Use Of Partly Inbred S 3 Lines For The Development Of Maize Single-crosses

Inbred lines (F≅1.0) are commonly used in the development of commercial maize (Zea mays L.) single-cross hybrids (SC) in the developed countries. Because of the high inbreeding depression for grain yield the higher price of the SC seeds limit its use by the majority of the farmers in the developing countries of Latin America. One way to circumvent the problem would be the use of partly inbred lines selected for combining ability and for uniformity within the lines. The maintenance of their genetic integrity due to the variability within partly inbred lines, however, could limit the development of SC from partly inbred lines. Therefore, the objective of this research was to compare original S 3 lines and maintained S 3 lines to study their feasibility to develop commercial SC from crosses of S 3 lines. Eight and 10 original S 3 lines from BR-105 and from BR-106 population, respectively, selected for combining ability and for uniformity, and their counterparts maintained by sib-mating and mild selection for five generations were evaluated per se, in testcrosses with two testers, and by AFLP-based genetic similarity analysis. The S 3 lines were maintained using 150 plants per line per generation with mild selection for uniformity; at least 75 plants per line per generation were saved. The results showed that three and two of the 12 traits evaluated as the line per se for the lines from BR-105 and from BR-106 population, respectively, changed significantly; whereas the testcrosses from original and maintained lines did not show any significant change. The genetic similarities estimates were high and the upper bound of the confidence interval for most of the lines reach the limit value (1.0). These results suggested that the genetic integrity of the S 3 lines was maintained, which could allow the use of partly inbred S 3 lines for the commercial development of maize single-crosses.502113121Bernardo, R., Correlation between testcross performance of lines at early and late selfing generations (1991) Theor. Appl. Genet., 82, pp. 17-21Borrero, J.C., Pandey, S., Ceballos, H., Performance and stability of tropical maize hybrids developed from lines with different levels of inbreeding (1992) Maydica, 37, pp. 251-258Carlone Jr., M.R., Russell, W.A., Evaluation of S 2 maize lines reproduced for several generations by random mating within lines. I. Comparisons between the original and maintained S 2 lines (1988) Crop Sci., 28, pp. 916-920Carlone Jr., M.R., Russell, W.A., Evaluation of S 2 maize lines reproduced for several generations by random mating within lines. II. Comparisons for testcross performance of original and advanced S 2 and S 8 lines (1989) Crop Sci., 29, pp. 899-904(1999) CIMMYT 1997/1998 World Maize Facts and Trends: Maize Production in Drought-Stressed Environments: Technical Options and Research Resource Allocation, , Mexico, D.FCockerham, C.C., Implications of genetic variances in a hybrid breeding program (1961) Crop Sci., 1, pp. 47-52Hallauer, A.R., Methods used in developing maize inbreeds (1990) Maydica, 35, pp. 1-16Hallauer, A.R., Sears, J.H., Changes in quantitative traits associated with inbreeding in a synthetic variety of maize (1973) Crop Sci., 13, pp. 327-330Hoisington, D., Khairallah, M., Gonzalez-De-Leon, D., (1994) Laboratory Protocols: CIMMYT Applied Molecular Genetics Laboratory. 2 nd Edn., , Mexico, D.FJaccard, P., Nouvelles recherches sur la distribution florale (1908) Bull. Sco. Vaud. Nat., 44, pp. 223-270Narro, L., Pandey, S., Crossa, J., De León, C., Salazar, F., Using line x tester interaction for the formation of yellow maize synthetics tolerant to acid soils (2003) Crop Sci., 43, pp. 1718-1728Province, M.A., Sequential methods of analysis for genome scans (2001) Adv. Genetics, 42, pp. 499-514Rezende, G.S.P., Souza Jr., C.L., A reciprocal recurrent selection procedure outlined to integrate hybrid program in maize (2000) J. Genet. & Breed., 54, pp. 57-66Souza Jr., C.L., Interpopulation genetic variances and hybrid breeding programs (1992) Brazil. J. Genetics, 15, pp. 643-656Souza Jr., C.L., Santos, M.X., Magnavaca, R., Gama, E.E.G., Estimativas de parâmetros genéticos na interpopulaç ão de milho BR-105 x BR-106 e suas implicações no melhoramento (1993) Pesq. Agropec. Bras., 28, pp. 473-479Stangland, G.R., Russell, W.A., Variability within single crosses of S 2 and S 8 inbred lines of maize (1981) Maydica, 26, pp. 227-238Tivang, J.G., Nienhuis, J., Smith, O.S., Estimation of sampling variance of molecular marker data using the bootstrap procedure (1994) Theor. Appl. Genet., 89, pp. 259-264Vos, P., Hogers, R., Bleeker, M., Reijans, M., Van De Lee, T., Hornes, M., Frijters, A., Zabeau, M., AFLP: A new technique for DNA fingerprinting (1995) Nucleic Acids Res., 23, pp. 4407-441