Sale, Luana (2014) Caratterizzazione genetica in Carciofo (Cynara cardunculus var scolymus L.). Doctoral Thesis.
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The globe artichoke (Cynara cardunculus var. scolymus (L.), presumably native of the Mediterranean Basin, is an horticultural species of relevant economic interest, mainly in the South of Italy. This crop is also highly important for the Sardinian agriculture, that recently has achieved for this local variety “Spinoso di Sardegna” the DOP (Protected Designation Origin) label.
The study of the genetic structure of plant populations represents a basilar task both for the parental choice in breeding programs and for a correct implementation of genome wide association studies (GWAS). Likewise, the comparison with the wild progenitor allow to deepen the knowledge of the domesticated species. In fact, it is possible to: evaluate the genetic diversity that is effectively present within a certain varietal collection; estimate the degree of the genetic differentiation among wild and cultivated gene pools; investigate whether the wild gene pool is a source of alleles that might be useful for breeding programs, and understand important aspects on the evolution and domestication of the cultivated materials.
The main aims of the PhD research activity were to: 1) determine and investigate the genetic diversity level and structure of a varietal collection of globe artichoke; 2) compare these materials with a collection of wild cardoon (the progenitor of the cultivated artichoke); 3) determine and investigate the genetic diversity of a collection of the cultivated variety “Spinoso Sardo”. These tasks were achieved by using nuclear and cytoplasmic microsatellite markers (nuSSR and cpSSR, respectively).
The analysis by means of nuSSRs has allowed the identification of different genetic groups associated to the most important varietal types (Catanesi, Romaneschi, Violetti and Spinosi). This confirmed what previously observed by means of other molecular markers, despite the genetic relationships among groups are not fully comparable. For the first time, it has been analyzed the cytoplasmic diversity in globe artichoke, that has been shown to be very low. It has been shown that, the identified genetic structures are related, at least in part, to the mutation rate of the different molecular markers used. Future studies of association mapping on this species might likely benefit from the information deriving from different types of molecular markers.
The cultivated and wild gene pools have shown a moderate-high differentiation level and a low gene-flow has been detected. Among the cultivated materials, the Spinosi, Violetti and Romaneschi types are closer to the wild cardoon. Moreover, based on the diversity levels and the phylogenetic relationships, the genetic group containing the most of the Spinosi type, seems to have an older origin.
A multi-level approach based on linkage disequilibrium analysis, inbreeding level analysis, and association analysis between nuclear and cytoplasmic polymorphisms, point to a well defined clonal structure of the analyzed materials; yet, a clear role of sexual recombination during the evolution of the varieties of cultivated artichoke can be hypothesized. Comparison between the collection of cultivated varieties and that of wild cardoon has evidenced a very high variability of the collection of the cultivated varieties, though a relevant number of wild alleles were shown to be absent in the cultivated gene pool.
The collection of ‘Spinoso Sardo’ has not evidenced any diversity both for nuSSR and cpSSR markers. Nonetheless, the genetic profile of this variety emerge to be clearly differentiated from the other varietal types, that is crucial for varietal identification purposes. The poor genetic diversity observed in ‘Spinoso Sardo’ contrasts with the observed phenotypic diversity and the feaseability of clonal selection often reported for this species. This raise questions on the role of the trangenerational epigenetic variation as source of phenotypic diversity in the globe artichoke.
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