Abstract
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 systems.
Similar content being viewed by others
References
Barnaud A, Trigueros G, Mckey D, Joly HI (2008) High outcrossing rates in fields with mixed sorghum landraces: how are landraces maintained? Heredity 101:445–452
Barnaud A, Deu M, Garine E, Chantereau J, Bolteu J, Koı¨da EO et al (2009) A weed–crop complex in sorghum: the dynamics of genetic diversity in a traditional farming system. Am J Bot 96:1869–1879
Barrett SCH, Kohn JR (1991) Genetic and evolutionary consequences of small population size in plants: implications for conservation. In: Falk DA, Holsinger KE (eds) Genetics and conservation of rare plants. Oxford University Press, New York, pp 3–30
Belkhir K, Borsa P, Chikhi L, Raufaste N, Bonhomme F (2004) GENETIX 4.05. Logiciel sous Windows TM pour la génétique des populations. Laboratoire Génome, Populations, Interactions, CNRS UMR 5000, Université de Montpellier II, Montpellier
Conner AJ, Glare TR, Nap JP (2003) The release of genetically modified crops into the environment. Part II. Overview of ecological risk assessment. Plant J 33:19–46
de Wet JMJ, Harlan JR, Price EG (1976) Variability in Sorghum bicolor. In: Harlan JR, de Wet JMJ, Stemler ABL (eds) Origins of African plant domestication. Mouton, The Hague, pp 453–463
Dje Y, Heuertz M, Ater M, Lefebvre C, Vekemans X (2004) In situ estimation of outcrossing rate in sorghum landraces using microsatellite markers. Euphytica 138:205–212
Doggett H (1965) Disruptive selection in crop development. Nature 206:279–280
Doggett H (1988) Sorghum. Longman Scientific and Technical Essex, New York
Doggett H, Majisu BN (1968) Disruptive selection in crop development. Heredity 23:1–23
Dray S, Dufour A (2007) The ade4 package: implementing the duality diagram for ecologists. J Stat Softw 22:1–20
Ellstrand NC, Elam DR (1993) Population genetic consequences of small population size: implications for plant conservation. Annu Rev Ecol Syst 24:217–242
Ellstrand NC, Prentice HC, Hancock JF (1999) Gene flow and introgression from domesticated plants into their wild relatives. Annu Rev Ecol Syst 30:539–563
Evanno S, Regnaut S, Goudet J (2005) Detecting the number of cluster of individuals using the software STRUCTURE: a simulation study. Mol Ecol 14:2611–2620
Hajjar R, Hodgkin T (2007) The use of wild relatives in crop improvement: a survey of developments over the last 20 years. Euphytica 156:1–13
Hardy OJ, Vekemans X (2002) SPaGeDi: a versatile computer program to analyse spatial genetic structure at the individual or population levels. Mol Ecol 2:618–620
Harlan JR, Stemler ABL (1976) The races of sorghum in Africa. In: Harlan JR, De Wet JMJ, Stemler ABL (eds) Origins of African plant domestication. Mouton, The Hague
Haygood R, Ives AR, Andow DA (2003) Consequences of recurrent gene flow from crops to wild relatives. Proc Biol Sci 270:1879–1886. doi:10.1098/rspb.2003.2426
Huenneke LF (1991) Ecological implications of genetic variation in plant populations. In: Falk DA, Holsinger KE (eds) Genetics and conservation of rare plants. Oxford University Press, New York, pp 31–44
Jarvis DI, Hodgkin T (1999) Wild relatives and crop cultivars: detecting natural introgression and farmer selection of new genetic combinations in agroecosystems. Mol Ecol 8:15–173
Jombart T (2008) adegenet: a R package for the multivariate analysis of genetic markers. Bioinformatics 24:1403–1405
Kalinowski S (2005) HP-RARE 1.0: a computer program for performing rarefaction on measures of allelic richness. Mol Ecol 5:187–189
Ladizinsky G (1999) Plant evolution under domestication. Kluwer, London
Martinez-Castillo J, Zizumbo-Villarreal D, Gepts P, Colunga-GarciaMarin P (2007) Gene flow and genetic structure in the wild–weedy-domesticated complex of Phaseolus lunatus L. in its Mesoamerican center of domestication and diversity. Crop Sci 47:58–66
Muraya MM, Mutegi E, Geiger HH, de Villiers SM, Sagnard F, Kanyenji BM et al (2011a) Wild sorghum from different eco-geographic regions of Kenya display a mixed mating system. Theor Appl Genet 122(8):1631–1639. doi:10.1007/s00122-011-1560-5
Muraya MM, Geiger HH, Sagnard F, Toure L, Traore PS, Togola S et al (2011b) Adaptive values of wild x cultivated sorghum (Sorghum bicolor (L.) Moench) hybrids in generations F1, F2 and F3. Genet Resour Crop Evol 59:83–93. doi:10.1007/s10722-011-9670-0
Mutegi E, Sagnard F, Muraya M, Kanyenji B, Rono B, Mwongera C et al (2010) Ecogeographical distribution of wild, weedy and cultivated Sorghum bicolor (L.) Moench in Kenya: implications for conservation and crop-to-wild gene flow. Genet Resour Crop Evol 57:243–253
Mutegi E, Sagnard F, Semagn K, Deu M, Muraya M, Kanyenji S et al (2011) Genetic structure and relationships within and between cultivated and wild sorghum (Sorghum bicolor (L.) Moench) in Kenya as revealed by microsatellite markers. Theor Appl Genet 122:989–1004
Papa R, Gepts P (2003) Asymmetry of gene flow and differential geographical structure of molecular diversity in wild and domesticated common bean (Phaseolus vulgaris L.) from Mesoamerica. Theor Appl Genet 106:239–250
Pedersen J, Toy JJ, Johnson B (1998) Natural outcrossing of Sorghum and Sudangrass in the central great plains. Crop Sci 38:937–939
Pritchard JK, Stephens M, Donnelly P (2000) Inference of population structure using multilocus genotype data. Genetics 155:945–959
R Development Core Team (2011) R: a language and environment for statistical computing. R Foundation for Statistical Computing: Vienna, Austria (http://www.r-project.org)
Riesberg LH, Wendel JF (1993) Introgression and its consequences in plants. In: Harrison RG (ed) Hybrid zones and the evolutionary processes. Oxford University Press, New York, pp 70–109
Ritland K (1996) Estimators for pairwise relatedness and individual inbreeding coefficients. Genet Res 67:175–185
Rousset F (1997) Genetic differentiation and estimation of gene flow from F-statistics under isolation by distance. Genetics 145:1219–1228
Sagnard F, Deu M, Dembe′le′ D, Leblois R, Toure′ L, Diakite′ M et al (2011) Genetic diversity, structure, gene flow and evolutionary relationships within the Sorghum bicolor wild–weedy–crop complex in a western African region. Theor Appl Genet 123(7):1231–1246. doi:10.1007/s00122-011-1662-0
Schuelke M (2000) An economic method for the fluorescent labeling of PCR fragments. A poor man’s approach to genotyping for research and high throughput diagnostics. Nat Biotechnol 18:233–234
Snow AA, Moran-Palma P (1997) Commercialization of transgenic plants: potential ecological risks. Bioscience 47:86–96
Tesso T, Kapran I, Grenier C, Snow A, Sweeney P, Pedersen J et al (2008) The potential for crop-to-wild gene flow in sorghum in Ethiopia and Niger: a geographic survey. Crop Sci 48:1425–1431
Weir BS, Cockerham CC (1984) Estimating F-statistics for the analysis of population structure. Evolution 38:1358–1370
Wilson GA, Rannala B (2003) Bayesian inference of recent migration rates using multilocus genotypes. Genetics 163:1177–1191
Wolf DE, Takebayashi N, Rieseberg LH (2001) Predicting the risk of extinction through hybridization. Conserv Biol 15:1039–1053
Wright S (1943) Isolation by distance. Genetics 28:114–138
Zizumbo-Villarreal D, Colunga-GarciaMarin P, de la Cruz EP, Gado-Valerio P, Gepts P (2005) Population structure and evolutionary dynamics of wild–weedy domesticated complexes of common bean in a Mesoamerican region. Crop Sci 45:1073–1083
Acknowledgments
This work was supported by the USAID Biotechnology and Biodiversity Interface (BBI) and Plant Biosafety Systems (PBS) Programmes within the project: “Environmental Risk Assessment of Genetically Engineered Sorghum in Mali and Kenya.’’ The authors owe gratitude to farmers within the study site for providing seed and information for this study.
Conflict of interest
The authors declare that they have no conflict of interest.
Author information
Authors and Affiliations
Corresponding author
Electronic supplementary material
Below is the link to the electronic supplementary material.
Rights and permissions
About this article
Cite this article
Mutegi, E., Sagnard, F., Labuschagne, M. et al. 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. Conserv Genet 13, 1059–1071 (2012). https://doi.org/10.1007/s10592-012-0353-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10592-012-0353-y