The Crop-Group and the inconsistent use of Linnean names in the taxonomy of domesticated plants

There have been several proposals for classification categories for systematic groups of domesticated plants. In the 6th edition of the International Code for Nomenclature of Cultivated Plants (ICNCP) only two main categories were included, the cultivar and the cultivar-group. The 7th edition of ICNCP saw the introduction of the Group to encompass the cultivar-group together with other kinds of groupings, also of unnamed material. Despite the existence of the ICNCP, many names for systematic groups of domesticated plants are still in purely Linnean form, following the rules of the International Code of Botanical Nomenclature (ICBN). This practice illustrates a lack of insight in the workings and logic of systematic thinking with respect to domesticated plants and muddles the borderline between the contexts of domestication and evolution. The inclusion of the Crop category in the ICNCP would accommodate the nomenclature and classification of all systematic groups of domesticated plants in one logically consistent system, setting it apart from the realm of the classical botanical classification in use for wild plants

The utility of NBS profiling for plant systematics: a first study in tuber-bearing Solanum species

Systematic relationships are important criteria for researchers and breeders to select materials. We evaluated a novel molecular technique, nucleotide binding site (NBS) profiling, for its potential in phylogeny reconstruction. NBS profiling produces multiple markers in resistance genes and their analogs (RGAs). Potato (Solanum tuberosum L.) is a crop with a large secondary genepool, which contains many important traits that can be exploited in breeding programs. In this study we used a set of over 100 genebank accessions, representing 49 tuber-bearing wild and cultivated Solanum species. NBS profiling was compared to amplified fragment length polymorphism (AFLP). Cladistic and phenetic analyses showed that the two techniques had similar resolving power and delivered trees with a similar topology. However, the different statistical tests used to demonstrate congruency of the trees were inconclusive. Visual inspection of the trees showed that, especially at the lower level, many accessions grouped together in the same way in both trees; at the higher level, when looking at the more basal nodes, only a few groups were well supported. Again this was similar for both techniques. The observation that higher level groups were poorly supported might be due to the nature of the material and the way the species evolved. The similarity of the NBS and AFLP results indicate that the role of disease resistance in speciation is limite

The nomenclatural history of Fritillaria eduardii and the correct names of its varieties

Material of a new fritillary was mentioned in four publications by Eduard Regel in 1884, but he used different names for this material. In the first publication it was named Fritillaria eduardii, but in the following publications the material was described as two varieties of F. imperialis L., both odourless, one with purplish flowers and one with yellow or yellow-red flowers. Both colour varieties, but especially the latter, have been taken into cultivation. Morphological observations and crossing experiments have established that both varieties do not belong to F. imperialis and should be accommodated in F. eduardii. New names for these varieties are proposed, following E. Regel's intention as closely as possibl

Species concepts and relationships in wild and cultivated potatoes

Wild and cultivated potatoes (Solanum section Petota) present challenges to taxonomists arising from lack of clearly defined morphological character differences among many species, phenotypic plasticity, a range of ploidy levels from diploid to hexaploid, and hybrid speciation and introgression. Taxonomic treatments of the group have differed greatly regarding numbers of species and hypotheses of their interrelationships at the series level. Recent morphological phenetic studies and molecular studies have confirmed the general lack of clearly defined species, have shown the need to use a number of character states with overlapping ranges for species delimitation (polythetic support), and have suggested the need for the reduction of species in section Petota. Molecular studies have sometimes confirmed hypotheses of hybridization and sometimes have failed to support them. Molecular studies have suggested the need for a reconsideration of the traditionally held series concepts. Currently, section Petota contains 196 wild species and a single cultivated species, Solanum tuberosum, with eight landrace cultivar groups, exclusive of the modern cultivars that are not yet classified into cultivar groups. The number of wild species likely will decrease with future study. These points are here illustrated by (1) a discussion of published species level studies in Solanum series Longipedicellata, the Solanum brevicaule complex, and the cultivated landrace populations of potatoes; (2) reinvestigations of hybridization in S. chacoense, S. raphanifolium and S. xrechei; and (3) studies of ingroup and outgroup relationships of section Petota

The crop concept in cultonomic classification

In the 1995 International Code of Nomenclature for Cultivated Plants (ICNCP) the cultivar and cultivar-group are used as the main categories to classify cultivated plants. In order to link the cultonomic classification to the taxonomic (botanical) classification it might be desirable to indicate to what botanical category the cultivated plants are to be assigned. This link between cultonomy and taxonomy is best established at a level above the cultivar-group. The sum total of cultivar-groups constitutes the crop, and it is suggested to recognize the crop as a culton and use it to define the relationship between groups of cultivated plants and the categories of the botanical classification governed by the International Code of Botanical Nomenclature (ICBN). The crop category is also the logical choice to function as denomination class. By applying the crop concept the dependence of classification and nomenclature of cultivated plants on botanical classification and nomenclature with its implicit threat of instability is reduced

Pollen morphology of the genus Begonia in Africa

The morphology of the pollen grains of African Begonias is described, leading to the recognition of 15 pollen types. These pollen types are assumed to constitute natural units produced by evolution and the main purpose of this study has been to reconstruct the course of evolution and to apply the resulting insights to the various taxonomical problems. It has been attempted to formulate a critical approach to the problem of applying pollen-morphological data to phylogenetic reconstruction. The evidence from pollen morphology is compared with that from other disciplines, viz. seed morphology, the study of placentation types, karyology and, especially, macromorphological taxonomy. The relation between pollen morphology and geographical distribution is discussed, while the pollen morphology of Madagascan Begonias as well as of the allegedly related family of the Datiscaceae is also investigated

Allele mining in solanum: conserved homologues of Rpi-blb 1 are identified in Solanum stoloniferum

Allele mining facilitates the discovery of novel resistance (R) genes that can be used in breeding programs and sheds light on the evolution of R genes. Here we focus on two R genes, Rpi-blb1 and Rpi-blb2, originally derived from Solanum bulbocastanum. The Rpi-blb1 gene is part of a cluster of four paralogues and is flanked by RGA1-blb and RGA3-blb. Highly conserved RGA1-blb homologues were discovered in all the tested tuber-bearing (TB) and non-tuber-bearing (NTB) Solanum species, suggesting RGA1-blb was present before the divergence of TB and NTB Solanum species. The frequency of the RGA3-blb gene was much lower. Interestingly, highly conserved Rpi-blb1 homologues were discovered not only in S. bulbocastanum but also in Solanum stoloniferum that is part of the series Longipedicellata. Resistance assays and genetic analyses in several F1 populations derived from the relevant late blight resistant parental genotypes harbouring the conserved Rpi-blb1 homologues, indicated the presence of four dominant R genes, designated as Rpi-sto1, Rpi-plt1, Rpi-pta1 and Rpi-pta2. Furthermore, Rpi-sto1 and Rpi-plt1 resided at the same position on chromosome VIII as Rpi-blb1 in S. bulbocastanum. Segregation data also indicated that an additional unknown late blight resistance gene was present in three populations. In contrast to Rpi-blb1, no homologues of Rpi-blb2 were detected in any material examined. Hypotheses are proposed to explain the presence of conserved Rpi-blb1 homologues in S. stoloniferum. The discovery of conserved homologues of Rpi-blb1 in EBN 2 tetraploid species offers the possibility to more easily transfer the late blight resistance genes to potato varieties by classical breeding

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

An annotated history of the principles of cultivated plant classification.

Important episodes in the history of the classification of cultivated plants are highlighted and commented upon in the light of recent developments in the systematics of cultivated plants. It is shown that throughout history, a division between classifying cultivated plants and plants as found in nature has existed in the minds of most taxonomists, but the slow development of systematic thought in cultivated plant taxonomy has slowed down progress in this field and left ample opportunity for too strong an influence of the taxon concept. As a result, the nomenclature of cultivated plants has always leaned heavily on the International Code of Botanical Nomenclature