Pattern of genetic variability of <Emphasis Type="Italic">Solanum habrochaites</Emphasis> in its natural area of distribution

The tomato wild relative species Solanum habrochaites (previously known as Lycopersicon hirsutum) is a potential source of novel genes for tomato breeding. It shows resistance to many diseases and pests, cold tolerance and fruit quality traits. This species inhabits the western Andean slopes at high elevations from central Ecuador to central Peru. In this study the genetic variation of S. habrochaites was studied using 91 accessions from the whole range of distribution of this species. To this end, we employed two kinds of markers: 9 SSRs and 6 AFLP combinations. The Principal Coordinate Analysis based on AFLP data showed the existence of clinal genetic variation from north to south. The accessions of the different geographic groups were sequentially arranged in the first axis from north to south and a clear separation between them was found. The groups from the centre of the area of distribution showed the highest variation and heterozygosis. The ones from the margins showed lower variability and presented higher homozygosis. The morphotypes typicum and glabratum considered by Müller constituted the extreme forms of the continuous variation in the pubescence grade. These differences in pubescence were not associated with the homozygosis grade.