Full text in pdf format
Multivariate genetic divergence and hybrid performance of cacao (Theobroma cacao L.) *
Luiz Antônio dos Santos DiasI; Paulo Yoshio KageyamaII
IEstação Experimental "Filogônio Peixoto", Centro de Pesquisas do Cacau. Present address: Departamento de Biologia Geral, Universidade Federal de Viçosa, 36571-000 Viçosa, MG, Brasil. Send correspondence to L.A.S.D.
IIDepartamento de Ciências Florestais, Escola Superior de Agricultura "Luiz de Queiroz" (ESALQ), Universidade de São Paulo (USP), Caixa Postal 9,13418-900 Piracicaba, SP, Brasil.
ABSTRACT
Genetic distances among cacao cultivars were calculated through multivariate analysis, using the D2 statistic, to examine racial group classification and to assess heterotic hybrids. A 5 x 5 complete diallel was evaluated. Over a five-year period (1986-1990), five cultivars of the S1 generation, pertaining to the Lower Amazon Forastero and Trinitario racial groups and 20 crosses between the corresponding S0 parents were analyzed, based upon five yield components - number of healthy and collected fruits per plant (NHFP and NCFP), wet seed weight per plant and per fruit (WSWP and WSWF), and percentage of diseased fruits per plant (PDFP). The diversity analysis suggested a close relationship between the Trinitario and Lower Amazon Forastero groups. A correlation coefficient (r) was calculated to determine the association between genetic diversity and heterosis. Genetic distance of parents by D2 was found to be linearly related to average performance of hybrids for WSWP and WSWF (r = 0.68, P < 0.05 and r = 0.76, P < 0.05, respectively). The heterotic performance for the same components was also correlated with D2, both with r = 0.66 (P < 0.05). A relationship between genetic divergence and combining ability effects was suggested because the most divergent cultivar exhibited a high general combining ability, generating the best performing hybrids. Results indicated that genetic diversity estimates can be useful in selecting parents for crosses and in assessing relationships among cacao racial groups.
Keywords: cacao; Genetic distances; diallel cross.
REFERENCES
Ali, M., Copeland, L.O., Elias, S.G. and Kelly, J.D. (1995). Relationship between genetic distance and heterosis for yield and morphological traits in winter canola (Brassica napus L.). Theor. Appl. Genet. 91: 118-121.
Arunachalam, V. (1977). Heterosis for characters governed by two genes. J. Genet. 63: 15-24.
Arunachalam, V. and Bandyopadhyay, A. (1984). Limits to genetic divergence for occurrence of heterosis - experimental evidence from crop plants. Indian J. Genet. Plant Breed. 44: 548-554.
Arunachalam, V., Bandyopadhyay, A., Nigam, S.N. and Gibbons, R.W. (1984). Heterosis in relation to genetic divergence and specific combining ability in groundnut (Arachis hipogaea L.). Euphytica 33: 33-39.
Atanda, O.A. (1973). Heterosis in crosses of Theobroma cacao. Exp. Agricult. 9: 23-29.
Bartley, B.G.D. (1970). Yield variation in the early productive years in trials with cacao (Theobroma cacao L.). Euphytica 19: 199-206.
Bekele, F.L., Kennedy, A.J., McDavid, C., Lauckner, F.B. and Bekele, I. (1994). Numerical taxonomic studies on cacao (Theobroma cacao L.) in Trinidad. Euphytica 75: 231-240.
Bhatt, G.M. (1973). Comparison of various methods of selecting parents for hybridization in common bread wheat (Triticum aestivum L.). Aust. J. Agric. Res. 24: 457-464.
Cheesman, E.E. (1944). Notes on the nomenclature, classification and possible relationships of cacao populations. Trop. Agric. 21: 144-159.
Cress, C.E. (1966). Heterosis of the hybrid related to gene frequency differences between two populations. Genetics 53: 269-274.
Cruz, C.D. (1990). Aplicação de algumas técnicas multivariadas no melhoramento de plantas. Doctoral thesis, ESALQ/USP, Piracicaba, SP.
Dias, L.A.S. (1995). Biotecnologia e melhoramento genético do cacaueiro (Theobroma cacao L.). Agrotrópica 7: 1-14.
Dias, L.A.S. and Kageyama, P.Y. (1995). Combining ability for cacao (Theobroma cacao L.) yield components under southern Bahia conditions. Theor. Appl. Genet. 90: 534-541.
Engels, J.M.M. (1983). A systematic description of cacao clones. III. Relationships between characteristics and some consequences for the cacao breeding. Euphytica 32: 719-733.
Falconer, D.S. (1960). Introduction to Quantitative Genetics. The Ronald Press, New York.
Ghaderi, A., Adams, M.W. and Nassib, A.M. (1984). Relationship between genetic distance and heterosis for yield and morphological traits in dry edible bean and faba bean. Crop Sci. 24: 37-42.
Gupta, V.P., Sekhon, M.S. and Satija, D.R. (1991). Studies on genetic diversity, heterosis and combining ability in Indian mustard [Brassica juncea L. (Czern & Coss)]. Indian J. Genet. Plant Breed. 51: 448-453.
Harris, R.J. (1975). A Primer of Multivariate Statistics. Academic Press, New York.
Kuppers, J.R. (1953). Some biometric observations on cacao fruit. Science 117: 354-355.
Lanaud, C. (1986). Utilisation des marqueurs enzymatiques pour l'etude génétique du cacaoyer: Theobroma cacao L. II. Etude du polymorphisme de six systemes enzymatiques. Café Cacao Thé 30: 271-280.
Lanaud, C., Laurent, V., N'Goran, J., Risterucci, A.M., Bouet, A. and Sounigo, O. (1993). Assessment of the genetic diversity of cocoa using biochemical and molecular markers at CIRAD. In: International Workshop on Conservation, Characterisation and Utilization of Cocoa Genetic Resources in the 21st Century, CRU/University of West Indies, Port-of-Spain, Trinidad, pp. 163-175.
Laurent, V. (1993). Etude de la diversité génétique du cacaoyer (Theobroma cacao L.) basée sur le polymorphisme de la longueur des fragments de restriction (RFLP). Doctoral thesis, Université de Paris, Paris.
Moll, R.H., Salhuana, W.S. and Robinson, H.F. (1962). Heterosis and genetic diversity in variety crosses of maize. Crop Sci. 2: 197-198.
N'Goran, J.A.K., Laurent, V., Risterucci, A.M. and Lanaud, C. (1994). Comparative genetic diversity studies ofTheobroma cacao L. using RFLP and RAPD markers.Heredity 73: 589-597.
Prasad, S.K. and Singh, T.P. (1986). Heterosis in relation to genetic divergence in maize (Zea mays L.). Euphytica 35: 919-924.
Raboin, L.M., Paulin, D., Cilas, C. and Eskes, A.B. (1993). Analyse génétique de quelques caracteres quantitatifs des fleurs du cacaoyer (Theobroma cacao L.). Leur intérêt pour l'évaluation de la diversité de l'espèce. Café Cacao Thé 37: 273-282.
Ramanujam, S., Tiwari, A.S. and Mehra, R.B. (1974). Genetic divergence and hybrid performance in mung bean. Theor. Appl. Genet. 45: 211-214.
Rao, C.R. (1952). Advanced Statistical Methods in Biometric Research. John Wiley, New York.
Ronning, C.M. and Schnell, R.J. (1994). Allozyme diversity in a germplasm collection of Theobroma cacao L.. J. Heredity 85: 291-295.
Russel, T.A. (1952). The vigour of some cacao hybrids. Trop. Agric. 29: 102-106.
Shamsuddin, A.K.M. (1985). Genetic diversity in relation to heterosis and combining ability in spring wheat. Theor. Appl. Genet. 70: 306-308.
Smith, J.S.C. and Smith, O.S. (1989). The description and assessment of distances between inbred lines of maize. II. The utility of morphological, biochemical, and genetic descriptors and a scheme for the testing of distinctiveness between inbred lines. Maydica 34: 151-161.
Steel, R.G.D. and Torrie, J.H. (1980). Principles and Procedures of Statistics. McGraw-Hill, New York.
Turner, H.N. and Young, S.Y. (1969). Quantitative Genetics in Sheep Breeding. Cornell University Press, Ithaca.
* Part of a thesis presented by L.A.S.D. to ESALQ, USP, in partial fulfillment of the requirements for the Doctoral degree.