The Journal of Heredity 1986:77(4):279-281
© 1986 The American Genetic Association 77:279-281
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Fertility improvement in induced tetraploid Theobroma cacao
The author is affiliated with the Cocoa Research Institute, P.O. Box 8, Tafo, Ghana, West Africa. She is grateful to P. E. Dautey and Juliana Manu for their technical assistance.
Abstract
Artificial Inducement of polyploids is one means of developing new types for use in solving problems of pests and diseases in plant cultivation. Yet autotetraploidization often results in poor seed-set with a subsequent reduction in productivity. This paper reports an investigation into the fertility of autotetraploids of Theobroma cacao, through selective crossings. All first and second generation seedlings (C1 and C2) derived from the initial colchicine-induced material were tetraploid, and was inferred that embryos with aberrant chromosome numbers must have aborted. The result showed an improvement in the uniformity in size and germinability of the pollen from the derived tetraploid plants over the initial ones. Using C0 and C1 as pod parents and also as pollen sources, larger percentages of pods with bean numbers exceeding 25 were obtained in crosses involving the derived (C1) plants. Both seed germination and seedling growth were satisfactory. This work suggests that it would be possible to appreciably raise the pod bean number of induced autotetraploid cocoa through continued selective crossings.