Marcelo Ayres Carvalho

Evaluating the composition and processing potential of novel sources of Brazilian biomass for sustainable biorenewables production

BackgroundThe search for promising and renewable sources of carbohydrates for the production of biofuels and other biorenewables has been stimulated by an increase in global energy demand in the face of growing concern over greenhouse gas emissions and fuel security. In particular, interest has focused on non-food lignocellulosic biomass as a potential source of abundant and sustainable feedstock for biorefineries. Here we investigate the potential of three Brazilian grasses (Panicum maximum, Pennisetum purpureum and Brachiaria brizantha), as well as bark residues from the harvesting of two commercial Eucalyptus clones (E. grandis and E. grandis x urophylla) for biofuel production, and compare these to sugarcane bagasse. The effects of hot water, acid, alkaline and sulfite pretreatments (at increasing temperatures) on the chemical composition, morphology and saccharification yields of these different biomass types were evaluated.ResultsThe average yield (per hectare), availability and general composition of all five biomasses were compared. Compositional analyses indicate a high level of hemicellulose and lignin removal in all grass varieties (including sugarcane bagasse) after acid and alkaline pretreatment with increasing temperatures, whilst the biomasses pretreated with hot water or sulfite showed little variation from the control. For all biomasses, higher cellulose enrichment resulted from treatment with sodium hydroxide at 130°C. At 180°C, a decrease in cellulose content was observed, which is associated with high amorphous cellulose removal and 5-hydroxymethyl-furaldehyde production. Morphological analysis showed the effects of different pretreatments on the biomass surface, revealing a high production of microfibrillated cellulose on grass surfaces, after treatment with 1% sodium hydroxide at 130°C for 30 minutes. This may explain the higher hydrolysis yields resulting from these pretreatments, since these cellulosic nanoparticles can be easily accessed and cleaved by cellulases.ConclusionOur results show the potential of three Brazilian grasses with high productivity yields as valuable sources of carbohydrates for ethanol production and other biomaterials. Sodium hydroxide at 130°C was found to be the most effective pretreatment for enhanced saccharification yields. It was also efficient in the production of microfibrillated cellulose on grass surfaces, thereby revealing their potential as a source of natural fillers used for bionanocomposites production.

Forage yield and nutritive value of Panicum maximum genotypes in the Brazilian savannah

The narrow genetic variability of grasslands and the incidence of new biotic and abiotic stresses have motivated the selection of new Panicum maximum genotypes for use as forage for beef cattle in the Brazilian savannah. This study aimed to evaluate forage yield and nutritive value of P. maximum genotypes including 14 accessions (PM30 to PM43), four intraspe- cifi c hybrids (PM44 to PM47) and six cultivars (Aruana, Massai, Milenio, Mombaca, Tanzania and Vencedor), examining 24 genotypes over two years (2003 and 2004). Milenio cultivar was the genotype with the highest dry matter yield (DMY) in both years (18.4 t ha -1 and 20.9 t ha -1 , respectively) although it presented a high proportion of stems (~ 30 %). Genotypes that showed higher Leaf DMY in both years were the accession PM34 (14.7 t ha -1 ) and the hybrid PM46 (14.0 t ha -1 ), while Mombaca and Tanzania yielded 12.5 and 11.0 t ha -1 , respectively. Leaf organic mat- ter digestibility and leaf DMY for PM40 and PM46 genotypes exceeded the mean (> 656 g kg -1

Using genetic diversity information to establish core collections of Stylosanthes capitata and Stylosanthes macrocephala.

Stylosanthes species are important forage legumes in tropical and subtropical areas. S. macrocephala and S. capitata germplasm collections that consist of 134 and 192 accessions, respectively, are maintained at the Brazilian Agricultural Research Corporation Cerrados (Embrapa-Cerrados). Polymorphic microsatellite markers were used to assess genetic diversity and population structure with the aim to assemble a core collection. The mean values of HO and HE for S. macrocephala were 0.08 and 0.36, respectively, whereas the means for S. capitata were 0.48 and 0.50, respectively. Roger’s genetic distance varied from 0 to 0.83 for S. macrocephala and from 0 to 0.85 for S. capitata. Analysis with STRUCTURE software distinguished five groups among the S. macrocephala accessions and four groups among those of S. capitata. Nei’s genetic diversity was 27% in S. macrocephala and 11% in S. capitata. Core collections were assembled for both species. For S. macrocephala, all of the allelic diversity was represented by 23 accessions, whereas only 13 accessions were necessary to represent all allelic diversity for S. capitata. The data presented herein evidence the population structure present in the Embrapa-Cerrados germplasm collections of S. macrocephala and S. capitata, which may be useful for breeding programs and germplasm conservation.

Genetic studies in Centrosema pubescens benth, a tropical forage legume: the mating system, genetic variability and genetic relationships between Centrosema species

In this study, we used microsatellite loci to estimate the outcrossing rate of Centrosema pubescens in open-pollinated populations of 10 progenies that each contained 20 genotypes. The multilocus outcrossing rate was 27%, which suggested a mixed mating system with a predominance of autogamy. The single locus outcrossing rate was 13%. The difference was 0.040, which indicated that only 4% of outcrossing occurs in related individuals. A paternity correlation of 14% suggests that there is a low probability of finding full sibs in the progeny. Cross-amplification of the 26 microsatellite loci available for C. pubescens was evaluated across 11 different Centrosema species. Nineteen of the 26 tested microsatellites were successfully transferable across the Centrosema species. The polymorphism information content and discriminating power evaluated had averages of 0.64 and 0.77, respectively. A total of three clusters were assembled to demonstrate the genetic relationships between Centrosema species. The transferable microsatellite loci should be useful for exploiting the genetic resources of the Centrosema species and determining the outcrossing rate, which are essential for proposing effective approaches for conservation and for establishing strategies for the selection and improvement of Centrosema spp.

Comparative assessment of variation in the USA Arachis pintoi (Krap. and Greg.) germplasm collection using RAPD profiling and tissue culture regeneration ability.

Arachis pintoi accessions were used to study genetic diversity using RAPD markers. Concurrently, two tissue culture protocols were evaluated for organogenesis and the capacity to generate somaclonal variation. Data were collected on callus growth, callus weight gain, and number of regenerated plants. Robust RAPD profiles were obtained and eight primers amplified 100 different bands with 98% polymorphisms. The proportion of polymorphic RAPD loci was 89%. Average genetic distance was 0.36 and indicated that a large amount of genetic diversity exists within the germplasm evaluated. Genetic distances were used to prepare a dendogram for the A. pintoi accessions that separated them into four groups. A large degree of variability for callus induction and callus weight gain was observed among the accessions. Shoot regeneration was achieved for several accessions on both media with no structures indicative of somatic embryogenesis detected. Root induction was difficult to obtain, and many shoots died during this process. RAPD band profiles of regenerated tissue culture plants were similar to their parent plants, and therefore no somaclonal variation was evident using these methods.

Molecular diversity, genetic structure and mating system of Calopogonium mucunoides Desv.

Calopogonium mucunoides Desv. is a species native of South and Central America that is used as green manure and a pasture crop. The molecular genetic diversity was characterized in 195 C. mucunoides accessions from a germplasm collection using 17 microsatellite markers. Outcrossing rate was estimated after the evaluation of six microsatellite loci in 200 genotypes originated from 10 open-pollinated progenies (20 genotypes per progeny). Six genetic clusters were identified in the germplasm collection by the STRUCTURE software analysis, neighbor-joining tree comparisons and principal component analysis, which highly correlated with the geographic locations where these accessions were originated or collected. These results were confirmed using AMOVA. The largest portion of the genetic variation was observed among clusters (64.38%). The results indicated that: multilocus outcrossing rate (tm) was 16.3%, suggesting a mixed mating system with a predominance of autogamy; single locus outcrossing rate (ts) was 11%; difference (tm−ts) was 0.054, indicating that only 5.4% of outcrossing occurred among related individuals; paternity correlation (rp) was 33% suggesting a low probability of finding full sibs among the progeny; parental coefficient of inbreeding (Fm) was 5.0%, indicating a low degree of inbreeding in each parent. A core collection for C. mucunoides was assembled to capture the allelic diversity found in this study. The complete allelic diversity was represented by only 15 accessions. These results should be useful for exploiting the genetic resources of C. mucunoides and could influence future conservation efforts and breeding programs.

Characterization of Meloidogyne arenaria, M. javanica, and M. incognita reaction of the USA Arachis pintoi (Krapov. & W.C. Gregory) germplasm collection

Abstract Arachis pintoi Krapov. & W.C. Gregory is a herbaceous, perennial legume, exclusively native to Brazil. It is considered a multiple use legume, being grown for forage; ground cover in fruit...

Microsatellite markers in tropical legume (Centrosema pubescens Benth): development, characterization, and cross-species amplification in Centrosema sp

Centrosema pubescens Benth is a forage legume widespread in tropical America. Twenty-six polymorphic microsatellite markers were isolated and characterized in 15 genotypes of C. pubescens from the Cerrados Research Center Germplasm Bank of the Brazilian Agricultural Research Corporation (Embrapa). The number of alleles observed for each locus ranged from 2 to 5, with an average of 3 alleles per locus. The polymorphism information content (PIC) varied between 0.39 and 0.86 (average 0.57) and the discriminating power (D) ranged from 0.45 to 0.98 (average 0.68). The observed heterozygosity (Ho) and the expected heterozygosity (He) were 0.01–0.81 and 0.10–0.86, respectively. A cross-amplification test in 11 Centrosema species suggested potential transferability of these microsatellites. The data indicated that the polymorphic microsatellite markers developed in this work should be useful for assessing genetic diversity in further breeding programs and germplasm conservation.

Forage yield and nutritive value of Arachis spp. genotypes in the Brazilian savanna.

Forage yield, nutritive value, ground cover and mineral concentration of 10 genotypes of Arachis spp. were evaluated over 3 years in Planaltina, Federal District, Brazil. Experimental plots were arranged in a randomized complete block design with 4 replications. Treatments were 5 genotypes of A. pintoi (accessions 2, 4, 5, 6 and 8), 2 genotypes of A. repens (accessions 1 and 7), 1 hybrid A. pintoi × A. repens (accession 3) and 2 A. pintoi cultivars, BRS Mandobi and Belmonte. All genotypes established well and achieved good ground cover in the first year. Cultivar Belmonte and accessions 2 and 4 produced the highest DM yields (means of 8.8, 8.5 and 8.8 t DM/ha/yr, respectively) throughout, while cv. BRS Mandobi and accession 6 were the worst (5.7 and 5.6 t DM/ha/yr). Most genotypes maintained ground cover above 80% throughout the study but cv. BRS Mandobi plus accessions 6 and 8 had declined to 60% or less by the third year. Mean crude protein concentration overall was 166 g/kg with a range of 154‒182 g/kg among genotypes. There was no major genotypic variation in mineral concentrations, which in all cases were considered marginal to adequate for tropical forage legumes. In conclusion, genotypes 2 and 4 (accessions BRA-039799 and BRA-039187, respectively) of A. pintoi are considered the most promising forage peanut options under the edaphoclimatic conditions of the experimental site. More effort is needed to improve seed set in these accessions to increase adoption by farmers. Their persistence under grazing and impact on production should also be demonstrated. Keywords : Arachis pintoi , Arachis repens , crude protein, digestibility, minerals.