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T Robert

Publications and source records attributed to T Robert.

8 recordsLinked to original sources
PubMed2006

Genetic diversity and gene flow among pearl millet crop/weed complex: a case study.

Weedy plants with intermediate (domesticated x wild) phenotypes occur in most pearl millet fields in West Africa, even in the absence of wild populations. They are usually found, in high numbers, both inside and outside of drills. Questions pertaining to the evolutionary dynamics of diversity within the pearl millet complex (domesticated-weedy-wild forms) were addressed in this study. The diversity of the different components of this complex sampled in two pearl millet fields in two villages of southwestern Niger was assessed at both molecular (AFLP) and morphological levels. Results show that, in both fields, weedy plants found outside of drills are morphologically distinct from weedy plants found inside drills, despite their close similarity at AFLP markers. The data suggest some introgression from the wild to the weedy population but nevertheless that the gene flow between the parapatric wild and domesticated populations is very low. This challenges the traditional view that regular hybridization between domesticated and wild pearl millets explains the abundance of these weedy plants despite farmers' seed selection. The level of genetic differentiation between fields from the two villages was low when considering domesticated and weedy plants. This could be explained by high gene flow resulting from substantial seed exchanges between farmers. The fact that it is very difficult for farmers to keep their own selected seeds, and the consequent substantial seed exchanges between them, is probably the main factor accounting for the maintenance and dispersal of weedy pearl millets in the region, even in areas where no wild forms have been observed.

Evolution, Molecular↗
PubMed2006

Three-dimensional assessment of the facial soft tissue changes that occur postoperatively in orthognathic patients.

With the development of 3-dimensional technology it has become increasingly possible to record the facial soft tissue changes that occur with growth and following orthodontic treatment. This article describes the use of the optical surface laser scanner to record and quantify the facial soft tissue changes following orthognathic surgery. Ten skeletal Class III patients were laser scanned, at previously determined time intervals, over a 6-month period following orthognathic surgery. Computer superimposition of the scanned images provided a graphic demonstration of the soft tissue changes as they occurred between the time intervals. Analysis of the results demonstrates a nonuniform, asymmetric resolution of facial swelling and adaptation of the soft tissues to the altered skeletal structure. This occurred principally over the initial 4 months following surgery. However, smaller changes continued to occur throughout the study period. This suggests that the facial soft tissues continue to change over a period of greater than 6 months. This knowledge is important as it is integral for obtaining informed consent from patients.

Cephalometry↗
PubMed2001

Unmanaged sexual reproduction and the dynamics of genetic diversity of a vegetatively propagated crop plant, cassava (Manihot esculenta Crantz), in a traditional farming system.

Occurrence of intervarietal or interspecific natural crosses has been reported for many crop plants in traditional farming systems, underlining the potential importance of this source of genetic exchange for the dynamics of genetic diversity of crop plants. In this study, we use microsatellite loci to investigate the role of volunteer seedlings (plants originating from unmanaged sexual reproduction) in the dynamics of genetic diversity of cassava (Manihot esculenta Crantz), a vegetatively propagated crop, in a traditional farming system in Guyana. A previous field study showed that farmers incorporate such plants into the germplasm for vegetative propagation, and that many of them are likely to be assigned by farmers to recognized varieties. Under strict vegetative propagation clonality of varieties is expected. The high proportion of polyclonal varieties observed suggests that incorporation of seedlings into the germplasm for propagation is a frequent event. The molecular variability assessed with microsatellite markers shows that there is high differentiation among heterozygous varieties, whereas populations of seedlings do not depart from the proportions expected under Hardy-Weinberg assumptions. Assignment of seedlings to a recognized variety on the basis of morphological similarity greatly increases genetic diversity within the variety. We argue that recombination and gene flow play a major role in the dynamics of genetic diversity of cassava in traditional farming systems. Documenting unmanaged sexual reproduction and its genetic consequences is a prerequisite for defining strategies of in situ conservation of crop plant genetic resources.

Alleles↗
PubMed2000

Assessment of genetic variability in a traditional cassava (Manihot esculenta Crantz) farming system, using AFLP markers.

Despite the urgent need to conserve domesticated plant genetic resources, and developing 'on farm' strategies of conservation, the impact of traditional farming practices and of their interaction with ecological factors on the structure and evolutionary dynamics of the genetic variability of crop populations has been little documented. We assessed the genetic variability of 31 varieties of cassava (M. esculenta Crantz) traditionally grown by Makushi Amerindians from Guyana, using AFLP markers. We used a sample of 38 varieties from an ex situ core collection as a reference. Accessions of wild cassava were also included. While clonality of the varieties was expected due to the vegetative propagation of cassava, 21 varieties presented intravarietal polymorphism. Among the varieties from a single site in Guyana, genetic diversity was the same as that in the accessions from the core collection. We suggest that incorporation of volunteer seedlings, produced by sexual reproduction, into the stock of varieties grown by the Makushi plays a major role in explaining both intravarietal polymorphism and the high level of genetic diversity. No correspondence was found between the structure of molecular diversity and variation observed for agronomic traits that are targets for selection by cultivators. As found in previous studies, all wild forms of cassava clustered together and separately from the cultivated varieties in a Neighbour-Joining dendrogram. These results are consistent with the hypothesis of a limited domestication event in a restricted area, followed by rapid diffusion of cultivated phenotypes and convergent evolution. Our results show that local varieties are an important source of genetic diversity, and highlight the importance of the interaction between human and ecological factors in the dynamics of this diversity.

Evolution, Molecular↗
PubMed1993

[Perineal pain and lesions of the internal pudendal nerves].

A number of chronic pain syndromes in the perineal area can be related to pudendal nerves suffering. The constancy of symptoms among various patients, and in duration for a particular one, alterations revealed by electrophysiologic studies, pain relief by diagnostic blocks, data from anatomic studies, preliminary results of medical and surgical applied therapies, give consistent arguments for possible organic lesions of pudendal nerves.

Female↗
PubMed1984

[Inter-observer variability in the interpretation of arteriographies of the carotid arteries and lower limbs].

This study attempts to measure inter-observer variability in reading 14 carotid angiograms and 8 aortograms. 24 surgeons and radiographs with training in arterial diseases participated in the study from different hospitals. The results were analysed with the Kappa statistical method which incorporate a correction for the extend of agreement expected by chance alone, in the evaluation of the reliability of diagnostic procedures. From a topographic point of view, the interpretation of the proximal arterial segments is more reliable than the distal segments, with the exception of the aorto-iliac bifurcation and the profunda femoral arteries. Inter-observer agreement is the most important for the occlusive lesions and the identification of stenosis is of poor reliability.

Angiography↗