JA-Biological Sciences
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Browsing JA-Biological Sciences by Author "Deu, M."
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Item Open Access Genetic structure and relationships within and between cultivated and wild sorghum (Sorghum bicolor (L.) Moench) in Kenya as revealed by microsatellite markers(2017-01-24) Mutegi, E.; Sagnard, F.; Semagn, K.; Deu, M.; Muraya, M.; Kanyenji, B.; de Villiers, S.; Kiambi, D.; Herselman, L.; Labuschagne, M.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 agroclimatic 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 movement.Item Open Access 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(2017-01-24) Mutegi, E.; Sagnard, F.; Labuschagne, M.; Herselman, L.; Semagn, K.; Deu, M.; de Villiers, S.; Kanyenji, B. M.; Mwongera, C.N.; Traore, P.C.S.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 geneflow and diversity between cultivated and wild sorghum. Our results indicate that geneflow is asymmetric with higher rates from crop to wild forms than viceversa. Surprisingly,our data suggests that the two congeners have retained substantial genetic distinctness in the face of geneflow. 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 con specifics 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 systems.Item Open Access Past and present dynamics of sorghum and pearl millet diversity in Mount Kenya region(Wiley: Evolutionary Applications, 2016-06-23) Kiambi, Dan K ; Labeyrie, V; Deu, M.; Dussert, Y.; Rono, B.; Lamy, F.; Marangu, C.; Calatayud, C.; Robert, T.; Leclerc, C.Crop populations in smallholder farming systems are shaped by the interaction of biological, ecological, and social processes, occurring on different spatio temporal scales. Understanding these dynamics is fundamental for the conservation of crop genetic resources. In this study, we investigated the processes involved in sorghum and pearl millet diversity dynamics on Mount Kenya. Surveys were conducted in ten sites distributed along two elevation transects and occupied by six ethno linguistic groups. Varieties of both species grown in each site were inventoried and characterized using SSR markers. Genetic diversity was analyzed using both individual- and population based approaches. Surveys of seed lot sources allowed characterizing seed-mediated gene flow. Past sorghum diffusion dynamics were explored by comparing Mount Kenya sorghum diversity with that of the African continent. The absence of structure in pearl millet genetic diversity indicated common ancestry and/or important pollen and seed-mediated gene flow. On the contrary, sorghum varietal and genetic diversity showed geographic patterns, pointing to different ancestry of varieties, limited pollen mediated gene flow, and geographic patterns in seed-mediated gene flow. Social and ecological processes involved in shaping seed-mediated gene flow are further discussed.