The objective of this study was estimate the combining abilities of 47 maize inbred lines, developed by the Universidade Estadual de Maringá, in order to identify the most promising ones regarding maize breeding programs focused on the second crop. For this, the lines were crossed in topcrosses scheme with two hybrids adapted to second crop (P30K75 e AG9010), used as narrow genetic base testers. Topcrosses were evaluated in randomized block design, with two repetitions, in four key-locations for the second crop along the states of Paraná, São Paulo and Mato Grosso do Sul. In addition, the lines per se were evaluated in Floresta-PR. The following traits were evaluated: (i) grain yield, in kg ha-1; (ii) male and female flowering; (iii) tolerance to drought stress. For the inbred lines per se, the mean squares were significant (p < 0.05) for both grain yield and flowering. The general combining ability of testers and lines and the specific combining ability between testers and lines were significant (p < 0.05) for all traits. The line 21 was outstanding because of the high general combining ability along the four environments. Among the lines 4, 37, 38, 39 e 47, relevant general combining ability effects () were verified for grain yield, at least in two environments including drought stress environment, and flowering. The combinations AG9010 × Line 37 and P30K75 × Line 18 was outstanding, 18 and 37 were indicated as testers for new lines coming the testers.
Zea mays; grain yield; second crop; topcrosses