Abstract
Gametophytic competition, demonstrated in pearl millet, has been shown to promote homogametic fertilization, especially in the case of wild/cultivated pollen mixtures. Therefore, gametophytic selection can reduce interbreeding between the two forms of pearl millet. A theoretical two-locus asymmetrical model was built in order to evaluate the potential role of pollen competition in the control of gene flow between wild and cultivated pearl millet populations in sympatry. Pollen selection coefficients, estimated in a previous experiment, were input in this model. It was shown that the wild/cultivated hybrid percentage in the cultivated field can be strongly reduced in the presence of strong gametophytic selection. The hybrid percentages obtained from this model were very similar to those observed in natural conditions with pollen migration rates from wild populations ranging between 10 and 40 per cent according to the selective pollen coefficient. It may be concluded from this that pollen competition can contribute to the continuing phenotypic integrity of cultivated forms even when there is an abundance of wild forms adjacent to the field. However, in most cases, an initial divergence between wild and cultivated populations at the homogamy locus, is required for pollen competition to reduce hybridization. This requirement makes it doubtful whether this aspect of reproductive isolation between wild and cultivated forms was involved in domestication.
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Amblard, S, and Pernes, J. 1989. The identification of cultivated Pearl Millet (Pennisetum) amongst plant impressions on pottery from Oued Chebbi (Dhar Oualata, Mauritania). Afr Archaeol Rev, 7, 117–126.
Belliard, J, and Pernes, J. 1977. Etude de l'organisation génétique et physiologique d'une barrière reproductive particulière chez le mil: contrôle photopériodique de la floraison. Physiol Veg, 15, 551–565.
Bianchi, A, and Lorenzoni, C. 1975. Gametophyte factors in Zea mays. In: Mulcahy, D. L. (ed.) Gamete Competition in Plants and Animals. North Holland Publishing Company, Amsterdam, pp. 257–263.
Caisse, M, and Antonovics, J. 1978. Evolution in closely adjacent plant populations. IX — Evolution of reproductive isolation in clinal populations. Heredity, 40, 371–384.
Dobzhansky, T. 1940. Speciation as a stage in evolutionary divergence. Am Nat, 74, 97–127.
Galinat, W C. 1978. The inheritance of some traits essential to maize and teosinte. In: Waiden, D. B. (ed.) Maize Breeding and Genetics. John Wiley & Sons, New York. 93–112.
Harlan, J R. 1971. Agricultural origins: centers and non centers. Science, 14, 468–474.
Harlan, J R. 1975. Crops and Man. American Society of Agronomy Inc. and Crop Science Society of America Inc. Madison.
Joly-Ichenhauser, H. 1984. Hérédité du syndrome de domestication chez le mil Etude comparée de descendances (F2 et rétrocroisements) issues de croisements entre plusieurs géniteurs cultivés et spontanés. Thèse de troisième cycle. Université Paris XI-Orsay.
Joly-Ichenhauser, H, and Sarr, A. 1985. Preferential associations among characters in crosses between pearl millet (P. thypoides) and its wild relatives. In: Jacquard, P., Heim, G. and Antonovics, J. (eds) Genetic Differentiation and Dispersal in Plants, Springer-Verlag, Berlin, pp. 95–111.
Langevin, S A, Clay, K, and Grace, J B. 1990. The incidence and effects of hybridization between cultivated rice and its related weed red rice (Oryza sativa L.). Evolution, 44, 1000–1008.
Laredo, C, and Pernes, J. 1988. Models of pearl millet domestication as an example of cereal domestication. I — A one locus asymmetrical model. J Theoret Biol, 131, 289–305.
McNeiixy, T, and Antonovics, J. 1968. Evolution in closely adjacent plant populations. IV — Barriers to gene flow. Heredity, 23, 205–218.
Marshall, D L, and Ellstrand, N C. 1986. Sexual selection in Raphanus sativus: experimental data on non random fertilization, maternal choice and consequences of multiple paternity. Am Nat, 127, 446–461.
Moore, W S. 1979. A single locus mass-action model of assortative mating, with comments on the process of speciation. Heredity, 42, 173–186.
Pernes, J. 1986. L'allogamie et la domestication des céréales: l'exemple du maïs (Zea mays L.) et du mil (Pennisetum americanum L.). Bull Soc Bot Fr 133 Actual Bot, 1, 27–34.
Rey-Herme, C. 1982. Les relations génétiques entre les formes spontanées et cultivées chez le mil (Pennisetum sp). Thèse de troisième cycle. Université Paris XI-Orsay.
Robert, T, Lespinasse, R, Pernes, J, and Sarr, A. 1991. Gametophytic competition as influencing gene flow between wild and cultivated forms of Pearl Millet. Génome, 34, 82–88.
Robert, T, Sarr, A, and Pernes, J. 1989. Sélections sur la phase haploïde chez le mil (Pennisetum thyphoides (Burm.) Stapf et Hubb.): effet de la température. Génome, 32, 946–952.
Sarr, A. 1987. Analyse génétique de l'organisation reproductive du mil (Pennisetum typhoides) Stapf et Hubb) Implication pour son amélioration et la gestion des ressources génétiques. Thèse d'Etat. Université Paris Sud-Orsay.
Sarr, A, Sandmeier, M, and Pernes, J. 1988. Gametophytic competition in pearl millet, Pennisetum typhoides (Stapf and Hubb.). Génome, 30, 924–929.
Stam, P. 1983. The evolution of reproductive isolation in closely adjacent plant populations through differential flowering time. Heredity, 50, 105–118.
Wilkes, H G. 1977. Hybridization of maize and teosinte in Mexico and Guatemala and the improvement of maize. Econ Bot, 31, 254–293.
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Dedicated to the memory of Professor Jean Pernès.
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Robert, T., Lamy, F. & Sarr, A. Evolutionary role of gametophytic selection in the domestication of Pennisetum thyphoides (pearl millet): a two-locus asymmetrical model. Heredity 69, 372–381 (1992). https://doi.org/10.1038/hdy.1992.137
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DOI: https://doi.org/10.1038/hdy.1992.137