Yield and combining ability of maize cultivars under different ecogeographic conditions

The objective of this study was to evaluate the yield and combining ability of maize cultivars (AG4051, AL30, AL25, D270, D170, and AG1051) in contrasting environments. The trials were conducted in the growing season 2002/2003, in Viçosa, Capinópolis and Florestal, state of Minas Gerais. The effects of hybrids were significant by the F test, as well as treatments x environments, hybrid combinations x environments, and controls x environments. This indicates the possibility of increasing the yield in these regions by capitalizing on the genotype x environment interaction, by selecting and recombining cultivars for each site. Among the cultivars and their hybrid combinations, AG1051 and AG4051 x AL30, respectively, performed best in the mean of the three locations. The most indicated combinations for each site were: AG4051 X AL30 and AL30 X D270 in Viçosa, AG4051 X AL25 and AL30 X D170 in Florestal and, D170 x AG4051 and AL25 x D270 in Capinópolis. Key-words: diallel, hybrids, Zea mays L. 1 Universidade Estadual de Maringá, Avenida Colombo, 5790, Bloco 5, Sala 1, 87.020-900, Maringá, PR, Brasil 2 Universidade Federal do Maranhão. C. P. 09, 65.500-000, Chapadinha, MA, Brasil. *E-mail: [email protected] 3 Departamento de Fitotecnia, Universidade Federal de Viçosa, 36.570-000, Viçosa, MG, Brasil INTRODUCTION The main objective of maize breeders, according to Russel et al. (1992), is the development of lines whose hybrid combinations present superior performance. However, the superiority of a cultivar in a particular environment may not be verified in another, as Allard (1971), Falconer (1987) and Cruz et al. (2004) pointed out. The phenotypic manifestation is result of the action of a genotype under environmental influence, so when different environments are considered, an additional effect, apart from the genetic and environmental effects, is detected, caused by their interaction. The genotype x environment interaction has been divided into simple and complex parts. The simple interaction is caused by differences of variability between the genotypes in the environments in which the superior performances of genotypes are measured. In this type of alteration the highest yielding genotype is the one that will be recommended. The second interaction is caused by the lack of repeatability of selection performance of the genotypes. It is important to know the type of the interaction so measures can be taken to minimize and/or exploit its effects. Two important parameters that must be considered as well in the hybrid evaluation are the general combining ability (GCA) and specific combining ability (SCA). These parameters were introduced by Sprague and Tatum (1942), who discussed the use of top-crosses