The potential role of hybridization in diversification and speciation in an insular plant lineage: insights from synthetic interspecific hybrids

Diversity and Cytogenomic Characterization of Wild Carrots in the Macaronesian Islands

The Macaronesian islands constitute an enormous reservoir of genetic variation of wild carrots (subtribe Daucinae; Apiaceae), including 10 endemic species, but an accurate understanding of the diversification processes within these islands is still lacking. We conducted a review of the morphology, ecology, and conservation status of the Daucinae species and, on the basis of a comprehensive dataset, we estimated the genome size variation for 16 taxa (around 320 samples) occurring in different habitats across the Macaronesian islands in comparison to mainland specimens. Results showed that taxa with larger genomes (e.g., Daucus crinitus: 2.544 pg) were generally found in mainland regions, while the insular endemic taxa from Azores and Cabo Verde have smaller genomes. Melanoselinum decipiens and Monizia edulis, both endemic to Madeira Island, showed intermediate values. Positive correlations were found between mean genome size and some morphological traits (e.g., spiny or winged fruits) and also with habit (herbaceous or woody). Despite the great morphological variation found within the Cabo Verde endemic species, the 2C-values obtained were quite homogeneous between these taxa and the subspecies of Daucus carota, supporting the close relationship among these taxa. Overall, this study improved the global knowledge of DNA content for Macaronesian endemics and shed light into the mechanisms underpinning diversity patterns of wild carrots in the western Mediterranean region.

Detecting Introgressed Populations in the Iberian Endemic Centaurea podospermifolia through Genome Size

Based on results from previous studies, populations of the Iberian endemic Centaurea podospermifolia north of the Ebro River are considered genetically pure, while those southward are introgressed, with genetic input from C. cephalariifolia. This phenomenon is particularly relevant, especially given both the endangered and protected status for the species, which can have consequences in how to best apply conservation strategies to maintain genetic resources in the species. The main goal of this study was to evaluate whether genome size assessments using flow cytometry can help distinguishing between pure, hybrid and introgressed populations, and hence become a powerful and cost-effective tool to complement comprehensive population genetic surveys. The results indicate that there are significant genome size differences between populations of C. podospermifolia, which are coincident with previous considerations of pure and introgressed populations. Given the simplicity and reproducibility of this technique, flow cytometry could become an effective tool for monitoring pure populations of this species and, indeed, become an integral part of the management plans that are mandatory for listed taxa.

Centromere Engineering as an Emerging Tool for Haploid Plant Production: Advances and Challenges

Haploid production is of great importance in plant breeding programs. Doubled haploid technology accelerates the generation of inbred lines with homozygosity in all loci in a single year. Haploids can be induced in vitro via cultivating the haploid gametes or in vivo through inter- and intraspecific hybridization. Haploid induction through centromere engineering is a novel system that is theoretically applicable to many plant species. The present review chapter discusses the proposed molecular mechanisms of selective chromosome elimination in early embryogenesis and the effects of kinetochore component modifications on proper chromosome segregation. Finally, the advantages and limitations of the CENH3-mediated haploidization approach and its applications are highlighted.

Molecular phylogeny of mulberries reconstructed from ITS and two cpDNA sequences

Background

Species in the genus Morus (Moraceae) are deciduous woody plants of great economic importance. The classification and phylogenetic relationships of Morus, especially the abundant mulberry resources in China, is still undetermined. Internal transcribed spacer (ITS) regions are among the most widely used molecular markers in phylogenetic analyses of angiosperms. However, according to the previous phylogenetic analyses of ITS sequences, most of the mulberry accessions collected in China were grouped into the largest clade lacking for phylogenetic resolution. Compared with functional ITS sequences, ITS pseudogenes show higher sequence diversity, so they can provide useful phylogenetic information.

Methods

We sequenced the ITS regions and the chloroplast DNA regions TrnL-TrnF and TrnT-TrnL from 33 mulberry accessions, and performed phylogenetic analyses to explore the evolution of mulberry.

Results

We found ITS pseudogenes in 11 mulberry accessions. In the phylogenetic tree constructed from ITS sequences, clade B was separated into short-type sequence clades (clades 1 and 2), and a long-type sequence clade (clade 3). Pseudogene sequences were separately clustered into two pseudogroups, designated as pseudogroup 1 and pseudogroup 2. The phylogenetic tree generated from cpDNA sequences also separated clade B into two clades.

Conclusions

Two species were separated in clade B. The existence of three connection patterns and incongruent distribution patterns between the phylogenetic trees generated from cpDNA and ITS sequences suggested that the ITS pseudogene sequences connect with genetic information from the female progenitor. Hybridization has played important roles in the evolution of mulberry, resulting in low resolution of the phylogenetic analysis based on ITS sequences. An evolutionary pattern illustrating the evolution history of mulberry is proposed. These findings have significance for the conservation of local mulberry resources. Polyploidy, hybridization, and concerted evolution have all played the roles in the evolution of ITS sequences in mulberry. This study will expand our understanding of mulberry evolution.