Association of ecogeographical variables and RAPD marker variation in wildpotato populations of the USA

The goal of germplasm conservation in genebanks is to maximize genetic vari ation. Collecting explorations would be more efficient if factors that pred ict areas and habitats associated with greater genetic differences and dive rsity could be identified. Therefore, the objective of this research was to investigate whether ecogeographical variables have significant association s with patterns of genetic variation in wild potato populations. This study examined 96 wild potato populations collected from the southwestern USA. T hese were 43 populations of Solanum fendleri (2n = 4x = 48) and 53 populati ons of S. jamesii (2n = 2x = 24). These species represent two of the most p redominant breeding systems found among Solanum species: tetraploid inbreed ers; and diploid outcrossers, respectively. Random amplified polymorphic DN A (RAPD) markers were used to assess populations in two ways: determination of simple genetic difference between pairs of populations, and genetic div ersity of a population based on the frequency of that population's RAPD mar kers in the whole set. Results from 2282 comparisons indicated that pattern s of genetic differences were not associated with any differences in ecogeo graphical structure assessed. Remarkably, even geographical separation of p opulations, a parameter usually considered important when collecting germpl asm, did not predict genetic differences very well. Latitude, longitude, an d heat-related factors significantly predicted genetic diversity in S. fend leri but not in S. jamesii. This experiment revealed few associations betwe en ecogeographic parameters and genetic variation in the wild. It follows, therefore, that one should collect many populations and incorporate a manag eable subset into the genebank on the basis of empirical measurements of ge netic diversity.