Eliana Regina Forni Martins

SNP genotyping allows an in-depth characterisation of the genome of sugarcane and other complex autopolyploids

Many plant species of great economic value (e.g., potato, wheat, cotton, and sugarcane) are polyploids. Despite the essential roles of autopolyploid plants in human activities, our genetic understanding of these species is still poor. Recent progress in instrumentation and biochemical manipulation has led to the accumulation of an incredible amount of genomic data. In this study, we demonstrate for the first time a successful genetic analysis in a highly polyploid genome (sugarcane) by the quantitative analysis of single-nucleotide polymorphism (SNP) allelic dosage and the application of a new data analysis framework. This study provides a better understanding of autopolyploid genomic structure and is a sound basis for genetic studies. The proposed methods can be employed to analyse the genome of any autopolyploid and will permit the future development of high-quality genetic maps to assist in the assembly of reference genome sequences for polyploid species.

Cytotaxonomy of LychnophoraMart. (Asteraceae: Vernonieae: Lychnophorinae) species

Abstract Most species of the genus Lychnophora Mart. are endemic to the Brazilian ”campos rupestres” of Minas Gerais, Bahia and Goiás, with high degree of endemism in many species. There is disagreement between different authors regarding delimitation of the species and, consequently, the amount of species (from 11 to 68). This interpretation difference leads to sinonimization and the transference of several species to closely related genera. The cytotaxonomic study of species of Lychnophora was made aiming at increase of knowledge of chromosome characteristics that could be useful to the understanding of the taxonomy of the group as a whole. Chromosome numbers of about eighteen species were determined, with 2n=34, 36 or 38. These chromosome numbers were distributed among species of four sections of Lychnophora, so they can’t be used as distinctive characters for intergeneric and infrageneric levels below section level. However, chromosome numbers were very important for the differentiation of some species of Lychnophora, whose taxonomic limits have been questioned. Other karyotype characters were analysed in three species of the subtribe, like chromosome size and morphology, showing constancy of these characters. The chromosomes are small, with 1.0 to 2.58μm, and they are mainly metacentric, however some submetacentrics were observed.

Cytogenetic markers for the characterization of Capsicum annuum L. cultivars

Abstract Karyotypic studies with conventional staining have been unsuccessful due to the uniformity of Capsicum chromosomes. In this study, we found diagnostic chromosome characters that permit to characterize cultivars; this is the first cytological characterization of both rDNAs (18S and 5S) in a species of Capsicum using a genus-specific probe and the most exhaustive in C. annuum to date. The heterochromatic banding patterns enabled us to identify cultivars, and fluorescent in situ hybridization (FISH) showed one 5S rDNA locus largely conserved within the cultivars, whereas high variation in the number of 18S rDNA loci was observed. One of the most obvious differences is the presence of an additional active nucleolar organizer region in pair #12 and the dispersal of inactive 18S rDNA signals. These results indicate that fluorochrome banding together with silver impregnation and FISH procedures are very useful for the identification of chromosomes and the interpretation of chromosomal variation between cultivars. The functional role of this variation is still uncertain, but our results show that copy number variation of repetitive DNA during the course of evolution might provide an excellent experimental system for studying genome rearrangements accompanying functional divergence in domesticated C. annuum.