Viviane Talamini

Determination of pesticides in coconut (Cocos nucifera Linn.) water and pulp using modified QuEChERS and LC-MS/MS

The use of pesticides is directly linked to improvements in productivity and to the preservation of coconut palms. However pesticide analysis is necessary to determine whether pesticide residues in the food products containing coconut are within the maximum residue limits (MRLs), ensuring the quality of these products. This work aimed to develop a method for multiresidue determination of ten pesticides in coconut water and pulp using QuEChERS and LC-MS/MS. The method was effective in terms of selectivity, linearity, matrix effect, accuracy and precision, providing LOD of 3μgkg(-1), LOQ of 10μgkg(-1) and recoveries between 70 and 120% with RSD lower than 20%. The developed method was applied to 36 samples in which residues of carbendazim, carbofuran, cyproconazole and thiabendazole were found below the LOQ in coconut water and pulp.

Diversidade genética de isolados de Ralstonia solanacearum e caracterização molecular quanto a filotipos e sequevares

The objective of this work was to identify Brazilian isolates of Ralstonia solanacearum according to phylotypes and sequevars, to determine their genetic diversity, to associate the pathogen genetic structure with its taxonomy and geographical origin, and to identify a specific molecular marker to diagnose banana moko disease. A group of 33 isolates of R. solanacearum, from the collection of Embrapa Tabuleiros Costeiros, collected from different plant hosts, was characterized using the repetitive extragenic palindromic sequence-based PCR (rep-PCR) and RAPD. From this group, 19 belonged to the pathogen race 2 and 14 to the race 1, and 15 isolates were associated with banana crop. Phylotypes and sequevars were characterized and determined by Multiplex PCR. It was verified that the isolates belonged to phylotypes II (82%) and III (12%). All isolates from banana plants belonged to phylotype II. The RAPD technique was efficient in grouping these isolates according to their geographical origin; however, it requires a large number of molecular markers. It was possible to establish the relationships among the isolates by rep-PCR. The enterobacterial repetitive intergenic consensus primer (ERIC) made it possible to separate the isolates according to the race, and the REP primer allowed for the discrimination among phylotypes.These were the two mostinformative analyses.

Response of banana genotypes to yellow Sigatoka in coastal tablelands of Sergipe, Brazil

O Brasil tem baixa disponibilidade de cultivares comerciais produtivas com porte adequado e resistencia a Sigatoka amarela. O objetivo deste estudo foi avaliar o comportamento de diferentes genotipos de bananeira em relacao a Sigatoka amarela em condicoes de tabuleiros costeiros de Sergipe. O experimento foi conduzido no Campo Experimental da Embrapa Tabuleiros Costeiros, no municipio de Nossa Senhora das Dores. O delineamento experimental foi de blocos ao acaso com 22 genotipos e tres repeticoes, seis plantas por parcela. Os genotipos testados foram: Enxerto-33, Japira-106, FHIA-23, YB42-17, YB42-47, FHIA-18, PA42-44, PA94-01, PV79-34, Pacovan Ken, Pacovan, Prata-Ana, Maravilha, Garantida, Princesa, Tropical, Maca, Grande Naine, FHIA-02, Caipira, Bucaneiro e Thap Maeo. A severidade da Sigatoka amarela foi avaliada em 60, 270 e 420 dias apos o plantio (DAP) (a partir de Julho/2009 ate Julho/2010), utilizando uma escala descritiva de Stover. Em seguida, o indice de infeccao foi calculado, aos 60, 270 e 420 DAP e comparados pelo teste de Scott-Knott a 5%. Observou-se que os genotipos tem o mesmo comportamento a 270 DAP. Aos 60 DAP, genotipos com menor indice de infeccao foram Bucaneiro, Enxerto-33, Japira-106, YB42-17, FHIA-02, FHIA-18, FHIA-23, PA42-44, PA94-01, Caipira, Maca, Prata-Ana e Thap Maeo. Aos 420 DAP, as taxas mais baixas foram obtidas para os genotipos YB42-17, FHIA-23, Princesa, YB42-47, Tropical, Grand Naine, Caipira, Maca, Garantida, Bucaneiro, Pacovan Ken e Thap Maeo.

Antimicrobial potential of Actinomycetes by NRPS and PKS-I pathways

BackgroundActinomycetes may account for 10 to 30% of the totalsoil rhizosphere microorganisms. The attention given tothe actinomycetes in biotechnological applications is aresult of their metabolic versatility that is accompaniedby the production of primary and secondary metabolitesof economic importance, which are a promising source ofproducts (e.g., antibiotics, enzyme inhibitors, antiparasiticand anticancer agents) [1,2]. Included in this range ofcompounds are secondary metabolites synthesized bypolyketide synthase (PKS) and non-ribosomal peptidesynthetase (NRPS) pathways. An effective method forassessing the presence of these biosynthetic pathways isthe detection of PKS and NRPS genes by PCR [3,4].Thus, this study was based on targeted analyses of 31 soilisolate actinomycetes aiming to evaluate their antimicro-bial potential through the NRPS and PKS-I pathways.MethodsThe antimicrobial activity was evaluated by the antagon-ism test against two economically important phyto-pathogens, the bacterium Xanthomonas campestris andthe fungus Thielaviopsis paradoxa,usingthetechniqueof double layer. TheX. campestris and T. paradoxawere propagated at 28°C in YM (yeast malt) pH 6.0 andPDB (potato dextrose broth) respectively. The resultswere statistically analyzed using the Bonferroni test.The presence of genes PKS and NRPS was evaluatedby PCR, using degenerate primers for highly conservedregions encoding enzymes associated with biosynthesisof polyketides and peptides.Results and conclusionsAccording to the experimental results, 52% of the iso-lates showed antimicrobial activity against at least oneof the target bacterial pathogens tested. Among theseactive isolates, some belong to rare families. Thus, thisfinding can be a source of novel biomolecules with anti-microbial activity. From those isolates that presentedone of the NRPS and PKS-I genes, 75% of them showedantagonistic activity against one of the phytopathogensevaluated. Preliminary data on this screening demon-strate the importance of the biotechnological potentialof these actinomycetes due to the antagonistic activityagainst plant pathogens of economic interest and thepossibility of be used as biocontrol, besides offering astrong area for metabolic research [2,5].