Population structure of Annona crassiflora: an endemic plant species of the Brazilian Cerrado.

Habitat fragmentation has numerous consequences, particularly to endemic species, and has a negative impact on the genetic diversity of neglected species, leading to genetic drift. Annona crassiflora Mart. is a species that is endemic to Brazil, and its incidence in the Cerrado biome has decreased. The identification and characterization of its remaining diversity is necessary for its conservation. Our aim was to study the population structure of A. crassiflora populations from different Cerrado regions in Minas Gerais State, Brazil (Corinto, Curvelo, Carmo da Mata, Boa Esperança, and Paraguaçu) using inter-simple sequence repeat (ISSR) markers and DNA content. Nuclear DNA content was estimated by flow cytometry using 10 individuals from each population. ISSR markers were used for genotyping accessions in order to study their genetic diversity and population structures. We found considerable genetic variation among populations, with the highest variability observed in the Curvelo population. There was a significant positive correlation between DNA content and latitude (r = 0.46, P = 0. 0003). A Bayesian-based cluster analysis grouped the populations into three clusters, which followed their geographical origins. There was some level of genetic diversity and differentiation among the populations, suggesting the need for a conservation plan for this species. The ISSR markers and DNA content analysis were effective in studying the genetic diversity and population structure of A. crassiflora.

Flow cytometry reliability analysis and variations in sugarcane DNA content.

The aim of this study was to evaluate the reliability of flow cytometry analysis and the use of this technique to differentiate species and varieties of sugarcane (Saccharum spp) according to their relative DNA content. We analyzed 16 varieties and three species belonging to this genus. To determine a reliable protocol, we evaluated three extraction buffers (LB01, Marie, and Tris·MgCl2), the presence and absence of RNase, six doses of propidium iodide (10, 15, 20, 25, and 30 µg), four periods of exposure to propidium iodide (0, 5, 10, and 20 min), and seven external reference standards (peas, beans, corn, radish, rye, soybean, and tomato) with reference to the coefficient of variation and the DNA content. For statistical analyses, we used the programs Sisvar(®) and Xlstat(®). We recommend using the Marie extraction buffer and at least 15 µg propidium iodide. The samples should not be analyzed immediately after the addition of propidium iodide. The use of RNase is optional, and tomato should be used as an external reference standard. The results show that sugarcane has a variable genome size (8.42 to 12.12 pg/2C) and the individuals analyzed could be separated into four groups according to their DNA content with relative equality in the genome sizes of the commercial varieties.