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Cassava is one of the most important subsistence crops in tropical regions. It is necessary to preserve and to know the genetic diversity existent for the adequate use of genetic resources. The evaluation of genetic diversity among genotypes results in information about potential parents in breeding programs, allows duplicates identification, and facilitates germplasm exchange between research institutions. The objective of this study was to characterize the genetic diversity of cassava accessions of North Brazil region. A total of 106 accessions were analyzed using ten microsatellite markers. The genetic parameters estimated were: expected heterozygosity (HE), observed heterozygosity (HO) and polymorphic information content (PIC). Clustering was performed using the UPGMA and Neighbor-Joining (NJ) method. Bayesian analysis, analysis of principal coordinates and identification of a core collection were also used. The ten loci amplified 8,40 alleles on average. The average heterozygosity estimates were: HE = 0.71, HO = 0.58 and PIC = 0.72. Genetic distances ranged from 0.158 to 0.908. Six (5,66%) accesses were redundant. Clustering and dispersion analysis didn’t differentiate bitter from sweet cassava, and there wasn’t correlation between groups and collect origin. The core collection consisted of 22 individuals that represented 94% of total allelic diversity and 20,75% of the base collection. The results indicate high dissimilarity between the accessions and allowed the detection of redundant genotypes, showing the use of genetic markers as informative tools for the management of collections.

The objective of this study was to test the efficiency of preservation and maceration methods for Euterpe precatoria leaflet tissue to obtain genomic DNA for molecular studies. The leaflets of E. precatoria were collected in an experimental field at Embrapa Acre, Brazil. The study was conducted in a completely randomized design with 10 replicates, in a 12 × 2 factorial structure, with 12 storage treatments (fresh; lyophiliser 3 days; refrigerator 3, 5, and 7 days; silica gel 7, 10, 20, and 30 days; and transport buffer 3, 5, and 7 days) and two leaf tissue maceration methods (liquid nitrogen and the TissueLyser®). Statistically significant differences in the obtained DNA concentration were found between the maceration and storage treatments. The TissueLyser® macerator produced higher DNA concentrations when compared to liquid nitrogen. For the storage treatments, five groups were formed based on DNA concentration when macerated with the TissueLyser® and two groups when macerated with liquid nitrogen. The DNA concentrations ranged from 285.00 ng/µL (7 days in transport buffer) to 702.00 ng/µL (30 days in silica gel) when the leaflets were macerated with liquid nitrogen, and from 572.73 ng/µL (30 days in silica gel) to 2,850.00 ng/µL (3 days in lyophiliser) using the TissueLyser® macerator. The DNA purity (A260/A280 nm) varied from 1.30 to 1.70 when the leaflets were macerated with liquid nitrogen and from 1.30 to 1.90 with the TissueLyser® macerator. Despite the variations in leaf tissue preservation and DNA concentration, all treatments were effective for DNA isolation and it was possible to amplify genomic regions of microsatellite markers by PCR. It was concluded that leaflets of E. precatoria stored in a lyophiliser and processed with an automatic macerator resulted in satisfactory DNA for molecular studies.

ABSTRACT Soil properties and classes can influence the occurrence of plants and the production of Brazil nut fruits and may have a different distribution between sites. This study aimed to evaluate the relationship of plants’ occurrence, production of Brazil nut fruits, and spatial variability of the properties in different soil classes in two Brazil nut stand in the state of Acre, Brazil. The study was conducted in two plots in two native Brazil nut stand, Cachoeira (CP01 and CP02 - plots 1 and 2) and Filipinas (FP01 and FP02 - plots 1 and 2). The soil profiles were described morphologically. Sixty soil samples were collected in each plot. The chemical properties, granulometry, soil density, particle density, and estimated total porosity were determined. The average fruit production was calculated by counting the fruits in a sample of Brazil nut trees. Subsequently, the trees were divided into three classes of production: low (≤1.5 can; the can unit has 18-L, which is able to hold 59 and 77 fruits, respectively, for Cachoeira and Filipinas), medium (1.6 to 3.9 cans), and high (≥4.0 cans). The can unit is the traditional measure of volume in the region and varies according to the locality. Cluster analysis was performed to determine whether there was a difference between Brazil nut stands and soil profiles, and geostatistics was used to evaluate the spatial dependence of soil properties. The highest occurrence of Brazil nut trees with high fruit production (≥4.0 cans) was found in the Latossolo Vermelho Distrófico argissólico (Oxisol) and Argissolo Vermelho-Amarelo Distrófico típico (Ultisol). However, the Argisol also hosted the plants with the lowest productions (≤1.5 can). The pH, total organic carbon, sum of bases, P, N, granulometry, and porosity showed a greater spatial variability, and FP02 showed a greater number of properties with high spatial variability compared to the other areas. Although the occurrence of plants and the production of Brazil nut fruits ( Bertholletia excelsa ) were associated with the classes and the physical and chemical properties of the soil, pyxidium production differed between areas. In general, soil physical properties were limiting factors for Brazil nut production and/or higher tree occurrence. Filipinas environment showed a low fruit production and a greater spatial variability of soil properties compared to Cachoeira.

DRIS, an Diagnosis and Recommendation Integrated System, is a tool to evaluate the nutritional status of plants. Different DRIS formulas have been proposed to improve the efficiency of the crop nutrition diagnoses. The objective of this study was to compare the nutritional diagnosis of the formulas of Beaufils (1973), of Jones (1981) and of Elwali and Gascho (1984), based on the degree of agreement in commercial orchards of Theobrama grandiflorum trees. Leaf samples of 5 to 18 year-old cupuaçu trees were collected from 153 commercial orchards in agroforestry and monoculture systems in the state of Rondonia, Brazil. Bivariate relationships between nutrition concentrations in healthy trees were used to calculate DRIS norms. DRIS indices were calculated based on the different formulas and interpreted by the Potential Fertilizer Response method, in five categories. The DRIS norms, DRIS index calculations and their interpretations were developed using the DRIS Cupuaçu computer program (www.dris.com.br). The different DRIS formulas resulted in similar diagnoses with a degree of agreement of > 90% for the nutrients N, P, K, Ca, and Mg.

O objetivo deste trabalho foi avaliar a performance de normas DRIS específicas ou gerais no diagnóstico do estado nutricional do cupuaçuzeiro (Theobroma grandiflorum), na Amazônia Sul-Ocidental. Amostras foliares de cupuaçu foram coletadas de 153 pomares comerciais, com idade entre 5 e 18 anos, cultivados em monocultivo ou em sistemas agroflorestais. Foram geradas normas DRIS específicas para cada sistema de produção e normas gerais, obtidas para o conjunto da população monitorada. Na obtenção das normas, foi considerada a relação nutricional entre N, P, K, Ca, Mg, Fe, Cu, Zn e Mn. A maioria das médias das relações bivariadas entre nutrientes e dos diagnósticos produzidos pelas normas DRIS específicas não diferiu em relação aos produzidos com o uso da norma DRIS genérica. Portanto, a avaliação do estado nutricional de cupuaçuzeiros pode ser realizada com o uso de normas DRIS genéricas, que independem do sistema de cultivo.The objective of this work was to evaluate the performance of specific or generic DRIS norms regarding diagnosis of the nutritional state of cupuaçu (Theobroma grandiflorum) orchards, in Southwestern Amazonia. Cupuaçu leaf samples were collected from 153 commercial orchards with ages ranging from 5 to 18 years, cultivated either in monoculture or in agroforestry systems. Specific DRIS norms, obtained for each production system, and generic norms, for the entire population, were generated. DRIS norms were obtained considering the nutritional relationship between N, P, K, Ca, Mg, Fe, Cu, Zn and Mn. The majority of bivariate relation means between nutrients and diagnostics obtained from the specific DRIS norms did not differ in comparison to the ones obtained when the generic DRIS norm was used. The evaluation of the nutritional state of cupuaçu orchards can be done using generic DRIS norms, which do not take into account the production system.

ABSTRACT The search for alternatives to increase productivity and sustainability of livestock production in the Amazon region without increasing deforestation is challenging. Mixed pastures of grasses with forage peanut (Arachis pintoi) have shown positive economic impacts. However, gaps in the knowledge of the reproductive biology of A. pintoi have limited the development of new cultivars adapted to the environmental variations in the Brazilian Amazon. Pasture consortiums of Brachiaria humidicola with forage peanuts (cv. Mandobi) resulted in a 42% increase in weight gain productivity. New cultivars better adapted to the Amazon climate should bring even greater gains. We evaluated the mating system in twenty A. pintoi accessions, and approximately 40 offspring per accession genotyped with eight microsatellites (or markers). The parameters of genetic diversity and inbreeding, the outcrossing rate and coancestry were calculated. The observed heterozygosity was significantly higher and the fixation index was significantly lower in adults compared with the offspring. The crossing rate was variable among genotypes (2 to 80%), and the mean outcrossing rate was 36%. These results indicate that pollinator presence in pastures can influence gene flow in A. pintoi more than expected. Arachis pintoi presented a mixed mating system with a predominance of selfing, and families presented inbreeding and different levels of relatedness. New strategies of genotype conservation are needed to avoid pollinator-mediated crossing between accessions.