French mosquito populations invaded by A2-B2 esterases causing insecticide resistance

In the mosquito Culex pipiens L., the two associated esterases A2 and B2 are responsible for resistance to organophosphorus (OP) insecticides in many countries of Africa, Asia and North America. We report here their presence and geographic spread in French populations based on the analysis of 168 samples collected from 1984 to 1990. First detected in 1986 in one sample from southern France, these esterases were progressively found in new geographic locations, so that in 1990 their distribution covered at least four contiguous French regions. RFLP analysis of the amplified B2 gene indicates that A2-B2 arrived in France most likely through migration. This genetic invasion is discussed in the light of the recent occurrence of A2-B2 in the mosquito genome, and of the consequences of this new resistance factor in natural populations already possessing other insecticide resistance genes.     

Effect of Phosphlnothricin (Glufosinate) on Photosynthesis and Chlorophyll Fluorescence Emission by Barley Leaves Illuminated Under Photorespiratory and Non-Photorespiratory Conditions

The effect of phosphinothricin (PPT), an inhibitor of glutaminesynthetase, on several aspects of photosynthesis has been studiedin primary leaves of barley (Hordeum vulgare L.). When photorespirationwas suppressed, either by increasing CO₂ concentration to 0.7%,or by decreasing O₂ concentration to 1%, feeding the illuminatedleaves with 0·5 or 1·0 mM PPT did not affect photosynthesisto a noticeable extent. Conversely, when PPT-fed leaves wereilluminated in air, CO₂ uptake decreased continuously. Modificationof the components of chlorophyll fluorescence quenching indicatedincreased reduction of Q_A, the primary acceptor of photosystemII, and increased chloroplast energization. Feeding of PPT toleaves illuminated in air increased the quantum requirementof photosynthesis and decreased photosynthetic rate of oxygenevolution in saturating [CO₂] and high light intensity. It isconcluded that the effect of PPT on the photochemical processesis indirect, through the inhibition of CO₂ assimilation probablycaused by the depletion of intermediates of the reductive pentosephosphate cycle. Key words: Feeding, Hordeumvulgare L., quenching coefficients