Genome divergence by mobile elements activity and recombination is a continuous process that plays a key role in the evolution of species. Nevertheless, knowledge on retrotransposon-related variability among species belonging to the same genus is still limited. Considering the importance of the genus Helianthus, a model system for studying the ecological genetics of speciation and adaptation, we performed a comparative analysis of the repetitive genome fraction across ten species and one subspecies of sunflower, focusing on long terminal repeat retrotransposons at superfamily, lineage and sublineage levels. After determining the relative genome size of each species, genomic DNA was isolated and subjected to Illumina sequencing. Then, different assembling and clustering approaches allowed exploring the repetitive component of all genomes. On average, repetitive DNA in Helianthus species represented more than 75% of the genome, being composed mostly by long terminal repeat retrotransposons. Also, the prevalence of Gypsy over Copia superfamily was observed and, among lineages, Chromovirus was by far the most represented. Although nearly all the same sublineages are present in all species, we found considerable variability in the abundance of diverse retrotransposon lineages and sublineages, especially between annual and perennial species. This large variability should indicate that different events of amplification or loss related to these elements occurred following species separation and should have been involved in species differentiation. Our data allowed us inferring on the extent of interspecific repetitive DNA variation related to LTR-RE abundance, investigating the relationship between changes of LTR-RE abundance and the evolution of the genus, and determining the degree of coevolution of different LTR-RE lineages or sublineages between and within species. Moreover, the data suggested that LTR-RE abundance in a species was affected by the annual or perennial habit of that species.

Bitter vetch (Vicia ervilia (L.) Willd.), one of the Near Eastern founder crops, is an annual cleistogamous legume domesticated during the Neolithic period. Originally used for human consumption, over time it was replaced by other pulses and downgraded to a fodder crop. When coupled with a small degree of cross hybridization, cleistogamy confers evolutive plasticity to the plant species. The aim of the present work consisted in setting up optimal conditions to overcome the existing cross hybridization barriers in V. ervilia. Genotypes of Turkish origin, characterized by an erect growth habit were crossed with Italian counterparts characterized by high seed production. A detailed cyto-histological analysis of flower development was undertaken to determine the optimal stage for emasculation and manual cross. Ninety-eight crosses were carried out and the hybrid nature of the putative F1 progenies was assessed by SSR (simple sequence repeat) DNA markers. Fifty-five seeds were obtained of which only five gave rise to hybrid plants. Among these, only three turned out to be fertile and two of which generated a consistent number of F2 seeds whose plants were assessed in greenhouse for seed production and plant growth habit. Most of the evaluated traits showed mean values of the F2 plants intermediate between the two initial parents, confirming that intraspecific hybridization is not only possible but also useful to exploit the diversity confined in different bitter vetch populations.

Geranium macrorrhizum L. is a herbaceous species native to southern Europe and was introduced in central Europe and North America. It is also widely distributed in Italy. In this study, molecular and cytogenetic analyses were carried out on 22 wild plants, collected in central and southern Italy, compared with five cultivated plants, with the main purpose to identify those living near the Marmore waterfalls in central Italy, recently described as the new species Geranium lucarinii . Four barcoding markers ( rbcL , matK , trnH-psbA intergenic spacer and internal transcribed spacer region) were sequenced and their variability among the plants was evaluated. Chromosome numbers were determined and 45S rDNA was physically mapped by fluorescence in situ hybridization. Moreover, genomic affinity between wild and cultivated plants was evaluated by genomic in situ hybridization. The results of this study supported that all the plants belong to G. macrorrhizum , including the Marmore population. Barcoding analyses showed a close similarity among the wild plants, and a differentiation, although not significant, between the wild plants on one hand and the cultivated plants on the other. Integrated studies focusing on morphological, genetic and ecological characterization of a larger number of wild populations would allow us to know the extent of the variability within the species.