Analytical Modeling of Insulated Dipole Applicators for Interstitial Hyperthermia: a Review

Microwave hyperthermia appears as an adjuvant technique to heat relatively small tumors in a minimally invasive way. As this technique is based on interstitial antennas, we propose a review of the physical phenomena involved in the radiation of such antennas in a dispersive medium, using the different analytical modeling developed since the 1970\'s. These modeling have been implemented in a freely available software tool, that will allow antenna designers and medical researchers to perform rapid parameter studies to further understand the role of the several parameters involved; this tool will also help the interpretation of results issued from numerical simulations. Simulation results associated with different antenna geometries are presented and compared to results obtained by several authors

Investigation of recent population bottlenecks in Kenyan wild sorghum populations (Sorghum bicolor (L.) Moench ssp. verticilliflorum (Steud.) De Wet) based on microsatellite diversity and genetic disequilibria

Identifying populations that have recently suffered a severe reduction in size is particularly important for their conservation as they are likely to suffer an increased risk of genetic erosion. We investigated the presence of recent bottlenecks in two wild sorghum populations from different eco-geographical conditions in Kenya employing 18 microsatellite markers. Microsatellite analysis showed high allelic diversity in the two populations, with a mean of 4.11 and 6.94 alleles per locus in the North-West wild sorghum population (NWWSP) and the South-East wild sorghum population (SEWSP), respectively. The mean observed heterozygosity was 0.34 and 0.56 in NWWSP and SEWSP, respectively. A large long-term effective populations size for both populations was observed assuming either an infinite allele model or a stepwise mutation model. There was no apparent loss of genetic variability for either of the populations. Test of heterozygosity excess indicated that a recent bottleneck in the two populations is highly unlikely. Furthermore, analysis of the allele frequency distribution revealed an L-shaped distribution which would not have been observed in case a recent bottleneck had reduced genetic variability in the two populations. The fact that most loci displayed a significant heterozygosity deficiency could be explained by population subdivision and the mixed mating system exhibited by wild sorghum populations. Furthermore, the possibility of a historical expansion of wild sorghum populations and presence of null alleles could not be ruled out

Analyse multiéchelle de la diversité génétique des sorghos : compréhension des processus évolutifs pour la conservation in situ

Using microsatellite genetic markers, we analyzed 1,518 sorghum samples collected at different spatial scales in Burkina Faso, Mali, Niger, and in the village of Wanté, from the landrace to the country scale. Genetic diversity and differentiation parameters were estimated to assess the effects of the main evolutionary processes on sorghum genetic diversity. The genetic variability found within a variety is mainly the result of the sorghum reproduction biology and the genetic drift process caused by the limited number of reproductive individuals at the time of variety introduction into a household or each year when farmers select their seeds. At the village scale, a low correlation is observed between the diversity of vernacular names and the genetic diversity assessed by microsatellites. No spatial genetic structuration is observed among villages more than 30 kilometers apart. This point highlights that traditional seed systems operate at a very local scale. In Mali, a similar proportion of allelic richness is observed along a longitudinal transect and a latitudinal gradient that crosses a larger range of agroclimatic conditions. At the country scale, sorghum exhibits more genetic diversity in Niger than in Mali despite a lower agroclimatic range in Niger. These results demonstrate that the diversity of human groups acts together with the agro-ecological factors to shape the structure of sorghum genetic diversity. An important proportion of the overall genetic diversity present in the Cirad (Centre de coopération internationale en recherche agronomique pour le développement) "core collection" is found in Mali and Niger. The tremendous diversity cultivated by farmers in traditional agroecosystems of Western Africa supports the relevance of in situ approaches for sorghum conservation programs in this region. Both conservation and crop improvement requirements can be achieved through a better use of local germplasm in decentralized breeding programs. (Summary in English)

Genetic structure and relationships within and between cultivated and wild sorghum ( Sorghum bicolor (L.) Moench) in Kenya as revealed by microsatellite markers

Understanding the extent and partitioning of diversity within and among crop landraces and their wild/weedy relatives constitutes the first step in conserving and unlocking their genetic potential. This study aimed to characterize the genetic structure and relationships within and between cultivated and wild sorghum at country scale in Kenya, and to elucidate some of the underlying evolutionary mechanisms. We analyzed at total of 439 individuals comprising 329 cultivated and 110 wild sorghums using 24 microsatellite markers. We observed a total of 295 alleles across all loci and individuals, with 257 different alleles being detected in the cultivated sorghum gene pool and 238 alleles in the wild sorghum gene pool. We found that the wild sorghum gene pool harbored significantly more genetic diversity than its domesticated counterpart, a reflection that domestication of sorghum was accompanied by a genetic bottleneck. Overall, our study found close genetic proximity between cultivated sorghum and its wild progenitor, with the extent of crop-wild divergence varying among cultivation regions. The observed genetic proximity may have arisen primarily due to historical and/or contemporary gene flow between the two congeners, with differences in farmers' practices explaining inter-regional gene flow differences. This suggests that deployment of transgenic sorghum in Kenya may lead to escape of transgenes into wild-weedy sorghum relatives. In both cultivated and wild sorghum, genetic diversity was found to be structured more along geographical level than agro-climatic level. This indicated that gene flow and genetic drift contributed to shaping the contemporary genetic structure in the two congeners. Spatial autocorrelation analysis revealed a strong spatial genetic structure in both cultivated and wild sorghums at the country scale, which could be explained by medium- to long-distance seed movemen

Geographical patterns of phenotypic diversity and structure of Kenyan wild sorghum populations (Sorghum spp.) as an aid to germplasm collection and conservation strategy

Kenya lies within sorghum centre of diversity. However, information on the relative extent of diversity patterns within and among genetically defined groups of distinct ecosystems is lacking. The objective was to assess the structure and phenotypic diversity of wild sorghum populations across a range of geographical and ecological conditions in the country. Sixty-two wild sorghum populations (30 individuals per population) sampled from four distinct sorghum growing regions of Kenya and covering different agroecologies were characterized for ten qualitative traits. Plant height, number of tillers, panicle sizes and flag leaf dimensions were also recorded. Frequencies of the phenotypic classes of each character were calculated. The Shannon diversity index (H') was used to estimate the magnitude of diversity. Principal component analysis was used to differentiate populations within and between regions. Wild sorghum is widely distributed in Kenya, occurring in sympatric ranges with cultivated sorghum, and both have overlapping flowering windows. All characters considered displayed great phenotypic diversity. Pooled over characters within regions, the mean H' ranged between 0.60 and 0.93 in Western and Coast regions, respectively. Wild sorghum was found to show a weak regional differentiation, probably reflecting the importance of seed-mediated gene flow in shaping the wild sorghum population structure. Trait distribution was variable among regions, but there was no conspicuous distribution of the traits studied in any given region. Spontaneous hybridization and introgression of genes from cultivated to wild sorghum seems to be likely, and may already have occurred for a long time, although undocumented. Implications for in situ and ex situ genetic resources conservation are discussed

Genetic structure and diversity of wild sorghum populations (Sorghum spp.) from different eco-geographical regions of Kenya

Wild sorghums are extremely diverse phenotypically, genetically and geographically. However, there is an apparent lack of knowledge on the genetic structure and diversity of wild sorghum populations within and between various eco-geographical regions. This is a major obstacle to both their effective conservation and potential use in breeding programs. The objective of this study was to assess the genetic diversity and structure of wild sorghum populations across a range of eco-geographical conditions in Kenya. Sixty-two wild sorghum populations collected from the 4 main sorghum growing regions in Kenya were genotyped using 18 simple sequence repeat markers. The study showed that wild sorghum is highly variable with the Coast region displaying the highest diversity. Analysis of molecular variance showed a significant variance component within and among wild sorghum populations within regions. The genetic structure of wild sorghum populations indicated that gene flow is not restricted to populations within the same geographic region. A weak regional differentiation was found among populations, reflecting human intervention in shaping wild sorghum genetic structure through seed-mediated gene flow. The sympatric occurrence of wild and cultivated sorghums coupled with extensive seed-mediated gene flow, suggests a potential crop-to-wild gene flow and vice versa across the regions. Wild sorghum displayed a mixed mating system. The wide range of estimated outcrossing rates indicate that some environmental conditions may exist where self-fertilisation is favoured while others cross-pollination is more advantageous

Adaptive values of wild X cultivated sorghum (Sorghum bicolor (L.) Moench) hybrids in generations F1, F2, and F3

Gene flow between cultivated and their wild relatives is one of the main ecological concerns associated with the introduction genetically modified (GM) cultivars. GM sorghum cultivar has been developed and its commercial production may be possible in the near future. The rate of gene flow depends on the fitness of wild 9 cultivated sorghum hybrids. The study aimed at estimating adaptive values of wild 9 cultivated sorghum hybrids in generations F1, F2, and F3 compared to their parents. Artificial crosses of four wild sorghums, five cultivated sorghums, and two male sterile lines were made to produce the F1 generation, which were advanced to F2 and F3. Each hybrid generation and their respective parents were evaluated for their adaptive value at two sites in a randomised complete block design with seven replicates. The resulting progenies did not show serious fitness penalties. Some hybrids were as fit as their respective wild parents and no consistent differences exist between the three generations studied. Thus, the resultant wild 9 cultivated hybrids may act as avenue for introgression

Local scale patterns of gene flow and genetic diversity in a crop–wild–weedy complex of sorghum (Sorghum bicolor (L.) Moench) under traditional agricultural field conditions in Kenya

Little information is available on the extent and patterns of gene flow and genetic diversity between cultivated sorghum and its wild related taxa under local agricultural conditions in Africa. As well as expanding knowledge on the evolutionary and domestication processes for sorghum, such information also has importance in biosafety, conservation and breeding programmes. Here, we examined the magnitude and dynamics of crop–wild gene flow and genetic variability in a crop–wild–weedy complex of sorghum under traditional farming in Meru South district, Kenya. We genotyped 110 cultivated sorghum, and 373 wild sorghum individuals using a panel of ten polymorphic microsatellite loci. We combined traditional measures of genetic diversity and differentiation with admixture analysis, population assignment, and analyses of spatial genetic structure to assess the extent and patterns of gene flow and diversity between cultivated and wild sorghum. Our results indicate that gene flow is asymmetric with higher rates from crop to wild forms than vice versa. Surprisingly, our data suggests that the two congeners have retained substantial genetic distinctness in the face of gene flow. Nevertheless, we found no significant differences in genetic diversity measures between them. Our study also did not find evidence of isolation by distance in cultivated or wild sorghum, which suggests that gene dispersal in the two conspecifics is not limited by geographic distance. Overall our study highlights likely escape and dispersal of transgenes within the sorghum crop–wild–weedy complex if genetically engineered varieties were to be introduced in Africa’s traditional farming system