Genetic variance and covariance components related to intra- and interpopulation recurrent selection in maize (Zea mays L.)

New genetic variance and covariance components related to intra- and interp opulational recurrent selection methods have been theoretically developed b y Souza Jr. (Rev. Bras. Genet. 16: 91-105, 1993) to explain the failure of these methods to concomitantly develop hybrid and per se populations. Intra - and interpopulation half-sib progenies of 100 genotypes were sampled from maize (Zea mays L.) populations BR-106 and BR-105 to estimate variance and covariance components and to compare the expected responses to reciprocal (RRS), intrapopulational (HSS), and modified (MRS) recurrent selection in i nterpopulation hybrid, populations per se, and to determine heterosis. Four sets of 100 progenies, two intra- and two interpopulational, were evaluate d in partially balanced 10 x 10 lattices arranged in split-blocks with two replications in two years (1991/92 and 1992/93) and two locations in Piraci caba, SP. Data for ear weight, plant and ear height, and ear by plant heigh t ratio were recorded. Populations and interpopulation crosses were high yi elding and showed high breeding potential for production of hybrids from in bred lines. Mid parent and the highest parent heterosis were relatively hig h, but lower than values reported for these populations under other environ mental conditions. Additive variance estimates of populations per se and in terpopulation crosses confirmed the high potential of these materials. The magnitude of the variance estimates for the deviations from intra- and inte rpopulation additive effects (sigma(tau 12)(2) for BR-106 and sigma(tau 21) (2) for BR-105) and covariance between additive effects with these deviatio ns (COV(A(1)tau(12))for BR-106 and Cov(A(2)tau(21)) for BR-105) indicated t hat these new components can significantly influence the effectiveness of b reeding methods. Genetic component estimates for BR-105 had relatively smal l errors, with Cov(A(2)tau(21)) negative for all traits. Estimates of sigma (tau 12)(2) and Cov(A(1)tau(12)) had relatively larger errors for BR-106. T he MRS method was more effective than the RRS and HSS methods in producing hybrids from inbred lines. The choice of a population tester for the MRS me thod based on population means per se may be incorrect. The additional use, when possible, of intra- and interpopulation additive genetic variances fr om each population would be more appropriate.