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Exotic germplasms introduced in a Brazilian maize breeding program

José Branco de Miranda Filho

Departamento de Genética, ESALQ-USP, Caixa Postal 83, 13418-900 Piracicaba, SP, Brasil

ABSTRACT

Fifteen maize populations, representing temperate and temperate x tropical germplasms were introduced from the United States. These populations and a check population (ESALQ-PB1) were evaluated in a randomized block experiment and the following traits were measured: PH-plant height, EH-ear height, TB-tassel branch number, EL-ear length, ED-ear diameter, RN-kernel row number, KR-kernels per row, EW - ear weight, GW - grain weight, and KW - 100 kernels weight. The exotic populations showed an average performance level lower than the check for all traits, except RN. Part of the variation among populations was attributed to differential adaptation to brazilian conditions. The positive phenotypic correlation among populations for all combinations of traits also gave some evidence of differential adaptation.
The exotic populations were divided into two groups and the following composite populations were planned: CEX-i, from crosses Exotics-I x ESALQ-PB1; CEX-2, from crosses Exotics-II x ESALQ-PB1; CX-3, from crosses among populations of group-I (Exotics-I); and CEX-4, from crosses among populations of group-II (Exotics-II). On average, the populations of Exotics-I showed a higher performance level than Exotics-II for all traits, except KW. Such differences were reflected in the predicted means of composites for all traits; prediction was based on the mean of parental varieties and on the hypothetical average heterosis, expressed as a proportion of varietal mean. For grain yield and 20% expected average heterosis, the predicted composite means were: 90.6%, 87.1%, 70.5% and 63.3% of ESALQ-PB1 for CEX-1, CEX-2, CEX-3 and CEX-4, respectively.

Keywords: Germplasms; Maize breeding.

REFERENCES

Brieger, E.G., Gurgel, J.T.A., Paterniani, E., Blumenschein, A. and Alleoni, M.R. (1958). Races of maize in Brazil and other eastern South American countries. NAS-NRC Publ. 593, Washington, D.C.

Brown, W.L. (1953). Maize of the West Indies. Trop. Agric. 30: 141-170.

Brown, W.L. and Goodman, M.M. (1977). Races of Maize. In: Corn and Corn Improvement (Sprague, G.F., ed.). Amer. Soc. Agron. Madison (Wis.).

Castro, M., Gardner, C.O. and Lonnquist, J.H. (1968). Cumulative gene effects and the nature of heterosis in maize crosses involving genetically divergent races. Crop. Sci. 8: 97-101.

Duvick, D.N. (1981). Genetic diversity in major crops on the farm and in reserve. In: Proceedings of Thirteenth Intern. Bot. Congress, Sidney, Australia.

Geraldi, I.O., Miranda Filho, J.B. and Vencovsky, R. (1985). Estimates of genetic parameters for tassel characteres in maize (Zea mays L.) and breeding perspectives. Maydica 30: 1-14.

Hallauer, A.R. (1978). Potential of exotic germplasm for maize improvement. In: Maize Genetics and Breeding (Walden, W.L., ed.).

Hallauer, A.R. and Miranda Filho, J.B. (1988). Quantitative Genetics in Maize Breeding. Iowa State Univ. Press., Ames (Iowa), 468 p. (2nd edition).

Lima, M., Gimenes Fernandes, N., Miranda Filho, J.B. and Pereira, J.C.V.A. (1982). Introduction of maize (Zea mays L.) germplasms as sources for downy mildew (Peronasclerospora sorghi) resistance. Maydica 27: 159-168.

Miranda Filho, J.B. (1978). Heterosis for ear traits in intervarietal diallel crosses. Rel. Cient. Inst. Genética (ESALQ-USP) 12: 131-137 (Abstract).

Miranda Filho, J.B. and Vencovsky, R. (1984). Analysis of diallel crosses among open-pollinated varieties of maize (Zea mays L.). Maydica 29: 217-234.

Miranda Filho, J.B. and Viegas, G.P. (1987). Milho Híbrido. In: Melhoramento e Produção do Milho (Paterniani, E. and Viegas, G.P., eds.). Edited by Fundação Cargill.

Moro, J.R., Naspolini Filho, V., Vianna, R.T. and Gama, E.E.G. (1981). Introdução de novos germoplasmas de milho no Brasil. Pesq. Agrop. Bras. 16: 867-882.

Paterniani, E. (1967). Cruzamentos intervarietais de milho. Rel. Cient. Inst. Genética (ESALQ-USP)1:49-50.

Paterniani, E. (1968). Cruzamentos interraciais de milho. Rel. Cient. Inst. Genética (ESALQ-USP) 2: 108-110.

Paterniani, E. and Goodman, M.M. (1977). Races of maize in Brazil and adjacent areas. CIMMYT (Mexico).

Paterniani, E. and Lonquist, J.H. (1963). Heterosis in interracial crosses of corn (Zea mays L.). Crop. Sci. 3: 504-507.

Souza Junior, C.L., Geraldi, I.O. and Zinsly, .1.R. (1985). Influences of tassel size on the expression of prolificacy in maize (Zea mays L.). Maydica 30: 321-328.

Troyer, A.F. and Hallauer, A.R. (1968). Analysis of a diallel set of maize. Crop. Sci. 8: 581-584.

Wellhausen, E.J. (1956). Improving American corn with exotic germplasm. Proc. Annu. Hybrid Corn Ind Res. Conf. 11: 85-96.

Wellhausen, E.J. (1965). Exotic germplasm for improvement of Corn Belt maize. Proc. Annu. Hybrid Corn Ind Res. Conf. 20: 31-45.