PLA and Montmorilonite Nanocomposites: Properties, Biodegradation and Potential Toxicity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The concern related to solid waste increases efforts to develop products based on biodegradable materials. At present, PLA has one of the highest potentials among biopolyesters, particularly for packaging. However, its application is limited in some fields. In order to optimize PLA properties, organo-modified montmorilonites have been extensively used to obtain nanocomposites. Although PLA nanocomposites studies are widely reported in the literature, there is still few information about the influence of organoclays on de biodegradation process, which is a relevant information, since one of the main purposals related to the final disposal of biopolymers as PLA is composting. Besides, in the last years some research has been conducted in order to evaluate the potential toxicity of montmorilonite, unmodified or organo-modified. Since the use of montmorilonite is expanding in different applications, human exposure and risk assessment are important issues to be investigated. In this context, this review intends to compile available information related to common organoclays used for PLA nanocomposites, its properties, biodegradation analysis and potential toxicity evaluation of nanocomposites, focused on montmorilonite as filler. Two issues of relevance were pointed out. The first is food safety and quality, and the second consideration is the environmental effect.213738759Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2011/14250-3, 2012/00227-2

Genetic diversity in tropical maize inbred lines: heterotic group assignment and hybrid performance determined by RFLP markers

Tropical maize inbred lines, eight derived from a Thai synthetic population (BR-105) and 10 from a Brazilian composite population (BR-106), were assayed for restriction fragment length polymorphisms with 185 clone-enzyme combinations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocation and hybrid performance. Genetic distances (GDs) were on average greater for BR-105 x BR-106 lines (0.77) than for BR-106 x BR-106 (0.71) and for BR-105 x BR-105 (0.69) lines. Cluster analysis resulted in a clear separation of BR-105 and BR-106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for grain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP-based GDs are efficient and reliable to assess and allocate genotypes from tropical maize populations into heterotic groups. However, RFLP-based GDs are not suitable for predicting the performance of line crosses from genetically different heterotic groups.119649149

Spatial distribution of aboveground biomass stock in tropical dry forest in Brazil

Climate change is being intensified by anthropogenic emission of greenhouse gasses, highlighting the value of forests for carbon dioxide storing carbon in their biomass. Seasonally dry tropical forests are a neglected, threatened, but potentially critical biome for helping mitigate climate change. In South America, knowing the amount and distribution of carbon in Caatinga seasonally dry vegetation is essential to understand its contribution to the global carbon cycle and subsequently design a strategic plan for its conservation. The present study aimed to model and map the spatial distribution of the potential forest biomass stock across 32 forest fragments of Caatinga, in the state of Bahia, Brazil, using regression kriging and Inverse Square of Distance techniques, building from point measurements of vegetation biomass made on-the-ground in ecological plots. First, a model for estimating biomass was fitted as a function of environmental variables to apply regression kriging, and then applied to the maps of the selected components. Elevation, temperature, and precipitation explained 46% of the biomass variations in the Caatinga. The model residuals showed strong spatial dependence and were mapped based on geostatistical criteria, selecting the spherical semivariogram model for interpolation by ordinary kriging. Biomass was also mapped by the Inverse Square of Distance approach. The quality of the regression model suggests that there is good potential for estimating biomass here from environmental variables. The regression kriging showed greater detail in the spatial distribution and revealed a spatial trend of increasing biomass from the north to south of the domain. Additional studies with greater sampling intensity and the use of other explanatory variables are suggested to improve the model, as well as to maximize the technique’s ability to capture the actual biomass behavior in this newly studied seasonally dry ecosystem

Microsatellite-assisted backcross selection in maize

A microsatellite marker (SSR) was chosen to simulate a target allele and three criteria (02, 04 and 06 markers per chromosome) were tested to evaluate the most efficient parameters for performing marker-assisted backcross (MAB) selection. We used 53 polymorphic SSRs to genotype 186 BC1 maize (Zea mays L.) plants produced by crossing the inbred maize lines L-08-05 (donor parent) and L-14-4B (recurrent parent). The second backcross (BC2) generation was produced with 180 plants and screened with markers which were not recovered from the first backcross (BC1) generation. A total of 480 plants were evaluated in the third backcross (BC3) generation from which 48 plants were selected for parental genotype recovery. Recurrent genotype recovery averages in three backcross generations were compatible with those expected in BC4 or BC5, indicating genetic gain due to the marker-assisted backcrossing. The target marker (polymorphic microsatellite PHI037) was efficiently transferred. Six markers per chromosome showed a high level of precision for parental estimates at different levels of maize genome saturation and donor alleles were not present in the selected recovered pure lines. Phenotypically, the plants chosen based on this criterion (06 markers per chromosome) were closer to the recurrent parent than any other selected by other criteria (02 or 04 markers per chromosome). This approach allowed the understanding that six microsatellites per chromosome is a more efficient parameter than 02 and 04 markers per chromosome for deriving a marker-assisted backcross (MAB) experiment in three backcross generations