS. stenophyllidium. In addition, some species and species groups (species groups indicated in parentheses) have unresolved taxonomic problems that needed clarification by additional field collections. These are (S. agrimonifolium and S.oxycarpum), (S. brachycarpum, S. guerreroense, S. hougasii, andS. iopetalum - theS. brachycarpum complex), (S. fendleri, S. papita, S. stoloniferum - theS. stoloniferum complex),S. leptosepalum, andS. macropilosum. We conducted a wild potato germplasm collecting expedition in Mexico from August 22 to October 31, 1997. Our 103 collections, 71 as germplasm collections, provide the first germplasm samples forS. hjertingii var.physaloides,S. leptosepalum, andS. macropilosum. They provide additional germplasm of the rare speciesS. clarum, S. xedinense, S. lesteri, S. xmichoacanum, S. xsambucinum, andS. stenophyllidium. We additionally gathered germplasm and field data to help resolve taxonomic difficulties inS. agrimonifolium andS. oxycarpum, theS. brachycarpum complex, and theS. stoloniferum complex.

AFLP data support the recognition of a new tuber-bearing Solanum species but are uninformative about its taxonomic relationships

Solanum section Petota, containing the cultivated potato and its wild relatives, is a group of around 200 species. Many of these species are morphologically very variable with unclear boundaries, and the group as a whole appears to be somewhat over-classified. Describing a new species in this group should only be undertaken with caution, and molecular data can be used to test the distinctness of any putative new taxon. AFLP markers have shown the ability to reliably distinguish species in several groups within the genus Solanum. We tested the distinctness of a new tuber-bearing Solanum species using morphological and AFLP data, and tried to establish its affiliation to the series within the section. There was clear support for the species status of the material known as Solanum hannemanii in genebank collections, but the AFLP data were inconclusive about its relationships to the other investigated species. Also, the distinction of the series Tuberosa and Megistacroloba, to which these species belong, was not supported.