Clone worth? Genetic diversity in obligate apomictic Miconia albicans (Melastomataceae).

Apomixis is the asexual production of seeds by plants and, in theory, would render low genetic diversity and even clonal lineages. However, recent studies have shown otherwise, although is not always clear where the genetic diversity of obligate apomicts comes from. We evaluated the genetic diversity among sister seedlings of M. albicans, an obligate apomictic species in Cerrado, Neotropical Savannas in Central Brazil. A total of 50 seedlings from five individuals were analysed using ISSR primers. We obtained 107 fragments, all with good resolution, consistently observed and replicable. The percentage of polymorphic loci ranged from 28.04% to 33.64% and Shannon's information index (I) averaged 0.173. The expected heterozygosity (He) averaged 0.117, similar to the observed for populations of M. albicans and other selfed species. Only two seedlings showed the same genotype (possible clones), but most differed at least for five loci. Most of variance was among progenies (62%), but we found that 38% was within progenies. Genetic distances separated the progenies in two groups, and analogous analyses between individuals reconstructed the original progenies clustering. The results confirmed a relatively high genetic diversity among sister seedling of this obligatory apomictic plant and clones were rare. This diversity can be generated during development, probably by restitutional meiosis or other recombination processes. These differences may accumulate into lineages and populations well adapted to heterogenous Cerrado environment.

Unexpectedly high genetic diversity and divergence among populations of the apomictic Neotropical tree Miconia albicans.

Since tropical trees often have long generation times and relatively small reproductive populations, breeding systems and genetic variation are important for population viability and have consequences for conservation. Miconia albicans is an obligate, diplosporous, apomictic species widespread in the Brazilian Cerrado, the savanna areas in central Brazil and elsewhere in the Neotropics. The genetic variability would be, theoretically, low within these male-sterile and possibly clonal populations, although some variation would be expected due to recombination during restitutional meiosis. We used ISSR markers to assess genetic diversity of M. albicans and to compare with other tropical trees, including invasive species of Melastomataceae. A total of 120 individuals from six populations were analysed using ten ISSR primers, which produced 153 fully reproducible fragments. The populations of M. albicans presented mean Shannon's information index (I) of 0.244 and expected heterozygosity (He ) of 0.168. Only two pairs of apparently clonal trees were identified, and genetic diversity was relatively high. A hierarchical amova for all ISSR datasets showed that 74% of the variance was found among populations, while only 26% of the variance was found within populations of this species. Multivariate and Bayesian analyses indicated marked separation between the studied populations. The genetic diversity generated by restitutional meiosis, polyploidy and possibly other genome changes may explain the morpho-physiological plasticity and the ability of these plants to differentiate and occupy such a wide territory and different environmental conditions. Producing enormous amounts of bird-dispersed fruits, M. albicans possess weedy potential that may rival other Melastomataceae alien invaders.

Castor bean (Ricinus communis L.) as a potential environmental bioindicator.

Biomonitoring of air quality using living organisms is a very interesting approach to environmental impact assessment. Organisms with a vast distribution, such as plants, are widely used for these purposes. The castor bean (Ricinus communis L.) is an oleaginous plant that can potentially be used as a bioindicator plant owing to its rapid growth and large leaves, which have a wide surface area of contact with the air and the pollutants therein. This study investigated the the bioindicator potential of the castor bean by performing several tests. We observed statistically significant differences in the concentrations of chlorophyll a and b in the leaves of plants in polluted areas compared to that in the control group plants, which were located in a pollution-free area. Leaves of plants in the former group had higher peroxidase activity and showed a greater buffering ability than those of plants in the control group. The pKa values obtained via buffering capacity tests, revealed the presence of aminoazobenzene (an industrial dye) in leaves of R. communis. Genotoxicity was evaluated through the comet assay technique and revealed that other than some differences in DNA fragmentation, there is no statistically significant difference in this parameter between places analyzed. Our data indicate that R. communis can be a highly useful biological indicator. Further, we hypothesized that the castor bean can be a potential candidate for phytoremediation owing its physiological buffering capacity when exposed to substantial pollution.

New efficient DNA extraction method to access the microbiome of Ricinus communis seeds.

Ricinus communis (castor bean) seeds are used to produce an alcohol-soluble oil that is used in more than 400 industrial processes. Despite its economic importance, there has been little research on the endophytic microbiota of castor bean seeds. This microbiota is important for plant metabolic processes and may have considerable biotechnological potential, such as production of lipases and plant growth promoter agents. We evaluated several DNA extraction methodologies in order to access the microbial diversity of castor bean through a metagenomic approach. Based on our observations, we developed a new methodology that takes advantage of the low solubility of calcium phosphates and the high affinity of these phosphates for proteins and polysaccharides. The extracted DNA quality was evaluated by PCR, using a selective primer pair for bacterial and mitochondrial 16S rDNA genes (799F and 1492R). We found this methodology quantitatively and qualitatively more efficient than the other approaches. In evaluating this new extraction methodology, we found that the difficulties of DNA extraction from castor bean seeds, such as abundant oil, polysaccharides, phenolic compounds, and plant enzymes, could be overcome. The resulting extracts had high concentration and purity, and they were obtained faster than with previous methods. The samples contained virtually all of the DNA, including the microbial DNA; this was validated by PCR analysis.