Search

A major justification for taxonomic and biogeographic research is its assumed ability to predict the presence of traits in a group for which the trait has been observed in only a representative subset of the group. Such predictors are regularly used by breeders interested in choosing potential sources of disease and pest resistant germplasm for cultivar improvement, by genebank managers to organize the collection, and by germplasm collectors planning to gather maximum diversity. The present study tests taxonomic and biogeographic associations with 10,738 disease and pest evaluations, derived from the literature and genebank records, of 32 pest and diseases in five classes of organisms (bacteria, fungi, insects, nematodes, and virus). The data show that ratings for only Colorado potato beetle [Leptinotarsa decemlineata (Say)] and one pathogen (Potato M Carlavirus) are reliably predicted both by host taxonomy and climatic variables. While it is logical to initially take both taxonomy and geographic origin into account while screening genebank materials for pest and disease resistances, such associations will hold for only for a small subset of resistance traits. Based on these results, a more effective strategy than taxonomic and biogeographic prediction is probably careful screening of core collections.

Chromosome pairing relationships within cultivated potato (Solanum tuberosum) and its wild tuber-bearing relatives (Solanum sect. Petota) have been interpreted by genome formulas, developed in the early 1900s, through techniques of classic meiotic analysis of interspecific hybrids. Here we reexamine potato genome hypotheses with the first phylogenetic anolysis of all major genomes of sect. Petota using cloned DNA sequences of the single-copy nuclear gene GBSSI (waxy). Our results provide the first molecular confirmation of allopolyploidy in wild potato. They both support prior hypotheses and identify novel genome origins never before proposed. The data will be useful to help design crossing strategies to incorporate wild species germplasm into cultivated potato.

The modern cultivated potato (Solanum tuberosum L.) was first recorded in Europe in the Canary Islands in 1567, but its origin has long been in dispute. Two competing hypotheses have proposed an 'Andean' area (somewhere from the Andean uplands from Venezuela to northern Argentina) or a lowland south-central 'Chilean' area, but the Andean origin hypothesis is today generally accepted. The identity of extant Canary Island potato landraces as exclusively of upland Andean origin is one part of a multicomponent argument that the European potato originated from there, rather than from Chile. We reassess these two competing hypotheses with nuclear microsatellite and chloroplast DNA analyses of 19 Canary Island landraces, 14 Andean landraces, 11 Chilean landraces, and two wild potato species as outgroups, and with chloroplast DNA data of 150 landraces from South America. Our molecular results document a wide variation of Andeanand Chilean-type cultivars on the Canary Islands and possible hybrids of the two. Our new data, integrated with historical, molecular, agronomic, and crossing data, support a hypothesis that there were multiple introductions of Andean and Chilean germplasm to the Canary Islands and that the early European potato was selected from Chilean introductions long before the late blight epiphytotics of the 1840s.

A major justification for taxonomic research is its assumed ability to predict the presence of traits in a group for which the trait has been observed in a representative subset of the group. Taxonomy is regularly used by breeders interested in choosing potential sources of disease-resistant germplasm for cultivar improvement. We designed this study as an empirical test of prediction by associating resistance to white mold [caused by the fungal pathogen Sclerotinia sclerotiorum (Lib.) de Bary] to diverse potato (Solanum spp.) taxonomies and biogeography, using 144 accessions of 34 wild relatives of potato in Solanum sections Petota and Etuberosum. Tremendous variation for resistance to white mold occurs both within and among species. No consistent association was observed between white mold resistance and taxonomic series (based on a phenetic concept), clades (based on a cladistic concept), ploidy, breeding system, geographic distance, or climate parameters. Species and individual accessions with high proportions of whitemold-resistant plants have been identified in this study, but both often exhibit extensive variation and designation of either as resistant or susceptible must take this variation into account. Therefore, taxonomic relationships and ecogeographic data cannot be reliably used to predict where additional sources of white mold resistance genes will be found.

This study tests the genetic difference between landrace populations of Solanum tuberosum L. subsp. tuberosum and subsp. andigenum (Juz. & Bukasov) Hawkes using nuclear DNA microsatellites. Microsatellite loci were amplified in subsp. andigenum (35 accessions), subsp. tuberosum (35 accessions), and other cultivated and wild species (22 accessions). A total of 208 alleles were scored from 18 microsatellite loci spread throughout all 12 chromosomes of potato. Using an infinite allele model and a least squares method of analysis, microsatellite loci separated subsp. tuberosum from subsp. andigenum, and cultivated and wild species. These results support the genetic difference of these two populations and their recognition at some classification level., THE POTATO AND ITS WILD RELATIVES (S. sect. Petota Dumort.) harbor a wealth of both wild and cultivated tuber-bearing species distributed from the southwestern USA to central Argentina and adjacent [...]