Número cromossômico e conteúdo de DNA nuclear em espécies do gênero Amaranthus (Amaranthaceae)

The objective of this work was to determine the chromosome number and nuclear DNA content of five species of the genus Amaranthus, which commonly occur in Brazil. Metaphase chromosomes were obtained through the flame drying technique and stained with 5% Giemsa, and DNA content was determined by flow cytometry. 2n=32 chromosomes were observed in A. hybridus and 2n=34 in the other studied species, indicating the occurrence of descendant dysploidy. The nuclear DNA content ranged from 1.28 to 1.79 pg, and A. deflexus had the highest value.O objetivo deste trabalho foi determinar o número de cromossomos e o conteúdo de DNA nuclear em cinco espécies do gênero Amaranthus, de ocorrência comum no Brasil. Cromossomos metafásicos foram obtidos pela técnica de secagem à chama e corados com Giemsa 5%, e o conteúdo de DNA foi determinado por citometria de fluxo. Observou-se 2n=32 cromossomos em A. hybridus e 2n=34 nas demais espécies estudadas, o que é indicativo de ocorrência de disploidia descendente. O conteúdo de DNA nuclear variou de 1,28 a 1,79 pg, e A. deflexus apresentou o maior valor

LD-CNV: rapid and simple discovery of chromosomal translocations using linkage disequilibrium between copy number variable loci.

Large-scale structural variations, such as chromosomal translocations, can have profound effects on fitness and phenotype, but are difficult to identify and characterize. Here, we describe a simple and effective method aimed at identifying translocations using only the dosage of sequence reads mapped on the reference genome. We binned reads on genomic segments sized according to sequencing coverage and identified instances when copy number segregated in populations. For each dosage-polymorphic 1 Mb bin, we tested independence, effectively an apparent linkage disequilibrium (LD), with other variable bins. In nine potato (Solanum tuberosum) dihaploid families translocations affecting pericentromeric regions were common and in two cases were due to genomic misassembly. In two populations, we found evidence for translocation affecting euchromatic arms. In cv. PI 310467, a nonreciprocal translocation between chromosomes (chr.) 7 and 8 resulted in a 5-3 copy number change affecting several Mb at the respective chromosome tips. In cv. "Alca Tarma," the terminal arm of chr. 4 translocated to the tip of chr. 1. Using oligonucleotide-based fluorescent in situ hybridization painting probes (oligo-FISH), we tested and confirmed the predicted arrangement in PI 310467. In 192 natural accessions of Arabidopsis thaliana, dosage haplotypes tended to vary continuously and resulted in higher noise, while apparent LD between pericentromeric regions suggested the effect of repeats. This method, LD-CNV, should be useful in species where translocations are suspected because it tests linkage without the need for genotyping

Unconventional vegetables collected in Brazil: chromosome number and description of nuclear DNA content

<div><p>Abstract The aim of this study was to perform chromosome counts and nuclear DNA quantification of the unconventional vegetables species: bertalha (Basella alba L.), vinagreira verde (Hibiscus sabdariffa L.), azedinha (Rumex acetosa L.), peixinho (Stachys byzantina K. Koch), and capuchinha (Tropaeolum majus L.). Metaphase chromosomes were obtained from the pre-treatment of root meristem with 8-hydroxyquinoline or colchicine and lides were prepared by the flame-drying technique and stained with 5% Giemsa. DNA quantification was performed by flow cytometry. Chromosome number and DNA content (pg) estimated for each species were: Rumex acetosa: 2n=2x=14 and 7.04 pg; Basella alba: 2n=2x=44 and 7.05 pg; Tropaeolum majus: 2n=2x=28 and 2.08 pg; Stachys byzantine: 2n=2x=30 and 1.54 pg, and Hibiscus sabdariffa: 2n=4x=72 and 5.12 pg.</p></div

Haploid identification using tropicalized haploid inducer progenies in maize

The aim of this study was to identify maize haploid plants and compare the efficiency of identification of maize haploid plants using the R1-nj morphological marker, plant vigor, flow cytometry, chromosome counting, and microsatellite molecular markers under tropical conditions. We also established a protocol for chromosome duplication in maize haploid plants. Fourteen S0:1 and seven S2:3 haploid inducer progenies were crossed with GNZ9501 in 2012/2013 and 2014/2015, respectively. Through use of the R1-nj trait, we were able to identify 552 putative haploid seeds in 2012/2013 and 260 putative haploid seeds in 2014/2015. Only 1.84% were true positives according to flow cytometry in 2012/2013. In 2014/2015, 75% of the putative haploids were true negatives according to molecular markers. Plant vigor had a high proportion of true negatives. Molecular markers and flow cytometry are more efficient in classifying plant ploidy level. Chromosome duplication was efficient in all plants