ABSTRACT. Cratylia argentea (Desv.) Kuntze (Fabaceae) is a droughttolerant, perennial legume found primarily in Brazil, Bolivia, and Peru. The shrub is well adapted to acid soils and exhibits high productivity and nutritional value, characteristics that would favor its use as a dry season animal forage supplement in semiarid regions. In plant improvement programs, the production of elite hybrids with superior traits is generally achieved by crossing parents that exhibit the highest level of genetic divergence. Therefore, the aim of the present study was to assess genetic diversity among 13 accessions of C. argentea from the same population maintained in the active germplasm bank of Embrapa Meio-Norte using inter-simple sequence repeat (ISSR) markers. Genetic similarities between C. argentea accessions were estimated from Jaccard coefficients, and a dendrogram was constructed using the unweighted pair group method with arithmetic average (UPGMA). The set of 15 primers selected for ISSR analysis generated a total of 313 loci of which 79.23% were polymorphic. The mean number of bands per primer was 20.87, and the amplicons 15243 Genetic diversity among accessions of Cratylia argentea ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (4): 15242-15248 (2015) ranged from 280 to 3000 bp in size. Primers UBC834 and UBC827 generated the largest number of polymorphic loci and exhibited 90.91 and 100% polymorphism, respectively. The coefficients of genetic similarity among accessions varied between 0.49 and 0.73. UPGMA cluster analysis allowed the identification of four genotypic groups and demonstrated the existence of considerable variability within the collection. Potential progenitors were selected that would offer good possibilities of obtaining unusual and favorable combinations of genes in a plant breeding program.

The mangabeira is a native fruit tree from Brazil with fruits that present significant potential for exploitation. This species is experiencing genetic erosion, which increases the importance of elucidating the genetic diversity that exists in mangabeira populations to support conservation programs. Thus, this study aimed to evaluate the diversity and genetic structure of mangabeira populations from the Germplasm Bank of Embrapa Meio-Norte using inter simple sequence repeat (ISSR) markers. A total of 29 accessions from Brazil were characterized, including one from Sergipe, one from Bahia, three from the Distrito Federal, 11 from Piauí and 13 from Paraíba. The 11 ISSR primers provided 166 loci, among which 120 were polymorphic. The analysis of molecular variance (AMOVA) indicated that 69.66% of the observed genetic variability occurred within populations and that the populations showed high genetic differentiation. The results obtained from the STRUCTURE analysis indicated the existence of two genetic groups. The Nei and Shannon indices of genetic diversity varied from 0.15 to 0.24 and from 0.22 to 0.34, respectively. The coefficient of similarity ranged from 0.57 to 0.94, with a mean of 0.76. The mean was used as the cut-off point in the dendrogram, and seven groups were identified. In conclusion, this study demonstrates the presence of low or moderate genetic diversity within the studied mangabeira populations and high genetic differentiation between the populations. The results indicate a need to increase the number of mangabeira population samples from different collection sites as a strategy to achieve more significant results for the conservation and genetic improvement of this species.

ABSTRACT. Mangabeira (Hancornia speciosa) is a native fruit tree found mainly in the Cerrado biome and shows great economic potential due to its multiple uses; the fruits are used in agriculture, are important as a food resource, and can be consumed in natura or processed. Due to a reduction in the area of ecosystems where it occurs, mangabeira is threatened by genetic erosion in Brazil. The characterization of the genetic diversity of plants can provide the basis for strategies to protect and conserve endangered populations, like mangabeira. This study aimed to compare eight DNA extraction methods in mangabeira because the key to success is the use of a pure genomic DNA for the characterization of genetic diversity in molecular biology techniques. The quality and concentration of DNA were revealed by agarose gel electrophoresis. Polymerase chain reaction amplifications were successfully by extractions using two commercial purification kits and by the method proposed by Khanuja et al. (1999), which produced sufficient genomic DNA of good quality from leaves of H. speciosa to perform techniques involving molecular biology. The protocol described by Khanuja et al. (1999) is less expensive when compared to the commercial purification kits.

Cajui (Anacardium spp.) is a native fruit tree (small cashew) of the Brazilian Cerrado and possesses the potential for commercialization. However, cajui exploitation occurs exclusively through extractivism in the absence of conservation strategies. The lack of conservation strategies may lead to a decrease in genetic diversity of Anacardium. In this work, the genetic diversity and population structure of three natural populations in Sete Cidades National Park (PNSC; PI, Brazil) were assessed using ISSR analysis of 56 cajui accessions and two A. occidentale accessions (outgroup) from Pacajus (CE, Brazil). A total of 112 markers were obtained, 93 (83.04%) of which were polymorphic. The diversity indices of these populations indicated moderate levels of genetic diversity. According to AMOVA, 96.17% of the genetic variability lay within populations, with low genetic differentiation among populations (ΦST = 0.03828). Furthermore, STRUCTURE analysis indicated the existence of four connected genetic groups. The findings show that the individuals from the three collection sites did not represent different subpopulations, likely due to the high gene flow (Nm = 6.7) favored by the floral biology of Anacardium, pollinators and small-animal seed dispersers. This research identifies genetically divergent individuals (C-03, C-05, C-22, C-26, C-34 and C-39), which should be considered priority individuals for conservation and can inform conservation programs for Anacardium spp.

The success of gene expression studies, protein synthesis, and construction of cDNA libraries directly depends on the purity and integrity of the RNA used in these tests, as even minor amounts of contaminant DNA (<1%) can produce a false positive amplification signal in quantitative real-time PCR. For RNA contaminated with genomic DNA, an essential step in the studies on gene expression is the treatment of the RNA samples with DNase. This study was conducted to test three different concentrations of DNase I (0.02, 0.04, and 0.06 μL/​​ng of RNA), which were chosen based on the results of the RNA sample quantifications and as indicated by the manufacturer, to digest genomic DNA present in the RNA samples extracted from sugarcane leaves with the Concert™ Plant RNA Reagent. The results showed that all three concentrations of DNase significantly reduced DNA concentrations. However, RNA was also degraded on DNase I treatment. In addition, the amount of DNA present in the RNA samples after purification with DNase I was sufficient for its amplification in the tests conducted with conventional PCR. Furthermore, the condition of RNA samples obtained after the treatments allowed for real-time PCR. Therefore, we concluded that 0.02 μL DNase I was the ideal concentration for sugarcane RNA purification, as higher concentrations do not increase the efficiency of the genomic DNA digestion in RNA samples and only make the purification process more expensive. This study provides important information on the effect of high concentrations of DNase I and complements previous studies that have so far tested only the DNase concentration recommended by the manufacturer.