Impact of natural and human selection on the frequency of the F1 hybrid between cultivated and wild pearl millet (Pennisetum glaucum (L.) R. Br.)

In the Sahel, pearl millet yields are affected by the proportion of hybrid phenotype plants resulting from genetic mixing between domesticated and wild forms. Man counteracts this mixing by applying a production method, the efficiency of which is quantified in this study. Under experimental conditions, cultivated and wild pearl millet were hybridised in order to obtain cultivated pearl millet seeds including a known proportion of F1 hybrids tagged by two different allozymes. These seeds were sown in the field and the cultivation was conducted following practices common in the Sahel. The evolution of the survival rate of plants and the frequency of hybrids were followed over several stages during the season: sowing, germinating, emergence, thinning, flowering and maturing of the seeds. Owing to plant mortality in the experiment, the average tendency was a hybrid frequency that decreased steadily in the first part of the growing season from 42% during germination, to 37% at emergence. It then fell to 17% after the thinning of the plantlets by the farmer. At the end of the cycle, after thinning, only 11% of mature plants were hybrids. Thus, under the combined pressures of natural and human selection, the frequency of hybrids in the field declined drastically. In interaction with natural pressure, the farmer's practices of selection of seeds, sowing in pockets and thinning have the combined effect of heavily selecting the cultivated genotype and limiting without completely preventing the introgression of wild pearl millet genes into the cultivated genome. This revised version was published online in July 2006 with corrections to the Cover Date.     

Postprandial kinetics of gene expression of proteins involved in the digestive process in rainbow trout (<Emphasis Type="Italic">O. mykiss</Emphasis>) and impact of diet composition

The impact of increased incorporation of plant ingredients on diets for rainbow trout was evaluated in terms of gene expression of gastric (gastric lipase, pepsinogen) and intestinal (prolidase, maltase, phospholipase A2) digestive enzymes and nutrient transporters (peptide and glucose transporters), as well as of postprandial levels of plasma glucose, triglycerides and total free amino acids. For that purpose, trout alevins were fed from the start of exogenous feeding one of three different experimental diets: a diet rich in fish meal and fish oil (FM–FO), a plant-based diet (noFM–noFO) totally free from fish meal and fish oil, but containing plant ingredients and a Mixed diet (Mixed) intermediate between the FM–FO and noFM–noFO diets. After 16 months of rearing, all fish were left unfed for 72 h and then given a single meal to satiation. Blood, stomach and anterior intestine were sampled before the meal and at 2, 6 and 12 h after this meal. The postprandial kinetics of gene expression of gastric and intestinal digestive enzymes and nutrient transporters were then followed in trout fed the FM–FO diet. The postprandial profiles showed that the expression of almost all genes studied was stimulated by the presence of nutrients in the digestive tract of trout, but the timing (appearance of peaks) varied between genes. Based on these data, we have focused on the molecular response to dietary factors in the stomach and the intestine at 6 and 12 h after feeding, respectively. The reduction in FM and FO levels of dietary incorporation induced a significant decrease in the gene expression of gastric lipase, GLUT2 and PEPT1. The plasma glucose and triglycerides levels were also reduced in trout fed the noFM–noFO diet. Consequently, the present study suggests a decrease in digestive capacities in trout fed a diet rich in plant ingredients.     

Genetic variation analysis in the genus Lathyrus using RAPD markers

RAPD analysis was applied to five species belonging to the genusLathyrus (Fabaceae): L.sativus, L.cicera, L.ochrus, L.sylvestris and L.latifolius. All the species under study belong to thesection Lathyrus except L.ochrus which is in section Clymenum.Nine populations representing these species were used and ten random10-mer primers were sampled. A total of 129 amplification products,ranging in size from 0.3 to 3 Kb, were generated. Partitioning ofvariation was studied using the AMOVA technique. The genetic variation proved tobe nearly equally distributed among species and among populations withinspecies. A similar approach was carried out to distinguish populations, whichproved to be efficient. The between population dissimilarities were calculatedand a dendrogram of genetic relationships was drawn. The RAPDs obtained weresufficient to distinguish between the two accessions of a species and toseparate these accessions by clustering them according to species. A highgenetic similarity between the populations of L.sylvestris and L.latifolius was established. A similar result is also shownfor the populations of L. sativus andL. cicera.     

Phenolic Pattern of Bean (Phaseolus vulgaris L.) as an Indicator of Chronic Ozone Stress

From sowing till emergence of the fourth trifoliolate leaf, beans were exposed for seven hr a day to four ozone concentrations in open-top chambers: filtered air (FA), non-filtered air (NF), non-filtered air plus 30 ppb ozone (NF+) and non-filtered air plus 60 ppb ozone (NF++). Controls in ambient air of open plots (AA) were also available. The free polyphenolic pool of the first trifoliolate leaf was systematically investigated using HPLC. The groups of phenolics to which the three main chromatographic signals belonged were identified as hydroxycinnamic acid derivative for peak No 1 and flavonoids for peaks Nos 4 and 6. The metabolic regulation of phenolic accumulation could be recognized as different clusters based on specific phenolic patterns that reflected some of the tested atmospheric conditions. The comparison of AA and NF conditions revealed a ‘chamber effect’. FA and NF atmospheres gave rise to almost the same phenolic equilibriums dominated by a hydroxycinnamic acid derivative (about 53% of the total phenolics). Ozone addition was associated with a regular reduction of the percentage of peak No 1: about 40% for NF+ and 19% for NF++. Therefore, the significant decrease of the vacuolar storage of this phenolic compound (from 23 mg g^-1 dry weight for NF to about 3 mg g^-1 dry weight for NF++) can be regarded as a useful tool for monitoring long-term exposure to elevated ozone concentrations.     

Modelling the effects of forest fragmentation on certain species of forest-breeding birds

Summary The influence of forest fragmentation was assessed on the abundance of six forest-breeding bird species. The study area (2327 sq Km) was located in south-west France. The forest cover, extracted from a Landsat MSS scene, was first reduced to a grid of 5865 quadrats, each 650 by 650 m. Two values were attributed with each quadrat: Quadrat Forest Cover (QFC), expressed in percent; and a local measure of forest fragmentation - the Neighbouring Forest Cover (NFC) - expressed on a 0–1000 scale. The distribution of six forest-breeding species was sampled on 556 quadrats.For each species, the local abundance appears to be more correlated with the fragmentation-oriented NFC value than with the local QFC value. For three species out of six (song thrush, robin, chaffinch) an incidence model, based on the Logistic regression, was built. A correct fit was obtained.An incidence map of these species was then built up over the whole study area. Their regional status was then estimated, for a sampling cost of less than 10% of censusing all the area.     

The Promoter of the Tnt1A Retrotransposon: A Biomarker to Monitor Ozone but not Formaldehyde and Benzene Pollution

Open top chambers (OTCs) are useful tools to assess the impact of atmospheric pollutants on plants in the natural environment. We have previously reported that, in tomato plants, the LTR-GUS construct derived from the Tnt1A promoter of tobacco was activated by a realistic level of ozone pollution. In this study, we used OTCs to fumigate tomato plants with benzene or formaldehyde in order to assess the impact of these pollutants on plant growth and development and evaluate the usefulness of the LTR-GUS construct as a biomarker in plants. Whereas the LTR-GUS construct could be used as an efficient biomarker of realistic levels of ozone pollution, it is to a lesser extent applicable to formaldehyde. Indeed, only unrealistic concentration of pollutant activated the construct though important injuries were observed at a lower concentration. For benzene, no activation could be demonstrated, however, we did not notice any visual impact on plant growth and health for this pollutant.