Carbon isotope compositions (δ(13) C) of leaf, wood and holocellulose differ among genotypes of poplar and between previous land uses in a short-rotation biomass plantation.

The efficiency of water use to produce biomass is a key trait in designing sustainable bioenergy-devoted systems. We characterized variations in the carbon isotope composition (δ(13) C) of leaves, current year wood and holocellulose (as proxies for water use efficiency, WUE) among six poplar genotypes in a short-rotation plantation. Values of δ(13) Cwood and δ(13) Cholocellulose were tightly and positively correlated, but the offset varied significantly among genotypes (0.79-1.01‰). Leaf phenology was strongly correlated with δ(13) C, and genotypes with a longer growing season showed a higher WUE. In contrast, traits related to growth and carbon uptake were poorly linked to δ(13) C. Trees growing on former pasture with higher N-availability displayed higher δ(13) C as compared with trees growing on former cropland. The positive relationships between δ(13) Cleaf and leaf N suggested that spatial variations in WUE over the plantation were mainly driven by an N-related effect on photosynthetic capacities. The very coherent genotype ranking obtained with δ(13) C in the different tree compartments has some practical outreach. Because WUE remains largely uncoupled from growth in poplar plantations, there is potential to identify genotypes with satisfactory growth and higher WUE.

Parallel evolution of cytochrome b mediated bifenazate resistance in the citrus red mite Panonychus citri.

Bifenazate is a recently developed acaricide that is mainly used to control spider mites on a variety of crops. Although first thought to be a neurotoxin, genetic evidence obtained from bifenazate resistant Tetranychus urticae strains suggested an alternative mode of action as a Qo pocket inhibitor of the mitochondrial complex III. In this study, we reveal how bifenazate resistance in strains of Panonychus citri is maternally inherited and can confer cross-resistance to the known Qo inhibitor acequinocyl. The mitochondrial genome of P. citri was sequenced and Qo pocket mutations were shown to be linked with the resistant trait. Parallel evolution of cytochrome b mediated bifenazate resistance corroborates the alternative mode of action and yet again illustrates that care should be taken when employing Qo inhibitors as crop protection compounds.

Wolbachia induces strong cytoplasmic incompatibility in the predatory bug Macrolophus pygmaeus.

Macrolophus pygmaeus is a heteropteran predator that is widely used in European glasshouses for the biological control of whiteflies, aphids, thrips and spider mites. We have demonstrated that the insect is infected with the endosymbiotic bacterium Wolbachia pipientis. Several gene fragments of the endosymbiont were sequenced and subsequently used for phylogenetic analysis, revealing that it belongs to the Wolbachia supergroup B. The endosymbiont was visualized within the ovarioles using immunolocalization. Tetracycline treatments were used to cure M. pygmaeus from its infection. Although a completely cured line could not be obtained by this approach, the application of a constant antibiotic pressure over 13 generations resulted in a line with a significantly reduced Wolbachia concentration. Crosses performed with this tetracycline-treated line revealed that the endosymbiont causes severe cytoplasmic incompatibility. This is the first report of a reproductive effect induced by Wolbachia in an economically important heteropteran predator that may have vital implications for its commercial production and use in biological control.

Preparation and sequencing of secreted proteins from the pharyngeal glands of the plant parasitic nematode Heterodera schachtii.

summary In order to gain insight into the biology of the parasitic relationship between Heterodera schachtii and its host plant, it is important to understand the functional role of the nematode's pharyngeal secretions. These secretions presumably play a key role in establishing and maintaining a feeding site for the nematode. An optimized method was used for the in vitro production of H. schachtii pharyngeal gland secretions. These pharyngeal secretions were mainly produced in an insoluble form and could be solubilized under denaturing conditions for further analysis. The soluble fraction was concentrated with StrataClean (Stratagene, La Jolla, CA) or with a phenol/ether extraction. These methods made it possible for the first time to separate the secreted proteins on two-dimensional gels. By combining a micropreparative sample preparation with mass spectrometry, two beta-1,4-endoglucanases were identified. A third spot was identified as a novel protein by microsequencing. This is the first report on protein sequence information from pharyngeal secretions of a plant parasitic nematode.