In Situ Production of Prebiotic AXOS by Hyperthermophilic Xylanase B from Thermotoga maritima in High‐Quality Bread

In situ enrichment of bread with arabinoxylan‐oligosaccharides (AXOS) through enzymic degradation of wheat flour arabinoxylan (AX) by the hyperthermophilic xylanase B from Thermotoga maritima (rXTMB) was studied. The xylanolytic activity of rXTMB during breadmaking was essentially restricted to the baking phase. This prevented problems with dough processability and bread quality that generally are associated with thorough hydrolysis of the flour AX during dough mixing and fermentation. rXTMB action did not affect loaf volume. Bread with a dry matter AXOS content of 1.5% was obtained. Further increase in bread AXOS levels was achieved by combining rXTMB with xylanases from Pseudoalteromonas haloplanktis or Bacillus subtilis. Remarkably, such a combination synergistically increased the specific bread loaf volume. Assuming an average daily consumption of 180 g of fresh bread, the bread AXOS levels suffice to provide a substantial part of the AXOS intake leading to desired physiological effects in humans.     

Effect of ploidy on the mortality of Crassostrea gigas spat caused by OsHV‐1 in France using unselected and selected OsHV‐1 resistant oysters

The effect of ploidy on the mortality of Crassostrea gigas spat caused by the ostreid herpesvirus (OsHV‐1) genotype μVar was investigated at five sites along the Atlantic coast in France in 2011. Sibling diploids and triploids were produced using either unselected or selected OsHV‐1‐resistant oysters. No significant interactions were found between the factors of environment, genotype and ploidy at the endpoint dates. The mean mortality rates at the sites were 62% and 59% for diploids and triploids, respectively, and the two rates were not significantly different. The mean mortality rates were 33% and 32% for sibling diploids and triploids, respectively, when OsHV‐1‐resistant parents were used and 91% and 85%, respectively, when unselected parents were used. The results were confirmed through other broodstocks tested in 2013. Our study is the first to clearly show that mortality related to OsHV‐1 is similar between diploids and triploids in C. gigas when the same germplasm is used for both ploidy. Furthermore, OsHV‐1 resistance was not substantially altered by triploidization, indicating that the achieved selective breeding of diploid oysters for OsHV‐1 resistance can be translated into improved survival in triploids.     

Benzimidazole resistance of sheep nematodes in Norway confirmed through controlled efficacy test

Background

Resistance against benzimidazoles (BZ) has recently been detected in Norwegian sheep flocks through a large scale prevalence survey based on the faecal egg count reduction test (FECRT). The use of this test in combination with bulk larval culture only gives an indication of which gastrointestinal nematodes genera that are involved and these results have to be confirmed by a controlled efficacy test (CET) to get accurate information about resistant nematodes populations at species level. A CET was therefore performed with larvae from two flocks where BZ resistance was previously detected through FECRT.

Results

The latter test confirmed the previous results in both flocks. In flock A, the BZ resistant nematode population consisted solely of Haemonchus contortus, whereas H. contortus and Teladorsagia circumcincta comprised the resistant worm population in flock B.

Conclusions

Some discrepancies that have been recorded between FECRT and CET results regarding time for post-treatment coproscopical examination and a temporary suppression of faecal egg excretion are discussed.     

Heterozygous genotypes are efficient testers for assessing between-population combining ability in the reciprocal recurrent selection of Coffea canephora

Coffea canephora Pierre breeding in Côte d’Ivoire is based on indirect reciprocal recurrent selection (RRSi) using the Congolese and Guinean populations. In practice, the genotypes of each population (78 Congolese genotypes and 100 Guinean genotypes) are tested with several testers from the reciprocal population: two Guinean and three Congolese testers. These testers are heterozygous as C. canephora is a strictly outcrossing species. After a first cycle of RRSi, we judged the efficiency of these testers for yield, susceptibility to coffee leaf rust (SCLR) and hundred bean weight (HBW). All the testers discriminated the tested genotypes highly significantly (P < 0.01), even though differences were found in the degrees of discrimination. For yield and SCLR, no interaction between tested genotypes and testers was observed and correlations between test values obtained from different testers were significant or highly significant. Furthermore, test values of tested genotypes could be used to predict the yield and SCLR of between-population (BP) hybrids. Prediction was always more accurate with the best tester than with the mean of several testers. As opposed to yield and SCLR, HBW showed significant interactions between tested genotypes and testers and HBW of hybrids could not be predicted from the test value of the genotypes. We conclude that only one reciprocal tester can be used in the next cycles of RRSi applied to C. canephora. This will allow either a reduced cost of selection or increased selection intensity.     

Odour and feeding preference of noctuid moth larvae conditioned to vanillin diet and non-vanillin diet

It is largely accepted that larval experience influence host-plant preference of larvae. In general, larval experience with a host plant induces both an odour and feeding preference for that plant. In a previous study, exposure of three noctuid stem borer species, i.e. Sesamia nonagrioides, Busseola fusca and B. nairobica, to a vanillin-enriched medium induced an olfactory preference for the odours of this medium in the larvae of these species. Here, we checked if the exposure to a vanillin-enriched medium also induced a feeding preference for this diet. Different life stages (i.e. neonate larvae to adults) of the three species were conditioned to an artificial diet enriched with vanillin over two generations. Thereafter, two-choice tests on third-generation larvae were done using a Y-tube olfactometer for odour preferences and diet choice experiments. Larvae of all three-species conditioned to the vanillin diet oriented significantly towards the odour of this diet, whereas the non-conditioned larvae did not. Still, apart for B. fusca, the conditioned larvae did not exhibit a feeding preference for this diet, thus odour preference did not match the feeding choice of the conditioned larvae. The implication of this result on insect’s adaptability to a new host plant in a changing environment is discussed.     

Metal soil pollution differentially affects both the behaviour and exposure of <Emphasis Type="Italic">A. caliginosa</Emphasis> and <Emphasis Type="Italic">L. terrestris</Emphasis>: a mesocosm study

The effects on two earthworm species of a gradient of metal contamination in soil collected close to a 50-year-old lead recycling factory were investigated in mesocosms filled with soil sampled at three distances from the factory (10, 30 and 60 m). After 5 weeks of exposure, earthworm litter consumption and weight change were measured. Burrow systems were analysed using X-ray tomography, and water infiltration was measured. No significant differences in earthworm weight or activity were observed between mesocosms filled with soil from 30 and 60 m. In contrast, both earthworm species significantly lost weight and burrowed less in the soil sampled at 10 m. In the cores filled with the soil collected at 10-m distance, Aporrectodea caliginosa avoided the highly contaminated first layer (0–5 cm) and burrowed deeper whereas Lumbricus terrestris burrowed relatively more in this layer. We assume that these different reactions are associated with their ecological types. Epi-anecic earthworms forage litter at the soil surface, whereas endogeic earthworms are geophagous and thus are able to forage deeper. This was further corroborated by the bioaccumulation factors measured for each species: for L. terrestris, BAF values for Pb and Cd only decreased slightly in the 10-m soil correlating with their overall reduced activity. However, BAF values for A. caliginosa were 20-fold lower compared to those observed in soil from 30 and 60 m. These modifications in burrowing behaviour in the 10-m mesocosms resulted in a significant and marked decrease in water infiltration rates but only for L. terrestris.     

Combining isotopic signatures of n(Sr)/n(Sr) and light stable elements (C,N, O,S) with multi-elemental profiling for the authentication of provenance of European cereal samples

The aim of this work (from the FP6 project TRACE) was to develop methods based on the use of geochemical markers for the authentication of the geographical origin of cereal samples in Europe (cf. EC regulations 2081/92 and 1898/06). For the first time, the potential usefulness of combining n(⁸⁷Sr)/n(⁸⁶Sr) and δ¹³C, δ¹⁵N, δ¹⁸O and δ³⁴S isotopic signatures, alone or with key element concentrations ([Na], [K], [Ca], [Cu] and [Rb], progressively identified out of 31 sets of results), was investigated through multiple step multivariate statistics for more than 500 cereal samples collected over 2 years from 17 sampling sites across Europe representing an extensive range of geographical and environmental characteristics.     

Study of grain cell wall structures by microscopic analysis with four different staining techniques

Four different grain cell wall staining techniques were compared. Two techniques specifically detected arabinoxylan (AX). The first technique used a xylanase probe, while the other one was based on immunolabeling of AX using monoclonal antibodies. The two other staining techniques, one based on Calcofluor and the other on immunolabeling using monoclonal antibodies, stained mixed-linkage β-glucan. Cell walls of wheat, barley, oat and rye grains, differing both in content and location of AX and β-glucan, were examined. The staining methods were complementary to each other in revealing the location and distribution of the major cereal dietary fiber components AX and β-glucan in the different grains. AX was mostly concentrated in nucellar epidermis and aleurone cells, whereas β-glucan was concentrated more in subaleurone cells. Furthermore, in the case of barley and rye, the endosperm cell walls also contained high amounts of β-glucan. Interestingly, β-glucan in rye and barley endosperm cell walls was located adjacent to the cell contents, suggesting that it is not evenly distributed in the endosperm cell walls. The results give new insight into the structure of the cereal dietary fiber complex. Further development of microscopic techniques will help in elucidating the cereal cell wall structure even in more detail.