Adriano Moreira Knupp

Bacterial community as an indicator of genetically modified common bean effect on nontarget organisms

The objective of this work was to evaluate the effect of genetically modified common bean for Bean Golden Mosaic Virus, BGMV, resistance (Olathe M1-4) on nontarget organisms. In a field experiment established in a completely randomized design with two treatments (Olathe Pinto cultivar and M1-4 Olathe elite event), two sampling periods (V4 and R6 stages) and ten replicates, cultivated and non-cultivated bacterial cells from rhizosphere soil and bulk soil were obtained, and their total DNA was extracted. The V6-V8 region of 16S rDNA was amplified for the whole bacterial community, and primers specific for the alpha (α) subgroup of the Proteobacteria phylum were obtained from uncultured cells and used for amplification. Using the Jaccard coefficient and UPGMA (Unweighted pair-group method with arithmetic mean), dendrograms comparing the conventional Olathe Pinto and the elite event Olathe M1-4 transgenic varieties were obtained. The clusters obtained from the 16S rDNA PCR-DGGE profiles indicate changes in the rhizosphere bacterial community in genetically modified plants, being more notable in the profiles obtained for alphaproteobacteria. Sample origin and plant development stages affect bacterial community profiles.

Eficiência da quantificação do carbono da biomassa microbiana por espectrofotometria comparada ao método titrimétrico - DOI:10.5039/agraria.v6i4a1071

Dentre os parâmetros de qualidade do solo, o carbono da biomassa microbiana (C mic ) e um dos mais utilizados, porem, o processo de analise mais adotado pelos laboratorios promove a geracao de residuos toxicos. Com o objetivo de reduzir a geracao de residuos no processo analitico, foram realizados testes comparativos entre a titrimetria e a espectrofotometria para a quantificacao do carbono microbiano, a partir de amostras de solo coletadas nas profundidades de 0-10 cm e 10-20 cm em tres tipos de solo com caracteristicas quimicas, fisicas e de manejo distintas. Os valores de C mic encontrados nos tres solos pelo metodo espectrofotometrico foram semelhantes aos valores encontrados pela titrimetria. Quando se utilizou a espectrofotometria, houve reducao de 42% na concentracao de dicromato de potassio para a nova formulacao da solucao digestora e de cerca de 20% no tempo de execucao da analise, alem de reducao no volume de residuos toxicos gerado. De acordo com os resultados obtidos, o uso da espectrofotometria apresentou-se vantajoso do ponto de vista ambiental, alem de nao diferir estatisticamente do metodo titrimetrico.