Abstract

Abstract Gustavsson, L. 2008. Genetic diversity in fruit and berry crops estimated with molecular markers. Doctoral dissertation. ISSN 1652-6880, ISBN 978-91-85913-37-4 The amount and structure of genetic diversity has been investigated in three fruit and berry crops which differ in their biological properties and history of domestication: Chaenomeles, lingonberry and apple. Genetic variability has been assessed by a variety of molecular markers: isozymes, RAPD, SSR, SCAR and CAPS with the aim to develop sampling strategies, select material for ex situ conservation and provide lasting identification of cultivars. Breeding of Chaenomeles, a newly domesticated fruit crop, is dependent on well-characterized plant material containing considerable amount of genetic variation. Phenetic relationships within the genus Chaenomeles, estimated on both cultivated plant material and on wild populations, were congruent and indicated that C. japonica is differentiated from all the other species, i.e., C. speciosa, C. cathayensis and C. thibetica, and the hybrid taxon, C. x superba. Furthermore, C. japonica and C. speciosa were found to be considerably more variable than C. cathayensis and C. thibetica, and thus different sampling strategies are called for. Lingonberry breeding is still to a large extent dependent on plant material derived from wildgrowing populations. A large-scale pattern of isolation-by-distance among European populations was encountered. Within-population variability was medium high, and thus in agreement with the mixed mating system and life history traits of this species. RAPD markers in combination with the Maximum diversity computer program allowed for selection of a diverse and representative plant material for future ex situ conservation. Commercially available apple cultivars must be provided with quick and lasting identification, which can guarantee that they are true-to-type. Reliable identification of apple cultivars in genetic resource collections is also very important for, e.g., scientists and breeders. In one study, 151 cultivars were characterised with RAPD markers. No pronounced groupings associated with geographic origin were found, and there were also no major changes in levels of diversity that could be associated with geographic or temporal origination of the different cultivars. In a second study, 68 mandate apple cultivars, aimed for preservation in Sweden, were provided with allelic profiles based on several SSR-loci and the self-incompatibility locus.