Biological aspects of Bemisia tabaci biotype B and the chemical causes of resistance in soybean genotypes

In Brazil, the silverleaf whitefly (SLW), Bemisia tabaci biotype B, is a serious soybean pest. SLW management is difficult and new control strategies, such as host–plant resistance, are required. Herein, we aimed to evaluate the biology of SLW, from eggs to adults, on seven soybean cultivars. The emergence of adult insects was monitored daily. Defense-related compounds were identified and quantified from the V3 to the V8 stages in SLW-infested and non-infested plants. The rates of emergence of SLW adults were lower in cultivars ‘IAC 17,’ ‘IAC 19’, and ‘IAC 24’ compared with the susceptible cultivar ‘IAC Holambra Stwart’. Rutin, genistin, genistein, and salicylic acid were identified and quantified in plant extracts. The rutin, genistin, and genistein levels decreased after SLW infestation. Rutin concentrations increased in infested plants of ‘IAC 17’ (V6) and ‘IAC 19’ (from V5 to V8). ‘Barreiras’ showed the highest genistein content in non-infested plants; from V5 growth stage, it was not detected in cultivars Doko (infested), Vencedora, ‘IAC 17’, and ‘IAC 24’ (non-infested). High levels of salicylic acid were observed in ‘IAC ‘19’-infested plants (at V3 and V5). The results suggest that rutin can be related to SLW adults’ emergence only when the feeding source was ‘IAC 19’. Consequently, further studies are needed to access the associated gene expressions and the effect of other secondary metabolites, mainly volatile compounds from SA pathway, including its consequences on feeding preference and mostly in relation to IAC cultivars.     

EXTRACELLULAR POLYSACCHARIDES FROM ANKISTRODESMUS DENSUS (CHLOROPHYCEAE)

The dissolved extracellular compounds produced by the Chlorococcalean Ankistrodesmus densus Kors. were investigated for their molecular masses and chemical composition. Gel permeation chromatography showed apparent relative molecular masses of 2 × 10⁶ and 10⁴, respectively, for two distinct fractions, termed A and B. The higher molecular weight fraction (A) contained mainly fucose and 3- O -methylgalactose, whereas galactose, glucose, mannose, and rhamnose were present in smaller amounts. Methylation analyses showed that the main structural features are fucose as a highly branched part of polymer A with substitutions in both position 2 and position 4, the substitutions on one of those positions being primarily terminal 3- O -methylgalactose and the other one involved as the linkage of the main chain of the polymer. Because of the presence of both fucose and 3- O -methylgalactose, this polymer is highly hydrophobic. In fraction B, mannose represented more than 60% of the carbohydrate material present, whereas the remaining part contained rhamnose, fucose, xylose, and glucose in almost equal amounts. 3- O -methylgalactose and galactose were present as minor elements. Fraction B is basically a mannose-containing polymer in which the mannose units are either 1→4 or 1→2 linked. Traces of glucuronic acid and protein were present in both fractions; neither sulfate nor phosphate was detected.     

A SIMPLE ALTERNATIVE TO GENERALIZED PROCRUSTES ANALYSIS: APPLICATION TO SENSORY PROFILING DATA

A statistical method for analyzing sensory profiling data obtained by means of fixed vocabulary or free choice profiling is discussed. The most interesting feature of this method is that it involves only simple statistical treatment and can therefore be performed using standard software packages. The outcomes of this method are compared to those of Generalized Procrustes Analysis on the basis of two data sets obtained, respectively, by means of fixed vocabulary and free choice profiling. A significance test is also discussed in order to assess whether the overall configuration of the products is meaningful. This significance test is based upon a simulation study involving the permutation procedure.     

Morphological changes and EGF expression in the granular convoluted tubule cells of submandibular glands of Trypanosoma cruzi infected rats

We have previously demonstrated in rats that Chagas' disease affects the salivary glands, by promoting an enlargement of the submandibular gland. In order to further investigate possible functional alterations on infected submandibular glands, the objective of the present study was to analyze epidermal growth factor (EGF) expression on rat submandibular glands during Trypanosoma cruzi infection. Results demonstrated that infected rats presented lower levels of testosterone, and morphological changes in the granular convoluted tubule (GCT) cells of the submandibular glands, along with acinar enlargement and delayed ductal maturation at the developing granular ducts. Immunohistochemistry analysis additionally showed that only few cells immunolabelled with anti-EGF on infected rats during the acute phase of Chagas' disease, while after 64 and 90 days (chronic phase) of infection, EGF expression was similar to non-infected rats. The present findings suggest that at the acute phase of Chagas' disease, lower levels of testosterone may lead to a delayed maturation of GCT, which positively correlates with decreased EGF production by submandibular glands cells.